Struct tags - genv (#1)

* Parse func - wip

* Parse func - strings only

* Add link to reflect examples

* Update readme

* Add multiple types support

* Add error handling

README.md

@@ -6,6 +6,13 @@
 
 - `IsProduction`, `IsDevelopment` and `IsTesting` checks for `ENVIRONMENT` dot env value.
 - `GetEnv` gets env value, fallback as second function argument.
+- `Parse` will fill given struct with env values or with fallbacks.
+```go
+	type serverConfig struct {
+		ServerPort string `genv:"SERVER_PORT,8080"`
+		MongoUrl   string `genv:"MONGO_URL,mongodb://localhost:27017"`
+	}
+```
 
 ## Install
 

gonvutils.go

@@ -1,7 +1,12 @@
 // Package genvutils provides useful environment operations
 package genvutils
 
-import "os"
+import (
+	"os"
+	"reflect"
+	"strconv"
+	"strings"
+)
 
 //IsProduction checks if ENVIRONMENT value is equal to "PROD".
 func IsProduction() bool {
@@ -61,3 +66,51 @@ func GetEnv(key string, fallback string) string {
 	}
 	return fallback
 }
+
+//Parse function will parse given pointer to struct and fill it with env values.
+//
+//  type serverConfig struct {
+//      ServerPort string `genv:"SERVER_PORT,8080"`
+//      MongoUrl   string `genv:"MONGO_URL,mongodb://localhost:27017"`
+//  }
+//
+// Here is an example of struct. Good reading about reflect https://github.com/a8m/reflect-examples
+func Parse(income interface{}) error {
+	t := reflect.TypeOf(income).Elem()
+	v := reflect.ValueOf(income).Elem()
+
+	for i := 0; i < t.NumField(); i++ {
+		field := t.Field(i)
+		value := v.FieldByName(field.Name)
+
+		tag := field.Tag.Get("genv")
+		tagS := strings.Split(tag, ",")
+
+		if value.CanSet() && value.IsValid() {
+			switch len(tagS) {
+			case 0:
+				break
+			default:
+				envVarValue := strings.TrimSpace(GetEnv(tagS[0], strings.Join(tagS[1:], ",")))
+				switch value.Kind() {
+				case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+					envVarValueF, _ := strconv.ParseInt(envVarValue, 10, 64)
+					value.SetInt(envVarValueF)
+				case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
+					envVarValueF, _ := strconv.ParseUint(envVarValue, 10, 64)
+					value.SetUint(envVarValueF)
+				case reflect.Float32, reflect.Float64:
+					envVarValueF, _ := strconv.ParseFloat(envVarValue, 64)
+					value.SetFloat(envVarValueF)
+				case reflect.String:
+					value.SetString(envVarValue)
+				case reflect.Bool:
+					envVarValueF, _ := strconv.ParseBool(envVarValue)
+					value.SetBool(envVarValueF)
+				}
+			}
+		}
+	}
+
+	return nil
+}

gonvutils_test.go

@@ -142,3 +142,58 @@ func TestGetEnv(t *testing.T) {
 
 	os.Unsetenv("SERVER_PORT")
 }
+
+func TestParse(t *testing.T) {
+
+	type serverConfig struct {
+		// simple test
+		ServerPort string `genv:"SERVER_PORT,8080"`
+		MongoUrl   string `genv:"MONGO_URL,mongodb://localhost:27017"`
+
+		// string join test
+		MongoClusterUrl string `genv:"MONGO_URL,mongodb://mongodb,mongodb1,mongodb2/?replicaSet=rs0"`
+
+		// edge cases
+		RedisUrl   string `genv:""`
+		RedisPort  int    `genv:"REDIS_PORT, 6371"`
+		Compress   bool   `genv:"COMPRES, true"`
+
+		// empty
+		Bla        bool
+	}
+
+	var srvConf serverConfig
+	err := Parse(&srvConf)
+	if err != nil {
+		t.Errorf("Parse(&srvConf) | return %v;", err)
+	}
+	if srvConf.ServerPort != "8080" {
+		t.Errorf("Parse(&srvConf) | ServerPort = %v; want 8080", srvConf.ServerPort)
+	}
+	if srvConf.MongoUrl != "mongodb://localhost:27017" {
+		t.Errorf("Parse(&srvConf) | MongoUrl = %v; want mongodb://localhost:27017", srvConf.MongoUrl)
+	}
+	if srvConf.RedisPort != 6371 {
+		t.Errorf("Parse(&srvConf) | RedisPort = %v; want 6371 as int", srvConf.RedisPort)
+	}
+	if srvConf.Compress != true {
+		t.Errorf("Parse(&srvConf) | Compress = %v; want true", srvConf.Compress)
+	}
+
+	os.Setenv("SERVER_PORT", "8181")
+	os.Setenv("MONGO_URL", "mongodb://localhost:76623")
+
+	err = Parse(&srvConf)
+	if err != nil {
+		t.Errorf("Parse(&srvConf) | return %v;", err)
+	}
+	if srvConf.ServerPort != "8181" {
+		t.Errorf("Parse(&srvConf) | ServerPort = %v; want 8181", srvConf.ServerPort)
+	}
+	if srvConf.MongoUrl != "mongodb://localhost:76623" {
+		t.Errorf("Parse(&srvConf) | MongoUrl = %v; want mongodb://localhost:76623", srvConf.MongoUrl)
+	}
+
+	os.Unsetenv("SERVER_PORT")
+	os.Unsetenv("MONGO_URL")
+}