bash-menu.sh

#!/bin/bash

# Define the function to encapsulate the menu script
menu_setup() {

    # Public Variables to Override
    # These can be passed into menuInit() rather than be set as global script variables
    #
    #   menuTop     # Top row of menu (defaults to row 2)
    #   menuLeft    # Left offset for menu item text (defaults to column 15)
    #   menuWidth   # Width of menu (defaults to 42 columns)
    #   menuMargin  # Left offset for menu border (defaults to column 4)
    #
    #   menuColour      # Colour of menu text (defaults to DRAW_COL_WHITE)
    #   menuHighlight   # Highlight colour for menu (defaults to DRAW_COL_GREEN)
    #
    #   menuTitle   # Title of menu
    #   menuFooter  # Footer text of menu
    #
    #   menuItems   # Array containing menu item text
    #   menuActions # Array containing functions to call upon menu item selection

    # Ensure we are running under bash (will not work under sh or dash etc)
    if [ "$BASH_SOURCE" = "" ]; then
        echo "ERROR: bash-menu requires to be running under bash"
        return 1
    fi

    # Get script root (as we are sourced from another script, $0 will not be us)
    declare -r menuScript=$(readlink -f ${BASH_SOURCE[0]})
    menuRoot=$(dirname "$menuScript")

    # Ensure we can access our dependencies
    if [ ! -s "$menuRoot/bash-draw.sh" ]; then
        echo "ERROR: Missing required draw.sh script"
        return 1
    fi

    # Load terminal drawing functions
    . "$menuRoot/bash-draw.sh"

    ################################
    # Private Variables
    #
    # These should not be overridden
    ################################
    declare -a menuItems
    declare -a menuActions

    menuHeaderText=""
    menuFooterText=""
    menuBorderText=""

    ################################
    # Setup Menu
    #
    # These are defaults which should
    # be overridden as required.
    ################################

    # Top of menu (row 2)
    menuTop=2

    # Left offset for menu items (not border)
    menuLeft=15

    # Width of menu
    menuWidth=42

    # Left offset for menu border (not menu items)
    menuMargin=4

    menuItems[0]="Exit"
    menuActions[0]="return 0"

    menuItemCount=1
    menuLastItem=0

    menuColour=$DRAW_COL_WHITE
    menuHighlight=$DRAW_COL_GREEN

    menuTitle=" Super Bash Menu System"
    menuFooter=" Enter=Select, Up/Down=Prev/Next Option"

    ################################
    # Initialise Menu
    ################################
    menuInit() {
        menuItemCount=${#menuItems[@]}
        menuLastItem=$((menuItemCount-1))

        # Ensure header and footer are padded appropriately
        menuHeaderText=`printf "%-${menuWidth}s" "$menuTitle"`
        menuFooterText=`printf "%-${menuWidth}s" "$menuFooter"`

        # Menu (side) borders
        local marginSpaces=$((menuMargin-1))
        local menuSpaces=$((menuWidth-2))
        local leftGap=`printf "%${marginSpaces}s" ""`
        local midGap=`printf "%${menuSpaces}s" ""`
        menuBorderText="${leftGap}x${midGap}x"
    }

    ################################
    # Show Menu
    ################################
    menu_Display() {
        local menuSize=$((menuItemCount+2))
        local menuEnd=$((menuSize+menuTop+1))

        drawClear
        drawColour $menuColour $menuHighlight

        # Menu header
        drawHighlightAt $menuTop $menuMargin "$menuHeaderText" 1

        # Menu (side) borders
        for row in $(seq 1 $menuSize); do
            drawSpecial "$menuBorderText" 1
        done

        # Menu footer
        drawHighlightAt $menuEnd $menuMargin "$menuFooterText" 1

        # Menu items
        for item in $(seq 0 $menuLastItem); do
            menu_ClearItem $item
        done
    }

    ################################
    # Mark Menu Items
    ################################

    # Ensure menu item is not highlighted
    menu_ClearItem() {
        local item=$1
        local top=$((menuTop+item+2))
        local menuText=${menuItems[$item]}

        drawPlainAt $top $menuLeft "$menuText"
    }

    # Highlight menu item
    menu_HighlightItem() {
        local item=$1
        local top=$((menuTop+item+2))
        local menuText=${menuItems[$item]}

        drawHighlightAt $top $menuLeft "$menuText"
    }

    ################################
    # Wait for and process user input
    ################################
    menu_HandleInput() {
        local choice=$1

        local after=$((choice+1))
        [[ $after -gt $menuLastItem ]] && after=0

        local before=$((choice-1))
        [[ $before -lt 0 ]] && before=$menuLastItem

        # Clear highlight from prev/next menu items
        menu_ClearItem $before
        menu_ClearItem $after

        # Highlight current menu item
        menu_HighlightItem $choice

        # Get keyboard input
        local key=""
        local extra=""

        read -s -n1 key 2> /dev/null >&2
        while read -s -n1 -t .05 extra 2> /dev/null >&2 ; do
            key="$key$extra"
        done

        # Handle known keys
        local escKey=`echo -en "\033"`
        local upKey=`echo -en "\033[A"`
        local downKey=`echo -en "\033[B"`

        if [[ $key = $upKey ]]; then
            return $before
        elif [[ $key = $downKey ]]; then
            return $after
        elif [[ $key = $escKey ]]; then
            if [[ $choice -eq $menuLastItem ]]; then
                # Pressing Esc while on last menu item will trigger action
                # This is a helper as we assume the last menu option is exit
                key=""
            else
                # Jumping possibly more than 1 (next/prev) item
                menu_ClearItem $choice
                return $menuLastItem
            fi
        elif [[ ${#key} -eq 1 ]]; then
            # See if we want to jump to a menu item
            # by entering the first character
            for index in $(seq 0 $menuLastItem) ; do
                local item=${menuItems[$index]}
                local startChar=${item:0:1}
                if [[ "$key" = "$startChar" ]]; then
                    # Jumping possibly more than 1 (next/prev) item
                    menu_ClearItem $choice
                    return $index
                fi
            done
        fi

        if [[ "$key" = "" ]]; then
            # Notify that Enter key was pressed
            return 255
        fi

        return $choice
    }

    ################################
    # Main Menu Loop
    ################################
    menuLoop() {
        local choice=0
        local running=1

        menu_Display

        while [[ $running -eq 1 ]]; do
            # Enable case insensitive matching
            local caseMatch=`shopt -p nocasematch`
            shopt -s nocasematch

            menu_HandleInput $choice
            local newChoice=$?

            # Revert to previous case matching
            $caseMatch

            if [[ $newChoice -eq 255 ]]; then
                # Enter pressed - run menu action
                drawClear
                action=${menuActions[$choice]}
                $action
                running=$?

                # Back from action
                # If we are still running, redraw menu
                [[ $running -eq 1 ]] && menu_Display

            elif [[ $newChoice -lt $menuItemCount ]]; then
                # Update selected menu item
                choice=$newChoice
            fi
        done

        # Cleanup screen
        drawClear
    }
}

# Source the function to make it available
menu_setup