moodlelib.php

<?php

// This file is part of Moodle - http://moodle.org/
//
// Moodle is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// Moodle is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.

/**
 * moodlelib.php - Moodle main library
 *
 * Main library file of miscellaneous general-purpose Moodle functions.
 * Other main libraries:
 *  - weblib.php      - functions that produce web output
 *  - datalib.php     - functions that access the database
 *
 * @package   moodlecore
 * @copyright 1999 onwards Martin Dougiamas  http://dougiamas.com
 * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */

/// CONSTANTS (Encased in phpdoc proper comments)/////////////////////////

/**
 * Used by some scripts to check they are being called by Moodle
 */
define('MOODLE_INTERNAL', true);

/// Date and time constants ///
/**
 * Time constant - the number of seconds in a year
 */
define('YEARSECS', 31536000);

/**
 * Time constant - the number of seconds in a week
 */
define('WEEKSECS', 604800);

/**
 * Time constant - the number of seconds in a day
 */
define('DAYSECS', 86400);

/**
 * Time constant - the number of seconds in an hour
 */
define('HOURSECS', 3600);

/**
 * Time constant - the number of seconds in a minute
 */
define('MINSECS', 60);

/**
 * Time constant - the number of minutes in a day
 */
define('DAYMINS', 1440);

/**
 * Time constant - the number of minutes in an hour
 */
define('HOURMINS', 60);

/// Parameter constants - every call to optional_param(), required_param()  ///
/// or clean_param() should have a specified type of parameter.  //////////////



/**
 * PARAM_ALPHA - contains only english ascii letters a-zA-Z.
 */
define('PARAM_ALPHA',    'alpha');

/**
 * PARAM_ALPHAEXT the same contents as PARAM_ALPHA plus the chars in quotes: "_-" allowed
 * NOTE: originally this allowed "/" too, please use PARAM_SAFEPATH if "/" needed
 */
define('PARAM_ALPHAEXT', 'alphaext');

/**
 * PARAM_ALPHANUM - expected numbers and letters only.
 */
define('PARAM_ALPHANUM', 'alphanum');

/**
 * PARAM_ALPHANUMEXT - expected numbers, letters only and _-.
 */
define('PARAM_ALPHANUMEXT', 'alphanumext');

/**
 * PARAM_AUTH - actually checks to make sure the string is a valid auth plugin
 */
define('PARAM_AUTH',  'auth');

/**
 * PARAM_BASE64 - Base 64 encoded format
 */
define('PARAM_BASE64',   'base64');

/**
 * PARAM_BOOL - converts input into 0 or 1, use for switches in forms and urls.
 */
define('PARAM_BOOL',     'bool');

/**
 * PARAM_CAPABILITY - A capability name, like 'moodle/role:manage'. Actually
 * checked against the list of capabilties in the database.
 */
define('PARAM_CAPABILITY',   'capability');

/**
 * PARAM_CLEANHTML - cleans submitted HTML code and removes slashes. It stays as HTML.
 */
define('PARAM_CLEANHTML', 'cleanhtml');

/**
 * PARAM_EMAIL - an email address following the RFC
 */
define('PARAM_EMAIL',   'email');

/**
 * PARAM_FILE - safe file name, all dangerous chars are stripped, protects against XSS, SQL injections and directory traversals
 */
define('PARAM_FILE',   'file');

/**
 * PARAM_FLOAT - a real/floating point number.
 */
define('PARAM_FLOAT',  'float');

/**
 * PARAM_HOST - expected fully qualified domain name (FQDN) or an IPv4 dotted quad (IP address)
 */
define('PARAM_HOST',     'host');

/**
 * PARAM_INT - integers only, use when expecting only numbers.
 */
define('PARAM_INT',      'int');

/**
 * PARAM_LANG - checks to see if the string is a valid installed language in the current site.
 */
define('PARAM_LANG',  'lang');

/**
 * PARAM_LOCALURL - expected properly formatted URL as well as one that refers to the local server itself. (NOT orthogonal to the others! Implies PARAM_URL!)
 */
define('PARAM_LOCALURL', 'localurl');

/**
 * PARAM_NOTAGS - all html tags are stripped from the text. Do not abuse this type.
 */
define('PARAM_NOTAGS',   'notags');

/**
 * PARAM_PATH - safe relative path name, all dangerous chars are stripped, protects against XSS, SQL injections and directory traversals
 * note: the leading slash is not removed, window drive letter is not allowed
 */
define('PARAM_PATH',     'path');

/**
 * PARAM_PEM - Privacy Enhanced Mail format
 */
define('PARAM_PEM',      'pem');

/**
 * PARAM_PERMISSION - A permission, one of CAP_INHERIT, CAP_ALLOW, CAP_PREVENT or CAP_PROHIBIT.
 */
define('PARAM_PERMISSION',   'permission');

/**
 * PARAM_RAW specifies a parameter that is not cleaned/processed in any way
 */
define('PARAM_RAW', 'raw');

/**
 * PARAM_SAFEDIR - safe directory name, suitable for include() and require()
 */
define('PARAM_SAFEDIR',  'safedir');

/**
 * PARAM_SAFEPATH - several PARAM_SAFEDIR joined by "/", suitable for include() and require(), plugin paths, etc.
 */
define('PARAM_SAFEPATH',  'safepath');

/**
 * PARAM_SEQUENCE - expects a sequence of numbers like 8 to 1,5,6,4,6,8,9.  Numbers and comma only.
 */
define('PARAM_SEQUENCE',  'sequence');

/**
 * PARAM_TAG - one tag (interests, blogs, etc.) - mostly international characters and space, <> not supported
 */
define('PARAM_TAG',   'tag');

/**
 * PARAM_TAGLIST - list of tags separated by commas (interests, blogs, etc.)
 */
define('PARAM_TAGLIST',   'taglist');

/**
 * PARAM_TEXT - general plain text compatible with multilang filter, no other html tags.
 */
define('PARAM_TEXT',  'text');

/**
 * PARAM_THEME - Checks to see if the string is a valid theme name in the current site
 */
define('PARAM_THEME',  'theme');

/**
 * PARAM_URL - expected properly formatted URL. Please note that domain part is required, http://localhost/ is not acceppted but http://localhost.localdomain/ is ok.
 */
define('PARAM_URL',      'url');

/**
 * PARAM_USERNAME - Clean username to only contains specified characters.
 */
define('PARAM_USERNAME',    'username');


///// DEPRECATED PARAM TYPES OR ALIASES - DO NOT USE FOR NEW CODE  /////
/**
 * PARAM_CLEAN - obsoleted, please use a more specific type of parameter.
 * It was one of the first types, that is why it is abused so much ;-)
 */
define('PARAM_CLEAN',    'clean');

/**
 * PARAM_INTEGER - deprecated alias for PARAM_INT
 */
define('PARAM_INTEGER',  'int');

/**
 * PARAM_NUMBER - deprecated alias of PARAM_FLOAT
 */
define('PARAM_NUMBER',  'float');

/**
 * PARAM_ACTION - deprecated alias for PARAM_ALPHANUMEXT, use for various actions in formas and urls
 * NOTE: originally alias for PARAM_APLHA
 */
define('PARAM_ACTION',   'alphanumext');

/**
 * PARAM_FORMAT - deprecated alias for PARAM_ALPHANUMEXT, use for names of plugins, formats, etc.
 * NOTE: originally alias for PARAM_APLHA
 */
define('PARAM_FORMAT',   'alphanumext');

/**
 * PARAM_MULTILANG - deprecated alias of PARAM_TEXT.
 */
define('PARAM_MULTILANG',  'text');

/**
 * PARAM_CLEANFILE - deprecated alias of PARAM_FILE; originally was removing regional chars too
 */
define('PARAM_CLEANFILE', 'file');

/// Web Services ///

/**
 * VALUE_REQUIRED - if the parameter is not supplied, there is an error
 */
define('VALUE_REQUIRED', 1);

/**
 * VALUE_OPTIONAL - if the parameter is not supplied, then the param has no value
 */
define('VALUE_OPTIONAL', 2);

/**
 * VALUE_DEFAULT - if the parameter is not supplied, then the default value is used
 */
define('VALUE_DEFAULT', 0);

/**
 * NULL_NOT_ALLOWED - the parameter can not be set to null in the database
 */
define('NULL_NOT_ALLOWED', false);

/**
 * NULL_ALLOWED - the parameter can be set to null in the database
 */
define('NULL_ALLOWED', true);

/// Page types ///
/**
 * PAGE_COURSE_VIEW is a definition of a page type. For more information on the page class see moodle/lib/pagelib.php.
 */
define('PAGE_COURSE_VIEW', 'course-view');

/** Get remote addr constant */
define('GETREMOTEADDR_SKIP_HTTP_CLIENT_IP', '1');
/** Get remote addr constant */
define('GETREMOTEADDR_SKIP_HTTP_X_FORWARDED_FOR', '2');

/// Blog access level constant declaration ///
define ('BLOG_USER_LEVEL', 1);
define ('BLOG_GROUP_LEVEL', 2);
define ('BLOG_COURSE_LEVEL', 3);
define ('BLOG_SITE_LEVEL', 4);
define ('BLOG_GLOBAL_LEVEL', 5);


///Tag constants///
/**
 * To prevent problems with multibytes strings,Flag updating in nav not working on the review page. this should not exceed the
 * length of "varchar(255) / 3 (bytes / utf-8 character) = 85".
 * TODO: this is not correct, varchar(255) are 255 unicode chars ;-)
 *
 * @todo define(TAG_MAX_LENGTH) this is not correct, varchar(255) are 255 unicode chars ;-)
 */
define('TAG_MAX_LENGTH', 50);

/// Password policy constants ///
define ('PASSWORD_LOWER', 'abcdefghijklmnopqrstuvwxyz');
define ('PASSWORD_UPPER', 'ABCDEFGHIJKLMNOPQRSTUVWXYZ');
define ('PASSWORD_DIGITS', '0123456789');
define ('PASSWORD_NONALPHANUM', '.,;:!?_-+/*@#&$');

/// Feature constants ///
// Used for plugin_supports() to report features that are, or are not, supported by a module.

/** True if module can provide a grade */
define('FEATURE_GRADE_HAS_GRADE', 'grade_has_grade');
/** True if module supports outcomes */
define('FEATURE_GRADE_OUTCOMES', 'outcomes');

/** True if module has code to track whether somebody viewed it */
define('FEATURE_COMPLETION_TRACKS_VIEWS', 'completion_tracks_views');
/** True if module has custom completion rules */
define('FEATURE_COMPLETION_HAS_RULES', 'completion_has_rules');

/** True if module supports outcomes */
define('FEATURE_IDNUMBER', 'idnumber');
/** True if module supports groups */
define('FEATURE_GROUPS', 'groups');
/** True if module supports groupings */
define('FEATURE_GROUPINGS', 'groupings');
/** True if module supports groupmembersonly */
define('FEATURE_GROUPMEMBERSONLY', 'groupmembersonly');

/** Type of module */
define('FEATURE_MOD_ARCHETYPE', 'mod_archetype');
/** True if module supports intro editor */
define('FEATURE_MOD_INTRO', 'mod_intro');
/** True if module has default completion */
define('FEATURE_MODEDIT_DEFAULT_COMPLETION', 'modedit_default_completion');

define('FEATURE_COMMENT', 'comment');

define('FEATURE_RATE', 'rate');
/** True if module supports backup/restore of moodle2 format */
define('FEATURE_BACKUP_MOODLE2', 'backup_moodle2');

/** Unspecified module archetype */
define('MOD_ARCHETYPE_OTHER', 0);
/** Resource-like type module */
define('MOD_ARCHETYPE_RESOURCE', 1);
/** Assignemnt module archetype */
define('MOD_ARCHETYPE_ASSIGNMENT', 2);

/**
 * Security token used for allowing access
 * from external application such as web services.
 * Scripts do not use any session, performance is relatively
 * low because we need to load access info in each request.
 * Scrits are executed in parallel.
 */
define('EXTERNAL_TOKEN_PERMANENT', 0);

/**
 * Security token used for allowing access
 * of embedded applications, the code is executed in the
 * active user session. Token is invalidated after user logs out.
 * Scripts are executed serially - normal session locking is used.
 */
define('EXTERNAL_TOKEN_EMBEDDED', 1);

/// PARAMETER HANDLING ////////////////////////////////////////////////////

/**
 * Returns a particular value for the named variable, taken from
 * POST or GET.  If the parameter doesn't exist then an error is
 * thrown because we require this variable.
 *
 * This function should be used to initialise all required values
 * in a script that are based on parameters.  Usually it will be
 * used like this:
 *    $id = required_param('id', PARAM_INT);
 *
 * @param string $parname the name of the page parameter we want,
 *                        default PARAM_CLEAN
 * @param int $type expected type of parameter
 * @return mixed
 */
function required_param($parname, $type=PARAM_CLEAN) {
    if (isset($_POST[$parname])) {       // POST has precedence
        $param = $_POST[$parname];
    } else if (isset($_GET[$parname])) {
        $param = $_GET[$parname];
    } else {
        print_error('missingparam', '', '', $parname);
    }

    return clean_param($param, $type);
}

/**
 * Returns a particular value for the named variable, taken from
 * POST or GET, otherwise returning a given default.
 *
 * This function should be used to initialise all optional values
 * in a script that are based on parameters.  Usually it will be
 * used like this:
 *    $name = optional_param('name', 'Fred', PARAM_TEXT);
 *
 * @param string $parname the name of the page parameter we want
 * @param mixed  $default the default value to return if nothing is found
 * @param int $type expected type of parameter, default PARAM_CLEAN
 * @return mixed
 */
function optional_param($parname, $default=NULL, $type=PARAM_CLEAN) {
    if (isset($_POST[$parname])) {       // POST has precedence
        $param = $_POST[$parname];
    } else if (isset($_GET[$parname])) {
        $param = $_GET[$parname];
    } else {
        return $default;
    }

    return clean_param($param, $type);
}

/**
 * Strict validation of parameter values, the values are only converted
 * to requested PHP type. Internally it is using clean_param, the values
 * before and after cleaning must be equal - otherwise
 * an invalid_parameter_exception is thrown.
 * Onjects and classes are not accepted.
 *
 * @param mixed $param
 * @param int $type PARAM_ constant
 * @param bool $allownull are nulls valid value?
 * @param string $debuginfo optional debug information
 * @return mixed the $param value converted to PHP type or invalid_parameter_exception
 */
function validate_param($param, $type, $allownull=NULL_NOT_ALLOWED, $debuginfo='') {
    if (is_null($param)) {
        if ($allownull == NULL_ALLOWED) {
            return null;
        } else {
            throw new invalid_parameter_exception($debuginfo);
        }
    }
    if (is_array($param) or is_object($param)) {
        throw new invalid_parameter_exception($debuginfo);
    }

    $cleaned = clean_param($param, $type);
    if ((string)$param !== (string)$cleaned) {
        // conversion to string is usually lossless
        throw new invalid_parameter_exception($debuginfo);
    }

    return $cleaned;
}

/**
 * Used by {@link optional_param()} and {@link required_param()} to
 * clean the variables and/or cast to specific types, based on
 * an options field.
 * <code>
 * $course->format = clean_param($course->format, PARAM_ALPHA);
 * $selectedgrade_item = clean_param($selectedgrade_item, PARAM_CLEAN);
 * </code>
 *
 * @global object
 * @uses PARAM_RAW
 * @uses PARAM_CLEAN
 * @uses PARAM_CLEANHTML
 * @uses PARAM_INT
 * @uses PARAM_FLOAT
 * @uses PARAM_NUMBER
 * @uses PARAM_ALPHA
 * @uses PARAM_ALPHAEXT
 * @uses PARAM_ALPHANUM
 * @uses PARAM_ALPHANUMEXT
 * @uses PARAM_SEQUENCE
 * @uses PARAM_BOOL
 * @uses PARAM_NOTAGS
 * @uses PARAM_TEXT
 * @uses PARAM_SAFEDIR
 * @uses PARAM_SAFEPATH
 * @uses PARAM_FILE
 * @uses PARAM_PATH
 * @uses PARAM_HOST
 * @uses PARAM_URL
 * @uses PARAM_LOCALURL
 * @uses PARAM_PEM
 * @uses PARAM_BASE64
 * @uses PARAM_TAG
 * @uses PARAM_SEQUENCE
 * @uses PARAM_USERNAME
 * @param mixed $param the variable we are cleaning
 * @param int $type expected format of param after cleaning.
 * @return mixed
 */
function clean_param($param, $type) {

    global $CFG;

    if (is_array($param)) {              // Let's loop
        $newparam = array();
        foreach ($param as $key => $value) {
            $newparam[$key] = clean_param($value, $type);
        }
        return $newparam;
    }

    switch ($type) {
        case PARAM_RAW:          // no cleaning at all
            return $param;

        case PARAM_CLEAN:        // General HTML cleaning, try to use more specific type if possible
            if (is_numeric($param)) {
                return $param;
            }
            return clean_text($param);     // Sweep for scripts, etc

        case PARAM_CLEANHTML:    // prepare html fragment for display, do not store it into db!!
            $param = clean_text($param);     // Sweep for scripts, etc
            return trim($param);

        case PARAM_INT:
            return (int)$param;  // Convert to integer

        case PARAM_FLOAT:
        case PARAM_NUMBER:
            return (float)$param;  // Convert to float

        case PARAM_ALPHA:        // Remove everything not a-z
            return preg_replace('/[^a-zA-Z]/i', '', $param);

        case PARAM_ALPHAEXT:     // Remove everything not a-zA-Z_- (originally allowed "/" too)
            return preg_replace('/[^a-zA-Z_-]/i', '', $param);

        case PARAM_ALPHANUM:     // Remove everything not a-zA-Z0-9
            return preg_replace('/[^A-Za-z0-9]/i', '', $param);

        case PARAM_ALPHANUMEXT:     // Remove everything not a-zA-Z0-9_-
            return preg_replace('/[^A-Za-z0-9_-]/i', '', $param);

        case PARAM_SEQUENCE:     // Remove everything not 0-9,
            return preg_replace('/[^0-9,]/i', '', $param);

        case PARAM_BOOL:         // Convert to 1 or 0
            $tempstr = strtolower($param);
            if ($tempstr === 'on' or $tempstr === 'yes' or $tempstr === 'true') {
                $param = 1;
            } else if ($tempstr === 'off' or $tempstr === 'no'  or $tempstr === 'false') {
                $param = 0;
            } else {
                $param = empty($param) ? 0 : 1;
            }
            return $param;

        case PARAM_NOTAGS:       // Strip all tags
            return strip_tags($param);

        case PARAM_TEXT:    // leave only tags needed for multilang
            return clean_param(strip_tags($param, '<lang><span>'), PARAM_CLEAN);

        case PARAM_SAFEDIR:      // Remove everything not a-zA-Z0-9_-
            return preg_replace('/[^a-zA-Z0-9_-]/i', '', $param);

        case PARAM_SAFEPATH:     // Remove everything not a-zA-Z0-9/_-
            return preg_replace('/[^a-zA-Z0-9\/_-]/i', '', $param);

        case PARAM_FILE:         // Strip all suspicious characters from filename
            $param = preg_replace('~[[:cntrl:]]|[&<>"`\|\':\\/]~u', '', $param);
            $param = preg_replace('~\.\.+~', '', $param);
            if ($param === '.') {
                $param = '';
            }
            return $param;

        case PARAM_PATH:         // Strip all suspicious characters from file path
            $param = str_replace('\\', '/', $param);
            $param = preg_replace('~[[:cntrl:]]|[&<>"`\|\':]~u', '', $param);
            $param = preg_replace('~\.\.+~', '', $param);
            $param = preg_replace('~//+~', '/', $param);
            return preg_replace('~/(\./)+~', '/', $param);

        case PARAM_HOST:         // allow FQDN or IPv4 dotted quad
            $param = preg_replace('/[^\.\d\w-]/','', $param ); // only allowed chars
            // match ipv4 dotted quad
            if (preg_match('/(\d{1,3})\.(\d{1,3})\.(\d{1,3})\.(\d{1,3})/',$param, $match)){
                // confirm values are ok
                if ( $match[0] > 255
                     || $match[1] > 255
                     || $match[3] > 255
                     || $match[4] > 255 ) {
                    // hmmm, what kind of dotted quad is this?
                    $param = '';
                }
            } elseif ( preg_match('/^[\w\d\.-]+$/', $param) // dots, hyphens, numbers
                       && !preg_match('/^[\.-]/',  $param) // no leading dots/hyphens
                       && !preg_match('/[\.-]$/',  $param) // no trailing dots/hyphens
                       ) {
                // all is ok - $param is respected
            } else {
                // all is not ok...
                $param='';
            }
            return $param;

        case PARAM_URL:          // allow safe ftp, http, mailto urls
            include_once($CFG->dirroot . '/lib/validateurlsyntax.php');
            if (!empty($param) && validateUrlSyntax($param, 's?H?S?F?E?u-P-a?I?p?f?q?r?')) {
                // all is ok, param is respected
            } else {
                $param =''; // not really ok
            }
            return $param;

        case PARAM_LOCALURL:     // allow http absolute, root relative and relative URLs within wwwroot
            $param = clean_param($param, PARAM_URL);
            if (!empty($param)) {
                if (preg_match(':^/:', $param)) {
                    // root-relative, ok!
                } elseif (preg_match('/^'.preg_quote($CFG->wwwroot, '/').'/i',$param)) {
                    // absolute, and matches our wwwroot
                } else {
                    // relative - let's make sure there are no tricks
                    if (validateUrlSyntax('/' . $param, 's-u-P-a-p-f+q?r?')) {
                        // looks ok.
                    } else {
                        $param = '';
                    }
                }
            }
            return $param;

        case PARAM_PEM:
            $param = trim($param);
            // PEM formatted strings may contain letters/numbers and the symbols
            // forward slash: /
            // plus sign:     +
            // equal sign:    =
            // , surrounded by BEGIN and END CERTIFICATE prefix and suffixes
            if (preg_match('/^-----BEGIN CERTIFICATE-----([\s\w\/\+=]+)-----END CERTIFICATE-----$/', trim($param), $matches)) {
                list($wholething, $body) = $matches;
                unset($wholething, $matches);
                $b64 = clean_param($body, PARAM_BASE64);
                if (!empty($b64)) {
                    return "-----BEGIN CERTIFICATE-----\n$b64\n-----END CERTIFICATE-----\n";
                } else {
                    return '';
                }
            }
            return '';

        case PARAM_BASE64:
            if (!empty($param)) {
                // PEM formatted strings may contain letters/numbers and the symbols
                // forward slash: /
                // plus sign:     +
                // equal sign:    =
                if (0 >= preg_match('/^([\s\w\/\+=]+)$/', trim($param))) {
                    return '';
                }
                $lines = preg_split('/[\s]+/', $param, -1, PREG_SPLIT_NO_EMPTY);
                // Each line of base64 encoded data must be 64 characters in
                // length, except for the last line which may be less than (or
                // equal to) 64 characters long.
                for ($i=0, $j=count($lines); $i < $j; $i++) {
                    if ($i + 1 == $j) {
                        if (64 < strlen($lines[$i])) {
                            return '';
                        }
                        continue;
                    }

                    if (64 != strlen($lines[$i])) {
                        return '';
                    }
                }
                return implode("\n",$lines);
            } else {
                return '';
            }

        case PARAM_TAG:
            //as long as magic_quotes_gpc is used, a backslash will be a
            //problem, so remove *all* backslash.
            //$param = str_replace('\\', '', $param);
            //remove some nasties
            $param = preg_replace('~[[:cntrl:]]|[<>`]~', '', $param);
            //convert many whitespace chars into one
            $param = preg_replace('/\s+/', ' ', $param);
            $textlib = textlib_get_instance();
            $param = $textlib->substr(trim($param), 0, TAG_MAX_LENGTH);
            return $param;


        case PARAM_TAGLIST:
            $tags = explode(',', $param);
            $result = array();
            foreach ($tags as $tag) {
                $res = clean_param($tag, PARAM_TAG);
                if ($res !== '') {
                    $result[] = $res;
                }
            }
            if ($result) {
                return implode(',', $result);
            } else {
                return '';
            }

        case PARAM_CAPABILITY:
            if (get_capability_info($param)) {
                return $param;
            } else {
                return '';
            }

        case PARAM_PERMISSION:
            $param = (int)$param;
            if (in_array($param, array(CAP_INHERIT, CAP_ALLOW, CAP_PREVENT, CAP_PROHIBIT))) {
                return $param;
            } else {
                return CAP_INHERIT;
            }

        case PARAM_AUTH:
            $param = clean_param($param, PARAM_SAFEDIR);
            if (exists_auth_plugin($param)) {
                return $param;
            } else {
                return '';
            }

        case PARAM_LANG:
            $param = clean_param($param, PARAM_SAFEDIR);
            if (get_string_manager()->translation_exists($param)) {
                return $param;
            } else {
                return ''; // Specified language is not installed or param malformed
            }

        case PARAM_THEME:
            $param = clean_param($param, PARAM_SAFEDIR);
            if (file_exists("$CFG->dirroot/theme/$param/config.php")) {
                return $param;
            } else if (!empty($CFG->themedir) and file_exists("$CFG->themedir/$param/config.php")) {
                return $param;
            } else {
                return '';  // Specified theme is not installed
            }

        case PARAM_USERNAME:
            $param = str_replace(" " , "", $param);
            $param = moodle_strtolower($param);  // Convert uppercase to lowercase MDL-16919
            if (empty($CFG->extendedusernamechars)) {
                // regular expression, eliminate all chars EXCEPT:
                // alphanum, dash (-), underscore (_), at sign (@) and period (.) characters.
                $param = preg_replace('/[^-\.@_a-z0-9]/', '', $param);
            }
            return $param;

        case PARAM_EMAIL:
            if (validate_email($param)) {
                return $param;
            } else {
                return '';
            }

        default:                 // throw error, switched parameters in optional_param or another serious problem
            print_error("unknownparamtype", '', '', $type);
    }
}

/**
 * Return true if given value is integer or string with integer value
 *
 * @param mixed $value String or Int
 * @return bool true if number, false if not
 */
function is_number($value) {
    if (is_int($value)) {
        return true;
    } else if (is_string($value)) {
        return ((string)(int)$value) === $value;
    } else {
        return false;
    }
}

/**
 * Returns host part from url
 * @param string $url full url
 * @return string host, null if not found
 */
function get_host_from_url($url) {
    preg_match('|^[a-z]+://([a-zA-Z0-9-.]+)|i', $url, $matches);
    if ($matches) {
        return $matches[1];
    }
    return null;
}

/**
 * Tests whether anything was returned by text editor
 *
 * This function is useful for testing whether something you got back from
 * the HTML editor actually contains anything. Sometimes the HTML editor
 * appear to be empty, but actually you get back a <br> tag or something.
 *
 * @param string $string a string containing HTML.
 * @return boolean does the string contain any actual content - that is text,
 * images, objcts, etc.
 */
function html_is_blank($string) {
    return trim(strip_tags($string, '<img><object><applet><input><select><textarea><hr>')) == '';
}

/**
 * Set a key in global configuration
 *
 * Set a key/value pair in both this session's {@link $CFG} global variable
 * and in the 'config' database table for future sessions.
 *
 * Can also be used to update keys for plugin-scoped configs in config_plugin table.
 * In that case it doesn't affect $CFG.
 *
 * A NULL value will delete the entry.
 *
 * @global object
 * @global object
 * @param string $name the key to set
 * @param string $value the value to set (without magic quotes)
 * @param string $plugin (optional) the plugin scope, default NULL
 * @return bool true or exception
 */
function set_config($name, $value, $plugin=NULL) {
    global $CFG, $DB;

    if (empty($plugin)) {
        if (!array_key_exists($name, $CFG->config_php_settings)) {
            // So it's defined for this invocation at least
            if (is_null($value)) {
                unset($CFG->$name);
            } else {
                $CFG->$name = (string)$value; // settings from db are always strings
            }
        }

        if ($DB->get_field('config', 'name', array('name'=>$name))) {
            if ($value === null) {
                $DB->delete_records('config', array('name'=>$name));
            } else {
                $DB->set_field('config', 'value', $value, array('name'=>$name));
            }
        } else {
            if ($value !== null) {
                $config = new object();
                $config->name  = $name;
                $config->value = $value;
                $DB->insert_record('config', $config, false);
            }
        }

    } else { // plugin scope
        if ($id = $DB->get_field('config_plugins', 'id', array('name'=>$name, 'plugin'=>$plugin))) {
            if ($value===null) {
                $DB->delete_records('config_plugins', array('name'=>$name, 'plugin'=>$plugin));
            } else {
                $DB->set_field('config_plugins', 'value', $value, array('id'=>$id));
            }
        } else {
            if ($value !== null) {
                $config = new object();
                $config->plugin = $plugin;
                $config->name   = $name;
                $config->value  = $value;
                $DB->insert_record('config_plugins', $config, false);
            }
        }
    }

    return true;
}

/**
 * Get configuration values from the global config table
 * or the config_plugins table.
 *
 * If called with no parameters it will do the right thing
 * generating $CFG safely from the database without overwriting
 * existing values.
 *
 * If called with one parameter, it will load all the config
 * variables for one pugin, and return them as an object.
 *
 * If called with 2 parameters it will return a $string single
 * value or false of the value is not found.
 *
 * @global object
 * @param string $plugin default NULL
 * @param string $name default NULL
 * @return mixed hash-like object or single value
 */
function get_config($plugin=NULL, $name=NULL) {
    global $CFG, $DB;

    if (!empty($name)) { // the user is asking for a specific value
        if (!empty($plugin)) {
            return $DB->get_field('config_plugins', 'value', array('plugin'=>$plugin, 'name'=>$name));
        } else {
            return $DB->get_field('config', 'value', array('name'=>$name));
        }
    }

    // the user is after a recordset
    if (!empty($plugin)) {
        $localcfg = $DB->get_records_menu('config_plugins', array('plugin'=>$plugin), '', 'name,value');
        if (!empty($localcfg)) {
            return (object)$localcfg;
        } else {
            return false;
        }
    } else {
        // this was originally in setup.php
        if ($configs = $DB->get_records('config')) {
            $localcfg = (array)$CFG;
            foreach ($configs as $config) {
                if (!isset($localcfg[$config->name])) {
                    $localcfg[$config->name] = $config->value;
                }
                // do not complain anymore if config.php overrides settings from db
            }

            $localcfg = (object)$localcfg;
            return $localcfg;
        } else {
            // preserve $CFG if DB returns nothing or error
            return $CFG;
        }

    }
}

/**
 * Removes a key from global configuration
 *
 * @param string $name the key to set
 * @param string $plugin (optional) the plugin scope
 * @global object
 * @return boolean whether the operation succeeded.
 */
function unset_config($name, $plugin=NULL) {
    global $CFG, $DB;

    if (empty($plugin)) {
        unset($CFG->$name);
        $DB->delete_records('config', array('name'=>$name));
    } else {
        $DB->delete_records('config_plugins', array('name'=>$name, 'plugin'=>$plugin));
    }

    return true;
}

/**
 * Remove all the config variables for a given plugin.
 *
 * @param string $plugin a plugin, for example 'quiz' or 'qtype_multichoice';
 * @return boolean whether the operation succeeded.
 */
function unset_all_config_for_plugin($plugin) {
    global $DB;
    $DB->delete_records('config_plugins', array('plugin' => $plugin));
    $DB->delete_records_select('config', 'name LIKE ?', array($plugin . '_%'));
    return true;
}

/**
 * Use this funciton to get a list of users from a config setting of type admin_setting_users_with_capability.
 * @param string $value the value of the config setting.
 * @param string $capability the capability - must match the one passed to the admin_setting_users_with_capability constructor.
 * @return array of user objects.
 */
function get_users_from_config($value, $capability) {
    global $CFG;
    if ($value == '$@ALL@$') {
        $users = get_users_by_capability(get_context_instance(CONTEXT_SYSTEM), $capability);
    } else {
        list($where, $params) = $DB->get_in_or_equal(explode(',', $CFG->courserequestnotify));
        $params[] = $CFG->mnet_localhost_id;
        $users = $DB->get_records_select('user', 'username ' . $where . ' AND mnethostid = ?', $params);
    }
    return $users;
}

/**
 * Get volatile flags
 *
 * @param string $type
 * @param int    $changedsince default null
 * @return records array
 */
function get_cache_flags($type, $changedsince=NULL) {
    global $DB;

    $params = array('type'=>$type, 'expiry'=>time());
    $sqlwhere = "flagtype = :type AND expiry >= :expiry";
    if ($changedsince !== NULL) {
        $params['changedsince'] = $changedsince;
        $sqlwhere .= " AND timemodified > :changedsince";
    }
    $cf = array();

    if ($flags = $DB->get_records_select('cache_flags', $sqlwhere, $params, '', 'name,value')) {
        foreach ($flags as $flag) {
            $cf[$flag->name] = $flag->value;
        }
    }
    return $cf;
}

/**
 * Get volatile flags
 *
 * @param string $type
 * @param string $name
 * @param int    $changedsince default null
 * @return records array
 */
function get_cache_flag($type, $name, $changedsince=NULL) {
    global $DB;

    $params = array('type'=>$type, 'name'=>$name, 'expiry'=>time());

    $sqlwhere = "flagtype = :type AND name = :name AND expiry >= :expiry";
    if ($changedsince !== NULL) {
        $params['changedsince'] = $changedsince;
        $sqlwhere .= " AND timemodified > :changedsince";
    }

    return $DB->get_field_select('cache_flags', 'value', $sqlwhere, $params);
}

/**
 * Set a volatile flag
 *
 * @param string $type the "type" namespace for the key
 * @param string $name the key to set
 * @param string $value the value to set (without magic quotes) - NULL will remove the flag
 * @param int $expiry (optional) epoch indicating expiry - defaults to now()+ 24hs
 * @return bool Always returns true
 */
function set_cache_flag($type, $name, $value, $expiry=NULL) {
    global $DB;

    $timemodified = time();
    if ($expiry===NULL || $expiry < $timemodified) {
        $expiry = $timemodified + 24 * 60 * 60;
    } else {
        $expiry = (int)$expiry;
    }

    if ($value === NULL) {
        unset_cache_flag($type,$name);
        return true;
    }

    if ($f = $DB->get_record('cache_flags', array('name'=>$name, 'flagtype'=>$type), '*', IGNORE_MULTIPLE)) { // this is a potentail problem in DEBUG_DEVELOPER
        if ($f->value == $value and $f->expiry == $expiry and $f->timemodified == $timemodified) {
            return true; //no need to update; helps rcache too
        }
        $f->value        = $value;
        $f->expiry       = $expiry;
        $f->timemodified = $timemodified;
        $DB->update_record('cache_flags', $f);
    } else {
        $f = new object();
        $f->flagtype     = $type;
        $f->name         = $name;
        $f->value        = $value;
        $f->expiry       = $expiry;
        $f->timemodified = $timemodified;
        $DB->insert_record('cache_flags', $f);
    }
    return true;
}

/**
 * Removes a single volatile flag
 *
 * @global object
 * @param string $type the "type" namespace for the key
 * @param string $name the key to set
 * @return bool
 */
function unset_cache_flag($type, $name) {
    global $DB;
    $DB->delete_records('cache_flags', array('name'=>$name, 'flagtype'=>$type));
    return true;
}

/**
 * Garbage-collect volatile flags
 *
 * @return bool Always returns true
 */
function gc_cache_flags() {
    global $DB;
    $DB->delete_records_select('cache_flags', 'expiry < ?', array(time()));
    return true;
}

/// FUNCTIONS FOR HANDLING USER PREFERENCES ////////////////////////////////////

/**
 * Refresh current $USER session global variable with all their current preferences.
 *
 * @global object
 * @param mixed $time default null
 * @return void
 */
function check_user_preferences_loaded($time = null) {
    global $USER, $DB;
    static $timenow = null; // Static cache, so we only check up-to-dateness once per request.

    if (!empty($USER->preference) && isset($USER->preference['_lastloaded'])) {
        // Already loaded. Are we up to date?

        if (is_null($timenow) || (!is_null($time) && $time != $timenow)) {
            $timenow = time();
            if (!get_cache_flag('userpreferenceschanged', $USER->id, $USER->preference['_lastloaded'])) {
                // We are up-to-date.
                return;
            }
        } else {
            // Already checked for up-to-date-ness.
            return;
        }
    }

    // OK, so we have to reload. Reset preference
    $USER->preference = array();

    if (!isloggedin() or isguestuser()) {
        // No permanent storage for not-logged-in user and guest

    } else if ($preferences = $DB->get_records('user_preferences', array('userid'=>$USER->id))) {
        foreach ($preferences as $preference) {
            $USER->preference[$preference->name] = $preference->value;
        }
    }

    $USER->preference['_lastloaded'] = $timenow;
}

/**
 * Called from set/delete_user_preferences, so that the prefs can be correctly reloaded.
 *
 * @global object
 * @global object
 * @param integer $userid the user whose prefs were changed.
 */
function mark_user_preferences_changed($userid) {
    global $CFG, $USER;
    if ($userid == $USER->id) {
        check_user_preferences_loaded(time());
    }
    set_cache_flag('userpreferenceschanged', $userid, 1, time() + $CFG->sessiontimeout);
}

/**
 * Sets a preference for the current user
 *
 * Optionally, can set a preference for a different user object
 *
 * @todo Add a better description and include usage examples. Add inline links to $USER and user functions in above line.
 *
 * @global object
 * @global object
 * @param string $name The key to set as preference for the specified user
 * @param string $value The value to set forthe $name key in the specified user's record
 * @param int $otheruserid A moodle user ID, default null
 * @return bool
 */
function set_user_preference($name, $value, $otheruserid=NULL) {
    global $USER, $DB;

    if (empty($name)) {
        return false;
    }

    $nostore = false;
    if (empty($otheruserid)){
        if (!isloggedin() or isguestuser()) {
            $nostore = true;
        }
        $userid = $USER->id;
    } else {
        if (isguestuser($otheruserid)) {
            $nostore = true;
        }
        $userid = $otheruserid;
    }

    if ($nostore) {
        // no permanent storage for not-logged-in user and guest

    } else if ($preference = $DB->get_record('user_preferences', array('userid'=>$userid, 'name'=>$name))) {
        if ($preference->value === $value) {
            return true;
        }
        $DB->set_field('user_preferences', 'value', (string)$value, array('id'=>$preference->id));

    } else {
        $preference = new object();
        $preference->userid = $userid;
        $preference->name   = $name;
        $preference->value  = (string)$value;
        $DB->insert_record('user_preferences', $preference);
    }

    mark_user_preferences_changed($userid);
    // update value in USER session if needed
    if ($userid == $USER->id) {
        $USER->preference[$name] = (string)$value;
        $USER->preference['_lastloaded'] = time();
    }

    return true;
}

/**
 * Sets a whole array of preferences for the current user
 *
 * @param array $prefarray An array of key/value pairs to be set
 * @param int $otheruserid A moodle user ID
 * @return bool
 */
function set_user_preferences($prefarray, $otheruserid=NULL) {

    if (!is_array($prefarray) or empty($prefarray)) {
        return false;
    }

    foreach ($prefarray as $name => $value) {
        set_user_preference($name, $value, $otheruserid);
    }
    return true;
}

/**
 * Unsets a preference completely by deleting it from the database
 *
 * Optionally, can set a preference for a different user id
 *
 * @global object
 * @param string  $name The key to unset as preference for the specified user
 * @param int $otheruserid A moodle user ID
 */
function unset_user_preference($name, $otheruserid=NULL) {
    global $USER, $DB;

    if (empty($otheruserid)){
        $userid = $USER->id;
        check_user_preferences_loaded();
    } else {
        $userid = $otheruserid;
    }

    //Then from DB
    $DB->delete_records('user_preferences', array('userid'=>$userid, 'name'=>$name));

    mark_user_preferences_changed($userid);
    //Delete the preference from $USER if needed
    if ($userid == $USER->id) {
        unset($USER->preference[$name]);
        $USER->preference['_lastloaded'] = time();
    }

    return true;
}

/**
 * Used to fetch user preference(s)
 *
 * If no arguments are supplied this function will return
 * all of the current user preferences as an array.
 *
 * If a name is specified then this function
 * attempts to return that particular preference value.  If
 * none is found, then the optional value $default is returned,
 * otherwise NULL.
 *
 * @global object
 * @global object
 * @param string $name Name of the key to use in finding a preference value
 * @param string $default Value to be returned if the $name key is not set in the user preferences
 * @param int $otheruserid A moodle user ID
 * @return string
 */
function get_user_preferences($name=NULL, $default=NULL, $otheruserid=NULL) {
    global $USER, $DB;

    if (empty($otheruserid) || (isloggedin() && ($USER->id == $otheruserid))){
        check_user_preferences_loaded();

        if (empty($name)) {
            return $USER->preference; // All values
        } else if (array_key_exists($name, $USER->preference)) {
            return $USER->preference[$name]; // The single value
        } else {
            return $default; // Default value (or NULL)
        }

    } else {
        if (empty($name)) {
            return $DB->get_records_menu('user_preferences', array('userid'=>$otheruserid), '', 'name,value'); // All values
        } else if ($value = $DB->get_field('user_preferences', 'value', array('userid'=>$otheruserid, 'name'=>$name))) {
            return $value; // The single value
        } else {
            return $default; // Default value (or NULL)
        }
    }
}

/// FUNCTIONS FOR HANDLING TIME ////////////////////////////////////////////

/**
 * Given date parts in user time produce a GMT timestamp.
 *
 * @todo Finish documenting this function
 * @param int $year The year part to create timestamp of
 * @param int $month The month part to create timestamp of
 * @param int $day The day part to create timestamp of
 * @param int $hour The hour part to create timestamp of
 * @param int $minute The minute part to create timestamp of
 * @param int $second The second part to create timestamp of
 * @param float $timezone Timezone modifier
 * @param bool $applydst Toggle Daylight Saving Time, default true
 * @return int timestamp
 */
function make_timestamp($year, $month=1, $day=1, $hour=0, $minute=0, $second=0, $timezone=99, $applydst=true) {

    $strtimezone = NULL;
    if (!is_numeric($timezone)) {
        $strtimezone = $timezone;
    }

    $timezone = get_user_timezone_offset($timezone);

    if (abs($timezone) > 13) {
        $time = mktime((int)$hour, (int)$minute, (int)$second, (int)$month, (int)$day, (int)$year);
    } else {
        $time = gmmktime((int)$hour, (int)$minute, (int)$second, (int)$month, (int)$day, (int)$year);
        $time = usertime($time, $timezone);
        if($applydst) {
            $time -= dst_offset_on($time, $strtimezone);
        }
    }

    return $time;

}

/**
 * Format a date/time (seconds) as weeks, days, hours etc as needed
 *
 * Given an amount of time in seconds, returns string
 * formatted nicely as weeks, days, hours etc as needed
 *
 * @uses MINSECS
 * @uses HOURSECS
 * @uses DAYSECS
 * @uses YEARSECS
 * @param int $totalsecs Time in seconds
 * @param object $str Should be a time object
 * @return string A nicely formatted date/time string
 */
 function format_time($totalsecs, $str=NULL) {

    $totalsecs = abs($totalsecs);

    if (!$str) {  // Create the str structure the slow way
        $str->day   = get_string('day');
        $str->days  = get_string('days');
        $str->hour  = get_string('hour');
        $str->hours = get_string('hours');
        $str->min   = get_string('min');
        $str->mins  = get_string('mins');
        $str->sec   = get_string('sec');
        $str->secs  = get_string('secs');
        $str->year  = get_string('year');
        $str->years = get_string('years');
    }


    $years     = floor($totalsecs/YEARSECS);
    $remainder = $totalsecs - ($years*YEARSECS);
    $days      = floor($remainder/DAYSECS);
    $remainder = $totalsecs - ($days*DAYSECS);
    $hours     = floor($remainder/HOURSECS);
    $remainder = $remainder - ($hours*HOURSECS);
    $mins      = floor($remainder/MINSECS);
    $secs      = $remainder - ($mins*MINSECS);

    $ss = ($secs == 1)  ? $str->sec  : $str->secs;
    $sm = ($mins == 1)  ? $str->min  : $str->mins;
    $sh = ($hours == 1) ? $str->hour : $str->hours;
    $sd = ($days == 1)  ? $str->day  : $str->days;
    $sy = ($years == 1)  ? $str->year  : $str->years;

    $oyears = '';
    $odays = '';
    $ohours = '';
    $omins = '';
    $osecs = '';

    if ($years)  $oyears  = $years .' '. $sy;
    if ($days)  $odays  = $days .' '. $sd;
    if ($hours) $ohours = $hours .' '. $sh;
    if ($mins)  $omins  = $mins .' '. $sm;
    if ($secs)  $osecs  = $secs .' '. $ss;

    if ($years) return trim($oyears .' '. $odays);
    if ($days)  return trim($odays .' '. $ohours);
    if ($hours) return trim($ohours .' '. $omins);
    if ($mins)  return trim($omins .' '. $osecs);
    if ($secs)  return $osecs;
    return get_string('now');
}

/**
 * Returns a formatted string that represents a date in user time
 *
 * Returns a formatted string that represents a date in user time
 * <b>WARNING: note that the format is for strftime(), not date().</b>
 * Because of a bug in most Windows time libraries, we can't use
 * the nicer %e, so we have to use %d which has leading zeroes.
 * A lot of the fuss in the function is just getting rid of these leading
 * zeroes as efficiently as possible.
 *
 * If parameter fixday = true (default), then take off leading
 * zero from %d, else mantain it.
 *
 * @param int $date the timestamp in UTC, as obtained from the database.
 * @param string $format strftime format. You should probably get this using
 *      get_string('strftime...', 'langconfig');
 * @param float $timezone by default, uses the user's time zone.
 * @param bool $fixday If true (default) then the leading zero from %d is removed.
 *      If false then the leading zero is mantained.
 * @return string the formatted date/time.
 */
function userdate($date, $format = '', $timezone = 99, $fixday = true) {

    global $CFG;

    $strtimezone = NULL;
    if (!is_numeric($timezone)) {
        $strtimezone = $timezone;
    }

    if (empty($format)) {
        $format = get_string('strftimedaydatetime', 'langconfig');
    }

    if (!empty($CFG->nofixday)) {  // Config.php can force %d not to be fixed.
        $fixday = false;
    } else if ($fixday) {
        $formatnoday = str_replace('%d', 'DD', $format);
        $fixday = ($formatnoday != $format);
    }

    $date += dst_offset_on($date, $strtimezone);

    $timezone = get_user_timezone_offset($timezone);

    if (abs($timezone) > 13) {   /// Server time
        if ($fixday) {
            $datestring = strftime($formatnoday, $date);
            $daystring  = str_replace(array(' 0', ' '), '', strftime(' %d', $date));
            $datestring = str_replace('DD', $daystring, $datestring);
        } else {
            $datestring = strftime($format, $date);
        }
    } else {
        $date += (int)($timezone * 3600);
        if ($fixday) {
            $datestring = gmstrftime($formatnoday, $date);
            $daystring  = str_replace(array(' 0', ' '), '', gmstrftime(' %d', $date));
            $datestring = str_replace('DD', $daystring, $datestring);
        } else {
            $datestring = gmstrftime($format, $date);
        }
    }

/// If we are running under Windows convert from windows encoding to UTF-8
/// (because it's impossible to specify UTF-8 to fetch locale info in Win32)

   if ($CFG->ostype == 'WINDOWS') {
       if ($localewincharset = get_string('localewincharset', 'langconfig')) {
           $textlib = textlib_get_instance();
           $datestring = $textlib->convert($datestring, $localewincharset, 'utf-8');
       }
   }

    return $datestring;
}

/**
 * Given a $time timestamp in GMT (seconds since epoch),
 * returns an array that represents the date in user time
 *
 * @todo Finish documenting this function
 * @uses HOURSECS
 * @param int $time Timestamp in GMT
 * @param float $timezone ?
 * @return array An array that represents the date in user time
 */
function usergetdate($time, $timezone=99) {

    $strtimezone = NULL;
    if (!is_numeric($timezone)) {
        $strtimezone = $timezone;
    }

    $timezone = get_user_timezone_offset($timezone);

    if (abs($timezone) > 13) {    // Server time
        return getdate($time);
    }

    // There is no gmgetdate so we use gmdate instead
    $time += dst_offset_on($time, $strtimezone);
    $time += intval((float)$timezone * HOURSECS);

    $datestring = gmstrftime('%B_%A_%j_%Y_%m_%w_%d_%H_%M_%S', $time);

    //be careful to ensure the returned array matches that produced by getdate() above
    list(
        $getdate['month'],
        $getdate['weekday'],
        $getdate['yday'],
        $getdate['year'],
        $getdate['mon'],
        $getdate['wday'],
        $getdate['mday'],
        $getdate['hours'],
        $getdate['minutes'],
        $getdate['seconds']
    ) = explode('_', $datestring);

    return $getdate;
}

/**
 * Given a GMT timestamp (seconds since epoch), offsets it by
 * the timezone.  eg 3pm in India is 3pm GMT - 7 * 3600 seconds
 *
 * @uses HOURSECS
 * @param  int $date Timestamp in GMT
 * @param float $timezone
 * @return int
 */
function usertime($date, $timezone=99) {

    $timezone = get_user_timezone_offset($timezone);

    if (abs($timezone) > 13) {
        return $date;
    }
    return $date - (int)($timezone * HOURSECS);
}

/**
 * Given a time, return the GMT timestamp of the most recent midnight
 * for the current user.
 *
 * @param int $date Timestamp in GMT
 * @param float $timezone Defaults to user's timezone
 * @return int Returns a GMT timestamp
 */
function usergetmidnight($date, $timezone=99) {

    $userdate = usergetdate($date, $timezone);

    // Time of midnight of this user's day, in GMT
    return make_timestamp($userdate['year'], $userdate['mon'], $userdate['mday'], 0, 0, 0, $timezone);

}

/**
 * Returns a string that prints the user's timezone
 *
 * @param float $timezone The user's timezone
 * @return string
 */
function usertimezone($timezone=99) {

    $tz = get_user_timezone($timezone);

    if (!is_float($tz)) {
        return $tz;
    }

    if(abs($tz) > 13) { // Server time
        return get_string('serverlocaltime');
    }

    if($tz == intval($tz)) {
        // Don't show .0 for whole hours
        $tz = intval($tz);
    }

    if($tz == 0) {
        return 'UTC';
    }
    else if($tz > 0) {
        return 'UTC+'.$tz;
    }
    else {
        return 'UTC'.$tz;
    }

}

/**
 * Returns a float which represents the user's timezone difference from GMT in hours
 * Checks various settings and picks the most dominant of those which have a value
 *
 * @global object
 * @global object
 * @param float $tz If this value is provided and not equal to 99, it will be returned as is and no other settings will be checked
 * @return float
 */
function get_user_timezone_offset($tz = 99) {

    global $USER, $CFG;

    $tz = get_user_timezone($tz);

    if (is_float($tz)) {
        return $tz;
    } else {
        $tzrecord = get_timezone_record($tz);
        if (empty($tzrecord)) {
            return 99.0;
        }
        return (float)$tzrecord->gmtoff / HOURMINS;
    }
}

/**
 * Returns an int which represents the systems's timezone difference from GMT in seconds
 *
 * @global object
 * @param mixed $tz timezone
 * @return int if found, false is timezone 99 or error
 */
function get_timezone_offset($tz) {
    global $CFG;

    if ($tz == 99) {
        return false;
    }

    if (is_numeric($tz)) {
        return intval($tz * 60*60);
    }

    if (!$tzrecord = get_timezone_record($tz)) {
        return false;
    }
    return intval($tzrecord->gmtoff * 60);
}

/**
 * Returns a float or a string which denotes the user's timezone
 * A float value means that a simple offset from GMT is used, while a string (it will be the name of a timezone in the database)
 * means that for this timezone there are also DST rules to be taken into account
 * Checks various settings and picks the most dominant of those which have a value
 *
 * @global object
 * @global object
 * @param float $tz If this value is provided and not equal to 99, it will be returned as is and no other settings will be checked
 * @return mixed
 */
function get_user_timezone($tz = 99) {
    global $USER, $CFG;

    $timezones = array(
        $tz,
        isset($CFG->forcetimezone) ? $CFG->forcetimezone : 99,
        isset($USER->timezone) ? $USER->timezone : 99,
        isset($CFG->timezone) ? $CFG->timezone : 99,
        );

    $tz = 99;

    while(($tz == '' || $tz == 99 || $tz == NULL) && $next = each($timezones)) {
        $tz = $next['value'];
    }

    return is_numeric($tz) ? (float) $tz : $tz;
}

/**
 * Returns cached timezone record for given $timezonename
 *
 * @global object
 * @global object
 * @param string $timezonename
 * @return mixed timezonerecord object or false
 */
function get_timezone_record($timezonename) {
    global $CFG, $DB;
    static $cache = NULL;

    if ($cache === NULL) {
        $cache = array();
    }

    if (isset($cache[$timezonename])) {
        return $cache[$timezonename];
    }

    return $cache[$timezonename] = $DB->get_record_sql('SELECT * FROM {timezone}
                                                        WHERE name = ? ORDER BY year DESC', array($timezonename), true);
}

/**
 * Build and store the users Daylight Saving Time (DST) table
 *
 * @global object
 * @global object
 * @global object
 * @param mixed $from_year Start year for the table, defaults to 1971
 * @param mixed $to_year End year for the table, defaults to 2035
 * @param mixed $strtimezone
 * @return bool
 */
function calculate_user_dst_table($from_year = NULL, $to_year = NULL, $strtimezone = NULL) {
    global $CFG, $SESSION, $DB;

    $usertz = get_user_timezone($strtimezone);

    if (is_float($usertz)) {
        // Trivial timezone, no DST
        return false;
    }

    if (!empty($SESSION->dst_offsettz) && $SESSION->dst_offsettz != $usertz) {
        // We have precalculated values, but the user's effective TZ has changed in the meantime, so reset
        unset($SESSION->dst_offsets);
        unset($SESSION->dst_range);
    }

    if (!empty($SESSION->dst_offsets) && empty($from_year) && empty($to_year)) {
        // Repeat calls which do not request specific year ranges stop here, we have already calculated the table
        // This will be the return path most of the time, pretty light computationally
        return true;
    }

    // Reaching here means we either need to extend our table or create it from scratch

    // Remember which TZ we calculated these changes for
    $SESSION->dst_offsettz = $usertz;

    if(empty($SESSION->dst_offsets)) {
        // If we 're creating from scratch, put the two guard elements in there
        $SESSION->dst_offsets = array(1 => NULL, 0 => NULL);
    }
    if(empty($SESSION->dst_range)) {
        // If creating from scratch
        $from = max((empty($from_year) ? intval(date('Y')) - 3 : $from_year), 1971);
        $to   = min((empty($to_year)   ? intval(date('Y')) + 3 : $to_year),   2035);

        // Fill in the array with the extra years we need to process
        $yearstoprocess = array();
        for($i = $from; $i <= $to; ++$i) {
            $yearstoprocess[] = $i;
        }

        // Take note of which years we have processed for future calls
        $SESSION->dst_range = array($from, $to);
    }
    else {
        // If needing to extend the table, do the same
        $yearstoprocess = array();

        $from = max((empty($from_year) ? $SESSION->dst_range[0] : $from_year), 1971);
        $to   = min((empty($to_year)   ? $SESSION->dst_range[1] : $to_year),   2035);

        if($from < $SESSION->dst_range[0]) {
            // Take note of which years we need to process and then note that we have processed them for future calls
            for($i = $from; $i < $SESSION->dst_range[0]; ++$i) {
                $yearstoprocess[] = $i;
            }
            $SESSION->dst_range[0] = $from;
        }
        if($to > $SESSION->dst_range[1]) {
            // Take note of which years we need to process and then note that we have processed them for future calls
            for($i = $SESSION->dst_range[1] + 1; $i <= $to; ++$i) {
                $yearstoprocess[] = $i;
            }
            $SESSION->dst_range[1] = $to;
        }
    }

    if(empty($yearstoprocess)) {
        // This means that there was a call requesting a SMALLER range than we have already calculated
        return true;
    }

    // From now on, we know that the array has at least the two guard elements, and $yearstoprocess has the years we need
    // Also, the array is sorted in descending timestamp order!

    // Get DB data

    static $presets_cache = array();
    if (!isset($presets_cache[$usertz])) {
        $presets_cache[$usertz] = $DB->get_records('timezone', array('name'=>$usertz), 'year DESC', 'year, gmtoff, dstoff, dst_month, dst_startday, dst_weekday, dst_skipweeks, dst_time, std_month, std_startday, std_weekday, std_skipweeks, std_time');
    }
    if(empty($presets_cache[$usertz])) {
        return false;
    }

    // Remove ending guard (first element of the array)
    reset($SESSION->dst_offsets);
    unset($SESSION->dst_offsets[key($SESSION->dst_offsets)]);

    // Add all required change timestamps
    foreach($yearstoprocess as $y) {
        // Find the record which is in effect for the year $y
        foreach($presets_cache[$usertz] as $year => $preset) {
            if($year <= $y) {
                break;
            }
        }

        $changes = dst_changes_for_year($y, $preset);

        if($changes === NULL) {
            continue;
        }
        if($changes['dst'] != 0) {
            $SESSION->dst_offsets[$changes['dst']] = $preset->dstoff * MINSECS;
        }
        if($changes['std'] != 0) {
            $SESSION->dst_offsets[$changes['std']] = 0;
        }
    }

    // Put in a guard element at the top
    $maxtimestamp = max(array_keys($SESSION->dst_offsets));
    $SESSION->dst_offsets[($maxtimestamp + DAYSECS)] = NULL; // DAYSECS is arbitrary, any "small" number will do

    // Sort again
    krsort($SESSION->dst_offsets);

    return true;
}

/**
 * Calculates the required DST change and returns a Timestamp Array
 *
 * @uses HOURSECS
 * @uses MINSECS
 * @param mixed $year Int or String Year to focus on
 * @param object $timezone Instatiated Timezone object
 * @return mixed Null, or Array dst=>xx, 0=>xx, std=>yy, 1=>yy
 */
function dst_changes_for_year($year, $timezone) {

    if($timezone->dst_startday == 0 && $timezone->dst_weekday == 0 && $timezone->std_startday == 0 && $timezone->std_weekday == 0) {
        return NULL;
    }

    $monthdaydst = find_day_in_month($timezone->dst_startday, $timezone->dst_weekday, $timezone->dst_month, $year);
    $monthdaystd = find_day_in_month($timezone->std_startday, $timezone->std_weekday, $timezone->std_month, $year);

    list($dst_hour, $dst_min) = explode(':', $timezone->dst_time);
    list($std_hour, $std_min) = explode(':', $timezone->std_time);

    $timedst = make_timestamp($year, $timezone->dst_month, $monthdaydst, 0, 0, 0, 99, false);
    $timestd = make_timestamp($year, $timezone->std_month, $monthdaystd, 0, 0, 0, 99, false);

    // Instead of putting hour and minute in make_timestamp(), we add them afterwards.
    // This has the advantage of being able to have negative values for hour, i.e. for timezones
    // where GMT time would be in the PREVIOUS day than the local one on which DST changes.

    $timedst += $dst_hour * HOURSECS + $dst_min * MINSECS;
    $timestd += $std_hour * HOURSECS + $std_min * MINSECS;

    return array('dst' => $timedst, 0 => $timedst, 'std' => $timestd, 1 => $timestd);
}

/**
 * Calculates the Daylight Saving Offest for a given date/time (timestamp)
 *
 * @global object
 * @param int $time must NOT be compensated at all, it has to be a pure timestamp
 * @return int
 */
function dst_offset_on($time, $strtimezone = NULL) {
    global $SESSION;

    if(!calculate_user_dst_table(NULL, NULL, $strtimezone) || empty($SESSION->dst_offsets)) {
        return 0;
    }

    reset($SESSION->dst_offsets);
    while(list($from, $offset) = each($SESSION->dst_offsets)) {
        if($from <= $time) {
            break;
        }
    }

    // This is the normal return path
    if($offset !== NULL) {
        return $offset;
    }

    // Reaching this point means we haven't calculated far enough, do it now:
    // Calculate extra DST changes if needed and recurse. The recursion always
    // moves toward the stopping condition, so will always end.

    if($from == 0) {
        // We need a year smaller than $SESSION->dst_range[0]
        if($SESSION->dst_range[0] == 1971) {
            return 0;
        }
        calculate_user_dst_table($SESSION->dst_range[0] - 5, NULL, $strtimezone);
        return dst_offset_on($time, $strtimezone);
    }
    else {
        // We need a year larger than $SESSION->dst_range[1]
        if($SESSION->dst_range[1] == 2035) {
            return 0;
        }
        calculate_user_dst_table(NULL, $SESSION->dst_range[1] + 5, $strtimezone);
        return dst_offset_on($time, $strtimezone);
    }
}

/**
 * ?
 *
 * @todo Document what this function does
 * @param int $startday
 * @param int $weekday
 * @param int $month
 * @param int $year
 * @return int
 */
function find_day_in_month($startday, $weekday, $month, $year) {

    $daysinmonth = days_in_month($month, $year);

    if($weekday == -1) {
        // Don't care about weekday, so return:
        //    abs($startday) if $startday != -1
        //    $daysinmonth otherwise
        return ($startday == -1) ? $daysinmonth : abs($startday);
    }

    // From now on we 're looking for a specific weekday

    // Give "end of month" its actual value, since we know it
    if($startday == -1) {
        $startday = -1 * $daysinmonth;
    }

    // Starting from day $startday, the sign is the direction

    if($startday < 1) {

        $startday = abs($startday);
        $lastmonthweekday  = strftime('%w', mktime(12, 0, 0, $month, $daysinmonth, $year, 0));

        // This is the last such weekday of the month
        $lastinmonth = $daysinmonth + $weekday - $lastmonthweekday;
        if($lastinmonth > $daysinmonth) {
            $lastinmonth -= 7;
        }

        // Find the first such weekday <= $startday
        while($lastinmonth > $startday) {
            $lastinmonth -= 7;
        }

        return $lastinmonth;

    }
    else {

        $indexweekday = strftime('%w', mktime(12, 0, 0, $month, $startday, $year, 0));

        $diff = $weekday - $indexweekday;
        if($diff < 0) {
            $diff += 7;
        }

        // This is the first such weekday of the month equal to or after $startday
        $firstfromindex = $startday + $diff;

        return $firstfromindex;

    }
}

/**
 * Calculate the number of days in a given month
 *
 * @param int $month The month whose day count is sought
 * @param int $year The year of the month whose day count is sought
 * @return int
 */
function days_in_month($month, $year) {
   return intval(date('t', mktime(12, 0, 0, $month, 1, $year, 0)));
}

/**
 * Calculate the position in the week of a specific calendar day
 *
 * @param int $day The day of the date whose position in the week is sought
 * @param int $month The month of the date whose position in the week is sought
 * @param int $year The year of the date whose position in the week is sought
 * @return int
 */
function dayofweek($day, $month, $year) {
    // I wonder if this is any different from
    // strftime('%w', mktime(12, 0, 0, $month, $daysinmonth, $year, 0));
    return intval(date('w', mktime(12, 0, 0, $month, $day, $year, 0)));
}

/// USER AUTHENTICATION AND LOGIN ////////////////////////////////////////

/**
 * Returns full login url.
 *
 * @global object
 * @param bool $loginguest add login guest param, return false
 * @return string login url
 */
function get_login_url($loginguest=false) {
    global $CFG;

    if (empty($CFG->loginhttps) or $loginguest) { //do not require https for guest logins
        $loginguest = $loginguest ? '?loginguest=true' : '';
        $url = "$CFG->wwwroot/login/index.php$loginguest";

    } else {
        $wwwroot = str_replace('http:','https:', $CFG->wwwroot);
        $url = "$wwwroot/login/index.php";
    }

    return $url;
}

/**
 * This function checks that the current user is logged in and has the
 * required privileges
 *
 * This function checks that the current user is logged in, and optionally
 * whether they are allowed to be in a particular course and view a particular
 * course module.
 * If they are not logged in, then it redirects them to the site login unless
 * $autologinguest is set and {@link $CFG}->autologinguests is set to 1 in which
 * case they are automatically logged in as guests.
 * If $courseid is given and the user is not enrolled in that course then the
 * user is redirected to the course enrolment page.
 * If $cm is given and the coursemodule is hidden and the user is not a teacher
 * in the course then the user is redirected to the course home page.
 *
 * When $cm parameter specified, this function sets page layout to 'module'.
 * You need to change it manually later if some other layout needed.
 *
 * @global object
 * @global object
 * @global object
 * @global object
 * @global string
 * @global object
 * @global object
 * @global object
 * @uses SITEID Define
 * @param mixed $courseorid id of the course or course object
 * @param bool $autologinguest default true
 * @param object $cm course module object
 * @param bool $setwantsurltome Define if we want to set $SESSION->wantsurl, defaults to
 *             true. Used to avoid (=false) some scripts (file.php...) to set that variable,
 *             in order to keep redirects working properly. MDL-14495
 * @return mixed Void, exit, and die depending on path
 */
function require_login($courseorid=0, $autologinguest=true, $cm=null, $setwantsurltome=true) {
    global $CFG, $SESSION, $USER, $COURSE, $FULLME, $PAGE, $SITE, $DB, $OUTPUT;

/// setup global $COURSE, themes, language and locale
    if (!empty($courseorid)) {
        if (is_object($courseorid)) {
            $course = $courseorid;
        } else if ($courseorid == SITEID) {
            $course = clone($SITE);
        } else {
            $course = $DB->get_record('course', array('id' => $courseorid));
            if (!$course) {
                throw new moodle_exception('invalidcourseid');
            }
        }
        if ($cm) {
            $PAGE->set_cm($cm, $course); // set's up global $COURSE
            $PAGE->set_pagelayout('incourse');
        } else {
            $PAGE->set_course($course); // set's up global $COURSE
        }
    } else {
        // do not touch global $COURSE via $PAGE->set_course() !!
    }

/// If the user is not even logged in yet then make sure they are
    if (!isloggedin()) {
        //NOTE: $USER->site check was obsoleted by session test cookie,
        //      $USER->confirmed test is in login/index.php
        if ($setwantsurltome) {
            $SESSION->wantsurl = $FULLME;
        }
        if (!empty($_SERVER['HTTP_REFERER'])) {
            $SESSION->fromurl  = $_SERVER['HTTP_REFERER'];
        }
        if ($autologinguest and !empty($CFG->guestloginbutton) and !empty($CFG->autologinguests) and ($COURSE->id == SITEID or $COURSE->guest) ) {
            $loginguest = true;
        } else {
            $loginguest = false;
        }
        redirect(get_login_url($loginguest));
        exit; // never reached
    }

/// loginas as redirection if needed
    if ($COURSE->id != SITEID and session_is_loggedinas()) {
        if ($USER->loginascontext->contextlevel == CONTEXT_COURSE) {
            if ($USER->loginascontext->instanceid != $COURSE->id) {
                print_error('loginasonecourse', '', $CFG->wwwroot.'/course/view.php?id='.$USER->loginascontext->instanceid);
            }
        }
    }

/// check whether the user should be changing password (but only if it is REALLY them)
    if (get_user_preferences('auth_forcepasswordchange') && !session_is_loggedinas()) {
        $userauth = get_auth_plugin($USER->auth);
        if ($userauth->can_change_password()) {
            $SESSION->wantsurl = $FULLME;
            if ($changeurl = $userauth->change_password_url()) {
                //use plugin custom url
                redirect($changeurl);
            } else {
                //use moodle internal method
                if (empty($CFG->loginhttps)) {
                    redirect($CFG->wwwroot .'/login/change_password.php');
                } else {
                    $wwwroot = str_replace('http:','https:', $CFG->wwwroot);
                    redirect($wwwroot .'/login/change_password.php');
                }
            }
        } else {
            print_error('nopasswordchangeforced', 'auth');
        }
    }

/// Check that the user account is properly set up
    if (user_not_fully_set_up($USER)) {
        $SESSION->wantsurl = $FULLME;
        redirect($CFG->wwwroot .'/user/edit.php?id='. $USER->id .'&amp;course='. SITEID);
    }

/// Make sure the USER has a sesskey set up.  Used for checking script parameters.
    sesskey();

    // Check that the user has agreed to a site policy if there is one
    if (!empty($CFG->sitepolicy)) {
        if (!$USER->policyagreed) {
            $SESSION->wantsurl = $FULLME;
            redirect($CFG->wwwroot .'/user/policy.php');
        }
    }

    // Fetch the system context, we are going to use it a lot.
    $sysctx = get_context_instance(CONTEXT_SYSTEM);

/// If the site is currently under maintenance, then print a message
    if (!empty($CFG->maintenance_enabled) and !has_capability('moodle/site:config', $sysctx)) {
        print_maintenance_message();
    }

/// groupmembersonly access control
    if (!empty($CFG->enablegroupmembersonly) and $cm and $cm->groupmembersonly and !has_capability('moodle/site:accessallgroups', get_context_instance(CONTEXT_MODULE, $cm->id))) {
        if (isguestuser() or !groups_has_membership($cm)) {
            print_error('groupmembersonlyerror', 'group', $CFG->wwwroot.'/course/view.php?id='.$cm->course);
        }
    }

    // Fetch the course context, and prefetch its child contexts
    $coursecontext = get_context_instance(CONTEXT_COURSE, $COURSE->id, MUST_EXIST);
    if ($cm) {
        $cmcontext = get_context_instance(CONTEXT_MODULE, $cm->id, MUST_EXIST);
    }

    // Conditional activity access control
    if (!empty($CFG->enableavailability) and $cm) {
        // We cache conditional access in session
        if (!isset($SESSION->conditionaccessok)) {
            $SESSION->conditionaccessok = array();
        }
        // If you have been allowed into the module once then you are allowed
        // in for rest of session, no need to do conditional checks
        if (!array_key_exists($cm->id, $SESSION->conditionaccessok)) {
            // Get condition info (does a query for the availability table)
            require_once($CFG->libdir.'/conditionlib.php');
            $ci = new condition_info($cm, CONDITION_MISSING_EXTRATABLE);
            // Check condition for user (this will do a query if the availability
            // information depends on grade or completion information)
            if ($ci->is_available($junk) || has_capability('moodle/course:viewhiddenactivities', $cmcontext)) {
                $SESSION->conditionaccessok[$cm->id] = true;
            } else {
                print_error('activityiscurrentlyhidden');
            }
        }
    }

    if ($COURSE->id == SITEID) {
        /// Eliminate hidden site activities straight away
        if ($cm && !$cm->visible && !has_capability('moodle/course:viewhiddenactivities', $cmcontext)) {
            redirect($CFG->wwwroot, get_string('activityiscurrentlyhidden'));
        }
        user_accesstime_log($COURSE->id); /// Access granted, update lastaccess times
        return;

    } else {

        /// Check if the user can be in a particular course
        if (empty($USER->access['rsw'][$coursecontext->path])) {
            //
            // MDL-13900 - If the course or the parent category are hidden
            // and the user hasn't the 'course:viewhiddencourses' capability, prevent access
            //
            if ( !($COURSE->visible && course_parent_visible($COURSE)) && !has_capability('moodle/course:viewhiddencourses', $coursecontext)) {
                echo $OUTPUT->header();
                notice(get_string('coursehidden'), $CFG->wwwroot .'/');
            }
        }

        if (is_enrolled($coursecontext) or is_viewing($coursecontext)) {
            // Enrolled user or allowed to visit course (managers, inspectors, etc.)
            if (session_is_loggedinas()) {   // Make sure the REAL person can also access this course
                $realuser = session_get_realuser();
                if (!is_enrolled($coursecontext, $realuser->id) and !is_viewing($coursecontext, $realuser->id) and !is_siteadmin($realuser->id)) {
                    echo $OUTPUT->header();
                    notice(get_string('studentnotallowed', '', fullname($USER, true)), $CFG->wwwroot .'/');
                }
            }

            // Make sure they can read this activity too, if specified
            if ($cm && !$cm->visible && !has_capability('moodle/course:viewhiddenactivities', $cmcontext)) {
                redirect($CFG->wwwroot.'/course/view.php?id='.$cm->course, get_string('activityiscurrentlyhidden'));
            }
            user_accesstime_log($COURSE->id); /// Access granted, update lastaccess times
            return;   // User is allowed to see this course

        } else {
            // guest access
            switch ($COURSE->guest) {    /// Check course policy about guest access

                case 1:    /// Guests always allowed
                    if ($cm and !$cm->visible) { // Not allowed to see module, send to course page
                        redirect($CFG->wwwroot.'/course/view.php?id='.$cm->course,
                                 get_string('activityiscurrentlyhidden'));
                    }

                    if ($USER->username != 'guest' and !empty($CFG->guestroleid)) {
                        // Non-guests who don't currently have access, check if they can be allowed in as a guest
                        // Temporarily assign them guest role for this context, if it fails later user is asked to enrol
                        $USER->access = load_temp_role($coursecontext, $CFG->guestroleid, $USER->access);
                    }

                    user_accesstime_log($COURSE->id); /// Access granted, update lastaccess times
                    return;   // User is allowed to see this course

                case 2:    /// Guests allowed with key
                    if (!empty($USER->enrolkey[$COURSE->id])) {   // Set by enrol/manual/enrol.php
                        user_accesstime_log($COURSE->id); /// Access granted, update lastaccess times
                        return true;
                    }
                    //  otherwise drop through to logic below (--> enrol.php)
                    break;

                default:    /// Guests not allowed
                    $strloggedinasguest = get_string('loggedinasguest');
                    $PAGE->navbar->add($strloggedinasguest);
                    echo $OUTPUT->header();
                    if (empty($USER->access['rsw'][$coursecontext->path])) {  // Normal guest
                        notice(get_string('guestsnotallowed', '', format_string($COURSE->fullname)), get_login_url());
                    } else {
                        echo $OUTPUT->notification(get_string('guestsnotallowed', '', format_string($COURSE->fullname)));
                        echo '<div class="notifyproblem">'.switchroles_form($COURSE->id).'</div>';
                        echo $OUTPUT->footer();
                        exit;
                    }
                    break;
            }
        }

        // Currently not enrolled in the course, so see if they want to enrol
        $SESSION->wantsurl = $FULLME;
        redirect($CFG->wwwroot .'/course/enrol.php?id='. $COURSE->id);
        die;
    }
}


/**
 * This function just makes sure a user is logged out.
 *
 * @global object
 */
function require_logout() {
    global $USER;

    if (isloggedin()) {
        add_to_log(SITEID, "user", "logout", "view.php?id=$USER->id&course=".SITEID, $USER->id, 0, $USER->id);

        $authsequence = get_enabled_auth_plugins(); // auths, in sequence
        foreach($authsequence as $authname) {
            $authplugin = get_auth_plugin($authname);
            $authplugin->prelogout_hook();
        }
    }

    session_get_instance()->terminate_current();
}

/**
 * Weaker version of require_login()
 *
 * This is a weaker version of {@link require_login()} which only requires login
 * when called from within a course rather than the site page, unless
 * the forcelogin option is turned on.
 * @see require_login()
 *
 * @global object
 * @param mixed $courseorid The course object or id in question
 * @param bool $autologinguest Allow autologin guests if that is wanted
 * @param object $cm Course activity module if known
 * @param bool $setwantsurltome Define if we want to set $SESSION->wantsurl, defaults to
 *             true. Used to avoid (=false) some scripts (file.php...) to set that variable,
 *             in order to keep redirects working properly. MDL-14495
 */
function require_course_login($courseorid, $autologinguest=true, $cm=null, $setwantsurltome=true) {
    global $CFG, $PAGE, $SITE;
    if (!empty($CFG->forcelogin)) {
        // login required for both SITE and courses
        require_login($courseorid, $autologinguest, $cm, $setwantsurltome);

    } else if (!empty($cm) and !$cm->visible) {
        // always login for hidden activities
        require_login($courseorid, $autologinguest, $cm, $setwantsurltome);

    } else if ((is_object($courseorid) and $courseorid->id == SITEID)
          or (!is_object($courseorid) and $courseorid == SITEID)) {
              //login for SITE not required
        if ($cm and empty($cm->visible)) {
            // hidden activities are not accessible without login
            require_login($courseorid, $autologinguest, $cm, $setwantsurltome);
        } else if ($cm and !empty($CFG->enablegroupmembersonly) and $cm->groupmembersonly) {
            // not-logged-in users do not have any group membership
            require_login($courseorid, $autologinguest, $cm, $setwantsurltome);
        } else {
            // We still need to instatiate PAGE vars properly so that things
            // that rely on it like navigation function correctly.
            if (!empty($courseorid)) {
                if (is_object($courseorid)) {
                    $course = $courseorid;
                } else {
                    $course = clone($SITE);
                }
                if ($cm) {
                    $PAGE->set_cm($cm, $course);
                    $PAGE->set_pagelayout('incourse');
                } else {
                    $PAGE->set_course($course);
                }
            } else {
                // If $PAGE->course, and hence $PAGE->context, have not already been set
                // up properly, set them up now.
                $PAGE->set_course($PAGE->course);
            }
            //TODO: verify conditional activities here
            user_accesstime_log(SITEID);
            return;
        }

    } else {
        // course login always required
        require_login($courseorid, $autologinguest, $cm, $setwantsurltome);
    }
}

/**
 * Require key login. Function terminates with error if key not found or incorrect.
 *
 * @global object
 * @global object
 * @global object
 * @global object
 * @uses NO_MOODLE_COOKIES
 * @uses PARAM_ALPHANUM
 * @param string $script unique script identifier
 * @param int $instance optional instance id
 * @return int Instance ID
 */
function require_user_key_login($script, $instance=null) {
    global $USER, $SESSION, $CFG, $DB;

    if (!NO_MOODLE_COOKIES) {
        print_error('sessioncookiesdisable');
    }

/// extra safety
    @session_write_close();

    $keyvalue = required_param('key', PARAM_ALPHANUM);

    if (!$key = $DB->get_record('user_private_key', array('script'=>$script, 'value'=>$keyvalue, 'instance'=>$instance))) {
        print_error('invalidkey');
    }

    if (!empty($key->validuntil) and $key->validuntil < time()) {
        print_error('expiredkey');
    }

    if ($key->iprestriction) {
        $remoteaddr = getremoteaddr();
        if ($remoteaddr == '' or !address_in_subnet($remoteaddr, $key->iprestriction)) {
            print_error('ipmismatch');
        }
    }

    if (!$user = $DB->get_record('user', array('id'=>$key->userid))) {
        print_error('invaliduserid');
    }

/// emulate normal session
    session_set_user($user);

/// note we are not using normal login
    if (!defined('USER_KEY_LOGIN')) {
        define('USER_KEY_LOGIN', true);
    }

/// return isntance id - it might be empty
    return $key->instance;
}

/**
 * Creates a new private user access key.
 *
 * @global object
 * @param string $script unique target identifier
 * @param int $userid
 * @param int $instance optional instance id
 * @param string $iprestriction optional ip restricted access
 * @param timestamp $validuntil key valid only until given data
 * @return string access key value
 */
function create_user_key($script, $userid, $instance=null, $iprestriction=null, $validuntil=null) {
    global $DB;

    $key = new object();
    $key->script        = $script;
    $key->userid        = $userid;
    $key->instance      = $instance;
    $key->iprestriction = $iprestriction;
    $key->validuntil    = $validuntil;
    $key->timecreated   = time();

    $key->value         = md5($userid.'_'.time().random_string(40)); // something long and unique
    while ($DB->record_exists('user_private_key', array('value'=>$key->value))) {
        // must be unique
        $key->value     = md5($userid.'_'.time().random_string(40));
    }
    $DB->insert_record('user_private_key', $key);
    return $key->value;
}

/**
 * Modify the user table by setting the currently logged in user's
 * last login to now.
 *
 * @global object
 * @global object
 * @return bool Always returns true
 */
function update_user_login_times() {
    global $USER, $DB;

    $user = new object();
    $USER->lastlogin = $user->lastlogin = $USER->currentlogin;
    $USER->currentlogin = $user->lastaccess = $user->currentlogin = time();

    $user->id = $USER->id;

    $DB->update_record('user', $user);
    return true;
}

/**
 * Determines if a user has completed setting up their account.
 *
 * @param user $user A {@link $USER} object to test for the existance of a valid name and email
 * @return bool
 */
function user_not_fully_set_up($user) {
    return ($user->username != 'guest' and (empty($user->firstname) or empty($user->lastname) or empty($user->email) or over_bounce_threshold($user)));
}

/**
 * Check whether the user has exceeded the bounce threshold
 *
 * @global object
 * @global object
 * @param user $user A {@link $USER} object
 * @return bool true=>User has exceeded bounce threshold
 */
function over_bounce_threshold($user) {
    global $CFG, $DB;

    if (empty($CFG->handlebounces)) {
        return false;
    }

    if (empty($user->id)) { /// No real (DB) user, nothing to do here.
        return false;
    }

    // set sensible defaults
    if (empty($CFG->minbounces)) {
        $CFG->minbounces = 10;
    }
    if (empty($CFG->bounceratio)) {
        $CFG->bounceratio = .20;
    }
    $bouncecount = 0;
    $sendcount = 0;
    if ($bounce = $DB->get_record('user_preferences', array ('userid'=>$user->id, 'name'=>'email_bounce_count'))) {
        $bouncecount = $bounce->value;
    }
    if ($send = $DB->get_record('user_preferences', array('userid'=>$user->id, 'name'=>'email_send_count'))) {
        $sendcount = $send->value;
    }
    return ($bouncecount >= $CFG->minbounces && $bouncecount/$sendcount >= $CFG->bounceratio);
}

/**
 * Used to increment or reset email sent count
 *
 * @global object
 * @param user $user object containing an id
 * @param bool $reset will reset the count to 0
 * @return void
 */
function set_send_count($user,$reset=false) {
    global $DB;

    if (empty($user->id)) { /// No real (DB) user, nothing to do here.
        return;
    }

    if ($pref = $DB->get_record('user_preferences', array('userid'=>$user->id, 'name'=>'email_send_count'))) {
        $pref->value = (!empty($reset)) ? 0 : $pref->value+1;
        $DB->update_record('user_preferences', $pref);
    }
    else if (!empty($reset)) { // if it's not there and we're resetting, don't bother.
        // make a new one
        $pref = new object();
        $pref->name   = 'email_send_count';
        $pref->value  = 1;
        $pref->userid = $user->id;
        $DB->insert_record('user_preferences', $pref, false);
    }
}

/**
 * Increment or reset user's email bounce count
 *
 * @global object
 * @param user $user object containing an id
 * @param bool $reset will reset the count to 0
 */
function set_bounce_count($user,$reset=false) {
    global $DB;

    if ($pref = $DB->get_record('user_preferences', array('userid'=>$user->id, 'name'=>'email_bounce_count'))) {
        $pref->value = (!empty($reset)) ? 0 : $pref->value+1;
        $DB->update_record('user_preferences', $pref);
    }
    else if (!empty($reset)) { // if it's not there and we're resetting, don't bother.
        // make a new one
        $pref = new object();
        $pref->name   = 'email_bounce_count';
        $pref->value  = 1;
        $pref->userid = $user->id;
        $DB->insert_record('user_preferences', $pref, false);
    }
}

/**
 * Keeps track of login attempts
 *
 * @global object
 */
function update_login_count() {
    global $SESSION;

    $max_logins = 10;

    if (empty($SESSION->logincount)) {
        $SESSION->logincount = 1;
    } else {
        $SESSION->logincount++;
    }

    if ($SESSION->logincount > $max_logins) {
        unset($SESSION->wantsurl);
        print_error('errortoomanylogins');
    }
}

/**
 * Resets login attempts
 *
 * @global object
 */
function reset_login_count() {
    global $SESSION;

    $SESSION->logincount = 0;
}

/**
 * Sync all meta courses
 * Goes through all enrolment records for the courses inside all metacourses and syncs with them.
 * @see sync_metacourse()
 *
 * @global object
 */
function sync_metacourses() {
    global $DB;

    if (!$courses = $DB->get_records('course', array('metacourse'=>1))) {
        return;
    }

    foreach ($courses as $course) {
        sync_metacourse($course);
    }
}

/**
 * Returns reference to full info about modules in course (including visibility).
 * Cached and as fast as possible (0 or 1 db query).
 *
 * @global object
 * @global object
 * @global object
 * @uses CONTEXT_MODULE
 * @uses MAX_MODINFO_CACHE_SIZE
 * @param mixed $course object or 'reset' string to reset caches, modinfo may be updated in db
 * @param int $userid Defaults to current user id
 * @return mixed courseinfo object or nothing if resetting
 */
function &get_fast_modinfo(&$course, $userid=0) {
    global $CFG, $USER, $DB;
    require_once($CFG->dirroot.'/course/lib.php');

    if (!empty($CFG->enableavailability)) {
        require_once($CFG->libdir.'/conditionlib.php');
    }

    static $cache = array();

    if ($course === 'reset') {
        $cache = array();
        $nothing = null;
        return $nothing; // we must return some reference
    }

    if (empty($userid)) {
        $userid = $USER->id;
    }

    if (array_key_exists($course->id, $cache) and $cache[$course->id]->userid == $userid) {
        return $cache[$course->id];
    }

    if (empty($course->modinfo)) {
        // no modinfo yet - load it
        rebuild_course_cache($course->id);
        $course->modinfo = $DB->get_field('course', 'modinfo', array('id'=>$course->id));
    }

    $modinfo = new object();
    $modinfo->courseid  = $course->id;
    $modinfo->userid    = $userid;
    $modinfo->sections  = array();
    $modinfo->cms       = array();
    $modinfo->instances = array();
    $modinfo->groups    = null; // loaded only when really needed - the only one db query

    $info = unserialize($course->modinfo);
    if (!is_array($info)) {
        // hmm, something is wrong - lets try to fix it
        rebuild_course_cache($course->id);
        $course->modinfo = $DB->get_field('course', 'modinfo', array('id'=>$course->id));
        $info = unserialize($course->modinfo);
        if (!is_array($info)) {
            return $modinfo;
        }
    }

    if ($info) {
        // detect if upgrade required
        $first = reset($info);
        if (!isset($first->id)) {
            rebuild_course_cache($course->id);
            $course->modinfo = $DB->get_field('course', 'modinfo', array('id'=>$course->id));
            $info = unserialize($course->modinfo);
            if (!is_array($info)) {
                return $modinfo;
            }
        }
    }

    $modlurals = array();

    // If we haven't already preloaded contexts for the course, do it now
    preload_course_contexts($course->id);

    foreach ($info as $mod) {
        if (empty($mod->name)) {
            // something is wrong here
            continue;
        }
        // reconstruct minimalistic $cm
        $cm = new object();
        $cm->id               = $mod->cm;
        $cm->instance         = $mod->id;
        $cm->course           = $course->id;
        $cm->modname          = $mod->mod;
        $cm->name             = $mod->name;
        $cm->visible          = $mod->visible;
        $cm->sectionnum       = $mod->section;
        $cm->groupmode        = $mod->groupmode;
        $cm->groupingid       = $mod->groupingid;
        $cm->groupmembersonly = $mod->groupmembersonly;
        $cm->indent           = $mod->indent;
        $cm->completion       = $mod->completion;
        $cm->extra            = isset($mod->extra) ? $mod->extra : '';
        $cm->icon             = isset($mod->icon) ? $mod->icon : '';
        $cm->iconcomponent    = isset($mod->iconcomponent) ? $mod->iconcomponent : '';
        $cm->uservisible      = true;
        if(!empty($CFG->enableavailability)) {
            // We must have completion information from modinfo. If it's not
            // there, cache needs rebuilding
            if(!isset($mod->availablefrom)) {
                debugging('enableavailability option was changed; rebuilding '.
                    'cache for course '.$course->id);
                rebuild_course_cache($course->id,true);
                // Re-enter this routine to do it all properly
                return get_fast_modinfo($course,$userid);
            }
            $cm->availablefrom    = $mod->availablefrom;
            $cm->availableuntil   = $mod->availableuntil;
            $cm->showavailability = $mod->showavailability;
            $cm->conditionscompletion = $mod->conditionscompletion;
            $cm->conditionsgrade  = $mod->conditionsgrade;
        }

        // preload long names plurals and also check module is installed properly
        if (!isset($modlurals[$cm->modname])) {
            if (!file_exists("$CFG->dirroot/mod/$cm->modname/lib.php")) {
                continue;
            }
            $modlurals[$cm->modname] = get_string('modulenameplural', $cm->modname);
        }
        $cm->modplural = $modlurals[$cm->modname];
        $modcontext = get_context_instance(CONTEXT_MODULE,$cm->id);

        if(!empty($CFG->enableavailability)) {
            // Unfortunately the next call really wants to call
            // get_fast_modinfo, but that would be recursive, so we fake up a
            // modinfo for it already
            if(empty($minimalmodinfo)) {
                $minimalmodinfo=new stdClass();
                $minimalmodinfo->cms=array();
                foreach($info as $mod) {
                    if (empty($mod->name)) {
                        // something is wrong here
                        continue;
                    }
                    $minimalcm = new stdClass();
                    $minimalcm->id = $mod->cm;
                    $minimalcm->name = $mod->name;
                    $minimalmodinfo->cms[$minimalcm->id]=$minimalcm;
                }
            }

            // Get availability information
            $ci = new condition_info($cm);
            $cm->available=$ci->is_available($cm->availableinfo, true, $userid, $minimalmodinfo);
        } else {
            $cm->available=true;
        }
        if ((!$cm->visible or !$cm->available) and !has_capability('moodle/course:viewhiddenactivities', $modcontext, $userid)) {
            $cm->uservisible = false;

        } else if (!empty($CFG->enablegroupmembersonly) and !empty($cm->groupmembersonly)
                and !has_capability('moodle/site:accessallgroups', $modcontext, $userid)) {
            if (is_null($modinfo->groups)) {
                $modinfo->groups = groups_get_user_groups($course->id, $userid);
            }
            if (empty($modinfo->groups[$cm->groupingid])) {
                $cm->uservisible = false;
            }
        }

        if (!isset($modinfo->instances[$cm->modname])) {
            $modinfo->instances[$cm->modname] = array();
        }
        $modinfo->instances[$cm->modname][$cm->instance] =& $cm;
        $modinfo->cms[$cm->id] =& $cm;

        // reconstruct sections
        if (!isset($modinfo->sections[$cm->sectionnum])) {
            $modinfo->sections[$cm->sectionnum] = array();
        }
        $modinfo->sections[$cm->sectionnum][] = $cm->id;

        unset($cm);
    }

    unset($cache[$course->id]); // prevent potential reference problems when switching users
    $cache[$course->id] = $modinfo;

    // Ensure cache does not use too much RAM
    if (count($cache) > MAX_MODINFO_CACHE_SIZE) {
        reset($cache);
        $key = key($cache);
        unset($cache[$key]);
    }

    return $cache[$course->id];
}

/**
 * Goes through all enrolment records for the courses inside the metacourse and sync with them.
 *
 * @todo finish timeend and timestart maybe we could rely on cron
 *       job to do the cleaning from time to time
 *
 * @global object
 * @global object
 * @uses CONTEXT_COURSE
 * @param mixed $course the metacourse to synch. Either the course object itself, or the courseid.
 * @return bool Success
 */
function sync_metacourse($course) {
    global $CFG, $DB;

    // Check the course is valid.
    if (!is_object($course)) {
        if (!$course = $DB->get_record('course', array('id'=>$course))) {
            return false; // invalid course id
        }
    }

    // Check that we actually have a metacourse.
    if (empty($course->metacourse)) {
        return false;
    }

    // Get a list of roles that should not be synced.
    if (!empty($CFG->nonmetacoursesyncroleids)) {
        $roleexclusions = 'ra.roleid NOT IN (' . $CFG->nonmetacoursesyncroleids . ') AND';
    } else {
        $roleexclusions = '';
    }

    // Get the context of the metacourse.
    $context = get_context_instance(CONTEXT_COURSE, $course->id); // SITEID can not be a metacourse

    // We do not ever want to unassign the list of metacourse manager, so get a list of them.
    if ($users = get_users_by_capability($context, 'moodle/course:managemetacourse')) {
        $managers = array_keys($users);
    } else {
        $managers = array();
    }

    // Get assignments of a user to a role that exist in a child course, but
    // not in the meta coure. That is, get a list of the assignments that need to be made.
    if (!$assignments = $DB->get_records_sql("
            SELECT ra.id, ra.roleid, ra.userid
              FROM {role_assignments} ra, {context} con, {course_meta} cm
             WHERE ra.contextid = con.id AND
                   con.contextlevel = ".CONTEXT_COURSE." AND
                   con.instanceid = cm.child_course AND
                   cm.parent_course = ? AND
                   $roleexclusions
                   NOT EXISTS (
                     SELECT 1
                       FROM {role_assignments} ra2
                      WHERE ra2.userid = ra.userid AND
                            ra2.roleid = ra.roleid AND
                            ra2.contextid = ?
                  )", array($course->id, $context->id))) {
        $assignments = array();
    }

    // Get assignments of a user to a role that exist in the meta course, but
    // not in any child courses. That is, get a list of the unassignments that need to be made.
    if (!$unassignments = $DB->get_records_sql("
            SELECT ra.id, ra.roleid, ra.userid
              FROM {role_assignments} ra
             WHERE ra.contextid = ? AND
                   $roleexclusions
                   NOT EXISTS (
                    SELECT 1
                      FROM {role_assignments} ra2, {context} con2, {course_meta} cm
                    WHERE ra2.userid = ra.userid AND
                          ra2.roleid = ra.roleid AND
                          ra2.contextid = con2.id AND
                          con2.contextlevel = " . CONTEXT_COURSE . " AND
                          con2.instanceid = cm.child_course AND
                          cm.parent_course = ?
                  )", array($context->id, $course->id))) {
        $unassignments = array();
    }

    $success = true;

    // Make the unassignments, if they are not managers.
    foreach ($unassignments as $unassignment) {
        if (!in_array($unassignment->userid, $managers)) {
            $success = role_unassign($unassignment->roleid, $unassignment->userid, 0, $context->id) && $success;
        }
    }

    // Make the assignments.
    foreach ($assignments as $assignment) {
        $success = role_assign($assignment->roleid, $assignment->userid, 0, $context->id, 0, 0) && $success;
    }

    return $success;

// TODO: finish timeend and timestart
// maybe we could rely on cron job to do the cleaning from time to time
}

/**
 * Adds a record to the metacourse table and calls sync_metacoures
 *
 * @global object
 * @param int $metacourseid The Metacourse ID for the metacourse to add to
 * @param int $courseid The Course ID of the course to add
 * @return bool Success
 */
function add_to_metacourse ($metacourseid, $courseid) {
    global $DB;

    if (!$metacourse = $DB->get_record("course", array("id"=>$metacourseid))) {
        return false;
    }

    if (!$course = $DB->get_record("course", array("id"=>$courseid))) {
        return false;
    }

    if (!$record = $DB->get_record("course_meta", array("parent_course"=>$metacourseid, "child_course"=>$courseid))) {
        $rec = new object();
        $rec->parent_course = $metacourseid;
        $rec->child_course  = $courseid;
        $DB->insert_record('course_meta', $rec);
        return sync_metacourse($metacourseid);
    }
    return true;

}

/**
 * Removes the record from the metacourse table and calls sync_metacourse
 *
 * @global object
 * @param int $metacourseid The Metacourse ID for the metacourse to remove from
 * @param int $courseid The Course ID of the course to remove
 * @return bool Success
 */
function remove_from_metacourse($metacourseid, $courseid) {
    global $DB;

    if ($DB->delete_records('course_meta', array('parent_course'=>$metacourseid, 'child_course'=>$courseid))) {
        return sync_metacourse($metacourseid);
    }
    return false;
}

/**
 * Determines if the currently logged in user is in editing mode.
 * Note: originally this function had $userid parameter - it was not usable anyway
 *
 * @deprecated since Moodle 2.0 - use $PAGE->user_is_editing() instead.
 * @todo Deprecated function remove when ready
 *
 * @global object
 * @uses DEBUG_DEVELOPER
 * @return bool
 */
function isediting() {
    global $PAGE;
    debugging('call to deprecated function isediting(). Please use $PAGE->user_is_editing() instead', DEBUG_DEVELOPER);
    return $PAGE->user_is_editing();
}

/**
 * Determines if the logged in user is currently moving an activity
 *
 * @global object
 * @param int $courseid The id of the course being tested
 * @return bool
 */
function ismoving($courseid) {
    global $USER;

    if (!empty($USER->activitycopy)) {
        return ($USER->activitycopycourse == $courseid);
    }
    return false;
}

/**
 * Returns a persons full name
 *
 * Given an object containing firstname and lastname
 * values, this function returns a string with the
 * full name of the person.
 * The result may depend on system settings
 * or language.  'override' will force both names
 * to be used even if system settings specify one.
 *
 * @global object
 * @global object
 * @param object $user A {@link $USER} object to get full name of
 * @param bool $override If true then the name will be first name followed by last name rather than adhering to fullnamedisplay setting.
 * @return string
 */
function fullname($user, $override=false) {
    global $CFG, $SESSION;

    if (!isset($user->firstname) and !isset($user->lastname)) {
        return '';
    }

    if (!$override) {
        if (!empty($CFG->forcefirstname)) {
            $user->firstname = $CFG->forcefirstname;
        }
        if (!empty($CFG->forcelastname)) {
            $user->lastname = $CFG->forcelastname;
        }
    }

    if (!empty($SESSION->fullnamedisplay)) {
        $CFG->fullnamedisplay = $SESSION->fullnamedisplay;
    }

    if (!isset($CFG->fullnamedisplay) or $CFG->fullnamedisplay === 'firstname lastname') {
        return $user->firstname .' '. $user->lastname;

    } else if ($CFG->fullnamedisplay == 'lastname firstname') {
        return $user->lastname .' '. $user->firstname;

    } else if ($CFG->fullnamedisplay == 'firstname') {
        if ($override) {
            return get_string('fullnamedisplay', '', $user);
        } else {
            return $user->firstname;
        }
    }

    return get_string('fullnamedisplay', '', $user);
}

/**
 * Returns whether a given authentication plugin exists.
 *
 * @global object
 * @param string $auth Form of authentication to check for. Defaults to the
 *        global setting in {@link $CFG}.
 * @return boolean Whether the plugin is available.
 */
function exists_auth_plugin($auth) {
    global $CFG;

    if (file_exists("{$CFG->dirroot}/auth/$auth/auth.php")) {
        return is_readable("{$CFG->dirroot}/auth/$auth/auth.php");
    }
    return false;
}

/**
 * Checks if a given plugin is in the list of enabled authentication plugins.
 *
 * @param string $auth Authentication plugin.
 * @return boolean Whether the plugin is enabled.
 */
function is_enabled_auth($auth) {
    if (empty($auth)) {
        return false;
    }

    $enabled = get_enabled_auth_plugins();

    return in_array($auth, $enabled);
}

/**
 * Returns an authentication plugin instance.
 *
 * @global object
 * @param string $auth name of authentication plugin
 * @return auth_plugin_base An instance of the required authentication plugin.
 */
function get_auth_plugin($auth) {
    global $CFG;

    // check the plugin exists first
    if (! exists_auth_plugin($auth)) {
        print_error('authpluginnotfound', 'debug', '', $auth);
    }

    // return auth plugin instance
    require_once "{$CFG->dirroot}/auth/$auth/auth.php";
    $class = "auth_plugin_$auth";
    return new $class;
}

/**
 * Returns array of active auth plugins.
 *
 * @param bool $fix fix $CFG->auth if needed
 * @return array
 */
function get_enabled_auth_plugins($fix=false) {
    global $CFG;

    $default = array('manual', 'nologin');

    if (empty($CFG->auth)) {
        $auths = array();
    } else {
        $auths = explode(',', $CFG->auth);
    }

    if ($fix) {
        $auths = array_unique($auths);
        foreach($auths as $k=>$authname) {
            if (!exists_auth_plugin($authname) or in_array($authname, $default)) {
                unset($auths[$k]);
            }
        }
        $newconfig = implode(',', $auths);
        if (!isset($CFG->auth) or $newconfig != $CFG->auth) {
            set_config('auth', $newconfig);
        }
    }

    return (array_merge($default, $auths));
}

/**
 * Returns true if an internal authentication method is being used.
 * if method not specified then, global default is assumed
 *
 * @param string $auth Form of authentication required
 * @return bool
 */
function is_internal_auth($auth) {
    $authplugin = get_auth_plugin($auth); // throws error if bad $auth
    return $authplugin->is_internal();
}

/**
 * Returns true if the user is a 'restored' one
 *
 * Used in the login process to inform the user
 * and allow him/her to reset the password
 *
 * @uses $CFG
 * @uses $DB
 * @param string $username username to be checked
 * @return bool
 */
function is_restored_user($username) {
    global $CFG, $DB;

    return $DB->record_exists('user', array('username'=>$username, 'mnethostid'=>$CFG->mnet_localhost_id, 'password'=>'restored'));
}

/**
 * Returns an array of user fields
 *
 * @return array User field/column names
 */
function get_user_fieldnames() {
    global $DB;

    $fieldarray = $DB->get_columns('user');
    unset($fieldarray['id']);
    $fieldarray = array_keys($fieldarray);

    return $fieldarray;
}

/**
 * Creates a bare-bones user record
 *
 * @todo Outline auth types and provide code example
 *
 * @global object
 * @global object
 * @param string $username New user's username to add to record
 * @param string $password New user's password to add to record
 * @param string $auth Form of authentication required
 * @return object A {@link $USER} object
 */
function create_user_record($username, $password, $auth='manual') {
    global $CFG, $DB;

    //just in case check text case
    $username = trim(moodle_strtolower($username));

    $authplugin = get_auth_plugin($auth);

    $newuser = new object();

    if ($newinfo = $authplugin->get_userinfo($username)) {
        $newinfo = truncate_userinfo($newinfo);
        foreach ($newinfo as $key => $value){
            $newuser->$key = $value;
        }
    }

    if (!empty($newuser->email)) {
        if (email_is_not_allowed($newuser->email)) {
            unset($newuser->email);
        }
    }

    if (!isset($newuser->city)) {
        $newuser->city = '';
    }

    $newuser->auth = $auth;
    $newuser->username = $username;

    // fix for MDL-8480
    // user CFG lang for user if $newuser->lang is empty
    // or $user->lang is not an installed language
    if (empty($newuser->lang) || !get_string_manager()->translation_exists($newuser->lang)) {
        $newuser->lang = $CFG->lang;
    }
    $newuser->confirmed = 1;
    $newuser->lastip = getremoteaddr();
    $newuser->timemodified = time();
    $newuser->mnethostid = $CFG->mnet_localhost_id;

    $DB->insert_record('user', $newuser);
    $user = get_complete_user_data('username', $newuser->username);
    if(!empty($CFG->{'auth_'.$newuser->auth.'_forcechangepassword'})){
        set_user_preference('auth_forcepasswordchange', 1, $user->id);
    }
    update_internal_user_password($user, $password);
    return $user;
}

/**
 * Will update a local user record from an external source
 *
 * @global object
 * @param string $username New user's username to add to record
 * @param string $authplugin Unused
 * @return user A {@link $USER} object
 */
function update_user_record($username, $authplugin) {
    global $DB;

    $username = trim(moodle_strtolower($username)); /// just in case check text case

    $oldinfo = $DB->get_record('user', array('username'=>$username), 'username, auth');
    $userauth = get_auth_plugin($oldinfo->auth);

    if ($newinfo = $userauth->get_userinfo($username)) {
        $newinfo = truncate_userinfo($newinfo);
        foreach ($newinfo as $key => $value){
            if ($key === 'username') {
                // 'username' is not a mapped updateable/lockable field, so skip it.
                continue;
            }
            $confval = $userauth->config->{'field_updatelocal_' . $key};
            $lockval = $userauth->config->{'field_lock_' . $key};
            if (empty($confval) || empty($lockval)) {
                continue;
            }
            if ($confval === 'onlogin') {
                // MDL-4207 Don't overwrite modified user profile values with
                // empty LDAP values when 'unlocked if empty' is set. The purpose
                // of the setting 'unlocked if empty' is to allow the user to fill
                // in a value for the selected field _if LDAP is giving
                // nothing_ for this field. Thus it makes sense to let this value
                // stand in until LDAP is giving a value for this field.
                if (!(empty($value) && $lockval === 'unlockedifempty')) {
                    $DB->set_field('user', $key, $value, array('username'=>$username));
                }
            }
        }
    }

    return get_complete_user_data('username', $username);
}

/**
 * Will truncate userinfo as it comes from auth_get_userinfo (from external auth)
 * which may have large fields
 *
 * @todo Add vartype handling to ensure $info is an array
 *
 * @param array $info Array of user properties to truncate if needed
 * @return array The now truncated information that was passed in
 */
function truncate_userinfo($info) {
    // define the limits
    $limit = array(
                    'username'    => 100,
                    'idnumber'    => 255,
                    'firstname'   => 100,
                    'lastname'    => 100,
                    'email'       => 100,
                    'icq'         =>  15,
                    'phone1'      =>  20,
                    'phone2'      =>  20,
                    'institution' =>  40,
                    'department'  =>  30,
                    'address'     =>  70,
                    'city'        =>  20,
                    'country'     =>   2,
                    'url'         => 255,
                    );

    // apply where needed
    foreach (array_keys($info) as $key) {
        if (!empty($limit[$key])) {
            $info[$key] = trim(substr($info[$key],0, $limit[$key]));
        }
    }

    return $info;
}

/**
 * Marks user deleted in internal user database and notifies the auth plugin.
 * Also unenrols user from all roles and does other cleanup.
 *
 * @todo Decide if this transaction is really needed (look for internal TODO:)
 *
 * @global object
 * @global object
 * @param object $user Userobject before delete    (without system magic quotes)
 * @return boolean success
 */
function delete_user($user) {
    global $CFG, $DB;
    require_once($CFG->libdir.'/grouplib.php');
    require_once($CFG->libdir.'/gradelib.php');
    require_once($CFG->dirroot.'/message/lib.php');

    // delete all grades - backup is kept in grade_grades_history table
    if ($grades = grade_grade::fetch_all(array('userid'=>$user->id))) {
        foreach ($grades as $grade) {
            $grade->delete('userdelete');
        }
    }

    //move unread messages from this user to read
    message_move_userfrom_unread2read($user->id);

    // remove from all cohorts
    $DB->delete_records('cohort_members', array('userid'=>$user->id));

    // remove from all groups
    $DB->delete_records('groups_members', array('userid'=>$user->id));

    // unenrol from all roles in all contexts
    role_unassign(0, $user->id); // this might be slow but it is really needed - modules might do some extra cleanup!

    // now do a final accesslib cleanup - removes all role assingments in user context and context itself
    delete_context(CONTEXT_USER, $user->id);

    require_once($CFG->dirroot.'/tag/lib.php');
    tag_set('user', $user->id, array());

    // workaround for bulk deletes of users with the same email address
    $delname = "$user->email.".time();
    while ($DB->record_exists('user', array('username'=>$delname))) { // no need to use mnethostid here
        $delname++;
    }

    // mark internal user record as "deleted"
    $updateuser = new object();
    $updateuser->id           = $user->id;
    $updateuser->deleted      = 1;
    $updateuser->username     = $delname;            // Remember it just in case
    $updateuser->email        = md5($user->username);// Store hash of username, useful importing/restoring users
    $updateuser->idnumber     = '';                  // Clear this field to free it up
    $updateuser->timemodified = time();

    $DB->update_record('user', $updateuser);

    // notify auth plugin - do not block the delete even when plugin fails
    $authplugin = get_auth_plugin($user->auth);
    $authplugin->user_delete($user);

    events_trigger('user_deleted', $user);

    return true;
}

/**
 * Retrieve the guest user object
 *
 * @global object
 * @global object
 * @return user A {@link $USER} object
 */
function guest_user() {
    global $CFG, $DB;

    if ($newuser = $DB->get_record('user', array('username'=>'guest', 'mnethostid'=>$CFG->mnet_localhost_id))) {
        $newuser->confirmed = 1;
        $newuser->lang = $CFG->lang;
        $newuser->lastip = getremoteaddr();
    }

    return $newuser;
}

/**
 * Authenticates a user against the chosen authentication mechanism
 *
 * Given a username and password, this function looks them
 * up using the currently selected authentication mechanism,
 * and if the authentication is successful, it returns a
 * valid $user object from the 'user' table.
 *
 * Uses auth_ functions from the currently active auth module
 *
 * After authenticate_user_login() returns success, you will need to
 * log that the user has logged in, and call complete_user_login() to set
 * the session up.
 *
 * @global object
 * @global object
 * @param string $username  User's username
 * @param string $password  User's password
 * @return user|flase A {@link $USER} object or false if error
 */
function authenticate_user_login($username, $password) {
    global $CFG, $DB, $OUTPUT;

    $authsenabled = get_enabled_auth_plugins();

    if ($user = get_complete_user_data('username', $username)) {
        $auth = empty($user->auth) ? 'manual' : $user->auth;  // use manual if auth not set
        if ($auth=='nologin' or !is_enabled_auth($auth)) {
            add_to_log(0, 'login', 'error', 'index.php', $username);
            error_log('[client '.getremoteaddr()."]  $CFG->wwwroot  Disabled Login:  $username  ".$_SERVER['HTTP_USER_AGENT']);
            return false;
        }
        $auths = array($auth);

    } else {
        // check if there's a deleted record (cheaply)
        if ($DB->get_field('user', 'id', array('username'=>$username, 'deleted'=>1))) {
            error_log('[client '.$_SERVER['REMOTE_ADDR']."]  $CFG->wwwroot  Deleted Login:  $username  ".$_SERVER['HTTP_USER_AGENT']);
            return false;
        }

        $auths = $authsenabled;
        $user = new object();
        $user->id = 0;     // User does not exist
    }

    foreach ($auths as $auth) {
        $authplugin = get_auth_plugin($auth);

        // on auth fail fall through to the next plugin
        if (!$authplugin->user_login($username, $password)) {
            continue;
        }

        // successful authentication
        if ($user->id) {                          // User already exists in database
            if (empty($user->auth)) {             // For some reason auth isn't set yet
                $DB->set_field('user', 'auth', $auth, array('username'=>$username));
                $user->auth = $auth;
            }
            if (empty($user->firstaccess)) { //prevent firstaccess from remaining 0 for manual account that never required confirmation
                $DB->set_field('user','firstaccess', $user->timemodified, array('id' => $user->id));
                $user->firstaccess = $user->timemodified;
            }

            update_internal_user_password($user, $password); // just in case salt or encoding were changed (magic quotes too one day)

            if (!$authplugin->is_internal()) {            // update user record from external DB
                $user = update_user_record($username, get_auth_plugin($user->auth));
            }
        } else {
            // if user not found, create him
            $user = create_user_record($username, $password, $auth);
        }

        $authplugin->sync_roles($user);

        foreach ($authsenabled as $hau) {
            $hauth = get_auth_plugin($hau);
            $hauth->user_authenticated_hook($user, $username, $password);
        }

    /// Log in to a second system if necessary
    /// NOTICE: /sso/ will be moved to auth and deprecated soon; use user_authenticated_hook() instead
        if (!empty($CFG->sso)) {
            include_once($CFG->dirroot .'/sso/'. $CFG->sso .'/lib.php');
            if (function_exists('sso_user_login')) {
                if (!sso_user_login($username, $password)) {   // Perform the signon process
                    echo $OUTPUT->notification('Second sign-on failed');
                }
            }
        }

        if ($user->id===0) {
            return false;
        }
        return $user;
    }

    // failed if all the plugins have failed
    add_to_log(0, 'login', 'error', 'index.php', $username);
    if (debugging('', DEBUG_ALL)) {
        error_log('[client '.getremoteaddr()."]  $CFG->wwwroot  Failed Login:  $username  ".$_SERVER['HTTP_USER_AGENT']);
    }
    return false;
}

/**
 * Call to complete the user login process after authenticate_user_login()
 * has succeeded. It will setup the $USER variable and other required bits
 * and pieces.
 *
 * NOTE:
 * - It will NOT log anything -- up to the caller to decide what to log.
 *
 * @global object
 * @global object
 * @global object
 * @param object $user
 * @param bool $setcookie
 * @return object A {@link $USER} object - BC only, do not use
 */
function complete_user_login($user, $setcookie=true) {
    global $CFG, $USER, $SESSION;

    // regenerate session id and delete old session,
    // this helps prevent session fixation attacks from the same domain
    session_regenerate_id(true);

    // check enrolments, load caps and setup $USER object
    session_set_user($user);

    update_user_login_times();
    set_login_session_preferences();

    if ($setcookie) {
        if (empty($CFG->nolastloggedin)) {
            set_moodle_cookie($USER->username);
        } else {
            // do not store last logged in user in cookie
            // auth plugins can temporarily override this from loginpage_hook()
            // do not save $CFG->nolastloggedin in database!
            set_moodle_cookie('nobody');
        }
    }

    /// Select password change url
    $userauth = get_auth_plugin($USER->auth);

    /// check whether the user should be changing password
    if (get_user_preferences('auth_forcepasswordchange', false)){
        if ($userauth->can_change_password()) {
            if ($changeurl = $userauth->change_password_url()) {
                redirect($changeurl);
            } else {
                redirect($CFG->httpswwwroot.'/login/change_password.php');
            }
        } else {
            print_error('nopasswordchangeforced', 'auth');
        }
    }
    return $USER;
}

/**
 * Compare password against hash stored in internal user table.
 * If necessary it also updates the stored hash to new format.
 *
 * @global object
 * @param object $user
 * @param string $password plain text password
 * @return bool is password valid?
 */
function validate_internal_user_password(&$user, $password) {
    global $CFG;

    if (!isset($CFG->passwordsaltmain)) {
        $CFG->passwordsaltmain = '';
    }

    $validated = false;

    // get password original encoding in case it was not updated to unicode yet
    $textlib = textlib_get_instance();
    $convpassword = $textlib->convert($password, 'utf-8', get_string('oldcharset', 'langconfig'));

    if ($user->password == md5($password.$CFG->passwordsaltmain) or $user->password == md5($password)
        or $user->password == md5($convpassword.$CFG->passwordsaltmain) or $user->password == md5($convpassword)) {
        $validated = true;
    } else {
        for ($i=1; $i<=20; $i++) { //20 alternative salts should be enough, right?
            $alt = 'passwordsaltalt'.$i;
            if (!empty($CFG->$alt)) {
                if ($user->password == md5($password.$CFG->$alt) or $user->password == md5($convpassword.$CFG->$alt)) {
                    $validated = true;
                    break;
                }
            }
        }
    }

    if ($validated) {
        // force update of password hash using latest main password salt and encoding if needed
        update_internal_user_password($user, $password);
    }

    return $validated;
}

/**
 * Calculate hashed value from password using current hash mechanism.
 *
 * @global object
 * @param string $password
 * @return string password hash
 */
function hash_internal_user_password($password) {
    global $CFG;

    if (isset($CFG->passwordsaltmain)) {
        return md5($password.$CFG->passwordsaltmain);
    } else {
        return md5($password);
    }
}

/**
 * Update pssword hash in user object.
 *
 * @global object
 * @global object
 * @param object $user
 * @param string $password plain text password
 * @return bool true if hash changed
 */
function update_internal_user_password(&$user, $password) {
    global $CFG, $DB;

    $authplugin = get_auth_plugin($user->auth);
    if ($authplugin->prevent_local_passwords()) {
        $hashedpassword = 'not cached';
    } else {
        $hashedpassword = hash_internal_user_password($password);
    }

    $DB->set_field('user', 'password',  $hashedpassword, array('id'=>$user->id));
    return true;
}

/**
 * Get a complete user record, which includes all the info
 * in the user record.
 *
 * Intended for setting as $USER session variable
 *
 * @global object
 * @global object
 * @uses SITEID
 * @param string $field The user field to be checked for a given value.
 * @param string $value The value to match for $field.
 * @param int $mnethostid
 * @return mixed False, or A {@link $USER} object.
 */
function get_complete_user_data($field, $value, $mnethostid=null) {
    global $CFG, $DB;

    if (!$field || !$value) {
        return false;
    }

/// Build the WHERE clause for an SQL query
    $params = array('fieldval'=>$value);
    $constraints = "$field = :fieldval AND deleted <> 1";

    // If we are loading user data based on anything other than id,
    // we must also restrict our search based on mnet host.
    if ($field != 'id') {
        if (empty($mnethostid)) {
            // if empty, we restrict to local users
            $mnethostid = $CFG->mnet_localhost_id;
        }
    }
    if (!empty($mnethostid)) {
        $params['mnethostid'] = $mnethostid;
        $constraints .= " AND mnethostid = :mnethostid";
    }

/// Get all the basic user data

    if (! $user = $DB->get_record_select('user', $constraints, $params)) {
        return false;
    }

/// Get various settings and preferences

    if ($displays = $DB->get_records('course_display', array('userid'=>$user->id))) {
        foreach ($displays as $display) {
            $user->display[$display->course] = $display->display;
        }
    }

    $user->preference = get_user_preferences(null, null, $user->id);
    $user->preference['_lastloaded'] = time();

    $user->lastcourseaccess    = array(); // during last session
    $user->currentcourseaccess = array(); // during current session
    if ($lastaccesses = $DB->get_records('user_lastaccess', array('userid'=>$user->id))) {
        foreach ($lastaccesses as $lastaccess) {
            $user->lastcourseaccess[$lastaccess->courseid] = $lastaccess->timeaccess;
        }
    }

    $sql = "SELECT g.id, g.courseid
              FROM {groups} g, {groups_members} gm
             WHERE gm.groupid=g.id AND gm.userid=?";

    // this is a special hack to speedup calendar display
    $user->groupmember = array();
    if ($groups = $DB->get_records_sql($sql, array($user->id))) {
        foreach ($groups as $group) {
            if (!array_key_exists($group->courseid, $user->groupmember)) {
                $user->groupmember[$group->courseid] = array();
            }
            $user->groupmember[$group->courseid][$group->id] = $group->id;
        }
    }

/// Add the custom profile fields to the user record
    require_once($CFG->dirroot.'/user/profile/lib.php');
    $customfields = (array)profile_user_record($user->id);
    foreach ($customfields as $cname=>$cvalue) {
        if (!isset($user->$cname)) { // Don't overwrite any standard fields
            $user->$cname = $cvalue;
        }
    }

/// Rewrite some variables if necessary
    if (!empty($user->description)) {
        $user->description = true;   // No need to cart all of it around
    }
    if ($user->username == 'guest') {
        $user->lang       = $CFG->lang;               // Guest language always same as site
        $user->firstname  = get_string('guestuser');  // Name always in current language
        $user->lastname   = ' ';
    }

    return $user;
}

/**
 * Validate a password against the confiured password policy
 *
 * @global object
 * @param string $password the password to be checked agains the password policy
 * @param string $errmsg the error message to display when the password doesn't comply with the policy.
 * @return bool true if the password is valid according to the policy. false otherwise.
 */
function check_password_policy($password, &$errmsg) {
    global $CFG;

    if (empty($CFG->passwordpolicy)) {
        return true;
    }

    $textlib = textlib_get_instance();
    $errmsg = '';
    if ($textlib->strlen($password) < $CFG->minpasswordlength) {
        $errmsg .= '<div>'. get_string('errorminpasswordlength', 'auth', $CFG->minpasswordlength) .'</div>';

    }
    if (preg_match_all('/[[:digit:]]/u', $password, $matches) < $CFG->minpassworddigits) {
        $errmsg .= '<div>'. get_string('errorminpassworddigits', 'auth', $CFG->minpassworddigits) .'</div>';

    }
    if (preg_match_all('/[[:lower:]]/u', $password, $matches) < $CFG->minpasswordlower) {
        $errmsg .= '<div>'. get_string('errorminpasswordlower', 'auth', $CFG->minpasswordlower) .'</div>';

    }
    if (preg_match_all('/[[:upper:]]/u', $password, $matches) < $CFG->minpasswordupper) {
        $errmsg .= '<div>'. get_string('errorminpasswordupper', 'auth', $CFG->minpasswordupper) .'</div>';

    }
    if (preg_match_all('/[^[:upper:][:lower:][:digit:]]/u', $password, $matches) < $CFG->minpasswordnonalphanum) {
        $errmsg .= '<div>'. get_string('errorminpasswordnonalphanum', 'auth', $CFG->minpasswordnonalphanum) .'</div>';
    }
    if (!check_consecutive_identical_characters($password, $CFG->maxconsecutiveidentchars)) {
        $errmsg .= '<div>'. get_string('errormaxconsecutiveidentchars', 'auth', $CFG->maxconsecutiveidentchars) .'</div>';
    }

    if ($errmsg == '') {
        return true;
    } else {
        return false;
    }
}


/**
 * When logging in, this function is run to set certain preferences
 * for the current SESSION
 *
 * @global object
 * @global object
 */
function set_login_session_preferences() {
    global $SESSION, $CFG;

    $SESSION->justloggedin = true;

    unset($SESSION->lang);

    // Restore the calendar filters, if saved
    if (intval(get_user_preferences('calendar_persistflt', 0))) {
        include_once($CFG->dirroot.'/calendar/lib.php');
        calendar_set_filters_status(get_user_preferences('calendar_savedflt', 0xff));
    }
}


/**
 * Delete a course, including all related data from the database,
 * and any associated files from the moodledata folder.
 *
 * @global object
 * @global object
 * @param mixed $courseorid The id of the course or course object to delete.
 * @param bool $showfeedback Whether to display notifications of each action the function performs.
 * @return bool true if all the removals succeeded. false if there were any failures. If this
 *             method returns false, some of the removals will probably have succeeded, and others
 *             failed, but you have no way of knowing which.
 */
function delete_course($courseorid, $showfeedback = true) {
    global $CFG, $DB, $OUTPUT;
    $result = true;

    if (is_object($courseorid)) {
        $courseid = $courseorid->id;
        $course   = $courseorid;
    } else {
        $courseid = $courseorid;
        if (!$course = $DB->get_record('course', array('id'=>$courseid))) {
            return false;
        }
    }

    // frontpage course can not be deleted!!
    if ($courseid == SITEID) {
        return false;
    }

    if (!remove_course_contents($courseid, $showfeedback)) {
        if ($showfeedback) {
            echo $OUTPUT->notification("An error occurred while deleting some of the course contents.");
        }
        $result = false;
    }

    $DB->delete_records("course", array("id"=>$courseid));

/// Delete all roles and overiddes in the course context
    if (!delete_context(CONTEXT_COURSE, $courseid)) {
        if ($showfeedback) {
            echo $OUTPUT->notification("An error occurred while deleting the main course context.");
        }
        $result = false;
    }

    if (!fulldelete($CFG->dataroot.'/'.$courseid)) {
        if ($showfeedback) {
            echo $OUTPUT->notification("An error occurred while deleting the course files.");
        }
        $result = false;
    }

    if ($result) {
        //trigger events
        events_trigger('course_deleted', $course);
    }

    return $result;
}

/**
 * Clear a course out completely, deleting all content
 * but don't delete the course itself
 *
 * @global object
 * @global object
 * @param int $courseid The id of the course that is being deleted
 * @param bool $showfeedback Whether to display notifications of each action the function performs.
 * @return bool true if all the removals succeeded. false if there were any failures. If this
 *             method returns false, some of the removals will probably have succeeded, and others
 *             failed, but you have no way of knowing which.
 */
function remove_course_contents($courseid, $showfeedback=true) {
    global $CFG, $DB, $OUTPUT;
    require_once($CFG->libdir.'/questionlib.php');
    require_once($CFG->libdir.'/gradelib.php');

    $result = true;

    if (! $course = $DB->get_record('course', array('id'=>$courseid))) {
        print_error('invalidcourseid');
    }
    $context = get_context_instance(CONTEXT_COURSE, $courseid);

    $strdeleted = get_string('deleted');

/// Clean up course formats (iterate through all formats in the even the course format was ever changed)
    $formats = get_plugin_list('format');
    foreach ($formats as $format=>$formatdir) {
        $formatdelete = $format.'_course_format_delete_course';
        $formatlib    = "$formatdir/lib.php";
        if (file_exists($formatlib)) {
            include_once($formatlib);
            if (function_exists($formatdelete)) {
                if ($showfeedback) {
                    echo $OUTPUT->notification($strdeleted.' '.$format);
                }
                $formatdelete($course->id);
            }
        }
    }

/// Delete every instance of every module

    if ($allmods = $DB->get_records('modules') ) {
        foreach ($allmods as $mod) {
            $modname = $mod->name;
            $modfile = $CFG->dirroot .'/mod/'. $modname .'/lib.php';
            $moddelete = $modname .'_delete_instance';       // Delete everything connected to an instance
            $moddeletecourse = $modname .'_delete_course';   // Delete other stray stuff (uncommon)
            $count=0;
            if (file_exists($modfile)) {
                include_once($modfile);
                if (function_exists($moddelete)) {
                    if ($instances = $DB->get_records($modname, array('course'=>$course->id))) {
                        foreach ($instances as $instance) {
                            if ($cm = get_coursemodule_from_instance($modname, $instance->id, $course->id)) {
                                /// Delete activity context questions and question categories
                                question_delete_activity($cm,  $showfeedback);
                            }
                            if ($moddelete($instance->id)) {
                                $count++;

                            } else {
                                echo $OUTPUT->notification('Could not delete '. $modname .' instance '. $instance->id .' ('. format_string($instance->name) .')');
                                $result = false;
                            }
                            if ($cm) {
                                // delete cm and its context in correct order
                                $DB->delete_records('course_modules', array('id'=>$cm->id));
                                delete_context(CONTEXT_MODULE, $cm->id);
                            }
                        }
                    }
                } else {
                    echo $OUTPUT->notification('Function '.$moddelete.'() doesn\'t exist!');
                    $result = false;
                }

                if (function_exists($moddeletecourse)) {
                    $moddeletecourse($course, $showfeedback);
                }
            }
            if ($showfeedback) {
                echo $OUTPUT->notification($strdeleted .' '. $count .' x '. $modname);
            }
        }
    } else {
        print_error('nomodules', 'debug');
    }

/// Delete course blocks
    blocks_delete_all_for_context($context->id);

/// Delete any groups, removing members and grouping/course links first.
    require_once($CFG->dirroot.'/group/lib.php');
    groups_delete_groupings($courseid, $showfeedback);
    groups_delete_groups($courseid, $showfeedback);

/// Delete all related records in other tables that may have a courseid
/// This array stores the tables that need to be cleared, as
/// table_name => column_name that contains the course id.

    $tablestoclear = array(
        'event' => 'courseid', // Delete events
        'log' => 'course', // Delete logs
        'course_sections' => 'course', // Delete any course stuff
        'course_modules' => 'course',
        'backup_courses' => 'courseid', // Delete scheduled backup stuff
        'user_lastaccess' => 'courseid',
        'backup_log' => 'courseid'
    );
    foreach ($tablestoclear as $table => $col) {
        if ($DB->delete_records($table, array($col=>$course->id))) {
            if ($showfeedback) {
                echo $OUTPUT->notification($strdeleted . ' ' . $table);
            }
        } else {
            $result = false;
        }
    }


/// Clean up metacourse stuff

    if ($course->metacourse) {
        $DB->delete_records("course_meta", array("parent_course"=>$course->id));
        sync_metacourse($course->id); // have to do it here so the enrolments get nuked. sync_metacourses won't find it without the id.
        if ($showfeedback) {
            echo $OUTPUT->notification("$strdeleted course_meta");
        }
    } else {
        if ($parents = $DB->get_records("course_meta", array("child_course"=>$course->id))) {
            foreach ($parents as $parent) {
                remove_from_metacourse($parent->parent_course,$parent->child_course); // this will do the unenrolments as well.
            }
            if ($showfeedback) {
                echo $OUTPUT->notification("$strdeleted course_meta");
            }
        }
    }

/// Delete questions and question categories
    question_delete_course($course, $showfeedback);

/// Remove all data from gradebook
    remove_course_grades($courseid, $showfeedback);
    remove_grade_letters($context, $showfeedback);

/// Delete course tags
    require_once($CFG->dirroot.'/tag/coursetagslib.php');
    coursetag_delete_course_tags($course->id, $showfeedback);

    return $result;
}

/**
 * Change dates in module - used from course reset.
 *
 * @global object
 * @global object
 * @param string $modname forum, assignent, etc
 * @param array $fields array of date fields from mod table
 * @param int $timeshift time difference
 * @param int $courseid
 * @return bool success
 */
function shift_course_mod_dates($modname, $fields, $timeshift, $courseid) {
    global $CFG, $DB;
    include_once($CFG->dirroot.'/mod/'.$modname.'/lib.php');

    $return = true;
    foreach ($fields as $field) {
        $updatesql = "UPDATE {".$modname."}
                          SET $field = $field + ?
                        WHERE course=? AND $field<>0 AND $field<>0";
        $return = $DB->execute($updatesql, array($timeshift, $courseid)) && $return;
    }

    $refreshfunction = $modname.'_refresh_events';
    if (function_exists($refreshfunction)) {
        $refreshfunction($courseid);
    }

    return $return;
}

/**
 * This function will empty a course of user data.
 * It will retain the activities and the structure of the course.
 *
 * @param object $data an object containing all the settings including courseid (without magic quotes)
 * @return array status array of array component, item, error
 */
function reset_course_userdata($data) {
    global $CFG, $USER, $DB;
    require_once($CFG->libdir.'/gradelib.php');
    require_once($CFG->dirroot.'/group/lib.php');

    $data->courseid = $data->id;
    $context = get_context_instance(CONTEXT_COURSE, $data->courseid);

    // calculate the time shift of dates
    if (!empty($data->reset_start_date)) {
        // time part of course startdate should be zero
        $data->timeshift = $data->reset_start_date - usergetmidnight($data->reset_start_date_old);
    } else {
        $data->timeshift = 0;
    }

    // result array: component, item, error
    $status = array();

    // start the resetting
    $componentstr = get_string('general');

    // move the course start time
    if (!empty($data->reset_start_date) and $data->timeshift) {
        // change course start data
        $DB->set_field('course', 'startdate', $data->reset_start_date, array('id'=>$data->courseid));
        // update all course and group events - do not move activity events
        $updatesql = "UPDATE {event}
                         SET timestart = timestart + ?
                       WHERE courseid=? AND instance=0";
        $DB->execute($updatesql, array($data->timeshift, $data->courseid));

        $status[] = array('component'=>$componentstr, 'item'=>get_string('datechanged'), 'error'=>false);
    }

    if (!empty($data->reset_logs)) {
        $DB->delete_records('log', array('course'=>$data->courseid));
        $status[] = array('component'=>$componentstr, 'item'=>get_string('deletelogs'), 'error'=>false);
    }

    if (!empty($data->reset_events)) {
        $DB->delete_records('event', array('courseid'=>$data->courseid));
        $status[] = array('component'=>$componentstr, 'item'=>get_string('deleteevents', 'calendar'), 'error'=>false);
    }

    if (!empty($data->reset_notes)) {
        require_once($CFG->dirroot.'/notes/lib.php');
        note_delete_all($data->courseid);
        $status[] = array('component'=>$componentstr, 'item'=>get_string('deletenotes', 'notes'), 'error'=>false);
    }

    if (!empty($data->delete_blog_associations)) {
        require_once($CFG->dirroot.'/blog/lib.php');
        blog_remove_associations_for_course($data->courseid);
        $status[] = array('component'=>$componentstr, 'item'=>get_string('deleteblogassociations', 'blog'), 'error'=>false);
    }

    $componentstr = get_string('roles');

    if (!empty($data->reset_roles_overrides)) {
        $children = get_child_contexts($context);
        foreach ($children as $child) {
            $DB->delete_records('role_capabilities', array('contextid'=>$child->id));
        }
        $DB->delete_records('role_capabilities', array('contextid'=>$context->id));
        //force refresh for logged in users
        mark_context_dirty($context->path);
        $status[] = array('component'=>$componentstr, 'item'=>get_string('deletecourseoverrides', 'role'), 'error'=>false);
    }

    if (!empty($data->reset_roles_local)) {
        $children = get_child_contexts($context);
        foreach ($children as $child) {
            role_unassign(0, 0, 0, $child->id);
        }
        //force refresh for logged in users
        mark_context_dirty($context->path);
        $status[] = array('component'=>$componentstr, 'item'=>get_string('deletelocalroles', 'role'), 'error'=>false);
    }

    // First unenrol users - this cleans some of related user data too, such as forum subscriptions, tracking, etc.
    $data->unenrolled = array();
    if (!empty($data->reset_roles)) {
        foreach($data->reset_roles as $roleid) {
            if ($users = get_role_users($roleid, $context, false, 'u.id', 'u.id ASC')) {
                foreach ($users as $user) {
                    role_unassign($roleid, $user->id, 0, $context->id);
                    if (!is_enrolled($context, $user->id)) {
                        $data->unenrolled[$user->id] = $user->id;
                    }
                }
            }
        }
    }
    if (!empty($data->unenrolled)) {
        $status[] = array('component'=>$componentstr, 'item'=>get_string('unenrol').' ('.count($data->unenrolled).')', 'error'=>false);
    }


    $componentstr = get_string('groups');

    // remove all group members
    if (!empty($data->reset_groups_members)) {
        groups_delete_group_members($data->courseid);
        $status[] = array('component'=>$componentstr, 'item'=>get_string('removegroupsmembers', 'group'), 'error'=>false);
    }

    // remove all groups
    if (!empty($data->reset_groups_remove)) {
        groups_delete_groups($data->courseid, false);
        $status[] = array('component'=>$componentstr, 'item'=>get_string('deleteallgroups', 'group'), 'error'=>false);
    }

    // remove all grouping members
    if (!empty($data->reset_groupings_members)) {
        groups_delete_groupings_groups($data->courseid, false);
        $status[] = array('component'=>$componentstr, 'item'=>get_string('removegroupingsmembers', 'group'), 'error'=>false);
    }

    // remove all groupings
    if (!empty($data->reset_groupings_remove)) {
        groups_delete_groupings($data->courseid, false);
        $status[] = array('component'=>$componentstr, 'item'=>get_string('deleteallgroupings', 'group'), 'error'=>false);
    }

    // Look in every instance of every module for data to delete
    $unsupported_mods = array();
    if ($allmods = $DB->get_records('modules') ) {
        foreach ($allmods as $mod) {
            $modname = $mod->name;
            if (!$DB->count_records($modname, array('course'=>$data->courseid))) {
                continue; // skip mods with no instances
            }
            $modfile = $CFG->dirroot.'/mod/'. $modname.'/lib.php';
            $moddeleteuserdata = $modname.'_reset_userdata';   // Function to delete user data
            if (file_exists($modfile)) {
                include_once($modfile);
                if (function_exists($moddeleteuserdata)) {
                    $modstatus = $moddeleteuserdata($data);
                    if (is_array($modstatus)) {
                        $status = array_merge($status, $modstatus);
                    } else {
                        debugging('Module '.$modname.' returned incorrect staus - must be an array!');
                    }
                } else {
                    $unsupported_mods[] = $mod;
                }
            } else {
                debugging('Missing lib.php in '.$modname.' module!');
            }
        }
    }

    // mention unsupported mods
    if (!empty($unsupported_mods)) {
        foreach($unsupported_mods as $mod) {
            $status[] = array('component'=>get_string('modulenameplural', $mod->name), 'item'=>'', 'error'=>get_string('resetnotimplemented'));
        }
    }


    $componentstr = get_string('gradebook', 'grades');
    // reset gradebook
    if (!empty($data->reset_gradebook_items)) {
        remove_course_grades($data->courseid, false);
        grade_grab_course_grades($data->courseid);
        grade_regrade_final_grades($data->courseid);
        $status[] = array('component'=>$componentstr, 'item'=>get_string('removeallcourseitems', 'grades'), 'error'=>false);

    } else if (!empty($data->reset_gradebook_grades)) {
        grade_course_reset($data->courseid);
        $status[] = array('component'=>$componentstr, 'item'=>get_string('removeallcoursegrades', 'grades'), 'error'=>false);
    }

    return $status;
}

/**
 * Generate an email processing address
 *
 * @param int $modid
 * @param string $modargs
 * @return string Returns email processing address
 */
function generate_email_processing_address($modid,$modargs) {
    global $CFG;

    $header = $CFG->mailprefix . substr(base64_encode(pack('C',$modid)),0,2).$modargs;
    return $header . substr(md5($header.get_site_identifier()),0,16).'@'.$CFG->maildomain;
}

/**
 * ?
 *
 * @todo Finish documenting this function
 *
 * @global object
 * @param string $modargs
 * @param string $body Currently unused
 */
function moodle_process_email($modargs,$body) {
    global $DB;

    // the first char should be an unencoded letter. We'll take this as an action
    switch ($modargs{0}) {
        case 'B': { // bounce
            list(,$userid) = unpack('V',base64_decode(substr($modargs,1,8)));
            if ($user = $DB->get_record("user", array('id'=>$userid), "id,email")) {
                // check the half md5 of their email
                $md5check = substr(md5($user->email),0,16);
                if ($md5check == substr($modargs, -16)) {
                    set_bounce_count($user);
                }
                // else maybe they've already changed it?
            }
        }
        break;
        // maybe more later?
    }
}

/// CORRESPONDENCE  ////////////////////////////////////////////////

/**
 * Get mailer instance, enable buffering, flush buffer or disable buffering.
 *
 * @global object
 * @param string $action 'get', 'buffer', 'close' or 'flush'
 * @return object|null reference to mailer instance if 'get' used or nothing
 */
function &get_mailer($action='get') {
    global $CFG;

    static $mailer  = null;
    static $counter = 0;

    if (!isset($CFG->smtpmaxbulk)) {
        $CFG->smtpmaxbulk = 1;
    }

    if ($action == 'get') {
        $prevkeepalive = false;

        if (isset($mailer) and $mailer->Mailer == 'smtp') {
            if ($counter < $CFG->smtpmaxbulk and empty($mailer->error_count)) {
                $counter++;
                // reset the mailer
                $mailer->Priority         = 3;
                $mailer->CharSet          = 'UTF-8'; // our default
                $mailer->ContentType      = "text/plain";
                $mailer->Encoding         = "8bit";
                $mailer->From             = "root@localhost";
                $mailer->FromName         = "Root User";
                $mailer->Sender           = "";
                $mailer->Subject          = "";
                $mailer->Body             = "";
                $mailer->AltBody          = "";
                $mailer->ConfirmReadingTo = "";

                $mailer->ClearAllRecipients();
                $mailer->ClearReplyTos();
                $mailer->ClearAttachments();
                $mailer->ClearCustomHeaders();
                return $mailer;
            }

            $prevkeepalive = $mailer->SMTPKeepAlive;
            get_mailer('flush');
        }

        include_once($CFG->libdir.'/phpmailer/moodle_phpmailer.php');
        $mailer = new moodle_phpmailer();

        $counter = 1;

        $mailer->Version   = 'Moodle '.$CFG->version;         // mailer version
        $mailer->PluginDir = $CFG->libdir.'/phpmailer/';      // plugin directory (eg smtp plugin)
        $mailer->CharSet   = 'UTF-8';

        // some MTAs may do double conversion of LF if CRLF used, CRLF is required line ending in RFC 822bis
        // hmm, this is a bit hacky because LE should be private
        if (isset($CFG->mailnewline) and $CFG->mailnewline == 'CRLF') {
            $mailer->LE = "\r\n";
        } else {
            $mailer->LE = "\n";
        }

        if ($CFG->smtphosts == 'qmail') {
            $mailer->IsQmail();                              // use Qmail system

        } else if (empty($CFG->smtphosts)) {
            $mailer->IsMail();                               // use PHP mail() = sendmail

        } else {
            $mailer->IsSMTP();                               // use SMTP directly
            if (!empty($CFG->debugsmtp)) {
                $mailer->SMTPDebug = true;
            }
            $mailer->Host          = $CFG->smtphosts;        // specify main and backup servers
            $mailer->SMTPKeepAlive = $prevkeepalive;         // use previous keepalive

            if ($CFG->smtpuser) {                            // Use SMTP authentication
                $mailer->SMTPAuth = true;
                $mailer->Username = $CFG->smtpuser;
                $mailer->Password = $CFG->smtppass;
            }
        }

        return $mailer;
    }

    $nothing = null;

    // keep smtp session open after sending
    if ($action == 'buffer') {
        if (!empty($CFG->smtpmaxbulk)) {
            get_mailer('flush');
            $m =& get_mailer();
            if ($m->Mailer == 'smtp') {
                $m->SMTPKeepAlive = true;
            }
        }
        return $nothing;
    }

    // close smtp session, but continue buffering
    if ($action == 'flush') {
        if (isset($mailer) and $mailer->Mailer == 'smtp') {
            if (!empty($mailer->SMTPDebug)) {
                echo '<pre>'."\n";
            }
            $mailer->SmtpClose();
            if (!empty($mailer->SMTPDebug)) {
                echo '</pre>';
            }
        }
        return $nothing;
    }

    // close smtp session, do not buffer anymore
    if ($action == 'close') {
        if (isset($mailer) and $mailer->Mailer == 'smtp') {
            get_mailer('flush');
            $mailer->SMTPKeepAlive = false;
        }
        $mailer = null; // better force new instance
        return $nothing;
    }
}

/**
 * Send an email to a specified user
 *
 * @global object
 * @global string
 * @global string IdentityProvider(IDP) URL user hits to jump to mnet peer.
 * @uses SITEID
 * @param user $user  A {@link $USER} object
 * @param user $from A {@link $USER} object
 * @param string $subject plain text subject line of the email
 * @param string $messagetext plain text version of the message
 * @param string $messagehtml complete html version of the message (optional)
 * @param string $attachment a file on the filesystem, relative to $CFG->dataroot
 * @param string $attachname the name of the file (extension indicates MIME)
 * @param bool $usetrueaddress determines whether $from email address should
 *          be sent out. Will be overruled by user profile setting for maildisplay
 * @param string $replyto Email address to reply to
 * @param string $replytoname Name of reply to recipient
 * @param int $wordwrapwidth custom word wrap width, default 79
 * @return bool|string Returns "true" if mail was sent OK, "emailstop" if email
 *          was blocked by user and "false" if there was another sort of error.
 */
function email_to_user($user, $from, $subject, $messagetext, $messagehtml='', $attachment='', $attachname='', $usetrueaddress=true, $replyto='', $replytoname='', $wordwrapwidth=79) {

    global $CFG, $FULLME, $MNETIDPJUMPURL;
    static $mnetjumps = array();

    if (empty($user) || empty($user->email)) {
        return false;
    }

    if (!empty($user->deleted)) {
        // do not mail delted users
        return false;
    }

    if (!empty($CFG->noemailever)) {
        // hidden setting for development sites, set in config.php if needed
        return true;
    }

    if (!empty($CFG->divertallemailsto)) {
        $subject = "[DIVERTED {$user->email}] $subject";
        $user = clone($user);
        $user->email = $CFG->divertallemailsto;
    }

    // skip mail to suspended users
    if (isset($user->auth) && $user->auth=='nologin') {
        return true;
    }

    if (!empty($user->emailstop)) {
        return 'emailstop';
    }

    if (over_bounce_threshold($user)) {
        error_log("User $user->id (".fullname($user).") is over bounce threshold! Not sending.");
        return false;
    }

    // If the user is a remote mnet user, parse the email text for URL to the
    // wwwroot and modify the url to direct the user's browser to login at their
    // home site (identity provider - idp) before hitting the link itself
    if (is_mnet_remote_user($user)) {
        require_once($CFG->dirroot.'/mnet/lib.php');

        $jumpurl = mnet_get_idp_jump_url($user);
        $callback = partial('mnet_sso_apply_redirection', $jumpurl);

        $messagetext = preg_replace_callback("%($CFG->wwwroot[^[:space:]]*)%",
                $callback,
                $messagetext);
        $messagehtml = preg_replace_callback("%href=[\"'`]($CFG->wwwroot[\w_:\?=#&@/;.~-]*)[\"'`]%",
                $callback,
                $messagehtml);
    }
    $mail =& get_mailer();

    if (!empty($mail->SMTPDebug)) {
        echo '<pre>' . "\n";
    }

/// We are going to use textlib services here
    $textlib = textlib_get_instance();

    $supportuser = generate_email_supportuser();

    // make up an email address for handling bounces
    if (!empty($CFG->handlebounces)) {
        $modargs = 'B'.base64_encode(pack('V',$user->id)).substr(md5($user->email),0,16);
        $mail->Sender = generate_email_processing_address(0,$modargs);
    } else {
        $mail->Sender = $supportuser->email;
    }

    if (is_string($from)) { // So we can pass whatever we want if there is need
        $mail->From     = $CFG->noreplyaddress;
        $mail->FromName = $from;
    } else if ($usetrueaddress and $from->maildisplay) {
        $mail->From     = $from->email;
        $mail->FromName = fullname($from);
    } else {
        $mail->From     = $CFG->noreplyaddress;
        $mail->FromName = fullname($from);
        if (empty($replyto)) {
            $mail->AddReplyTo($CFG->noreplyaddress,get_string('noreplyname'));
        }
    }

    if (!empty($replyto)) {
        $mail->AddReplyTo($replyto,$replytoname);
    }

    $mail->Subject = substr($subject, 0, 900);

    $mail->AddAddress($user->email, fullname($user) );

    $mail->WordWrap = $wordwrapwidth;                   // set word wrap

    if (!empty($from->customheaders)) {                 // Add custom headers
        if (is_array($from->customheaders)) {
            foreach ($from->customheaders as $customheader) {
                $mail->AddCustomHeader($customheader);
            }
        } else {
            $mail->AddCustomHeader($from->customheaders);
        }
    }

    if (!empty($from->priority)) {
        $mail->Priority = $from->priority;
    }

    if ($messagehtml && $user->mailformat == 1) { // Don't ever send HTML to users who don't want it
        $mail->IsHTML(true);
        $mail->Encoding = 'quoted-printable';           // Encoding to use
        $mail->Body    =  $messagehtml;
        $mail->AltBody =  "\n$messagetext\n";
    } else {
        $mail->IsHTML(false);
        $mail->Body =  "\n$messagetext\n";
    }

    if ($attachment && $attachname) {
        if (preg_match( "~\\.\\.~" ,$attachment )) {    // Security check for ".." in dir path
            $mail->AddAddress($supportuser->email, fullname($supportuser, true) );
            $mail->AddStringAttachment('Error in attachment.  User attempted to attach a filename with a unsafe name.', 'error.txt', '8bit', 'text/plain');
        } else {
            require_once($CFG->libdir.'/filelib.php');
            $mimetype = mimeinfo('type', $attachname);
            $mail->AddAttachment($CFG->dataroot .'/'. $attachment, $attachname, 'base64', $mimetype);
        }
    }



/// If we are running under Unicode and sitemailcharset or allowusermailcharset are set, convert the email
/// encoding to the specified one
    if ((!empty($CFG->sitemailcharset) || !empty($CFG->allowusermailcharset))) {
    /// Set it to site mail charset
        $charset = $CFG->sitemailcharset;
    /// Overwrite it with the user mail charset
        if (!empty($CFG->allowusermailcharset)) {
            if ($useremailcharset = get_user_preferences('mailcharset', '0', $user->id)) {
                $charset = $useremailcharset;
            }
        }
    /// If it has changed, convert all the necessary strings
        $charsets = get_list_of_charsets();
        unset($charsets['UTF-8']);
        if (in_array($charset, $charsets)) {
        /// Save the new mail charset
            $mail->CharSet = $charset;
        /// And convert some strings
            $mail->FromName = $textlib->convert($mail->FromName, 'utf-8', $mail->CharSet); //From Name
            foreach ($mail->ReplyTo as $key => $rt) {                                      //ReplyTo Names
                $mail->ReplyTo[$key][1] = $textlib->convert($rt[1], 'utf-8', $mail->CharSet);
            }
            $mail->Subject = $textlib->convert($mail->Subject, 'utf-8', $mail->CharSet);   //Subject
            foreach ($mail->to as $key => $to) {
                $mail->to[$key][1] = $textlib->convert($to[1], 'utf-8', $mail->CharSet);      //To Names
            }
            $mail->Body = $textlib->convert($mail->Body, 'utf-8', $mail->CharSet);         //Body
            $mail->AltBody = $textlib->convert($mail->AltBody, 'utf-8', $mail->CharSet);   //Subject
        }
    }

    if ($mail->Send()) {
        set_send_count($user);
        $mail->IsSMTP();                               // use SMTP directly
        if (!empty($mail->SMTPDebug)) {
            echo '</pre>';
        }
        return true;
    } else {
        mtrace('ERROR: '. $mail->ErrorInfo);
        add_to_log(SITEID, 'library', 'mailer', $FULLME, 'ERROR: '. $mail->ErrorInfo);
        if (!empty($mail->SMTPDebug)) {
            echo '</pre>';
        }
        return false;
    }
}

/**
 * Generate a signoff for emails based on support settings
 *
 * @global object
 * @return string
 */
function generate_email_signoff() {
    global $CFG;

    $signoff = "\n";
    if (!empty($CFG->supportname)) {
        $signoff .= $CFG->supportname."\n";
    }
    if (!empty($CFG->supportemail)) {
        $signoff .= $CFG->supportemail."\n";
    }
    if (!empty($CFG->supportpage)) {
        $signoff .= $CFG->supportpage."\n";
    }
    return $signoff;
}

/**
 * Generate a fake user for emails based on support settings
 * @global object
 * @return object user info
 */
function generate_email_supportuser() {
    global $CFG;

    static $supportuser;

    if (!empty($supportuser)) {
        return $supportuser;
    }

    $supportuser = new object;
    $supportuser->email = $CFG->supportemail ? $CFG->supportemail : $CFG->noreplyaddress;
    $supportuser->firstname = $CFG->supportname ? $CFG->supportname : get_string('noreplyname');
    $supportuser->lastname = '';
    $supportuser->maildisplay = true;

    return $supportuser;
}


/**
 * Sets specified user's password and send the new password to the user via email.
 *
 * @global object
 * @global object
 * @param user $user A {@link $USER} object
 * @return boolean|string Returns "true" if mail was sent OK, "emailstop" if email
 *          was blocked by user and "false" if there was another sort of error.
 */
function setnew_password_and_mail($user) {
    global $CFG, $DB;

    $site  = get_site();

    $supportuser = generate_email_supportuser();

    $newpassword = generate_password();

    $DB->set_field('user', 'password', md5($newpassword), array('id'=>$user->id));

    $a = new object();
    $a->firstname   = fullname($user, true);
    $a->sitename    = format_string($site->fullname);
    $a->username    = $user->username;
    $a->newpassword = $newpassword;
    $a->link        = $CFG->wwwroot .'/login/';
    $a->signoff     = generate_email_signoff();

    $message = get_string('newusernewpasswordtext', '', $a);

    $subject = format_string($site->fullname) .': '. get_string('newusernewpasswordsubj');

    return email_to_user($user, $supportuser, $subject, $message);

}

/**
 * Resets specified user's password and send the new password to the user via email.
 *
 * @global object
 * @param user $user A {@link $USER} object
 * @return bool|string Returns "true" if mail was sent OK, "emailstop" if email
 *          was blocked by user and "false" if there was another sort of error.
 */
function reset_password_and_mail($user) {
    global $CFG;

    $site  = get_site();
    $supportuser = generate_email_supportuser();

    $userauth = get_auth_plugin($user->auth);
    if (!$userauth->can_reset_password() or !is_enabled_auth($user->auth)) {
        trigger_error("Attempt to reset user password for user $user->username with Auth $user->auth.");
        return false;
    }

    $newpassword = generate_password();

    if (!$userauth->user_update_password($user, $newpassword)) {
        print_error("cannotsetpassword");
    }

    $a = new object();
    $a->firstname   = $user->firstname;
    $a->lastname    = $user->lastname;
    $a->sitename    = format_string($site->fullname);
    $a->username    = $user->username;
    $a->newpassword = $newpassword;
    $a->link        = $CFG->httpswwwroot .'/login/change_password.php';
    $a->signoff     = generate_email_signoff();

    $message = get_string('newpasswordtext', '', $a);

    $subject  = format_string($site->fullname) .': '. get_string('changedpassword');

    return email_to_user($user, $supportuser, $subject, $message);

}

/**
 * Send email to specified user with confirmation text and activation link.
 *
 * @global object
 * @param user $user A {@link $USER} object
 * @return bool|string Returns "true" if mail was sent OK, "emailstop" if email
 *          was blocked by user and "false" if there was another sort of error.
 */
 function send_confirmation_email($user) {
    global $CFG;

    $site = get_site();
    $supportuser = generate_email_supportuser();

    $data = new object();
    $data->firstname = fullname($user);
    $data->sitename  = format_string($site->fullname);
    $data->admin     = generate_email_signoff();

    $subject = get_string('emailconfirmationsubject', '', format_string($site->fullname));

    $data->link  = $CFG->wwwroot .'/login/confirm.php?data='. $user->secret .'/'. urlencode($user->username);
    $message     = get_string('emailconfirmation', '', $data);
    $messagehtml = text_to_html(get_string('emailconfirmation', '', $data), false, false, true);

    $user->mailformat = 1;  // Always send HTML version as well

    return email_to_user($user, $supportuser, $subject, $message, $messagehtml);

}

/**
 * send_password_change_confirmation_email.
 *
 * @global object
 * @param user $user A {@link $USER} object
 * @return bool|string Returns "true" if mail was sent OK, "emailstop" if email
 *          was blocked by user and "false" if there was another sort of error.
 */
function send_password_change_confirmation_email($user) {
    global $CFG;

    $site = get_site();
    $supportuser = generate_email_supportuser();

    $data = new object();
    $data->firstname = $user->firstname;
    $data->lastname  = $user->lastname;
    $data->sitename  = format_string($site->fullname);
    $data->link      = $CFG->httpswwwroot .'/login/forgot_password.php?p='. $user->secret .'&s='. urlencode($user->username);
    $data->admin     = generate_email_signoff();

    $message = get_string('emailpasswordconfirmation', '', $data);
    $subject = get_string('emailpasswordconfirmationsubject', '', format_string($site->fullname));

    return email_to_user($user, $supportuser, $subject, $message);

}

/**
 * send_password_change_info.
 *
 * @global object
 * @param user $user A {@link $USER} object
 * @return bool|string Returns "true" if mail was sent OK, "emailstop" if email
 *          was blocked by user and "false" if there was another sort of error.
 */
function send_password_change_info($user) {
    global $CFG;

    $site = get_site();
    $supportuser = generate_email_supportuser();
    $systemcontext = get_context_instance(CONTEXT_SYSTEM);

    $data = new object();
    $data->firstname = $user->firstname;
    $data->lastname  = $user->lastname;
    $data->sitename  = format_string($site->fullname);
    $data->admin     = generate_email_signoff();

    $userauth = get_auth_plugin($user->auth);

    if (!is_enabled_auth($user->auth) or $user->auth == 'nologin') {
        $message = get_string('emailpasswordchangeinfodisabled', '', $data);
        $subject = get_string('emailpasswordchangeinfosubject', '', format_string($site->fullname));
        return email_to_user($user, $supportuser, $subject, $message);
    }

    if ($userauth->can_change_password() and $userauth->change_password_url()) {
        // we have some external url for password changing
        $data->link .= $userauth->change_password_url();

    } else {
        //no way to change password, sorry
        $data->link = '';
    }

    if (!empty($data->link) and has_capability('moodle/user:changeownpassword', $systemcontext, $user->id)) {
        $message = get_string('emailpasswordchangeinfo', '', $data);
        $subject = get_string('emailpasswordchangeinfosubject', '', format_string($site->fullname));
    } else {
        $message = get_string('emailpasswordchangeinfofail', '', $data);
        $subject = get_string('emailpasswordchangeinfosubject', '', format_string($site->fullname));
    }

    return email_to_user($user, $supportuser, $subject, $message);

}

/**
 * Check that an email is allowed.  It returns an error message if there
 * was a problem.
 *
 * @global object
 * @param  string $email Content of email
 * @return string|false
 */
function email_is_not_allowed($email) {
    global $CFG;

    if (!empty($CFG->allowemailaddresses)) {
        $allowed = explode(' ', $CFG->allowemailaddresses);
        foreach ($allowed as $allowedpattern) {
            $allowedpattern = trim($allowedpattern);
            if (!$allowedpattern) {
                continue;
            }
            if (strpos($allowedpattern, '.') === 0) {
                if (strpos(strrev($email), strrev($allowedpattern)) === 0) {
                    // subdomains are in a form ".example.com" - matches "xxx@anything.example.com"
                    return false;
                }

            } else if (strpos(strrev($email), strrev('@'.$allowedpattern)) === 0) { // Match!   (bug 5250)
                return false;
            }
        }
        return get_string('emailonlyallowed', '', $CFG->allowemailaddresses);

    } else if (!empty($CFG->denyemailaddresses)) {
        $denied = explode(' ', $CFG->denyemailaddresses);
        foreach ($denied as $deniedpattern) {
            $deniedpattern = trim($deniedpattern);
            if (!$deniedpattern) {
                continue;
            }
            if (strpos($deniedpattern, '.') === 0) {
                if (strpos(strrev($email), strrev($deniedpattern)) === 0) {
                    // subdomains are in a form ".example.com" - matches "xxx@anything.example.com"
                    return get_string('emailnotallowed', '', $CFG->denyemailaddresses);
                }

            } else if (strpos(strrev($email), strrev('@'.$deniedpattern)) === 0) { // Match!   (bug 5250)
                return get_string('emailnotallowed', '', $CFG->denyemailaddresses);
            }
        }
    }

    return false;
}

/**
 * Send welcome email to specified user
 *
 * @global object
 * @global object
 * @param object $course
 * @param user $user A {@link $USER} object
 * @return bool
 */
function email_welcome_message_to_user($course, $user=NULL) {
    global $CFG, $USER;

    if (isset($CFG->sendcoursewelcomemessage) and !$CFG->sendcoursewelcomemessage) {
        return;
    }

    if (empty($user)) {
        if (!isloggedin()) {
            return false;
        }
        $user = $USER;
    }

    if (!empty($course->welcomemessage)) {
        $message = $course->welcomemessage;
    } else {
        $a = new object();
        $a->coursename = $course->fullname;
        $a->profileurl = "$CFG->wwwroot/user/view.php?id=$user->id&course=$course->id";
        $message = get_string("welcometocoursetext", "", $a);
    }

    /// If you don't want a welcome message sent, then make the message string blank.
    if (!empty($message)) {
        $subject = get_string('welcometocourse', '', format_string($course->fullname));

         $context = get_context_instance(CONTEXT_COURSE, $course->id);
        // TODO: replace with $CFG->coursemanager test, 'moodle/course:update' is very wrong!!
        if ($users = get_users_by_capability($context, 'moodle/course:update', 'u.*', 'u.id ASC','', '', '', '', false, true)) {
            $users = sort_by_roleassignment_authority($users, $context);
            $teacher = array_shift($users);
        } else {
            $teacher = get_admin();
        }
        email_to_user($user, $teacher, $subject, $message);
    }
}

/// FILE HANDLING  /////////////////////////////////////////////

/**
 * Returns local file storage instance
 *
 * @return file_storage
 */
function get_file_storage() {
    global $CFG;

    static $fs = null;

    if ($fs) {
        return $fs;
    }

    require_once("$CFG->libdir/filelib.php");

    if (isset($CFG->filedir)) {
        $filedir = $CFG->filedir;
    } else {
        $filedir = $CFG->dataroot.'/filedir';
    }

    if (isset($CFG->trashdir)) {
        $trashdirdir = $CFG->trashdir;
    } else {
        $trashdirdir = $CFG->dataroot.'/trashdir';
    }

    $fs = new file_storage($filedir, $trashdirdir, $CFG->directorypermissions, $CFG->filepermissions);

    return $fs;
}

/**
 * Returns local file storage instance
 *
 * @return file_browser
 */
function get_file_browser() {
    global $CFG;

    static $fb = null;

    if ($fb) {
        return $fb;
    }

    require_once("$CFG->libdir/filelib.php");

    $fb = new file_browser();

    return $fb;
}

/**
 * Returns file packer
 *
 * @param string $mimetype default application/zip
 * @return file_packer
 */
function get_file_packer($mimetype='application/zip') {
    global $CFG;

    static $fp = array();;

    if (isset($fp[$mimetype])) {
        return $fp[$mimetype];
    }

    switch ($mimetype) {
        case 'application/zip':
            $classname = 'zip_packer';
            break;
        case 'application/x-tar':
//            $classname = 'tar_packer';
//            break;
        default:
            return false;
    }

    require_once("$CFG->libdir/packer/$classname.php");
    $fp[$mimetype] = new $classname();

    return $fp[$mimetype];
}

/**
 * Makes a directory for a particular user.
 *
 * @global object
 * @param int $userid The id of the user in question - maps to id field of 'user' table.
 * @param bool $test Whether we are only testing the return value (do not create the directory)
 * @return string|false Returns full path to directory if successful, false if not
 */
function make_user_directory($userid, $test=false) {
    global $CFG, $OUTPUT;

    if (is_bool($userid) || $userid < 0 || !preg_match('/^[0-9]{1,10}$/', $userid) || $userid > 2147483647) {
        if (!$test) {
            echo $OUTPUT->notification("Given userid was not a valid integer! (" . gettype($userid) . " $userid)");
        }
        return false;
    }

    // Generate a two-level path for the userid. First level groups them by slices of 1000 users, second level is userid
    $level1 = floor($userid / 1000) * 1000;

    $userdir = "user/$level1/$userid";
    if ($test) {
        return $CFG->dataroot . '/' . $userdir;
    } else {
        return make_upload_directory($userdir);
    }
}

/**
 * Returns an array of full paths to user directories, indexed by their userids.
 *
 * @global object
 * @param bool $only_non_empty Only return directories that contain files
 * @param bool $legacy Search for user directories in legacy location (dataroot/users/userid) instead of (dataroot/user/section/userid)
 * @return array An associative array: userid=>array(basedir => $basedir, userfolder => $userfolder)
 */
function get_user_directories($only_non_empty=true, $legacy=false) {
    global $CFG, $OUTPUT;

    $rootdir = $CFG->dataroot."/user";

    if ($legacy) {
        $rootdir = $CFG->dataroot."/users";
    }
    $dirlist = array();

    //Check if directory exists
    if (check_dir_exists($rootdir, true)) {
        if ($legacy) {
            if ($userlist = get_directory_list($rootdir, '', true, true, false)) {
                foreach ($userlist as $userid) {
                    $dirlist[$userid] = array('basedir' => $rootdir, 'userfolder' => $userid);
                }
            } else {
                echo $OUTPUT->notification("no directories found under $rootdir");
            }
        } else {
            if ($grouplist =get_directory_list($rootdir, '', true, true, false)) { // directories will be in the form 0, 1000, 2000 etc...
                foreach ($grouplist as $group) {
                    if ($userlist = get_directory_list("$rootdir/$group", '', true, true, false)) {
                        foreach ($userlist as $userid) {
                            $dirlist[$userid] = array('basedir' => $rootdir, 'userfolder' => $group . '/' . $userid);
                        }
                    }
                }
            }
        }
    } else {
        echo $OUTPUT->notification("$rootdir does not exist!");
        return false;
    }
    return $dirlist;
}

/**
 * Returns current name of file on disk if it exists.
 *
 * @param string $newfile File to be verified
 * @return string Current name of file on disk if true
 */
function valid_uploaded_file($newfile) {
    if (empty($newfile)) {
        return '';
    }
    if (is_uploaded_file($newfile['tmp_name']) and $newfile['size'] > 0) {
        return $newfile['tmp_name'];
    } else {
        return '';
    }
}

/**
 * Returns the maximum size for uploading files.
 *
 * There are seven possible upload limits:
 * 1. in Apache using LimitRequestBody (no way of checking or changing this)
 * 2. in php.ini for 'upload_max_filesize' (can not be changed inside PHP)
 * 3. in .htaccess for 'upload_max_filesize' (can not be changed inside PHP)
 * 4. in php.ini for 'post_max_size' (can not be changed inside PHP)
 * 5. by the Moodle admin in $CFG->maxbytes
 * 6. by the teacher in the current course $course->maxbytes
 * 7. by the teacher for the current module, eg $assignment->maxbytes
 *
 * These last two are passed to this function as arguments (in bytes).
 * Anything defined as 0 is ignored.
 * The smallest of all the non-zero numbers is returned.
 *
 * @todo Finish documenting this function
 *
 * @param int $sizebytes Set maximum size
 * @param int $coursebytes Current course $course->maxbytes (in bytes)
 * @param int $modulebytes Current module ->maxbytes (in bytes)
 * @return int The maximum size for uploading files.
 */
function get_max_upload_file_size($sitebytes=0, $coursebytes=0, $modulebytes=0) {

    if (! $filesize = ini_get('upload_max_filesize')) {
        $filesize = '5M';
    }
    $minimumsize = get_real_size($filesize);

    if ($postsize = ini_get('post_max_size')) {
        $postsize = get_real_size($postsize);
        if ($postsize < $minimumsize) {
            $minimumsize = $postsize;
        }
    }

    if ($sitebytes and $sitebytes < $minimumsize) {
        $minimumsize = $sitebytes;
    }

    if ($coursebytes and $coursebytes < $minimumsize) {
        $minimumsize = $coursebytes;
    }

    if ($modulebytes and $modulebytes < $minimumsize) {
        $minimumsize = $modulebytes;
    }

    return $minimumsize;
}

/**
 * Returns an array of possible sizes in local language
 *
 * Related to {@link get_max_upload_file_size()} - this function returns an
 * array of possible sizes in an array, translated to the
 * local language.
 *
 * @todo Finish documenting this function
 *
 * @global object
 * @uses SORT_NUMERIC
 * @param int $sizebytes Set maximum size
 * @param int $coursebytes Current course $course->maxbytes (in bytes)
 * @param int $modulebytes Current module ->maxbytes (in bytes)
 * @return int
 */
function get_max_upload_sizes($sitebytes=0, $coursebytes=0, $modulebytes=0) {
    global $CFG;

    if (!$maxsize = get_max_upload_file_size($sitebytes, $coursebytes, $modulebytes)) {
        return array();
    }

    $filesize[$maxsize] = display_size($maxsize);

    $sizelist = array(10240, 51200, 102400, 512000, 1048576, 2097152,
                      5242880, 10485760, 20971520, 52428800, 104857600);

    // Allow maxbytes to be selected if it falls outside the above boundaries
    if( isset($CFG->maxbytes) && !in_array($CFG->maxbytes, $sizelist) ){
            $sizelist[] = $CFG->maxbytes;
    }

    foreach ($sizelist as $sizebytes) {
       if ($sizebytes < $maxsize) {
           $filesize[$sizebytes] = display_size($sizebytes);
       }
    }

    krsort($filesize, SORT_NUMERIC);

    return $filesize;
}

/**
 * If there has been an error uploading a file, print the appropriate error message
 * Numerical constants used as constant definitions not added until PHP version 4.2.0
 *
 * $filearray is a 1-dimensional sub-array of the $_FILES array
 * eg $filearray = $_FILES['userfile1']
 * If left empty then the first element of the $_FILES array will be used
 *
 * @uses $_FILES
 * @param array $filearray  A 1-dimensional sub-array of the $_FILES array
 * @param bool $returnerror If true then a string error message will be returned. Otherwise the user will be notified of the error in a notify() call.
 * @return bool|string
 */
function print_file_upload_error($filearray = '', $returnerror = false) {
    global $OUTPUT;
    if ($filearray == '' or !isset($filearray['error'])) {

        if (empty($_FILES)) return false;

        $files = $_FILES; /// so we don't mess up the _FILES array for subsequent code
        $filearray = array_shift($files); /// use first element of array
    }

    switch ($filearray['error']) {

        case 0: // UPLOAD_ERR_OK
            if ($filearray['size'] > 0) {
                $errmessage = get_string('uploadproblem', $filearray['name']);
            } else {
                $errmessage = get_string('uploadnofilefound'); /// probably a dud file name
            }
            break;

        case 1: // UPLOAD_ERR_INI_SIZE
            $errmessage = get_string('uploadserverlimit');
            break;

        case 2: // UPLOAD_ERR_FORM_SIZE
            $errmessage = get_string('uploadformlimit');
            break;

        case 3: // UPLOAD_ERR_PARTIAL
            $errmessage = get_string('uploadpartialfile');
            break;

        case 4: // UPLOAD_ERR_NO_FILE
            $errmessage = get_string('uploadnofilefound');
            break;

        default:
            $errmessage = get_string('uploadproblem', $filearray['name']);
    }

    if ($returnerror) {
        return $errmessage;
    } else {
        echo $OUTPUT->notification($errmessage);
        return true;
    }

}

/**
 * Handy function for resolving file conflicts
 *
 * handy function to loop through an array of files and resolve any filename conflicts
 * both in the array of filenames and for what is already on disk.
 * not really compatible with the similar function in uploadlib.php
 * but this could be used for files/index.php for moving files around.
 * @see check_potential_filename()
 *
 * @param string $destincation destincation folder
 * @param array $files
 * @param string $format
 * @return array Array of now resolved file names
 */

function resolve_filename_collisions($destination,$files,$format='%s_%d.%s') {
    foreach ($files as $k => $f) {
        if (check_potential_filename($destination,$f,$files)) {
            $bits = explode('.', $f);
            for ($i = 1; true; $i++) {
                $try = sprintf($format, $bits[0], $i, $bits[1]);
                if (!check_potential_filename($destination,$try,$files)) {
                    $files[$k] = $try;
                    break;
                }
            }
        }
    }
    return $files;
}

/**
 * Checks a file name for any conflicts
 * @see resolve_filename_collisions()
 *
 * @param string $destination Destination directory
 * @param string $filename Desired filename
 * @param array $files Array of other file naems to check against
 */
function check_potential_filename($destination,$filename,$files) {
    if (file_exists($destination.'/'.$filename)) {
        return true;
    }
    if (count(array_keys($files,$filename)) > 1) {
        return true;
    }
    return false;
}


/**
 * Returns an array with all the filenames in all subdirectories, relative to the given rootdir.
 *
 * If excludefile is defined, then that file/directory is ignored
 * If getdirs is true, then (sub)directories are included in the output
 * If getfiles is true, then files are included in the output
 * (at least one of these must be true!)
 *
 * @todo Finish documenting this function. Add examples of $excludefile usage.
 *
 * @param string $rootdir A given root directory to start from
 * @param string|array $excludefile If defined then the specified file/directory is ignored
 * @param bool $descend If true then subdirectories are recursed as well
 * @param bool $getdirs If true then (sub)directories are included in the output
 * @param bool $getfiles  If true then files are included in the output
 * @return array An array with all the filenames in
 * all subdirectories, relative to the given rootdir
 */
function get_directory_list($rootdir, $excludefiles='', $descend=true, $getdirs=false, $getfiles=true) {

    $dirs = array();

    if (!$getdirs and !$getfiles) {   // Nothing to show
        return $dirs;
    }

    if (!is_dir($rootdir)) {          // Must be a directory
        return $dirs;
    }

    if (!$dir = opendir($rootdir)) {  // Can't open it for some reason
        return $dirs;
    }

    if (!is_array($excludefiles)) {
        $excludefiles = array($excludefiles);
    }

    while (false !== ($file = readdir($dir))) {
        $firstchar = substr($file, 0, 1);
        if ($firstchar == '.' or $file == 'CVS' or in_array($file, $excludefiles)) {
            continue;
        }
        $fullfile = $rootdir .'/'. $file;
        if (filetype($fullfile) == 'dir') {
            if ($getdirs) {
                $dirs[] = $file;
            }
            if ($descend) {
                $subdirs = get_directory_list($fullfile, $excludefiles, $descend, $getdirs, $getfiles);
                foreach ($subdirs as $subdir) {
                    $dirs[] = $file .'/'. $subdir;
                }
            }
        } else if ($getfiles) {
            $dirs[] = $file;
        }
    }
    closedir($dir);

    asort($dirs);

    return $dirs;
}


/**
 * Adds up all the files in a directory and works out the size.
 *
 * @todo Finish documenting this function
 *
 * @param string $rootdir  The directory to start from
 * @param string $excludefile A file to exclude when summing directory size
 * @return int The summed size of all files and subfiles within the root directory
 */
function get_directory_size($rootdir, $excludefile='') {
    global $CFG;

    // do it this way if we can, it's much faster
    if (!empty($CFG->pathtodu) && is_executable(trim($CFG->pathtodu))) {
        $command = trim($CFG->pathtodu).' -sk '.escapeshellarg($rootdir);
        $output = null;
        $return = null;
        exec($command,$output,$return);
        if (is_array($output)) {
            return get_real_size(intval($output[0]).'k'); // we told it to return k.
        }
    }

    if (!is_dir($rootdir)) {          // Must be a directory
        return 0;
    }

    if (!$dir = @opendir($rootdir)) {  // Can't open it for some reason
        return 0;
    }

    $size = 0;

    while (false !== ($file = readdir($dir))) {
        $firstchar = substr($file, 0, 1);
        if ($firstchar == '.' or $file == 'CVS' or $file == $excludefile) {
            continue;
        }
        $fullfile = $rootdir .'/'. $file;
        if (filetype($fullfile) == 'dir') {
            $size += get_directory_size($fullfile, $excludefile);
        } else {
            $size += filesize($fullfile);
        }
    }
    closedir($dir);

    return $size;
}

/**
 * Converts bytes into display form
 *
 * @todo Finish documenting this function. Verify return type.
 *
 * @staticvar string $gb Localized string for size in gigabytes
 * @staticvar string $mb Localized string for size in megabytes
 * @staticvar string $kb Localized string for size in kilobytes
 * @staticvar string $b Localized string for size in bytes
 * @param int $size  The size to convert to human readable form
 * @return string
 */
function display_size($size) {

    static $gb, $mb, $kb, $b;

    if (empty($gb)) {
        $gb = get_string('sizegb');
        $mb = get_string('sizemb');
        $kb = get_string('sizekb');
        $b  = get_string('sizeb');
    }

    if ($size >= 1073741824) {
        $size = round($size / 1073741824 * 10) / 10 . $gb;
    } else if ($size >= 1048576) {
        $size = round($size / 1048576 * 10) / 10 . $mb;
    } else if ($size >= 1024) {
        $size = round($size / 1024 * 10) / 10 . $kb;
    } else {
        $size = $size .' '. $b;
    }
    return $size;
}

/**
 * Cleans a given filename by removing suspicious or troublesome characters
 * @see clean_param()
 *
 * @uses PARAM_FILE
 * @param string $string  file name
 * @return string cleaned file name
 */
function clean_filename($string) {
    return clean_param($string, PARAM_FILE);
}


/// STRING TRANSLATION  ////////////////////////////////////////

/**
 * Returns the code for the current language
 *
 * @return string
 */
function current_language() {
    global $CFG, $USER, $SESSION, $COURSE;

    if (!empty($COURSE->id) and $COURSE->id != SITEID and !empty($COURSE->lang)) {    // Course language can override all other settings for this page
        $return = $COURSE->lang;

    } else if (!empty($SESSION->lang)) {    // Session language can override other settings
        $return = $SESSION->lang;

    } else if (!empty($USER->lang)) {
        $return = $USER->lang;

    } else if (isset($CFG->lang)) {
        $return = $CFG->lang;

    } else {
        $return = 'en';
    }

    return $return;
}

/**
 * Returns parent language of current active language if defined
 *
 * @uses COURSE
 * @uses SESSION
 * @param string $lang null means current language
 * @return string
 */
function get_parent_language($lang=null) {
    global $COURSE, $SESSION;

    //let's hack around the current language
    if (!empty($lang)) {
        $old_course_lang  = empty($COURSE->lang) ? '' : $COURSE->lang;
        $old_session_lang = empty($SESSION->lang) ? '' : $SESSION->lang;
        $COURSE->lang  = '';
        $SESSION->lang = $lang;
    }

    $parentlang = get_string('parentlanguage', 'langconfig');
    if ($parentlang === 'en') {
        $parentlang = '';
    }

    //let's hack around the current language
    if (!empty($lang)) {
        $COURSE->lang  = $old_course_lang;
        $SESSION->lang = $old_session_lang;
    }

    return $parentlang;
}

/**
 * Returns current string_manager instance.
 * @return string_manager
 */
function get_string_manager() {
    global $CFG;

    static $singleton = null;

    if ($singleton === null) {
        if (empty($CFG->early_install_lang)) {
            $singleton = new core_string_manager($CFG->langotherroot, $CFG->langlocalroot);
        } else {
            $singleton = new install_string_manager();
        }
    }

    return $singleton;
}


/**
 * Interface describing class which is responsible for getting
 * of localised strings from language packs.
 *
 * @package    moodlecore
 * @copyright  2010 Petr Skoda (http://skodak.org)
 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */
interface string_manager {
    /**
     * Get String returns a requested string
     *
     * @param string $identifier The identifier of the string to search for
     * @param string $component The module the string is associated with
     * @param string|object|array $a An object, string or number that can be used
     *      within translation strings
     * @param string $lang moodle translation language, NULL means use current
     * @return string The String !
     */
    public function get_string($identifier, $component = '', $a = NULL, $lang = NULL);

    /**
     * Does the string actually exist?
     *
     * get_string() is throwing debug warnings, sometimes we do not want them
     * or we want to display better explanation of the problem.
     *
     * Use with care!
     *
     * @param string $identifier The identifier of the string to search for
     * @param string $component The module the string is associated with
     * @return boot true if exists
     */
    public function string_exists($identifier, $component);

    /**
     * Returns a localised list of all country names, sorted by country keys.
     * @param bool $returnall return all or just enabled
     * @param string $lang moodle translation language, NULL means use current
     * @return array two-letter country code => translated name.
     */
    public function get_list_of_countries($returnall = false, $lang = NULL);

    /**
     * Returns a localised list of languages, sorted by code keys.
     *
     * @param string $lang moodle translation language, NULL means use current
     * @param string $standard language list standard
     *                     iso6392: three-letter language code (ISO 639-2/T) => translated name.
     * @return array language code => translated name
     */
    public function get_list_of_languages($lang = NULL, $standard = 'iso6392');

    /**
     * Does the translation exist?
     *
     * @param string $lang moodle translation language code
     * @param bool include also disabled translations?
     * @return boot true if exists
     */
    public function translation_exists($lang, $includeall = true);

    /**
     * Returns localised list of installed translations
     * @param bool $returnall return all or just enabled
     * @return array moodle translation code => localised translation name
     */
    public function get_list_of_translations($returnall = false);

    /**
     * Returns localised list of currencies.
     *
     * @param string $lang moodle translation language, NULL means use current
     * @return array currency code => localised currency name
     */
    public function get_list_of_currencies($lang = NULL);

    /**
     * Load all strings for one component
     * @param string $component The module the string is associated with
     * @param string $lang
     * @return array of all string for given component and lang
     */
    public function load_component_strings($component, $lang);
}


/**
 * Standard string_manager implementation
 *
 * TODO: implement lang precompilation
 *
 * @package    moodlecore
 * @copyright  2010 Petr Skoda (http://skodak.org)
 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */
class core_string_manager implements string_manager {
    /** @var string location of all packs except 'en' */
    protected $otherroot;
    /** @var string location of all lang pack local modifications */
    protected $localroot;

    /** @var array lang string cache - it will be optimised more later */
    protected $cache = array();

    /**
     * Crate new instance of amos string manager
     *
     * @param string $otherroot location of downlaoded lang packs - usually $CFG->dataroot/lang
     * @param string $localroot usually the same as $otherroot
     */
    public function __construct($otherroot, $localroot) {
        $this->otherroot  = $otherroot;
        $this->localroot  = $localroot;
    }

    /**
     * Returns dependencies of current language, en is not included.
     * @param string $lang
     * @return array all parents, the lang itself is last
     */
    public function get_language_dependencies($lang) {
        if ($lang === 'en') {
            return array();
        }
        if (!file_exists("$this->otherroot/$lang/langconfig.php")) {
            return array();
        }
        $string = array();
        include("$this->otherroot/$lang/langconfig.php");

        if (empty($string['parentlanguage'])) {
            return array($lang);
        } else {
            $parentlang = $string['parentlanguage'];
            unset($string);
            return array_merge($this->get_language_dependencies($parentlang), array($lang));
        }
    }

    /**
     * Load all strings for one component
     * @param string $component The module the string is associated with
     * @param string $lang
     * @return array of all string for given component and lang
     */
    public function load_component_strings($component, $lang) {
        global $CFG;

        list($plugintype, $pluginname) = normalize_component($component);

        if (!isset($this->cache[$lang])) {
            $this->cache[$lang] = array();
        }

        if (isset($this->cache[$lang][$plugintype.$pluginname])) {
            return $this->cache[$lang][$plugintype.$pluginname];
        }

        if ($plugintype === 'core') {
            $file = $pluginname;
            if ($file === null) {
                $file = 'moodle';
            }
            $string = array();
            // first load english pack
            if (!file_exists("$CFG->dirroot/lang/en/$file.php")) {
                return array();
            }
            include("$CFG->dirroot/lang/en/$file.php");
            $originalkeys = array_keys($string);
            $originalkeys = array_flip($originalkeys);

            // and then corresponding local if present
            if (file_exists("$this->localroot/en_local/$file.php")) {
                include("$this->localroot/en_local/$file.php");
            }
            // now loop through all langs in correct order
            $deps = $this->get_language_dependencies($lang);
            foreach ($deps as $dep) {
                // the main lang string location
                if (file_exists("$this->otherroot/$dep/$file.php")) {
                    include("$this->otherroot/$dep/$file.php");
                }
                if (file_exists("$this->localroot/{$dep}_local/$file.php")) {
                    include("$this->localroot/{$dep}_local/$file.php");
                }
            }

        } else {
            if (!$location = get_plugin_directory($plugintype, $pluginname) or !is_dir($location)) {
                return array();
            }
            if ($plugintype === 'mod') {
                // bloody mod hack
                $file = $pluginname;
            } else {
                $file = $plugintype . '_' . $pluginname;
            }
            $string = array();
            // first load english pack
            if (!file_exists("$location/lang/en/$file.php")) {
                //english pack does not exist, so do not try to load anything else
                return array();
            }
            include("$location/lang/en/$file.php");
            $originalkeys = array_keys($string);
            $originalkeys = array_flip($originalkeys);

            // now loop through all langs in correct order
            $deps = $this->get_language_dependencies($lang);
            foreach ($deps as $dep) {
                // legacy location - used by contrib only
                if (file_exists("$location/lang/$dep/$file.php")) {
                    include("$location/lang/$dep/$file.php");
                }
                // the main lang string location
                if (file_exists("$this->otherroot/$dep/$file.php")) {
                    include("$this->otherroot/$dep/$file.php");
                }
                // local customisations
                if (file_exists("$this->localroot/{$dep}_local/$file.php")) {
                    include("$this->localroot/{$dep}_local/$file.php");
                }
            }
        }

        // we do not want any extra strings from other languages - everything must be in en lang pack
        $string = array_intersect_key($string, $originalkeys);

        $this->cache[$lang][$plugintype.$pluginname] = $string;

        return $string;
    }

    /**
     * Does the string actually exist?
     *
     * get_string() is throwing debug warnings, sometimes we do not want them
     * or we want to display better explanation of the problem.
     *
     * Use with care!
     *
     * @param string $identifier The identifier of the string to search for
     * @param string $component The module the string is associated with
     * @return boot true if exists
     */
    public function string_exists($identifier, $component) {
        $lang = current_language();
        $string = $this->load_component_strings($component, $lang);
        return isset($string[$identifier]);
    }

    /**
     * Get String returns a requested string
     *
     * @param string $identifier The identifier of the string to search for
     * @param string $component The module the string is associated with
     * @param string|object|array $a An object, string or number that can be used
     *      within translation strings
     * @param string $lang moodle translation language, NULL means use current
     * @return string The String !
     */
    public function get_string($identifier, $component = '', $a = NULL, $lang = NULL) {
        // there are very many uses of these time formating strings without the 'langconfig' component,
        // it would not be reasonable to expect that all of them would be converted during 2.0 migration
        static $langconfigstrs = array(
                'strftimedate' => 1,
                'strftimedatefullshort' => 1,
                'strftimedateshort' => 1,
                'strftimedatetime' => 1,
                'strftimedatetimeshort' => 1,
                'strftimedaydate' => 1,
                'strftimedaydatetime' => 1,
                'strftimedayshort' => 1,
                'strftimedaytime' => 1,
                'strftimemonthyear' => 1,
                'strftimerecent' => 1,
                'strftimerecentfull' => 1,
                'strftimetime' => 1);

        if (empty($component)) {
            if (isset($langconfigstrs[$identifier])) {
                $component = 'langconfig';
            } else {
                $component = 'moodle';
            }
        }

        if ($lang === NULL) {
            $lang = current_language();
        }

        $string = $this->load_component_strings($component, $lang);

        if (!isset($string[$identifier])) {
            if ($component === 'pix' or $component === 'core_pix') {
                // this component contains only alt tags for emoticons,
                // not all of them are supposed to be defined
                return '';
            }
            if ($identifier === 'parentlanguage' and ($component === 'langconfig' or $component === 'core_langconfig')) {
                // parentlanguage is a special string, undefined means use english if not defined
                return 'en';
            }
            debugging("Invalid get_string() identifier: '$identifier' or component '$component'", DEBUG_DEVELOPER);
            return "[[$identifier]]";
        }

        $string = $string[$identifier];

        if ($a !== NULL) {
            if (is_object($a) or is_array($a)) {
                $a = (array)$a;
                $search = array();
                $replace = array();
                foreach ($a as $key=>$value) {
                    if (is_int($key)) {
                        // we do not support numeric keys - sorry!
                        continue;
                    }
                    if (is_object($value) or is_array($value)) {
                        // we support just string as value
                        continue;
                    }
                    $search[]  = '{$a->'.$key.'}';
                    $replace[] = (string)$value;
                }
                if ($search) {
                    $string = str_replace($search, $replace, $string);
                }
            } else {
                $string = str_replace('{$a}', (string)$a, $string);
            }
        }

        return $string;
    }

    /**
     * Returns a localised list of all country names, sorted by country keys.
     *
     * @param bool $returnall return all or just enabled
     * @param string $lang moodle translation language, NULL means use current
     * @return array two-letter country code => translated name.
     */
    public function get_list_of_countries($returnall = false, $lang = NULL) {
        global $CFG;

        if ($lang === NULL) {
            $lang = current_language();
        }

        $countries = $this->load_component_strings('core_countries', $lang);
        ksort($countries);

        if (!$returnall and !empty($CFG->allcountrycodes)) {
            $enabled = explode(',', $CFG->allcountrycodes);
            $return = array();
            foreach ($enabled as $c) {
                if (isset($countries[$c])) {
                    $return[$c] = $countries[$c];
                }
            }
            return $return;
        }

        return $countries;
    }

    /**
     * Returns a localised list of languages, sorted by code keys.
     *
     * @param string $lang moodle translation language, NULL means use current
     * @param string $standard language list standard
     *    - iso6392: three-letter language code (ISO 639-2/T) => translated name
     *    - iso6391: two-letter langauge code (ISO 639-1) => translated name
     * @return array language code => translated name
     */
    public function get_list_of_languages($lang = NULL, $standard = 'iso6391') {
        if ($lang === NULL) {
            $lang = current_language();
        }

        if ($standard === 'iso6392') {
            $langs = $this->load_component_strings('core_iso6392', $lang);
            ksort($langs);
            return $langs;

        } else if ($standard === 'iso6391') {
            $langs2 = $this->load_component_strings('core_iso6392', $lang);
            static $mapping = array('aar' => 'aa', 'abk' => 'ab', 'afr' => 'af', 'aka' => 'ak', 'sqi' => 'sq', 'amh' => 'am', 'ara' => 'ar', 'arg' => 'an', 'hye' => 'hy',
                'asm' => 'as', 'ava' => 'av', 'ave' => 'ae', 'aym' => 'ay', 'aze' => 'az', 'bak' => 'ba', 'bam' => 'bm', 'eus' => 'eu', 'bel' => 'be', 'ben' => 'bn', 'bih' => 'bh',
                'bis' => 'bi', 'bos' => 'bs', 'bre' => 'br', 'bul' => 'bg', 'mya' => 'my', 'cat' => 'ca', 'cha' => 'ch', 'che' => 'ce', 'zho' => 'zh', 'chu' => 'cu', 'chv' => 'cv',
                'cor' => 'kw', 'cos' => 'co', 'cre' => 'cr', 'ces' => 'cs', 'dan' => 'da', 'div' => 'dv', 'nld' => 'nl', 'dzo' => 'dz', 'eng' => 'en', 'epo' => 'eo', 'est' => 'et',
                'ewe' => 'ee', 'fao' => 'fo', 'fij' => 'fj', 'fin' => 'fi', 'fra' => 'fr', 'fry' => 'fy', 'ful' => 'ff', 'kat' => 'ka', 'deu' => 'de', 'gla' => 'gd', 'gle' => 'ga',
                'glg' => 'gl', 'glv' => 'gv', 'ell' => 'el', 'grn' => 'gn', 'guj' => 'gu', 'hat' => 'ht', 'hau' => 'ha', 'heb' => 'he', 'her' => 'hz', 'hin' => 'hi', 'hmo' => 'ho',
                'hrv' => 'hr', 'hun' => 'hu', 'ibo' => 'ig', 'isl' => 'is', 'ido' => 'io', 'iii' => 'ii', 'iku' => 'iu', 'ile' => 'ie', 'ina' => 'ia', 'ind' => 'id', 'ipk' => 'ik',
                'ita' => 'it', 'jav' => 'jv', 'jpn' => 'ja', 'kal' => 'kl', 'kan' => 'kn', 'kas' => 'ks', 'kau' => 'kr', 'kaz' => 'kk', 'khm' => 'km', 'kik' => 'ki', 'kin' => 'rw',
                'kir' => 'ky', 'kom' => 'kv', 'kon' => 'kg', 'kor' => 'ko', 'kua' => 'kj', 'kur' => 'ku', 'lao' => 'lo', 'lat' => 'la', 'lav' => 'lv', 'lim' => 'li', 'lin' => 'ln',
                'lit' => 'lt', 'ltz' => 'lb', 'lub' => 'lu', 'lug' => 'lg', 'mkd' => 'mk', 'mah' => 'mh', 'mal' => 'ml', 'mri' => 'mi', 'mar' => 'mr', 'msa' => 'ms', 'mlg' => 'mg',
                'mlt' => 'mt', 'mon' => 'mn', 'nau' => 'na', 'nav' => 'nv', 'nbl' => 'nr', 'nde' => 'nd', 'ndo' => 'ng', 'nep' => 'ne', 'nno' => 'nn', 'nob' => 'nb', 'nor' => 'no',
                'nya' => 'ny', 'oci' => 'oc', 'oji' => 'oj', 'ori' => 'or', 'orm' => 'om', 'oss' => 'os', 'pan' => 'pa', 'fas' => 'fa', 'pli' => 'pi', 'pol' => 'pl', 'por' => 'pt',
                'pus' => 'ps', 'que' => 'qu', 'roh' => 'rm', 'ron' => 'ro', 'run' => 'rn', 'rus' => 'ru', 'sag' => 'sg', 'san' => 'sa', 'sin' => 'si', 'slk' => 'sk', 'slv' => 'sl',
                'sme' => 'se', 'smo' => 'sm', 'sna' => 'sn', 'snd' => 'sd', 'som' => 'so', 'sot' => 'st', 'spa' => 'es', 'srd' => 'sc', 'srp' => 'sr', 'ssw' => 'ss', 'sun' => 'su',
                'swa' => 'sw', 'swe' => 'sv', 'tah' => 'ty', 'tam' => 'ta', 'tat' => 'tt', 'tel' => 'te', 'tgk' => 'tg', 'tgl' => 'tl', 'tha' => 'th', 'bod' => 'bo', 'tir' => 'ti',
                'ton' => 'to', 'tsn' => 'tn', 'tso' => 'ts', 'tuk' => 'tk', 'tur' => 'tr', 'twi' => 'tw', 'uig' => 'ug', 'ukr' => 'uk', 'urd' => 'ur', 'uzb' => 'uz', 'ven' => 've',
                'vie' => 'vi', 'vol' => 'vo', 'cym' => 'cy', 'wln' => 'wa', 'wol' => 'wo', 'xho' => 'xh', 'yid' => 'yi', 'yor' => 'yo', 'zha' => 'za', 'zul' => 'zu');
            $langs1 = array();
            foreach ($mapping as $c2=>$c1) {
                $langs1[$c1] = $langs2[$c2];
            }
            ksort($langs1);
            return $langs1;

        } else {
            debugging('Unsupported $standard parameter in get_list_of_languages() method: '.$standard);
        }

        return array();
    }

    /**
     * Does the translation exist?
     *
     * @param string $lang moodle translation language code
     * @param bool include also disabled translations?
     * @return boot true if exists
     */
    public function translation_exists($lang, $includeall = true) {
        global $CFG;

        if (strpos($lang, '_local') !== false) {
            // _local packs are not real translations
            return false;
        }
        if (!$includeall and !empty($CFG->langlist)) {
            $enabled = explode(',', $CFG->langlist);
            if (!in_array($lang, $enabled)) {
                return false;
            }
        }
        if ($lang === 'en') {
            // part of distribution
            return true;
        }
        return file_exists("$this->otherroot/$lang/langconfig.php");
    }

    /**
     * Returns localised list of installed translations
     * @param bool $returnall return all or just enabled
     * @return array moodle translation code => localised translation name
     */
    public function get_list_of_translations($returnall = false) {
        global $CFG;

        $languages = array();

        if (!$returnall && !empty($CFG->langlist)) {
            // return only languages allowed in langlist admin setting
            $langlist = explode(',', $CFG->langlist);
            // find existing langs from langlist
            foreach ($langlist as $lang) {
                $lang = trim($lang);   //Just trim spaces to be a bit more permissive
                if (strstr($lang, '_local') !== false) {
                    continue;
                }
                if (strstr($lang, '_utf8') !== false) {
                    continue;
                }
                if ($lang !== 'en' and !file_exists("$this->otherroot/$lang/langconfig.php")) {
                    // some broken or missing lang - can not swith to it anyway
                    continue;
                }
                $string = $this->load_component_strings('langconfig', $lang);
                if (!empty($string['thislanguage'])) {
                    $languages[$lang] = $string['thislanguage'].' ('. $lang .')';
                }
                unset($string);
            }

        } else {
            // return all languages available in system
            $langdirs = get_list_of_plugins('', '', $this->otherroot);

            $langdirs = array_merge($langdirs, array("$CFG->dirroot/lang/en"=>'en'));
            // Sort all

            asort($langdirs);
            // Loop through all langs and get info
            foreach ($langdirs as $lang) {
                if (strstr($lang, '_local') !== false) {
                    continue;
                }
                if (strstr($lang, '_utf8') !== false) {
                    continue;
                }
                $string = $this->load_component_strings('langconfig', $lang);
                if (!empty($string['thislanguage'])) {
                    $languages[$lang] = $string['thislanguage'].' ('. $lang .')';
                }
                unset($string);
            }
        }

        return $languages;
    }

    /**
     * Returns localised list of currencies.
     *
     * @param string $lang moodle translation language, NULL means use current
     * @return array currency code => localised currency name
     */
    public function get_list_of_currencies($lang = NULL) {
        if ($lang === NULL) {
            $lang = current_language();
        }

        $currencies = $this->load_component_strings('core_currencies', $lang);
        asort($currencies);

        return $currencies;
    }
}


/**
 * Minimalistic string fetching implementation
 * that is used in installer before we getch the wanted
 * language pack from moodle.org lang download site.
 *
 * @package    moodlecore
 * @copyright  2010 Petr Skoda (http://skodak.org)
 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */
class install_string_manager implements string_manager {
    /** @var string location of pre-install packs for all langs */
    protected $installroot;

    /**
     * Crate new instance of install string manager
     */
    public function __construct() {
        global $CFG;
        $this->installroot = "$CFG->dirroot/install/lang";
    }

    /**
     * Load all strings for one component
     * @param string $component The module the string is associated with
     * @param string $lang
     * @return array of all string for given component and lang
     */
    public function load_component_strings($component, $lang) {
        // not needed in installer
        return array();
    }

    /**
     * Does the string actually exist?
     *
     * get_string() is throwing debug warnings, sometimes we do not want them
     * or we want to display better explanation of the problem.
     *
     * Use with care!
     *
     * @param string $identifier The identifier of the string to search for
     * @param string $component The module the string is associated with
     * @return boot true if exists
     */
    public function string_exists($identifier, $component) {
        // simple old style hack ;)
        $str = get_string($identifier, $component);
        return (strpos($str, '[[') === false);
    }

    /**
     * Get String returns a requested string
     *
     * @param string $identifier The identifier of the string to search for
     * @param string $component The module the string is associated with
     * @param string|object|array $a An object, string or number that can be used
     *      within translation strings
     * @param string $lang moodle translation language, NULL means use current
     * @return string The String !
     */
    public function get_string($identifier, $component = '', $a = NULL, $lang = NULL) {
        if (!$component) {
            $component = 'moodle';
        }

        if ($lang === NULL) {
            $lang = current_language();
        }

        //get parent lang
        $parent = '';
        if ($lang !== 'en' and $identifier !== 'parentlanguage' and $component !== 'langconfig') {
            if (file_exists("$this->installroot/$lang/langconfig.php")) {
                $string = array();
                include("$this->installroot/$lang/langconfig.php");
                if (isset($string['parentlanguage'])) {
                    $parent = $string['parentlanguage'];
                }
                unset($string);
            }
        }

        // include en string first
        if (!file_exists("$this->installroot/en/$component.php")) {
            return "[[$identifier]]";
        }
        $string = array();
        include("$this->installroot/en/$component.php");

        // now override en with parent if defined
        if ($parent and $parent !== 'en' and file_exists("$this->installroot/$parent/$component.php")) {
            include("$this->installroot/$parent/$component.php");
        }

        // finally override with requested language
        if ($lang !== 'en' and file_exists("$this->installroot/$lang/$component.php")) {
            include("$this->installroot/$lang/$component.php");
        }

        if (!isset($string[$identifier])) {
            return "[[$identifier]]";
        }

        $string = $string[$identifier];

        if ($a !== NULL) {
            if (is_object($a) or is_array($a)) {
                $a = (array)$a;
                $search = array();
                $replace = array();
                foreach ($a as $key=>$value) {
                    if (is_int($key)) {
                        // we do not support numeric keys - sorry!
                        continue;
                    }
                    $search[]  = '{$a->'.$key.'}';
                    $replace[] = (string)$value;
                }
                if ($search) {
                    $string = str_replace($search, $replace, $string);
                }
            } else {
                $string = str_replace('{$a}', (string)$a, $string);
            }
        }

        return $string;
    }

    /**
     * Returns a localised list of all country names, sorted by country keys.
     *
     * @param bool $returnall return all or just enabled
     * @param string $lang moodle translation language, NULL means use current
     * @return array two-letter country code => translated name.
     */
    public function get_list_of_countries($returnall = false, $lang = NULL) {
        //not used in installer
        return array();
    }

    /**
     * Returns a localised list of languages, sorted by code keys.
     *
     * @param string $lang moodle translation language, NULL means use current
     * @param string $standard language list standard
     *                     iso6392: three-letter language code (ISO 639-2/T) => translated name.
     * @return array language code => translated name
     */
    public function get_list_of_languages($lang = NULL, $standard = 'iso6392') {
        //not used in installer
        return array();
    }

    /**
     * Does the translation exist?
     *
     * @param string $lang moodle translation language code
     * @param bool include also disabled translations?
     * @return boot true if exists
     */
    public function translation_exists($lang, $includeall = true) {
        return file_exists($this->installroot.'/'.$lang.'/langconfig.php');
    }

    /**
     * Returns localised list of installed translations
     * @param bool $returnall return all or just enabled
     * @return array moodle translation code => localised translation name
     */
    public function get_list_of_translations($returnall = false) {
        // return all is ignored here - we need to know all langs in installer
        $languages = array();
        // Get raw list of lang directories
        $langdirs = get_list_of_plugins('install/lang');
        asort($langdirs);
        // Get some info from each lang
        foreach ($langdirs as $lang) {
            if (file_exists($this->installroot.'/'.$lang.'/langconfig.php')) {
                $string = array();
                include($this->installroot.'/'.$lang.'/langconfig.php');
                if (!empty($string['thislanguage'])) {
                    $languages[$lang] = $string['thislanguage'].' ('.$lang.')';
                }
            }
        }
        // Return array
        return $languages;
    }

    /**
     * Returns localised list of currencies.
     *
     * @param string $lang moodle translation language, NULL means use current
     * @return array currency code => localised currency name
     */
    public function get_list_of_currencies($lang = NULL) {
        // not used in installer
        return array();
    }
}


/**
 * Returns a localized string.
 *
 * Returns the translated string specified by $identifier as
 * for $module.  Uses the same format files as STphp.
 * $a is an object, string or number that can be used
 * within translation strings
 *
 * eg 'hello {$a->firstname} {$a->lastname}'
 * or 'hello {$a}'
 *
 * If you would like to directly echo the localized string use
 * the function {@link print_string()}
 *
 * Example usage of this function involves finding the string you would
 * like a local equivalent of and using its identifier and module information
 * to retrive it.<br/>
 * If you open moodle/lang/en/moodle.php and look near line 278
 * you will find a string to prompt a user for their word for 'course'
 * <code>
 * $string['course'] = 'Course';
 * </code>
 * So if you want to display the string 'Course'
 * in any language that supports it on your site
 * you just need to use the identifier 'course'
 * <code>
 * $mystring = '<strong>'. get_string('course') .'</strong>';
 * or
 * </code>
 * If the string you want is in another file you'd take a slightly
 * different approach. Looking in moodle/lang/en/calendar.php you find
 * around line 75:
 * <code>
 * $string['typecourse'] = 'Course event';
 * </code>
 * If you want to display the string "Course event" in any language
 * supported you would use the identifier 'typecourse' and the module 'calendar'
 * (because it is in the file calendar.php):
 * <code>
 * $mystring = '<h1>'. get_string('typecourse', 'calendar') .'</h1>';
 * </code>
 *
 * As a last resort, should the identifier fail to map to a string
 * the returned string will be [[ $identifier ]]
 *
 * @param string $identifier The key identifier for the localized string
 * @param string $component The module where the key identifier is stored,
 *      usually expressed as the filename in the language pack without the
 *      .php on the end but can also be written as mod/forum or grade/export/xls.
 *      If none is specified then moodle.php is used.
 * @param string|object|array $a An object, string or number that can be used
 *      within translation strings
 * @return string The localized string.
 */
function get_string($identifier, $component = '', $a = NULL) {
    if (func_num_args() > 3) {
        debugging('extralocations parameter in get_string() is not supported any more, please use standard lang locations only.');
    }

    if (strpos($component, '/') !== false) {
        debugging('The module name you passed to get_string is the deprecated format ' .
                'like mod/mymod or block/myblock. The correct form looks like mymod, or block_myblock.' , DEBUG_DEVELOPER);
        $componentpath = split('/', $component);

        switch ($componentpath[0]) {
            case 'mod':
                $component = $componentpath[1];
                break;
            case 'blocks':
            case 'block':
                $component = 'block_'.$componentpath[1];
                break;
            case 'enrol':
                $component = 'enrol_'.$componentpath[1];
                break;
            case 'format':
                $component = 'format_'.$componentpath[1];
                break;
            case 'grade':
                $component = 'grade'.$componentpath[1].'_'.$componentpath[2];
                break;
        }
    }

    return get_string_manager()->get_string($identifier, $component, $a);
}

/**
 * Converts an array of strings to their localized value.
 *
 * @param array $array An array of strings
 * @param string $module The language module that these strings can be found in.
 * @return array and array of translated strings.
 */
function get_strings($array, $component = '') {
   $string = new stdClass;
   foreach ($array as $item) {
       $string->$item = get_string($item, $component);
   }
   return $string;
}

/**
 * Prints out a translated string.
 *
 * Prints out a translated string using the return value from the {@link get_string()} function.
 *
 * Example usage of this function when the string is in the moodle.php file:<br/>
 * <code>
 * echo '<strong>';
 * print_string('course');
 * echo '</strong>';
 * </code>
 *
 * Example usage of this function when the string is not in the moodle.php file:<br/>
 * <code>
 * echo '<h1>';
 * print_string('typecourse', 'calendar');
 * echo '</h1>';
 * </code>
 *
 * @param string $identifier The key identifier for the localized string
 * @param string $component The module where the key identifier is stored. If none is specified then moodle.php is used.
 * @param mixed $a An object, string or number that can be used within translation strings
 */
function print_string($identifier, $component = '', $a = NULL) {
    echo get_string($identifier, $component, $a);
}

/**
 * Returns a list of charset codes
 *
 * Returns a list of charset codes. It's hardcoded, so they should be added manually
 * (cheking that such charset is supported by the texlib library!)
 *
 * @return array And associative array with contents in the form of charset => charset
 */
function get_list_of_charsets() {

    $charsets = array(
        'EUC-JP'     => 'EUC-JP',
        'ISO-2022-JP'=> 'ISO-2022-JP',
        'ISO-8859-1' => 'ISO-8859-1',
        'SHIFT-JIS'  => 'SHIFT-JIS',
        'GB2312'     => 'GB2312',
        'GB18030'    => 'GB18030', // gb18030 not supported by typo and mbstring
        'UTF-8'      => 'UTF-8');

    asort($charsets);

    return $charsets;
}

/**
 * Returns a list of valid and compatible themes
 *
 * @global object
 * @return array
 */
function get_list_of_themes() {
    global $CFG;

    $themes = array();

    if (!empty($CFG->themelist)) {       // use admin's list of themes
        $themelist = explode(',', $CFG->themelist);
    } else {
        $themelist = array_keys(get_plugin_list("theme"));
    }

    foreach ($themelist as $key => $themename) {
        $theme = theme_config::load($themename);
        $themes[$themename] = $theme;
    }
    asort($themes);

    return $themes;
}

/**
 * Returns a list of timezones in the current language
 *
 * @global object
 * @global object
 * @return array
 */
function get_list_of_timezones() {
    global $CFG, $DB;

    static $timezones;

    if (!empty($timezones)) {    // This function has been called recently
        return $timezones;
    }

    $timezones = array();

    if ($rawtimezones = $DB->get_records_sql("SELECT MAX(id), name FROM {timezone} GROUP BY name")) {
        foreach($rawtimezones as $timezone) {
            if (!empty($timezone->name)) {
                if (get_string_manager()->string_exists(strtolower($timezone->name), 'timezones')) {
                    $timezones[$timezone->name] = get_string(strtolower($timezone->name), 'timezones');
                } else {
                    $timezones[$timezone->name] = $timezone->name;
                }
                if (substr($timezones[$timezone->name], 0, 1) == '[') {  // No translation found
                    $timezones[$timezone->name] = $timezone->name;
                }
            }
        }
    }

    asort($timezones);

    for ($i = -13; $i <= 13; $i += .5) {
        $tzstring = 'UTC';
        if ($i < 0) {
            $timezones[sprintf("%.1f", $i)] = $tzstring . $i;
        } else if ($i > 0) {
            $timezones[sprintf("%.1f", $i)] = $tzstring . '+' . $i;
        } else {
            $timezones[sprintf("%.1f", $i)] = $tzstring;
        }
    }

    return $timezones;
}

/// ENCRYPTION  ////////////////////////////////////////////////

/**
 * rc4encrypt
 *
 * @todo Finish documenting this function
 *
 * @param string $data Data to encrypt
 * @return string The now encrypted data
 */
function rc4encrypt($data) {
    $password = 'nfgjeingjk';
    return endecrypt($password, $data, '');
}

/**
 * rc4decrypt
 *
 * @todo Finish documenting this function
 *
 * @param string $data Data to decrypt
 * @return string The now decrypted data
 */
function rc4decrypt($data) {
    $password = 'nfgjeingjk';
    return endecrypt($password, $data, 'de');
}

/**
 * Based on a class by Mukul Sabharwal [mukulsabharwal @ yahoo.com]
 *
 * @todo Finish documenting this function
 *
 * @param string $pwd The password to use when encrypting or decrypting
 * @param string $data The data to be decrypted/encrypted
 * @param string $case Either 'de' for decrypt or '' for encrypt
 * @return string
 */
function endecrypt ($pwd, $data, $case) {

    if ($case == 'de') {
        $data = urldecode($data);
    }

    $key[] = '';
    $box[] = '';
    $temp_swap = '';
    $pwd_length = 0;

    $pwd_length = strlen($pwd);

    for ($i = 0; $i <= 255; $i++) {
        $key[$i] = ord(substr($pwd, ($i % $pwd_length), 1));
        $box[$i] = $i;
    }

    $x = 0;

    for ($i = 0; $i <= 255; $i++) {
        $x = ($x + $box[$i] + $key[$i]) % 256;
        $temp_swap = $box[$i];
        $box[$i] = $box[$x];
        $box[$x] = $temp_swap;
    }

    $temp = '';
    $k = '';

    $cipherby = '';
    $cipher = '';

    $a = 0;
    $j = 0;

    for ($i = 0; $i < strlen($data); $i++) {
        $a = ($a + 1) % 256;
        $j = ($j + $box[$a]) % 256;
        $temp = $box[$a];
        $box[$a] = $box[$j];
        $box[$j] = $temp;
        $k = $box[(($box[$a] + $box[$j]) % 256)];
        $cipherby = ord(substr($data, $i, 1)) ^ $k;
        $cipher .= chr($cipherby);
    }

    if ($case == 'de') {
        $cipher = urldecode(urlencode($cipher));
    } else {
        $cipher = urlencode($cipher);
    }

    return $cipher;
}

/// ENVIRONMENT CHECKING  ////////////////////////////////////////////////////////////

/**
 * Returns the exact absolute path to plugin directory.
 *
 * @param string $plugintype type of plugin
 * @param string $name name of the plugin
 * @return string full path to plugin directory; NULL if not found
 */
function get_plugin_directory($plugintype, $name) {
    if ($plugintype === '') {
        $plugintype = 'mod';
    }

    $types = get_plugin_types(true);
    if (!array_key_exists($plugintype, $types)) {
        return NULL;
    }
    $name = clean_param($name, PARAM_SAFEDIR); // just in case ;-)

    return $types[$plugintype].'/'.$name;
}

/**
 * Return exact absolute path to a plugin directory,
 * this method support "simpletest_" prefix designed for unit testing.
 *
 * @param string $component name such as 'moodle', 'mod_forum' or special simpletest value
 * @return string full path to component directory; NULL if not found
 */
function get_component_directory($component) {
    global $CFG;
/*
    $simpletest = false;
    if (strpos($component, 'simpletest_') === 0) {
        $subdir = substr($component, strlen('simpletest_'));
        //TODO: this looks borked, where is it used actually?
        return $subdir;
    }
*/
    list($type, $plugin) = normalize_component($component);

    if ($type === 'core') {
        if ($plugin === NULL ) {
            $path = $CFG->libdir;
        } else {
            $subsystems = get_core_subsystems();
            if (isset($subsystems[$plugin])) {
                $path = $CFG->dirroot.'/'.$subsystems[$plugin];
            } else {
                $path = NULL;
            }
        }

    } else {
        $path = get_plugin_directory($type, $plugin);
    }

    return $path;
}

/**
 * Normalize the component name using the "frankenstyle" names.
 * @param string $component
 * @return array $type+$plugin elements
 */
function normalize_component($component) {
    if ($component === 'moodle' or $component === 'core') {
        $type = 'core';
        $plugin = NULL;

    } else if (strpos($component, '_') === false) {
        $subsystems = get_core_subsystems();
        if (array_key_exists($component, $subsystems)) {
            $type   = 'core';
            $plugin = $component;
        } else {
            // everything else is a module
            $type   = 'mod';
            $plugin = $component;
        }

    } else {
        list($type, $plugin) = explode('_', $component, 2);
    }

    return array($type, $plugin);
}

/**
 * List all core subsystems and their location
 *
 * This is a whitelist of components that are part of the core and their
 * language strings are defined in /lang/en/<<subsystem>>.php. If a given
 * plugin is not listed here and it does not have proper plugintype prefix,
 * then it is considered as course activity module.
 *
 * The location is dirroot relative path. NULL means there is no special
 * directory for this subsystem. If the location is set, the subsystem's
 * renderer.php is expected to be there.
 *
 * @return array of (string)name => (string|null)location
 */
function get_core_subsystems() {
    global $CFG;

    static $info = null;

    if (!$info) {
        $info = array(
            'access'      => NULL,
            'admin'       => $CFG->admin,
            'auth'        => 'auth',
            'block'       => 'blocks',
            'blog'        => 'blog',
            'bulkusers'   => NULL,
            'calendar'    => 'calendar',
            'cohort'      => 'cohort',
            'condition'   => NULL,
            'completion'  => NULL,
            'countries'   => NULL,
            'currencies'  => NULL,
            'dbtransfer'  => NULL,
            'debug'       => NULL,
            'dock'        => NULL,
            'editor'      => 'lib/editor',
            'error'       => NULL,
            'filepicker'  => NULL,
            'filters'     => NULL,
            'flashdetect' => NULL,
            'fonts'       => NULL,
            'form'        => 'lib/form',
            'grades'      => 'grade',
            'group'       => 'group',
            'help'        => NULL,
            'imscc'       => NULL,
            'install'     => NULL,
            'iso6392'     => NULL,
            'langconfig'  => NULL,
            'license'     => NULL,
            'message'     => 'message',
            'mimetypes'   => NULL,
            'mnet'        => 'mnet',
            'moodle.org'  => NULL, // the dot is nasty, watch out! should be renamed to moodleorg
            'my'          => 'my',
            'notes'       => 'notes',
            'pagetype'    => NULL,
            'pix'         => NULL,
            'portfolio'   => 'portfolio',
            'question'    => 'question',
            'rating'      => 'rating',
            'repository'  => 'repository',
            'role'        => $CFG->admin.'/role',
            'simpletest'  => NULL,
            'search'      => 'search',
            'table'       => NULL,
            'tag'         => 'tag',
            'timezones'   => NULL,
            'userkey'     => NULL,
            'webservice'  => 'webservice',
            'xmldb'       => NULL,
        );
    }

    return $info;
}

/**
 * Lists all plugin types
 * @param bool $fullpaths false means relative paths from dirroot
 * @return array Array of strings - name=>location
 */
function get_plugin_types($fullpaths=true) {
    global $CFG;

    static $info     = null;
    static $fullinfo = null;

    if (!$info) {
        $info = array('mod'           => 'mod',
                      'auth'          => 'auth',
                      'enrol'         => 'enrol',
                      'message'       => 'message/output',
                      'block'         => 'blocks',
                      'filter'        => 'filter',
                      'editor'        => 'lib/editor',
                      'format'        => 'course/format',
                      'import'        => 'course/import',
                      'profilefield'  => 'user/profile/field',
                      'report'        => $CFG->admin.'/report',
                      'coursereport'  => 'course/report', // must be after system reports
                      'gradeexport'   => 'grade/export',
                      'gradeimport'   => 'grade/import',
                      'gradereport'   => 'grade/report',
                      'webservice'    => 'webservice',
                      'repository'    => 'repository',
                      'portfolio'     => 'portfolio',
                      'qtype'         => 'question/type',
                      'qformat'       => 'question/format',
                      'theme'         => 'theme'); // this is a bit hacky, themes may be in dataroot too

        $mods = get_plugin_list('mod');
        foreach ($mods as $mod => $moddir) {
            if (file_exists("$moddir/db/subplugins.php")) {
                $subplugins = array();
                include("$moddir/db/subplugins.php");
                foreach ($subplugins as $subtype=>$dir) {
                    $info[$subtype] = $dir;
                }
            }
        }

        // local is always last!
        $info['local'] = 'local';

        $fullinfo = array();
        foreach ($info as $type => $dir) {
            $fullinfo[$type] = $CFG->dirroot.'/'.$dir;
        }
    }

    return ($fullpaths ? $fullinfo : $info);
}

/**
 * Simplified version of get_list_of_plugins()
 * @param string $plugintype type of plugin
 * @return array name=>fulllocation pairs of plugins of given type
 */
function get_plugin_list($plugintype) {
    global $CFG;

    $ignored = array('CVS', '_vti_cnf', 'simpletest', 'db');
    if ($plugintype == 'auth') {
        // Historically we have had an auth plugin called 'db', so allow a special case.
        $key = array_search('db', $ignored);
        if ($key !== false) {
            unset($ignored[$key]);
        }
    }

    if ($plugintype === '') {
        $plugintype = 'mod';
    }

    $fulldirs = array();

    if ($plugintype === 'mod') {
        // mod is an exception because we have to call this function from get_plugin_types()
        $fulldirs[] = $CFG->dirroot.'/mod';

    } else if ($plugintype === 'theme') {
        $fulldirs[] = $CFG->dirroot.'/theme';
        // themes are special because they may be stored also in separate directory
        if (!empty($CFG->themedir) and file_exists($CFG->themedir) and is_dir($CFG->themedir) ) {
            $fulldirs[] = $CFG->themedir;
        }

    } else {
        $types = get_plugin_types(true);
        if (!array_key_exists($plugintype, $types)) {
            return array();
        }
        $fulldir = $types[$plugintype];
        if (!file_exists($fulldir)) {
            return array();
        }
        $fulldirs[] = $fulldir;
    }

    $result = array();

    foreach ($fulldirs as $fulldir) {
        if (!is_dir($fulldir)) {
            continue;
        }
        $items = new DirectoryIterator($fulldir);
        foreach ($items as $item) {
            if ($item->isDot() or !$item->isDir()) {
                continue;
            }
            $pluginname = $item->getFilename();
            if (in_array($pluginname, $ignored)) {
                continue;
            }
            if ($pluginname !== clean_param($pluginname, PARAM_SAFEDIR)) {
                // better ignore plugins with problematic names here
                continue;
            }
            $result[$pluginname] = $fulldir.'/'.$pluginname;
            unset($item);
        }
        unset($items);
    }

    ksort($result);
    return $result;
}

/**
 * Lists plugin-like directories within specified directory
 *
 * This function was originally used for standar Moodle plugins, please use
 * new get_plugin_list() now.
 *
 * This function is used for general directory listing and backwards compability.
 *
 * @param string $directory relatice directory from root
 * @param string $exclude dir name to exclude from the list (defaults to none)
 * @param string $basedir full path to the base dir where $plugin resides (defaults to $CFG->dirroot)
 * @return array Sorted array of directory names found under the requested parameters
 */
function get_list_of_plugins($directory='mod', $exclude='', $basedir='') {
    global $CFG;

    $plugins = array();

    if (empty($basedir)) {
        $basedir = $CFG->dirroot .'/'. $directory;

    } else {
        $basedir = $basedir .'/'. $directory;
    }

    if (file_exists($basedir) && filetype($basedir) == 'dir') {
        $dirhandle = opendir($basedir);
        while (false !== ($dir = readdir($dirhandle))) {
            $firstchar = substr($dir, 0, 1);
            if ($firstchar == '.' or $dir == 'CVS' or $dir == '_vti_cnf' or $dir == 'simpletest' or $dir == $exclude) {
                continue;
            }
            if (filetype($basedir .'/'. $dir) != 'dir') {
                continue;
            }
            $plugins[] = $dir;
        }
        closedir($dirhandle);
    }
    if ($plugins) {
        asort($plugins);
    }
    return $plugins;
}


/**
 * invoke plugin's callback functions
 *
 * @param string $type Plugin type e.g. 'mod'
 * @param string $name Plugin name
 * @param string $feature Feature code (FEATURE_xx constant)
 * @param string $action Feature's action
 * @param string $options parameters of callback function, should be an array
 * @param mixed $default default value if callback function hasn't been defined
 * @return mixed
 */
function plugin_callback($type, $name, $feature, $action, $options = null, $default=null) {
    global $CFG;

    $name = clean_param($name, PARAM_SAFEDIR);
    $function = $name.'_'.$feature.'_'.$action;

    switch($type) {
        case 'mod' :
            $file = $CFG->dirroot.'/mod/'.$name.'/lib.php';
            break;
        case 'block' :
            // load block_base class
            require_once($CFG->dirroot . '/blocks/moodleblock.class.php');
            // block uses class based callback functions
            // see blocks/moodleblock.class.php
            $file = $CFG->dirroot.'/blocks/'.$name.'/block_'.$name.'.php';
            $function = array('block_' . $name, 'comment_'.$action);
            break;
        case 'moodle':
            // for special plugins, such as blog and tag
            $file = $CFG->dirroot.'/'.$name.'/lib.php';
            break;
        default:
            throw new Exception('Unsupported callback type ('.$type.')');
    }

    // Load library and look for function
    if (file_exists($file)) {
        require_once($file);
    }
    if (is_array($function) || function_exists($function)) {
        // Function exists, so just return function result
        $ret = call_user_func_array($function, (array)$options);
        if (is_null($ret)) {
            return $default;
        } else {
            return $ret;
        }
    } else {
        switch($feature) {
            // If some features can also be checked in other ways
            // for legacy support, this could be added here
            default: return $default;
        }
    }
}

/**
 * Checks whether a plugin supports a specified feature.
 *
 * @param string $type Plugin type e.g. 'mod'
 * @param string $name Plugin name
 * @param string $feature Feature code (FEATURE_xx constant)
 * @param mixed $default default value if feature support unknown
 * @return mixed Feature result (false if not supported, null if feature is unknown,
 *         otherwise usually true but may have other feature-specific value such as array)
 */
function plugin_supports($type, $name, $feature, $default=null) {
    global $CFG;

    $name = clean_param($name, PARAM_SAFEDIR); //bit of extra security

    if ($type === 'mod') {
        // we need this special case because we support subplugins in modules,
        // otherwise it would end up in infinite loop
        if ($name === 'NEWMODULE') {
            //somebody forgot to rename the module template
            return false;
        }
        include_once("$CFG->dirroot/mod/$name/lib.php");

        $function = $name.'_supports';

    }

    if (function_exists($function)) {
        $supports = $function($feature);
        if (is_null($supports)) {
            // plugin does not know - use default
            return $default;
        } else {
            return $supports;
        }
    }

    //plugin does not care, so use default
    return $default;
}

/**
 * Returns true if the current version of PHP is greater that the specified one.
 *
 * @todo Check PHP version being required here is it too low?
 *
 * @param string $version The version of php being tested.
 * @return bool
 */
function check_php_version($version='5.2.4') {
    return (version_compare(phpversion(), $version) >= 0);
}

/**
 * Checks to see if is the browser operating system matches the specified
 * brand.
 *
 * Known brand: 'Windows','Linux','Macintosh','SGI','SunOS','HP-UX'
 *
 * @uses $_SERVER
 * @param string $brand The operating system identifier being tested
 * @return bool true if the given brand below to the detected operating system
 */
 function check_browser_operating_system($brand) {
    if (empty($_SERVER['HTTP_USER_AGENT'])) {
        return false;
    }

    if (preg_match("/$brand/i", $_SERVER['HTTP_USER_AGENT'])) {
        return true;
    }

    return false;
 }

/**
 * Checks to see if is a browser matches the specified
 * brand and is equal or better version.
 *
 * @uses $_SERVER
 * @param string $brand The browser identifier being tested
 * @param int $version The version of the browser
 * @return bool true if the given version is below that of the detected browser
 */
 function check_browser_version($brand='MSIE', $version=5.5) {
    if (empty($_SERVER['HTTP_USER_AGENT'])) {
        return false;
    }

    $agent = $_SERVER['HTTP_USER_AGENT'];

    switch ($brand) {

      case 'Camino':   /// Mozilla Firefox browsers

              if (preg_match("/Camino\/([0-9\.]+)/i", $agent, $match)) {
                  if (version_compare($match[1], $version) >= 0) {
                      return true;
                  }
              }
              break;


      case 'Firefox':   /// Mozilla Firefox browsers

          if (preg_match("/(Iceweasel|Firefox)\/([0-9\.]+)/i", $agent, $match)) {
              if (version_compare($match[2], $version) >= 0) {
                  return true;
              }
          }
          break;


      case 'Gecko':   /// Gecko based browsers

          if (substr_count($agent, 'Camino')) {
              // MacOS X Camino support
              $version = 20041110;
          }

          // the proper string - Gecko/CCYYMMDD Vendor/Version
          // Faster version and work-a-round No IDN problem.
          if (preg_match("/Gecko\/([0-9]+)/i", $agent, $match)) {
              if ($match[1] > $version) {
                      return true;
                  }
              }
          break;


      case 'MSIE':   /// Internet Explorer

          if (strpos($agent, 'Opera')) {     // Reject Opera
              return false;
          }
          $string = explode(';', $agent);
          if (!isset($string[1])) {
              return false;
          }
          $string = explode(' ', trim($string[1]));
          if (!isset($string[0]) and !isset($string[1])) {
              return false;
          }
          if ($string[0] == $brand and (float)$string[1] >= $version ) {
              return true;
          }
          break;

      case 'Opera':  /// Opera

          if (preg_match("/Opera\/([0-9\.]+)/i", $agent, $match)) {
              if (version_compare($match[1], $version) >= 0) {
                  return true;
              }
          }
          break;

      case 'Safari':  /// Safari
          // Look for AppleWebKit, excluding strings with OmniWeb, Shiira and SimbianOS
          if (strpos($agent, 'OmniWeb')) { // Reject OmniWeb
              return false;
          } elseif (strpos($agent, 'Shiira')) { // Reject Shiira
              return false;
          } elseif (strpos($agent, 'SimbianOS')) { // Reject SimbianOS
              return false;
          }

          if (preg_match("/AppleWebKit\/([0-9]+)/i", $agent, $match)) {
              if (version_compare($match[1], $version) >= 0) {
                  return true;
              }
          }

          break;

    }

    return false;
}

/**
 * Returns one or several CSS class names that match the user's browser. These can be put
 * in the body tag of the page to apply browser-specific rules without relying on CSS hacks
 *
 * @return array An array of browser version classes
 */
function get_browser_version_classes() {
    $classes = array();

    if (check_browser_version("MSIE", "0")) {
        $classes[] = 'ie';
        if (check_browser_version("MSIE", 8)) {
            $classes[] = 'ie8';
        } elseif (check_browser_version("MSIE", 7)) {
            $classes[] = 'ie7';
        } elseif (check_browser_version("MSIE", 6)) {
            $classes[] = 'ie6';
        }

    } elseif (check_browser_version("Firefox", 0) || check_browser_version("Gecko", 0) || check_browser_version("Camino", 0)) {
        $classes[] = 'gecko';
        if (preg_match('/rv\:([1-2])\.([0-9])/', $_SERVER['HTTP_USER_AGENT'], $matches)) {
            $classes[] = "gecko{$matches[1]}{$matches[2]}";
        }

    } elseif (check_browser_version("Safari", 0)) {
        $classes[] = 'safari';

    } elseif (check_browser_version("Opera", 0)) {
        $classes[] = 'opera';

    }

    return $classes;
}

/**
 * This function makes the return value of ini_get consistent if you are
 * setting server directives through the .htaccess file in apache.
 *
 * Current behavior for value set from php.ini On = 1, Off = [blank]
 * Current behavior for value set from .htaccess On = On, Off = Off
 * Contributed by jdell @ unr.edu
 *
 * @todo Finish documenting this function
 *
 * @param string $ini_get_arg The argument to get
 * @return bool True for on false for not
 */
function ini_get_bool($ini_get_arg) {
    $temp = ini_get($ini_get_arg);

    if ($temp == '1' or strtolower($temp) == 'on') {
        return true;
    }
    return false;
}

/**
 * Can handle rotated text. Whether it is safe to use the trickery in textrotate.js.
 *
 * @return bool True for yes, false for no
 */
function can_use_rotated_text() {
    global $USER;
    return ajaxenabled(array('Firefox' => 2.0)) && !$USER->screenreader;;
}

/**
 * Hack to find out the GD version by parsing phpinfo output
 *
 * @return int GD version (1, 2, or 0)
 */
function check_gd_version() {
    $gdversion = 0;

    if (function_exists('gd_info')){
        $gd_info = gd_info();
        if (substr_count($gd_info['GD Version'], '2.')) {
            $gdversion = 2;
        } else if (substr_count($gd_info['GD Version'], '1.')) {
            $gdversion = 1;
        }

    } else {
        ob_start();
        phpinfo(INFO_MODULES);
        $phpinfo = ob_get_contents();
        ob_end_clean();

        $phpinfo = explode("\n", $phpinfo);


        foreach ($phpinfo as $text) {
            $parts = explode('</td>', $text);
            foreach ($parts as $key => $val) {
                $parts[$key] = trim(strip_tags($val));
            }
            if ($parts[0] == 'GD Version') {
                if (substr_count($parts[1], '2.0')) {
                    $parts[1] = '2.0';
                }
                $gdversion = intval($parts[1]);
            }
        }
    }

    return $gdversion;   // 1, 2 or 0
}

/**
 * Determine if moodle installation requires update
 *
 * Checks version numbers of main code and all modules to see
 * if there are any mismatches
 *
 * @global object
 * @global object
 * @return bool
 */
function moodle_needs_upgrading() {
    global $CFG, $DB, $OUTPUT;

    if (empty($CFG->version)) {
        return true;
    }

    // main versio nfirst
    $version = null;
    include($CFG->dirroot.'/version.php');  // defines $version and upgrades
    if ($version > $CFG->version) {
        return true;
    }

    // modules
    $mods = get_plugin_list('mod');
    $installed = $DB->get_records('modules', array(), '', 'name, version');
    foreach ($mods as $mod => $fullmod) {
        if ($mod === 'NEWMODULE') {   // Someone has unzipped the template, ignore it
            continue;
        }
        $module = new object();
        if (!is_readable($fullmod.'/version.php')) {
            continue;
        }
        include($fullmod.'/version.php');  // defines $module with version etc
        if (empty($installed[$mod])) {
            return true;
        } else if ($module->version > $installed[$mod]->version) {
            return true;
        }
    }
    unset($installed);

    // blocks
    $blocks = get_plugin_list('block');
    $installed = $DB->get_records('block', array(), '', 'name, version');
    require_once($CFG->dirroot.'/blocks/moodleblock.class.php');
    foreach ($blocks as $blockname=>$fullblock) {
        if ($blockname === 'NEWBLOCK') {   // Someone has unzipped the template, ignore it
            continue;
        }
        if (!is_readable($fullblock.'/block_'.$blockname.'.php')) {
            continue;
        }
        include_once($fullblock.'/block_'.$blockname.'.php');
        $classname = 'block_'.$blockname;
        if (!class_exists($classname)) {
            continue;
        }
        $blockobj = new $classname;
        if (empty($installed[$blockname])) {
            return true;
        } else if ($blockobj->get_version() > $installed[$blockname]->version) {
            return true;
        }
    }
    unset($installed);

    // now the rest of plugins
    $plugintypes = get_plugin_types();
    unset($plugintypes['mod']);
    unset($plugintypes['block']);
    foreach ($plugintypes as $type=>$unused) {
        $plugs = get_plugin_list($type);
        foreach ($plugs as $plug=>$fullplug) {
            $component = $type.'_'.$plug;
            if (!is_readable($fullplug.'/version.php')) {
                continue;
            }
            $plugin = new object();
            include($fullplug.'/version.php');  // defines $plugin with version etc
            $installedversion = get_config($component, 'version');
            if (empty($installedversion)) { // new installation
                return true;
            } else if ($installedversion < $plugin->version) { // upgrade
                return true;
            }
        }
    }

    return false;
}

/**
 * Sets maximum expected time needed for upgrade task.
 * Please always make sure that upgrade will not run longer!
 *
 * The script may be automatically aborted if upgrade times out.
 *
 * @global object
 * @param int $max_execution_time in seconds (can not be less than 60 s)
 */
function upgrade_set_timeout($max_execution_time=300) {
    global $CFG;

    if (!isset($CFG->upgraderunning) or $CFG->upgraderunning < time()) {
        $upgraderunning = get_config(null, 'upgraderunning');
    } else {
        $upgraderunning = $CFG->upgraderunning;
    }

    if (!$upgraderunning) {
        // upgrade not running or aborted
        print_error('upgradetimedout', 'admin', "$CFG->wwroot/$CFG->admin/");
        die;
    }

    if ($max_execution_time < 60) {
        // protection against 0 here
        $max_execution_time = 60;
    }

    $expected_end = time() + $max_execution_time;

    if ($expected_end < $upgraderunning + 10 and $expected_end > $upgraderunning - 10) {
        // no need to store new end, it is nearly the same ;-)
        return;
    }

    set_time_limit($max_execution_time);
    set_config('upgraderunning', $expected_end); // keep upgrade locked until this time
}

/// MISCELLANEOUS ////////////////////////////////////////////////////////////////////

/**
 * Notify admin users or admin user of any failed logins (since last notification).
 *
 * Note that this function must be only executed from the cron script
 * It uses the cache_flags system to store temporary records, deleting them
 * by name before finishing
 *
 * @global object
 * @global object
 * @uses HOURSECS
 */
function notify_login_failures() {
    global $CFG, $DB, $OUTPUT;

    $recip = get_users_from_config($CFG->notifyloginfailures, 'moodle/site:config');

    if (empty($CFG->lastnotifyfailure)) {
        $CFG->lastnotifyfailure=0;
    }

    // we need to deal with the threshold stuff first.
    if (empty($CFG->notifyloginthreshold)) {
        $CFG->notifyloginthreshold = 10; // default to something sensible.
    }

/// Get all the IPs with more than notifyloginthreshold failures since lastnotifyfailure
/// and insert them into the cache_flags temp table
    $sql = "SELECT ip, COUNT(*)
              FROM {log}
             WHERE module = 'login' AND action = 'error'
                   AND time > ?
          GROUP BY ip
            HAVING COUNT(*) >= ?";
    $params = array($CFG->lastnotifyfailure, $CFG->notifyloginthreshold);
    if ($rs = $DB->get_recordset_sql($sql, $params)) {
        foreach ($rs as $iprec) {
            if (!empty($iprec->ip)) {
                set_cache_flag('login_failure_by_ip', $iprec->ip, '1', 0);
            }
        }
        $rs->close();
    }

/// Get all the INFOs with more than notifyloginthreshold failures since lastnotifyfailure
/// and insert them into the cache_flags temp table
    $sql = "SELECT info, count(*)
              FROM {log}
             WHERE module = 'login' AND action = 'error'
                   AND time > ?
          GROUP BY info
            HAVING count(*) >= ?";
    $params = array($CFG->lastnotifyfailure, $CFG->notifyloginthreshold);
    if ($rs = $DB->get_recordset_sql($sql, $params)) {
        foreach ($rs as $inforec) {
            if (!empty($inforec->info)) {
                set_cache_flag('login_failure_by_info', $inforec->info, '1', 0);
            }
        }
        $rs->close();
    }

/// Now, select all the login error logged records belonging to the ips and infos
/// since lastnotifyfailure, that we have stored in the cache_flags table
    $sql = "SELECT l.*, u.firstname, u.lastname
              FROM {log} l
              JOIN {cache_flags} cf ON l.ip = cf.name
         LEFT JOIN {user} u         ON l.userid = u.id
             WHERE l.module = 'login' AND l.action = 'error'
                   AND l.time > ?
                   AND cf.flagtype = 'login_failure_by_ip'
        UNION ALL
            SELECT l.*, u.firstname, u.lastname
              FROM {log} l
              JOIN {cache_flags} cf ON l.info = cf.name
         LEFT JOIN {user} u         ON l.userid = u.id
             WHERE l.module = 'login' AND l.action = 'error'
                   AND l.time > ?
                   AND cf.flagtype = 'login_failure_by_info'
          ORDER BY time DESC";
    $params = array($CFG->lastnotifyfailure, $CFG->lastnotifyfailure);

/// Init some variables
    $count = 0;
    $messages = '';
/// Iterate over the logs recordset
    if ($rs = $DB->get_recordset_sql($sql, $params)) {
        foreach ($rs as $log) {
            $log->time = userdate($log->time);
            $messages .= get_string('notifyloginfailuresmessage','',$log)."\n";
            $count++;
        }
        $rs->close();
    }

/// If we haven't run in the last hour and
/// we have something useful to report and we
/// are actually supposed to be reporting to somebody
    if ((time() - HOURSECS) > $CFG->lastnotifyfailure && $count > 0 && is_array($recip) && count($recip) > 0) {
        $site = get_site();
        $subject = get_string('notifyloginfailuressubject', '', format_string($site->fullname));
    /// Calculate the complete body of notification (start + messages + end)
        $body = get_string('notifyloginfailuresmessagestart', '', $CFG->wwwroot) .
                (($CFG->lastnotifyfailure != 0) ? '('.userdate($CFG->lastnotifyfailure).')' : '')."\n\n" .
                $messages .
                "\n\n".get_string('notifyloginfailuresmessageend','',$CFG->wwwroot)."\n\n";

    /// For each destination, send mail
        mtrace('Emailing admins about '. $count .' failed login attempts');
        foreach ($recip as $admin) {
            email_to_user($admin,get_admin(), $subject, $body);
        }

    /// Update lastnotifyfailure with current time
        set_config('lastnotifyfailure', time());
    }

/// Finally, delete all the temp records we have created in cache_flags
    $DB->delete_records_select('cache_flags', "flagtype IN ('login_failure_by_ip', 'login_failure_by_info')");
}

/**
 * Sets the system locale
 *
 * @todo Finish documenting this function
 *
 * @global object
 * @param string $locale Can be used to force a locale
 */
function moodle_setlocale($locale='') {
    global $CFG;

    static $currentlocale = ''; // last locale caching

    $oldlocale = $currentlocale;

/// Fetch the correct locale based on ostype
    if ($CFG->ostype == 'WINDOWS') {
        $stringtofetch = 'localewin';
    } else {
        $stringtofetch = 'locale';
    }

/// the priority is the same as in get_string() - parameter, config, course, session, user, global language
    if (!empty($locale)) {
        $currentlocale = $locale;
    } else if (!empty($CFG->locale)) { // override locale for all language packs
        $currentlocale = $CFG->locale;
    } else {
        $currentlocale = get_string($stringtofetch, 'langconfig');
    }

/// do nothing if locale already set up
    if ($oldlocale == $currentlocale) {
        return;
    }

/// Due to some strange BUG we cannot set the LC_TIME directly, so we fetch current values,
/// set LC_ALL and then set values again. Just wondering why we cannot set LC_ALL only??? - stronk7
/// Some day, numeric, monetary and other categories should be set too, I think. :-/

/// Get current values
    $monetary= setlocale (LC_MONETARY, 0);
    $numeric = setlocale (LC_NUMERIC, 0);
    $ctype   = setlocale (LC_CTYPE, 0);
    if ($CFG->ostype != 'WINDOWS') {
        $messages= setlocale (LC_MESSAGES, 0);
    }
/// Set locale to all
    setlocale (LC_ALL, $currentlocale);
/// Set old values
    setlocale (LC_MONETARY, $monetary);
    setlocale (LC_NUMERIC, $numeric);
    if ($CFG->ostype != 'WINDOWS') {
        setlocale (LC_MESSAGES, $messages);
    }
    if ($currentlocale == 'tr_TR' or $currentlocale == 'tr_TR.UTF-8') { // To workaround a well-known PHP problem with Turkish letter Ii
        setlocale (LC_CTYPE, $ctype);
    }
}

/**
 * Converts string to lowercase using most compatible function available.
 *
 * @todo Remove this function when no longer in use
 * @deprecated Use textlib->strtolower($text) instead.
 *
 * @param string $string The string to convert to all lowercase characters.
 * @param string $encoding The encoding on the string.
 * @return string
 */
function moodle_strtolower ($string, $encoding='') {

    //If not specified use utf8
    if (empty($encoding)) {
        $encoding = 'UTF-8';
    }
    //Use text services
    $textlib = textlib_get_instance();

    return $textlib->strtolower($string, $encoding);
}

/**
 * Count words in a string.
 *
 * Words are defined as things between whitespace.
 *
 * @param string $string The text to be searched for words.
 * @return int The count of words in the specified string
 */
function count_words($string) {
    $string = strip_tags($string);
    return count(preg_split("/\w\b/", $string)) - 1;
}

/** Count letters in a string.
 *
 * Letters are defined as chars not in tags and different from whitespace.
 *
 * @param string $string The text to be searched for letters.
 * @return int The count of letters in the specified text.
 */
function count_letters($string) {
/// Loading the textlib singleton instance. We are going to need it.
    $textlib = textlib_get_instance();

    $string = strip_tags($string); // Tags are out now
    $string = preg_replace('/[[:space:]]*/','',$string); //Whitespace are out now

    return $textlib->strlen($string);
}

/**
 * Generate and return a random string of the specified length.
 *
 * @param int $length The length of the string to be created.
 * @return string
 */
function random_string ($length=15) {
    $pool  = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';
    $pool .= 'abcdefghijklmnopqrstuvwxyz';
    $pool .= '0123456789';
    $poollen = strlen($pool);
    mt_srand ((double) microtime() * 1000000);
    $string = '';
    for ($i = 0; $i < $length; $i++) {
        $string .= substr($pool, (mt_rand()%($poollen)), 1);
    }
    return $string;
}

/**
 * Generate a complex random string (usefull for md5 salts)
 *
 * This function is based on the above {@link random_string()} however it uses a
 * larger pool of characters and generates a string between 24 and 32 characters
 *
 * @param int $length Optional if set generates a string to exactly this length
 * @return string
 */
function complex_random_string($length=null) {
    $pool  = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
    $pool .= '`~!@#%^&*()_+-=[];,./<>?:{} ';
    $poollen = strlen($pool);
    mt_srand ((double) microtime() * 1000000);
    if ($length===null) {
        $length = floor(rand(24,32));
    }
    $string = '';
    for ($i = 0; $i < $length; $i++) {
        $string .= $pool[(mt_rand()%$poollen)];
    }
    return $string;
}

/**
 * Given some text (which may contain HTML) and an ideal length,
 * this function truncates the text neatly on a word boundary if possible
 *
 * @global object
 * @param string $text - text to be shortened
 * @param int $ideal - ideal string length
 * @param boolean $exact if false, $text will not be cut mid-word
 * @param string $ending The string to append if the passed string is truncated
 * @return string $truncate - shortened string
 */
function shorten_text($text, $ideal=30, $exact = false, $ending='...') {

    global $CFG;

    // if the plain text is shorter than the maximum length, return the whole text
    if (strlen(preg_replace('/<.*?>/', '', $text)) <= $ideal) {
        return $text;
    }

    // Splits on HTML tags. Each open/close/empty tag will be the first thing
    // and only tag in its 'line'
    preg_match_all('/(<.+?>)?([^<>]*)/s', $text, $lines, PREG_SET_ORDER);

    $total_length = strlen($ending);
    $truncate = '';

    // This array stores information about open and close tags and their position
    // in the truncated string. Each item in the array is an object with fields
    // ->open (true if open), ->tag (tag name in lower case), and ->pos
    // (byte position in truncated text)
    $tagdetails = array();

    foreach ($lines as $line_matchings) {
        // if there is any html-tag in this line, handle it and add it (uncounted) to the output
        if (!empty($line_matchings[1])) {
            // if it's an "empty element" with or without xhtml-conform closing slash (f.e. <br/>)
            if (preg_match('/^<(\s*.+?\/\s*|\s*(img|br|input|hr|area|base|basefont|col|frame|isindex|link|meta|param)(\s.+?)?)>$/is', $line_matchings[1])) {
                    // do nothing
            // if tag is a closing tag (f.e. </b>)
            } else if (preg_match('/^<\s*\/([^\s]+?)\s*>$/s', $line_matchings[1], $tag_matchings)) {
                // record closing tag
                $tagdetails[] = (object)array('open'=>false,
                    'tag'=>strtolower($tag_matchings[1]), 'pos'=>strlen($truncate));
            // if tag is an opening tag (f.e. <b>)
            } else if (preg_match('/^<\s*([^\s>!]+).*?>$/s', $line_matchings[1], $tag_matchings)) {
                // record opening tag
                $tagdetails[] = (object)array('open'=>true,
                    'tag'=>strtolower($tag_matchings[1]), 'pos'=>strlen($truncate));
            }
            // add html-tag to $truncate'd text
            $truncate .= $line_matchings[1];
        }

        // calculate the length of the plain text part of the line; handle entities as one character
        $content_length = strlen(preg_replace('/&[0-9a-z]{2,8};|&#[0-9]{1,7};|&#x[0-9a-f]{1,6};/i', ' ', $line_matchings[2]));
        if ($total_length+$content_length > $ideal) {
            // the number of characters which are left
            $left = $ideal - $total_length;
            $entities_length = 0;
            // search for html entities
            if (preg_match_all('/&[0-9a-z]{2,8};|&#[0-9]{1,7};|&#x[0-9a-f]{1,6};/i', $line_matchings[2], $entities, PREG_OFFSET_CAPTURE)) {
                // calculate the real length of all entities in the legal range
                foreach ($entities[0] as $entity) {
                    if ($entity[1]+1-$entities_length <= $left) {
                        $left--;
                        $entities_length += strlen($entity[0]);
                    } else {
                        // no more characters left
                        break;
                    }
                }
            }
            $truncate .= substr($line_matchings[2], 0, $left+$entities_length);
            // maximum lenght is reached, so get off the loop
            break;
        } else {
            $truncate .= $line_matchings[2];
            $total_length += $content_length;
        }

        // if the maximum length is reached, get off the loop
        if($total_length >= $ideal) {
            break;
        }
    }

    // if the words shouldn't be cut in the middle...
    if (!$exact) {
        // ...search the last occurance of a space...
        for ($k=strlen($truncate);$k>0;$k--) {
            if (!empty($truncate[$k]) && ($char = $truncate[$k])) {
                if ($char == '.' or $char == ' ') {
                    $breakpos = $k+1;
                    break;
                } else if (ord($char) >= 0xE0) {  // Chinese/Japanese/Korean text
                    $breakpos = $k;               // can be truncated at any UTF-8
                    break;                        // character boundary.
                }
            }
        }

        if (isset($breakpos)) {
            // ...and cut the text in this position
            $truncate = substr($truncate, 0, $breakpos);
        }
    }

    // add the defined ending to the text
    $truncate .= $ending;

    // Now calculate the list of open html tags based on the truncate position
    $open_tags = array();
    foreach ($tagdetails as $taginfo) {
        if(isset($breakpos) && $taginfo->pos >= $breakpos) {
            // Don't include tags after we made the break!
            break;
        }
        if($taginfo->open) {
            // add tag to the beginning of $open_tags list
            array_unshift($open_tags, $taginfo->tag);
        } else {
            $pos = array_search($taginfo->tag, array_reverse($open_tags, true)); // can have multiple exact same open tags, close the last one
            if ($pos !== false) {
                unset($open_tags[$pos]);
            }
        }
    }

    // close all unclosed html-tags
    foreach ($open_tags as $tag) {
        $truncate .= '</' . $tag . '>';
    }

    return $truncate;
}


/**
 * Given dates in seconds, how many weeks is the date from startdate
 * The first week is 1, the second 2 etc ...
 *
 * @todo Finish documenting this function
 *
 * @uses WEEKSECS
 * @param int $startdate Timestamp for the start date
 * @param int $thedate Timestamp for the end date
 * @return string
 */
function getweek ($startdate, $thedate) {
    if ($thedate < $startdate) {   // error
        return 0;
    }

    return floor(($thedate - $startdate) / WEEKSECS) + 1;
}

/**
 * returns a randomly generated password of length $maxlen.  inspired by
 *
 * {@link http://www.phpbuilder.com/columns/jesus19990502.php3} and
 * {@link http://es2.php.net/manual/en/function.str-shuffle.php#73254}
 *
 * @global object
 * @param int $maxlen  The maximum size of the password being generated.
 * @return string
 */
function generate_password($maxlen=10) {
    global $CFG;

    if (empty($CFG->passwordpolicy)) {
        $fillers = PASSWORD_DIGITS;
        $wordlist = file($CFG->wordlist);
        $word1 = trim($wordlist[rand(0, count($wordlist) - 1)]);
        $word2 = trim($wordlist[rand(0, count($wordlist) - 1)]);
        $filler1 = $fillers[rand(0, strlen($fillers) - 1)];
        $password = $word1 . $filler1 . $word2;
    } else {
        $maxlen = !empty($CFG->minpasswordlength) ? $CFG->minpasswordlength : 0;
        $digits = $CFG->minpassworddigits;
        $lower = $CFG->minpasswordlower;
        $upper = $CFG->minpasswordupper;
        $nonalphanum = $CFG->minpasswordnonalphanum;
        $additional = $maxlen - ($lower + $upper + $digits + $nonalphanum);

        // Make sure we have enough characters to fulfill
        // complexity requirements
        $passworddigits = PASSWORD_DIGITS;
        while ($digits > strlen($passworddigits)) {
            $passworddigits .= PASSWORD_DIGITS;
        }
        $passwordlower = PASSWORD_LOWER;
        while ($lower > strlen($passwordlower)) {
            $passwordlower .= PASSWORD_LOWER;
        }
        $passwordupper = PASSWORD_UPPER;
        while ($upper > strlen($passwordupper)) {
            $passwordupper .= PASSWORD_UPPER;
        }
        $passwordnonalphanum = PASSWORD_NONALPHANUM;
        while ($nonalphanum > strlen($passwordnonalphanum)) {
            $passwordnonalphanum .= PASSWORD_NONALPHANUM;
        }

        // Now mix and shuffle it all
        $password = str_shuffle (substr(str_shuffle ($passwordlower), 0, $lower) .
                                 substr(str_shuffle ($passwordupper), 0, $upper) .
                                 substr(str_shuffle ($passworddigits), 0, $digits) .
                                 substr(str_shuffle ($passwordnonalphanum), 0 , $nonalphanum) .
                                 substr(str_shuffle ($passwordlower .
                                                     $passwordupper .
                                                     $passworddigits .
                                                     $passwordnonalphanum), 0 , $additional));
    }

    return substr ($password, 0, $maxlen);
}

/**
 * Given a float, prints it nicely.
 * Localized floats must not be used in calculations!
 *
 * @param float $flaot The float to print
 * @param int $places The number of decimal places to print.
 * @param bool $localized use localized decimal separator
 * @return string locale float
 */
function format_float($float, $decimalpoints=1, $localized=true) {
    if (is_null($float)) {
        return '';
    }
    if ($localized) {
        return number_format($float, $decimalpoints, get_string('decsep', 'langconfig'), '');
    } else {
        return number_format($float, $decimalpoints, '.', '');
    }
}

/**
 * Converts locale specific floating point/comma number back to standard PHP float value
 * Do NOT try to do any math operations before this conversion on any user submitted floats!
 *
 * @param  string $locale_float locale aware float representation
 * @return float
 */
function unformat_float($locale_float) {
    $locale_float = trim($locale_float);

    if ($locale_float == '') {
        return null;
    }

    $locale_float = str_replace(' ', '', $locale_float); // no spaces - those might be used as thousand separators

    return (float)str_replace(get_string('decsep', 'langconfig'), '.', $locale_float);
}

/**
 * Given a simple array, this shuffles it up just like shuffle()
 * Unlike PHP's shuffle() this function works on any machine.
 *
 * @param array $array The array to be rearranged
 * @return array
 */
function swapshuffle($array) {

    srand ((double) microtime() * 10000000);
    $last = count($array) - 1;
    for ($i=0;$i<=$last;$i++) {
        $from = rand(0,$last);
        $curr = $array[$i];
        $array[$i] = $array[$from];
        $array[$from] = $curr;
    }
    return $array;
}

/**
 * Like {@link swapshuffle()}, but works on associative arrays
 *
 * @param array $array The associative array to be rearranged
 * @return array
 */
function swapshuffle_assoc($array) {

    $newarray = array();
    $newkeys = swapshuffle(array_keys($array));

    foreach ($newkeys as $newkey) {
        $newarray[$newkey] = $array[$newkey];
    }
    return $newarray;
}

/**
 * Given an arbitrary array, and a number of draws,
 * this function returns an array with that amount
 * of items.  The indexes are retained.
 *
 * @todo Finish documenting this function
 *
 * @param array $array
 * @param int $draws
 * @return array
 */
function draw_rand_array($array, $draws) {
    srand ((double) microtime() * 10000000);

    $return = array();

    $last = count($array);

    if ($draws > $last) {
        $draws = $last;
    }

    while ($draws > 0) {
        $last--;

        $keys = array_keys($array);
        $rand = rand(0, $last);

        $return[$keys[$rand]] = $array[$keys[$rand]];
        unset($array[$keys[$rand]]);

        $draws--;
    }

    return $return;
}

/**
 * Calculate the difference between two microtimes
 *
 * @param string $a The first Microtime
 * @param string $b The second Microtime
 * @return string
 */
function microtime_diff($a, $b) {
    list($a_dec, $a_sec) = explode(' ', $a);
    list($b_dec, $b_sec) = explode(' ', $b);
    return $b_sec - $a_sec + $b_dec - $a_dec;
}

/**
 * Given a list (eg a,b,c,d,e) this function returns
 * an array of 1->a, 2->b, 3->c etc
 *
 * @param string $list The string to explode into array bits
 * @param string $separator The seperator used within the list string
 * @return array The now assembled array
 */
function make_menu_from_list($list, $separator=',') {

    $array = array_reverse(explode($separator, $list), true);
    foreach ($array as $key => $item) {
        $outarray[$key+1] = trim($item);
    }
    return $outarray;
}

/**
 * Creates an array that represents all the current grades that
 * can be chosen using the given grading type.
 *
 * Negative numbers
 * are scales, zero is no grade, and positive numbers are maximum
 * grades.
 *
 * @todo Finish documenting this function
 *
 * @global object
 * @param int $gradingtype
 * @return int
 */
function make_grades_menu($gradingtype) {
    global $DB;

    $grades = array();
    if ($gradingtype < 0) {
        if ($scale = $DB->get_record('scale', array('id'=> (-$gradingtype)))) {
            return make_menu_from_list($scale->scale);
        }
    } else if ($gradingtype > 0) {
        for ($i=$gradingtype; $i>=0; $i--) {
            $grades[$i] = $i .' / '. $gradingtype;
        }
        return $grades;
    }
    return $grades;
}

/**
 * This function returns the nummber of activities
 * using scaleid in a courseid
 *
 * @todo Finish documenting this function
 *
 * @global object
 * @global object
 * @param int $courseid ?
 * @param int $scaleid ?
 * @return int
 */
function course_scale_used($courseid, $scaleid) {
    global $CFG, $DB;

    $return = 0;

    if (!empty($scaleid)) {
        if ($cms = get_course_mods($courseid)) {
            foreach ($cms as $cm) {
                //Check cm->name/lib.php exists
                if (file_exists($CFG->dirroot.'/mod/'.$cm->modname.'/lib.php')) {
                    include_once($CFG->dirroot.'/mod/'.$cm->modname.'/lib.php');
                    $function_name = $cm->modname.'_scale_used';
                    if (function_exists($function_name)) {
                        if ($function_name($cm->instance,$scaleid)) {
                            $return++;
                        }
                    }
                }
            }
        }

        // check if any course grade item makes use of the scale
        $return += $DB->count_records('grade_items', array('courseid'=>$courseid, 'scaleid'=>$scaleid));

        // check if any outcome in the course makes use of the scale
        $return += $DB->count_records_sql("SELECT COUNT('x')
                                             FROM {grade_outcomes_courses} goc,
                                                  {grade_outcomes} go
                                            WHERE go.id = goc.outcomeid
                                                  AND go.scaleid = ? AND goc.courseid = ?",
                                          array($scaleid, $courseid));
    }
    return $return;
}

/**
 * This function returns the nummber of activities
 * using scaleid in the entire site
 *
 * @param int $scaleid
 * @param array $courses
 * @return int
 */
function site_scale_used($scaleid, &$courses) {
    $return = 0;

    if (!is_array($courses) || count($courses) == 0) {
        $courses = get_courses("all",false,"c.id,c.shortname");
    }

    if (!empty($scaleid)) {
        if (is_array($courses) && count($courses) > 0) {
            foreach ($courses as $course) {
                $return += course_scale_used($course->id,$scaleid);
            }
        }
    }
    return $return;
}

/**
 * make_unique_id_code
 *
 * @todo Finish documenting this function
 *
 * @uses $_SERVER
 * @param string $extra Extra string to append to the end of the code
 * @return string
 */
function make_unique_id_code($extra='') {

    $hostname = 'unknownhost';
    if (!empty($_SERVER['HTTP_HOST'])) {
        $hostname = $_SERVER['HTTP_HOST'];
    } else if (!empty($_ENV['HTTP_HOST'])) {
        $hostname = $_ENV['HTTP_HOST'];
    } else if (!empty($_SERVER['SERVER_NAME'])) {
        $hostname = $_SERVER['SERVER_NAME'];
    } else if (!empty($_ENV['SERVER_NAME'])) {
        $hostname = $_ENV['SERVER_NAME'];
    }

    $date = gmdate("ymdHis");

    $random =  random_string(6);

    if ($extra) {
        return $hostname .'+'. $date .'+'. $random .'+'. $extra;
    } else {
        return $hostname .'+'. $date .'+'. $random;
    }
}


/**
 * Function to check the passed address is within the passed subnet
 *
 * The parameter is a comma separated string of subnet definitions.
 * Subnet strings can be in one of three formats:
 *   1: xxx.xxx.xxx.xxx/nn or xxxx:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx/nnn          (number of bits in net mask)
 *   2: xxx.xxx.xxx.xxx-yyy or  xxxx:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx::xxxx-yyyy (a range of IP addresses in the last group)
 *   3: xxx.xxx or xxx.xxx. or xxx:xxx:xxxx or xxx:xxx:xxxx.                  (incomplete address, a bit non-technical ;-)
 * Code for type 1 modified from user posted comments by mediator at
 * {@link http://au.php.net/manual/en/function.ip2long.php}
 *
 * @param string $addr    The address you are checking
 * @param string $subnetstr    The string of subnet addresses
 * @return bool
 */
function address_in_subnet($addr, $subnetstr) {

    $subnets = explode(',', $subnetstr);
    $found = false;
    $addr = trim($addr);
    $addr = cleanremoteaddr($addr, false); // normalise
    if ($addr === null) {
        return false;
    }
    $addrparts = explode(':', $addr);

    $ipv6 = strpos($addr, ':');

    foreach ($subnets as $subnet) {
        $subnet = trim($subnet);
        if ($subnet === '') {
            continue;
        }

        if (strpos($subnet, '/') !== false) {
        ///1: xxx.xxx.xxx.xxx/nn or xxxx:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx/nnn
            list($ip, $mask) = explode('/', $subnet);
            $mask = trim($mask);
            if (!is_number($mask)) {
                continue; // incorect mask number, eh?
            }
            $ip = cleanremoteaddr($ip, false); // normalise
            if ($ip === null) {
                continue;
            }
            if (strpos($ip, ':') !== false) {
                // IPv6
                if (!$ipv6) {
                    continue;
                }
                if ($mask > 128 or $mask < 0) {
                    continue; // nonsense
                }
                if ($mask == 0) {
                    return true; // any address
                }
                if ($mask == 128) {
                    if ($ip === $addr) {
                        return true;
                    }
                    continue;
                }
                $ipparts = explode(':', $ip);
                $modulo  = $mask % 16;
                $ipnet   = array_slice($ipparts, 0, ($mask-$modulo)/16);
                $addrnet = array_slice($addrparts, 0, ($mask-$modulo)/16);
                if (implode(':', $ipnet) === implode(':', $addrnet)) {
                    if ($modulo == 0) {
                        return true;
                    }
                    $pos     = ($mask-$modulo)/16;
                    $ipnet   = hexdec($ipparts[$pos]);
                    $addrnet = hexdec($addrparts[$pos]);
                    $mask    = 0xffff << (16 - $modulo);
                    if (($addrnet & $mask) == ($ipnet & $mask)) {
                        return true;
                    }
                }

            } else {
                // IPv4
                if ($ipv6) {
                    continue;
                }
                if ($mask > 32 or $mask < 0) {
                    continue; // nonsense
                }
                if ($mask == 0) {
                    return true;
                }
                if ($mask == 32) {
                    if ($ip === $addr) {
                        return true;
                    }
                    continue;
                }
                $mask = 0xffffffff << (32 - $mask);
                if (((ip2long($addr) & $mask) == (ip2long($ip) & $mask))) {
                    return true;
                }
            }

        } else if (strpos($subnet, '-') !== false)  {
        /// 2: xxx.xxx.xxx.xxx-yyy or  xxxx:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx::xxxx-yyyy ...a range of IP addresses in the last group.
            $parts = explode('-', $subnet);
            if (count($parts) != 2) {
                continue;
            }

            if (strpos($subnet, ':') !== false) {
                // IPv6
                if (!$ipv6) {
                    continue;
                }
                $ipstart = cleanremoteaddr(trim($parts[0]), false); // normalise
                if ($ipstart === null) {
                    continue;
                }
                $ipparts = explode(':', $ipstart);
                $start = hexdec(array_pop($ipparts));
                $ipparts[] = trim($parts[1]);
                $ipend = cleanremoteaddr(implode(':', $ipparts), false); // normalise
                if ($ipend === null) {
                    continue;
                }
                $ipparts[7] = '';
                $ipnet = implode(':', $ipparts);
                if (strpos($addr, $ipnet) !== 0) {
                    continue;
                }
                $ipparts = explode(':', $ipend);
                $end = hexdec($ipparts[7]);

                $addrend = hexdec($addrparts[7]);

                if (($addrend >= $start) and ($addrend <= $end)) {
                    return true;
                }

            } else {
                // IPv4
                if ($ipv6) {
                    continue;
                }
                $ipstart = cleanremoteaddr(trim($parts[0]), false); // normalise
                if ($ipstart === null) {
                    continue;
                }
                $ipparts = explode('.', $ipstart);
                $ipparts[3] = trim($parts[1]);
                $ipend = cleanremoteaddr(implode('.', $ipparts), false); // normalise
                if ($ipend === null) {
                    continue;
                }

                if ((ip2long($addr) >= ip2long($ipstart)) and (ip2long($addr) <= ip2long($ipend))) {
                    return true;
                }
            }

        } else {
        /// 3: xxx.xxx or xxx.xxx. or xxx:xxx:xxxx or xxx:xxx:xxxx.
            if (strpos($subnet, ':') !== false) {
                // IPv6
                if (!$ipv6) {
                    continue;
                }
                $parts = explode(':', $subnet);
                $count = count($parts);
                if ($parts[$count-1] === '') {
                    unset($parts[$count-1]); // trim trailing :
                    $count--;
                    $subnet = implode('.', $parts);
                }
                $isip = cleanremoteaddr($subnet, false); // normalise
                if ($isip !== null) {
                    if ($isip === $addr) {
                        return true;
                    }
                    continue;
                } else if ($count > 8) {
                    continue;
                }
                $zeros = array_fill(0, 8-$count, '0');
                $subnet = $subnet.':'.implode(':', $zeros).'/'.($count*16);
                if (address_in_subnet($addr, $subnet)) {
                    return true;
                }

            } else {
                // IPv4
                if ($ipv6) {
                    continue;
                }
                $parts = explode('.', $subnet);
                $count = count($parts);
                if ($parts[$count-1] === '') {
                    unset($parts[$count-1]); // trim trailing .
                    $count--;
                    $subnet = implode('.', $parts);
                }
                if ($count == 4) {
                    $subnet = cleanremoteaddr($subnet, false); // normalise
                    if ($subnet === $addr) {
                        return true;
                    }
                    continue;
                } else if ($count > 4) {
                    continue;
                }
                $zeros = array_fill(0, 4-$count, '0');
                $subnet = $subnet.'.'.implode('.', $zeros).'/'.($count*8);
                if (address_in_subnet($addr, $subnet)) {
                    return true;
                }
            }
        }
    }

    return false;
}

/**
 * This function sets the $HTTPSPAGEREQUIRED global
 * (used in some parts of moodle to change some links)
 * and calculate the proper wwwroot to be used
 *
 * By using this function properly, we can ensure 100% https-ized pages
 * at our entire discretion (login, forgot_password, change_password)
 */
function httpsrequired() {
    global $PAGE;
    $PAGE->https_required();
}

/**
 * For outputting debugging info
 *
 * @uses STDOUT
 * @param string $string The string to write
 * @param string $eol The end of line char(s) to use
 * @param string $sleep Period to make the application sleep
 *                      This ensures any messages have time to display before redirect
 */
function mtrace($string, $eol="\n", $sleep=0) {

    if (defined('STDOUT')) {
        fwrite(STDOUT, $string.$eol);
    } else {
        echo $string . $eol;
    }

    flush();

    //delay to keep message on user's screen in case of subsequent redirect
    if ($sleep) {
        sleep($sleep);
    }
}

/**
 * Replace 1 or more slashes or backslashes to 1 slash
 *
 * @param string $path The path to strip
 * @return string the path with double slashes removed
 */
function cleardoubleslashes ($path) {
    return preg_replace('/(\/|\\\){1,}/','/',$path);
}

/**
 * Is current ip in give list?
 *
 * @param string $list
 * @return bool
 */
function remoteip_in_list($list){
    $inlist = false;
    $client_ip = getremoteaddr();

    if(!$client_ip){
        // ensure access on cli
        return true;
    }

    $list = explode("\n", $list);
    foreach($list as $subnet) {
        $subnet = trim($subnet);
        if (address_in_subnet($client_ip, $subnet)) {
            $inlist = true;
            break;
        }
    }
    return $inlist;
}

/**
 * Returns most reliable client address
 *
 * @global object
 * @return string The remote IP address
 */
function getremoteaddr() {
    global $CFG;

    if (empty($CFG->getremoteaddrconf)) {
        // This will happen, for example, before just after the upgrade, as the
        // user is redirected to the admin screen.
        $variablestoskip = 0;
    } else {
        $variablestoskip = $CFG->getremoteaddrconf;
    }
    if (!($variablestoskip & GETREMOTEADDR_SKIP_HTTP_CLIENT_IP)) {
        if (!empty($_SERVER['HTTP_CLIENT_IP'])) {
            return cleanremoteaddr($_SERVER['HTTP_CLIENT_IP']);
        }
    }
    if (!($variablestoskip & GETREMOTEADDR_SKIP_HTTP_X_FORWARDED_FOR)) {
        if (!empty($_SERVER['HTTP_X_FORWARDED_FOR'])) {
            return cleanremoteaddr($_SERVER['HTTP_X_FORWARDED_FOR']);
        }
    }
    if (!empty($_SERVER['REMOTE_ADDR'])) {
        return cleanremoteaddr($_SERVER['REMOTE_ADDR']);
    } else {
        return null;
    }
}

/**
 * Cleans an ip address. Internal addresses are now allowed.
 * (Originally local addresses were not allowed.)
 *
 * @param string $addr IPv4 or IPv6 address
 * @param bool $compress use IPv6 address compression
 * @return string normalised ip address string, null if error
 */
function cleanremoteaddr($addr, $compress=false) {
    $addr = trim($addr);

    //TODO: maybe add a separate function is_addr_public() or something like this

    if (strpos($addr, ':') !== false) {
        // can be only IPv6
        $parts = explode(':', $addr);
        $count = count($parts);

        if (strpos($parts[$count-1], '.') !== false) {
            //legacy ipv4 notation
            $last = array_pop($parts);
            $ipv4 = cleanremoteaddr($last, true);
            if ($ipv4 === null) {
                return null;
            }
            $bits = explode('.', $ipv4);
            $parts[] = dechex($bits[0]).dechex($bits[1]);
            $parts[] = dechex($bits[2]).dechex($bits[3]);
            $count = count($parts);
            $addr = implode(':', $parts);
        }

        if ($count < 3 or $count > 8) {
            return null; // severly malformed
        }

        if ($count != 8) {
            if (strpos($addr, '::') === false) {
                return null; // malformed
            }
            // uncompress ::
            $insertat = array_search('', $parts, true);
            $missing = array_fill(0, 1 + 8 - $count, '0');
            array_splice($parts, $insertat, 1, $missing);
            foreach ($parts as $key=>$part) {
                if ($part === '') {
                    $parts[$key] = '0';
                }
            }
        }

        $adr = implode(':', $parts);
        if (!preg_match('/^([0-9a-f]{1,4})(:[0-9a-f]{1,4})*$/i', $adr)) {
            return null; // incorrect format - sorry
        }

        // normalise 0s and case
        $parts = array_map('hexdec', $parts);
        $parts = array_map('dechex', $parts);

        $result = implode(':', $parts);

        if (!$compress) {
            return $result;
        }

        if ($result === '0:0:0:0:0:0:0:0') {
            return '::'; // all addresses
        }

        $compressed = preg_replace('/(:0)+:0$/', '::', $result, 1);
        if ($compressed !== $result) {
            return $compressed;
        }

        $compressed = preg_replace('/^(0:){2,7}/', '::', $result, 1);
        if ($compressed !== $result) {
            return $compressed;
        }

        $compressed = preg_replace('/(:0){2,6}:/', '::', $result, 1);
        if ($compressed !== $result) {
            return $compressed;
        }

        return $result;
    }

    // first get all things that look like IPv4 addresses
    $parts = array();
    if (!preg_match('/^(\d{1,3})\.(\d{1,3})\.(\d{1,3})\.(\d{1,3})$/', $addr, $parts)) {
        return null;
    }
    unset($parts[0]);

    foreach ($parts as $key=>$match) {
        if ($match > 255) {
            return null;
        }
        $parts[$key] = (int)$match; // normalise 0s
    }

    return implode('.', $parts);
}

/**
 * This function will make a complete copy of anything it's given,
 * regardless of whether it's an object or not.
 *
 * @param mixed $thing Something you want cloned
 * @return mixed What ever it is you passed it
 */
function fullclone($thing) {
    return unserialize(serialize($thing));
}


/**
 * This function expects to called during shutdown
 * should be set via register_shutdown_function()
 * in lib/setup.php .
 *
 * Right now we do it only if we are under apache, to
 * make sure apache children that hog too much mem are
 * killed.
 *
 * @global object
 */
function moodle_request_shutdown() {
    global $CFG;

    // initially, we are only ever called under apache
    // but check just in case
    if (function_exists('apache_child_terminate')
        && function_exists('memory_get_usage')
        && ini_get_bool('child_terminate')) {
        if (empty($CFG->apachemaxmem)) {
            $CFG->apachemaxmem = 25000000; // default 25MiB
        }
        if (memory_get_usage() > (int)$CFG->apachemaxmem) {
            trigger_error('Mem usage over $CFG->apachemaxmem: marking child for reaping.');
            @apache_child_terminate();
        }
    }
    if (defined('MDL_PERF') || (!empty($CFG->perfdebug) and $CFG->perfdebug > 7)) {
        if (defined('MDL_PERFTOLOG')) {
            $perf = get_performance_info();
            error_log("PERF: " . $perf['txt']);
        }
        if (defined('MDL_PERFINC')) {
            $inc = get_included_files();
            $ts  = 0;
            foreach($inc as $f) {
                if (preg_match(':^/:', $f)) {
                    $fs  =  filesize($f);
                    $ts  += $fs;
                    $hfs =  display_size($fs);
                    error_log(substr($f,strlen($CFG->dirroot)) . " size: $fs ($hfs)"
                              , NULL, NULL, 0);
                } else {
                    error_log($f , NULL, NULL, 0);
                }
            }
            if ($ts > 0 ) {
                $hts = display_size($ts);
                error_log("Total size of files included: $ts ($hts)");
            }
        }
    }
}

/**
 * If new messages are waiting for the current user, then load the
 * JavaScript required to pop up the messaging window.
 */
function message_popup_window() {
    global $USER, $DB, $PAGE;

    if (defined('MESSAGE_WINDOW') || empty($CFG->messaging)) {
        return;
    }

    if (!isset($USER->id) || isguestuser()) {
        return;
    }

    if (!isset($USER->message_lastpopup)) {
        $USER->message_lastpopup = 0;
    }

    $popuplimit = 30;     // Minimum seconds between popups
    if ((time() - $USER->message_lastpopup) <= $popuplimit) {  /// It's been long enough
        return;
    }

    if (!get_user_preferences('message_showmessagewindow', 1)) {
        return;
    }

    if ($DB->count_records_select('message', 'useridto = ? AND timecreated > ?', array($USER->id, $USER->message_lastpopup))) {
        $USER->message_lastpopup = time();
        $PAGE->requires->js_function_call('openpopup', array('/message/index.php', 'message',
                'menubar=0,location=0,scrollbars,status,resizable,width=400,height=500', 0));
    }
}

/**
 * Used to make sure that $min <= $value <= $max
 *
 * Make sure that value is between min, and max
 *
 * @param int $min The minimum value
 * @param int $value The value to check
 * @param int $max The maximum value
 */
function bounded_number($min, $value, $max) {
    if($value < $min) {
        return $min;
    }
    if($value > $max) {
        return $max;
    }
    return $value;
}

/**
 * Check if there is a nested array within the passed array
 *
 * @param array $array
 * @return bool true if there is a nested array false otherwise
 */
function array_is_nested($array) {
    foreach ($array as $value) {
        if (is_array($value)) {
            return true;
        }
    }
    return false;
}

/**
 * get_performance_info() pairs up with init_performance_info()
 * loaded in setup.php. Returns an array with 'html' and 'txt'
 * values ready for use, and each of the individual stats provided
 * separately as well.
 *
 * @global object
 * @global object
 * @global object
 * @return array
 */
function get_performance_info() {
    global $CFG, $PERF, $DB;

    $info = array();
    $info['html'] = '';         // holds userfriendly HTML representation
    $info['txt']  = me() . ' '; // holds log-friendly representation

    $info['realtime'] = microtime_diff($PERF->starttime, microtime());

    $info['html'] .= '<span class="timeused">'.$info['realtime'].' secs</span> ';
    $info['txt'] .= 'time: '.$info['realtime'].'s ';

    if (function_exists('memory_get_usage')) {
        $info['memory_total'] = memory_get_usage();
        $info['memory_growth'] = memory_get_usage() - $PERF->startmemory;
        $info['html'] .= '<span class="memoryused">RAM: '.display_size($info['memory_total']).'</span> ';
        $info['txt']  .= 'memory_total: '.$info['memory_total'].'B (' . display_size($info['memory_total']).') memory_growth: '.$info['memory_growth'].'B ('.display_size($info['memory_growth']).') ';
    }

    if (function_exists('memory_get_peak_usage')) {
        $info['memory_peak'] = memory_get_peak_usage();
        $info['html'] .= '<span class="memoryused">RAM peak: '.display_size($info['memory_peak']).'</span> ';
        $info['txt']  .= 'memory_peak: '.$info['memory_peak'].'B (' . display_size($info['memory_peak']).') ';
    }

    $inc = get_included_files();
    //error_log(print_r($inc,1));
    $info['includecount'] = count($inc);
    $info['html'] .= '<span class="included">Included '.$info['includecount'].' files</span> ';
    $info['txt']  .= 'includecount: '.$info['includecount'].' ';

    $filtermanager = filter_manager::instance();
    if (method_exists($filtermanager, 'get_performance_summary')) {
        list($filterinfo, $nicenames) = $filtermanager->get_performance_summary();
        $info = array_merge($filterinfo, $info);
        foreach ($filterinfo as $key => $value) {
            $info['html'] .= "<span class='$key'>$nicenames[$key]: $value </span> ";
            $info['txt'] .= "$key: $value ";
        }
    }

    if (!empty($PERF->logwrites)) {
        $info['logwrites'] = $PERF->logwrites;
        $info['html'] .= '<span class="logwrites">Log DB writes '.$info['logwrites'].'</span> ';
        $info['txt'] .= 'logwrites: '.$info['logwrites'].' ';
    }

    $info['dbqueries'] = $DB->perf_get_reads().'/'.($DB->perf_get_writes() - $PERF->logwrites);
    $info['html'] .= '<span class="dbqueries">DB reads/writes: '.$info['dbqueries'].'</span> ';
    $info['txt'] .= 'db reads/writes: '.$info['dbqueries'].' ';

    if (!empty($PERF->profiling) && $PERF->profiling) {
        require_once($CFG->dirroot .'/lib/profilerlib.php');
        $info['html'] .= '<span class="profilinginfo">'.Profiler::get_profiling(array('-R')).'</span>';
    }

    if (function_exists('posix_times')) {
        $ptimes = posix_times();
        if (is_array($ptimes)) {
            foreach ($ptimes as $key => $val) {
                $info[$key] = $ptimes[$key] -  $PERF->startposixtimes[$key];
            }
            $info['html'] .= "<span class=\"posixtimes\">ticks: $info[ticks] user: $info[utime] sys: $info[stime] cuser: $info[cutime] csys: $info[cstime]</span> ";
            $info['txt'] .= "ticks: $info[ticks] user: $info[utime] sys: $info[stime] cuser: $info[cutime] csys: $info[cstime] ";
        }
    }

    // Grab the load average for the last minute
    // /proc will only work under some linux configurations
    // while uptime is there under MacOSX/Darwin and other unices
    if (is_readable('/proc/loadavg') && $loadavg = @file('/proc/loadavg')) {
        list($server_load) = explode(' ', $loadavg[0]);
        unset($loadavg);
    } else if ( function_exists('is_executable') && is_executable('/usr/bin/uptime') && $loadavg = `/usr/bin/uptime` ) {
        if (preg_match('/load averages?: (\d+[\.,:]\d+)/', $loadavg, $matches)) {
            $server_load = $matches[1];
        } else {
            trigger_error('Could not parse uptime output!');
        }
    }
    if (!empty($server_load)) {
        $info['serverload'] = $server_load;
        $info['html'] .= '<span class="serverload">Load average: '.$info['serverload'].'</span> ';
        $info['txt'] .= "serverload: {$info['serverload']} ";
    }

/*    if (isset($rcache->hits) && isset($rcache->misses)) {
        $info['rcachehits'] = $rcache->hits;
        $info['rcachemisses'] = $rcache->misses;
        $info['html'] .= '<span class="rcache">Record cache hit/miss ratio : '.
            "{$rcache->hits}/{$rcache->misses}</span> ";
        $info['txt'] .= 'rcache: '.
            "{$rcache->hits}/{$rcache->misses} ";
    }*/
    $info['html'] = '<div class="performanceinfo">'.$info['html'].'</div>';
    return $info;
}

/**
 * @todo Document this function linux people
 */
function apd_get_profiling() {
    return shell_exec('pprofp -u ' . ini_get('apd.dumpdir') . '/pprof.' . getmypid() . '.*');
}

/**
 * Delete directory or only it's content
 *
 * @param string $dir directory path
 * @param bool $content_only
 * @return bool success, true also if dir does not exist
 */
function remove_dir($dir, $content_only=false) {
    if (!file_exists($dir)) {
        // nothing to do
        return true;
    }
    $handle = opendir($dir);
    $result = true;
    while (false!==($item = readdir($handle))) {
        if($item != '.' && $item != '..') {
            if(is_dir($dir.'/'.$item)) {
                $result = remove_dir($dir.'/'.$item) && $result;
            }else{
                $result = unlink($dir.'/'.$item) && $result;
            }
        }
    }
    closedir($handle);
    if ($content_only) {
        return $result;
    }
    return rmdir($dir); // if anything left the result will be false, noo need for && $result
}

/**
 * Function to check if a directory exists and optionally create it.
 *
 * @param string absolute directory path (must be under $CFG->dataroot)
 * @param boolean create directory if does not exist
 * @param boolean create directory recursively
 * @return boolean true if directory exists or created
 */
function check_dir_exists($dir, $create=false, $recursive=false) {
    global $CFG;

    if (strstr(cleardoubleslashes($dir), cleardoubleslashes($CFG->dataroot.'/')) === false) {
        debugging('Warning. Wrong call to check_dir_exists(). $dir must be an absolute path under $CFG->dataroot ("' . $dir . '" is incorrect)', DEBUG_DEVELOPER);
    }

    $status = true;

    if (!is_dir($dir)) {
        if (!$create) {
            $status = false;
        } else {
            $status = mkdir($dir, $CFG->directorypermissions, $recursive);
        }
    }
    return $status;
}

/**
 * Detect if an object or a class contains a given property
 * will take an actual object or the name of a class
 *
 * @param mix $obj Name of class or real object to test
 * @param string $property name of property to find
 * @return bool true if property exists
 */
function object_property_exists( $obj, $property ) {
    if (is_string( $obj )) {
        $properties = get_class_vars( $obj );
    }
    else {
        $properties = get_object_vars( $obj );
    }
    return array_key_exists( $property, $properties );
}


/**
 * Detect a custom script replacement in the data directory that will
 * replace an existing moodle script
 *
 * @param string $urlpath path to the original script
 * @return string|bool full path name if a custom script exists, false if no custom script exists
 */
function custom_script_path($urlpath='') {
    global $CFG;

    // set default $urlpath, if necessary
    if (empty($urlpath)) {
        $urlpath = qualified_me(); // e.g. http://www.this-server.com/moodle/this-script.php
    }

    // $urlpath is invalid if it is empty or does not start with the Moodle wwwroot
    if (empty($urlpath) or (strpos($urlpath, $CFG->wwwroot) === false )) {
        return false;
    }

    // replace wwwroot with the path to the customscripts folder and clean path
    $scriptpath = $CFG->customscripts . clean_param(substr($urlpath, strlen($CFG->wwwroot)), PARAM_PATH);

    // remove the query string, if any
    if (($strpos = strpos($scriptpath, '?')) !== false) {
        $scriptpath = substr($scriptpath, 0, $strpos);
    }

    // remove trailing slashes, if any
    $scriptpath = rtrim($scriptpath, '/\\');

    // append index.php, if necessary
    if (is_dir($scriptpath)) {
        $scriptpath .= '/index.php';
    }

    // check the custom script exists
    if (file_exists($scriptpath)) {
        return $scriptpath;
    } else {
        return false;
    }
}

/**
 * Returns whether or not the user object is a remote MNET user. This function
 * is in moodlelib because it does not rely on loading any of the MNET code.
 *
 * @global object
 * @param object $user A valid user object
 * @return bool        True if the user is from a remote Moodle.
 */
function is_mnet_remote_user($user) {
    global $CFG;

    if (!isset($CFG->mnet_localhost_id)) {
        include_once $CFG->dirroot . '/mnet/lib.php';
        $env = new mnet_environment();
        $env->init();
        unset($env);
    }

    return (!empty($user->mnethostid) && $user->mnethostid != $CFG->mnet_localhost_id);
}

/**
 * Checks if a given plugin is in the list of enabled enrolment plugins.
 *
 * @global object
 * @param string $auth Enrolment plugin.
 * @return boolean Whether the plugin is enabled.
 */
function is_enabled_enrol($enrol='') {
    global $CFG;

    // use the global default if not specified
    if ($enrol == '') {
        $enrol = $CFG->enrol;
    }
    return in_array($enrol, explode(',', $CFG->enrol_plugins_enabled));
}

/**
 * This function will search for browser prefereed languages, setting Moodle
 * to use the best one available if $SESSION->lang is undefined
 *
 * @global object
 * @global object
 * @global object
 */
function setup_lang_from_browser() {

    global $CFG, $SESSION, $USER;

    if (!empty($SESSION->lang) or !empty($USER->lang) or empty($CFG->autolang)) {
        // Lang is defined in session or user profile, nothing to do
        return;
    }

    if (!isset($_SERVER['HTTP_ACCEPT_LANGUAGE'])) { // There isn't list of browser langs, nothing to do
        return;
    }

/// Extract and clean langs from headers
    $rawlangs = $_SERVER['HTTP_ACCEPT_LANGUAGE'];
    $rawlangs = str_replace('-', '_', $rawlangs);         // we are using underscores
    $rawlangs = explode(',', $rawlangs);                  // Convert to array
    $langs = array();

    $order = 1.0;
    foreach ($rawlangs as $lang) {
        if (strpos($lang, ';') === false) {
            $langs[(string)$order] = $lang;
            $order = $order-0.01;
        } else {
            $parts = explode(';', $lang);
            $pos = strpos($parts[1], '=');
            $langs[substr($parts[1], $pos+1)] = $parts[0];
        }
    }
    krsort($langs, SORT_NUMERIC);

/// Look for such langs under standard locations
    foreach ($langs as $lang) {
        $lang = strtolower(clean_param($lang, PARAM_SAFEDIR)); // clean it properly for include
        if (get_string_manager()->translation_exists($lang, false)) {
            $SESSION->lang = $lang; /// Lang exists, set it in session
            break; /// We have finished. Go out
        }
    }
    return;
}

/**
 * check if $url matches anything in proxybypass list
 *
 * any errors just result in the proxy being used (least bad)
 *
 * @global object
 * @param string $url url to check
 * @return boolean true if we should bypass the proxy
 */
function is_proxybypass( $url ) {
    global $CFG;

    // sanity check
    if (empty($CFG->proxyhost) or empty($CFG->proxybypass)) {
        return false;
    }

    // get the host part out of the url
    if (!$host = parse_url( $url, PHP_URL_HOST )) {
        return false;
    }

    // get the possible bypass hosts into an array
    $matches = explode( ',', $CFG->proxybypass );

    // check for a match
    // (IPs need to match the left hand side and hosts the right of the url,
    // but we can recklessly check both as there can't be a false +ve)
    $bypass = false;
    foreach ($matches as $match) {
        $match = trim($match);

        // try for IP match (Left side)
        $lhs = substr($host,0,strlen($match));
        if (strcasecmp($match,$lhs)==0) {
            return true;
        }

        // try for host match (Right side)
        $rhs = substr($host,-strlen($match));
        if (strcasecmp($match,$rhs)==0) {
            return true;
        }
    }

    // nothing matched.
    return false;
}


////////////////////////////////////////////////////////////////////////////////

/**
 * Check if the passed navigation is of the new style
 *
 * @param mixed $navigation
 * @return bool true for yes false for no
 */
function is_newnav($navigation) {
    if (is_array($navigation) && !empty($navigation['newnav'])) {
        return true;
    } else {
        return false;
    }
}

/**
 * Checks whether the given variable name is defined as a variable within the given object.
 *
 * This will NOT work with stdClass objects, which have no class variables.
 *
 * @param string $var The variable name
 * @param object $object The object to check
 * @return boolean
 */
function in_object_vars($var, $object) {
    $class_vars = get_class_vars(get_class($object));
    $class_vars = array_keys($class_vars);
    return in_array($var, $class_vars);
}

/**
 * Returns an array without repeated objects.
 * This function is similar to array_unique, but for arrays that have objects as values
 *
 * @param array $array
 * @param bool $keep_key_assoc
 * @return array
 */
function object_array_unique($array, $keep_key_assoc = true) {
    $duplicate_keys = array();
    $tmp         = array();

    foreach ($array as $key=>$val) {
        // convert objects to arrays, in_array() does not support objects
        if (is_object($val)) {
            $val = (array)$val;
        }

        if (!in_array($val, $tmp)) {
            $tmp[] = $val;
        } else {
            $duplicate_keys[] = $key;
        }
    }

    foreach ($duplicate_keys as $key) {
        unset($array[$key]);
    }

    return $keep_key_assoc ? $array : array_values($array);
}

/**
 * Returns the language string for the given plugin.
 *
 * @param string $plugin the plugin code name
 * @param string $type the type of plugin (mod, block, filter)
 * @return string The plugin language string
 */
function get_plugin_name($plugin, $type='mod') {
    $plugin_name = '';

    switch ($type) {
        case 'mod':
            $plugin_name = get_string('modulename', $plugin);
            break;
        case 'blocks':
            $plugin_name = get_string('pluginname', "block_$plugin");
            if (empty($plugin_name) || $plugin_name == '[[pluginname]]') {
                if (($block = block_instance($plugin)) !== false) {
                    $plugin_name = $block->get_title();
                } else {
                    $plugin_name = "[[$plugin]]";
                }
            }
            break;
        case 'filter':
            $plugin_name = filter_get_name('filter/' . $plugin);
            break;
        default:
            $plugin_name = $plugin;
            break;
    }

    return $plugin_name;
}

/**
 * Is a userid the primary administrator?
 *
 * @param int $userid int id of user to check
 * @return boolean
 */
function is_primary_admin($userid){
    $primaryadmin =  get_admin();

    if($userid == $primaryadmin->id){
        return true;
    }else{
        return false;
    }
}

/**
 * Returns the site identifier
 *
 * @global object
 * @return string $CFG->siteidentifier, first making sure it is properly initialised.
 */
function get_site_identifier() {
    global $CFG;
    // Check to see if it is missing. If so, initialise it.
    if (empty($CFG->siteidentifier)) {
        set_config('siteidentifier', random_string(32) . $_SERVER['HTTP_HOST']);
    }
    // Return it.
    return $CFG->siteidentifier;
}

/**
 * Check whether the given password has no more than the specified
 * number of consecutive identical characters.
 *
 * @param string $password   password to be checked agains the password policy
 * @param integer $maxchars  maximum number of consecutive identical characters
 */
function check_consecutive_identical_characters($password, $maxchars) {

    if ($maxchars < 1) {
        return true; // 0 is to disable this check
    }
    if (strlen($password) <= $maxchars) {
        return true; // too short to fail this test
    }

    $previouschar = '';
    $consecutivecount = 1;
    foreach (str_split($password) as $char) {
        if ($char != $previouschar) {
            $consecutivecount = 1;
        }
        else {
            $consecutivecount++;
            if ($consecutivecount > $maxchars) {
                return false; // check failed already
            }
        }

        $previouschar = $char;
    }

    return true;
}

/**
 * helper function to do partial function binding
 * so we can use it for preg_replace_callback, for example
 * this works with php functions, user functions, static methods and class methods
 * it returns you a callback that you can pass on like so:
 *
 * $callback = partial('somefunction', $arg1, $arg2);
 *     or
 * $callback = partial(array('someclass', 'somestaticmethod'), $arg1, $arg2);
 *     or even
 * $obj = new someclass();
 * $callback = partial(array($obj, 'somemethod'), $arg1, $arg2);
 *
 * and then the arguments that are passed through at calltime are appended to the argument list.
 *
 * @param mixed $function a php callback
 * $param mixed $arg1.. $argv arguments to partially bind with
 *
 * @return callback
 */
function partial() {
    if (!class_exists('partial')) {
        class partial{
            var $values = array();
            var $func;

            function __construct($func, $args) {
                $this->values = $args;
                $this->func = $func;
            }

            function method() {
                $args = func_get_args();
                return call_user_func_array($this->func, array_merge($this->values, $args));
            }
        }
    }
    $args = func_get_args();
    $func = array_shift($args);
    $p = new partial($func, $args);
    return array($p, 'method');
}

/**
 * helper function to load up and initialise the mnet environment
 * this must be called before you use mnet functions.
 *
 * @return mnet_environment the equivalent of old $MNET global
 */
function get_mnet_environment() {
    global $CFG;
    require_once($CFG->dirroot . '/mnet/lib.php');
    static $instance = null;
    if (empty($instance)) {
        $instance = new mnet_environment();
        $instance->init();
    }
    return $instance;
}

/**
 * during xmlrpc server code execution, any code wishing to access
 * information about the remote peer must use this to get it.
 *
 * @return mnet_remote_client the equivalent of old $MNET_REMOTE_CLIENT global
 */
function get_mnet_remote_client() {
    if (!defined('MNET_SERVER')) {
        debugging(get_string('notinxmlrpcserver', 'mnet'));
        return false;
    }
    global $MNET_REMOTE_CLIENT;
    if (isset($MNET_REMOTE_CLIENT)) {
        return $MNET_REMOTE_CLIENT;
    }
    return false;
}

/**
 * during the xmlrpc server code execution, this will be called
 * to setup the object returned by {@see get_mnet_remote_client}
 *
 * @param mnet_remote_client $client the client to set up
 */
function set_mnet_remote_client($client) {
    if (!defined('MNET_SERVER')) {
        throw new moodle_exception('notinxmlrpcserver', 'mnet');
    }
    global $MNET_REMOTE_CLIENT;
    $MNET_REMOTE_CLIENT = $client;
}

/**
 * return the jump url for a given remote user
 * this is used for rewriting forum post links in emails, etc
 *
 * @param stdclass $user the user to get the idp url for
 */
function mnet_get_idp_jump_url($user) {
    static $mnetjumps = array();
    if (!array_key_exists($user->mnethostid, $mnetjumps)) {
        $idp = mnet_get_peer_host($user->mnethostid);
        $idpjumppath = mnet_get_app_jumppath($idp->applicationid);
        $mnetjumps[$user->mnethostid] = $idp->wwwroot . $idpjumppath . '?hostwwwroot=' . $CFG->wwwroot . '&wantsurl=';
    }
    return $mnetjumps[$user->mnethostid];
}