config/util.go

package config

import (
	"bytes"
	"encoding/json"
	"errors"
	"fmt"
	"io/ioutil"
	"os"
	"path/filepath"
	"reflect"
	"runtime"
	"strings"

	"github.com/BurntSushi/toml"
	yaml "gopkg.in/yaml.v2"
)

func absPathify(inPath string) (string, error) {
	if strings.HasPrefix(inPath, "$HOME") {
		inPath = userHomeDir() + inPath[5:]
	}

	if strings.HasPrefix(inPath, "$") {
		end := strings.Index(inPath, string(os.PathSeparator))
		inPath = os.Getenv(inPath[1:end]) + inPath[end:]
	}

	if filepath.IsAbs(inPath) {
		return filepath.Clean(inPath), nil
	}

	p, err := filepath.Abs(inPath)
	if err == nil {
		return filepath.Clean(p), nil
	}

	return "", err
}

func userHomeDir() string {
	if runtime.GOOS == "windows" {
		home := os.Getenv("HOMEDRIVE") + os.Getenv("HOMEPATH")
		if home == "" {
			home = os.Getenv("USERPROFILE")
		}
		return home
	}
	return os.Getenv("HOME")
}

func exists(path string) bool {
	if fileInfo, err := os.Stat(path); err == nil && fileInfo.Mode().IsRegular() {
		return true
	}
	return false
}

func unmarshalFile(target interface{}, file string) error {
	data, err := ioutil.ReadFile(file)
	if err != nil {
		return err
	}

	return unmarshalData(target, filepath.Ext(file), data)
}

func unmarshalData(target interface{}, ext string, data []byte) error {
	switch ext {
	case ".yaml", ".yml":
		return yaml.Unmarshal(data, target)
	case ".toml":
		return toml.Unmarshal(data, target)
	case ".json":
		return json.Unmarshal(data, target)
	default:
		if toml.Unmarshal(data, target) != nil {
			if json.Unmarshal(data, target) != nil {
				if yaml.Unmarshal(data, target) != nil {
					return errors.New("failed to decode config")
				}
			}
		}
		return nil
	}
}

func unmarshalTags(target interface{}, prefixes ...string) error {
	targetValue := reflect.Indirect(reflect.ValueOf(target))
	if targetValue.Kind() != reflect.Struct {
		return errors.New("invalid config, should be struct")
	}

	targetType := targetValue.Type()
	for i := 0; i < targetType.NumField(); i++ {
		var (
			envNames    []string
			fieldStruct = targetType.Field(i)
			field       = targetValue.Field(i)
			envName     = fieldStruct.Tag.Get(ConfigTagEnv) // read configuration from shell env
		)
		if !field.CanAddr() || !field.CanInterface() {
			continue
		}
		if envName == "" {
			envNames = append(envNames, strings.Join(append(prefixes, fieldStruct.Name), "_"))                  // Configor_DB_Name
			envNames = append(envNames, strings.ToUpper(strings.Join(append(prefixes, fieldStruct.Name), "_"))) // CONFIGOR_DB_NAME
		} else {
			envNames = []string{envName}
		}
		// Load From Shell ENV
		for _, env := range envNames {
			if value := os.Getenv(env); value != "" {
				if err := yaml.Unmarshal([]byte(value), field.Addr().Interface()); err != nil {
					return err
				}
				break
			}
		}
		if isBlank := reflect.DeepEqual(field.Interface(), reflect.Zero(field.Type()).Interface()); isBlank {
			// Set default configuration if blank
			if value := fieldStruct.Tag.Get("default"); value != "" {
				if err := yaml.Unmarshal([]byte(value), field.Addr().Interface()); err != nil {
					return err
				}
			} else if fieldStruct.Tag.Get("required") == "true" {
				// return error if it is required but blank
				return fmt.Errorf("Field[%s] is required", fieldStruct.Name)
			}
		}
		for field.Kind() == reflect.Ptr {
			field = field.Elem()
		}
		if field.Kind() == reflect.Struct {
			if err := unmarshalTags(field.Addr().Interface(), getPrefixForStruct(prefixes, &fieldStruct)...); err != nil {
				return err
			}
		}

		if field.Kind() == reflect.Slice {
			for i := 0; i < field.Len(); i++ {
				if reflect.Indirect(field.Index(i)).Kind() == reflect.Struct {
					if err := unmarshalTags(field.Index(i).Addr().Interface(), append(getPrefixForStruct(prefixes, &fieldStruct), fmt.Sprint(i))...); err != nil {
						return err
					}
				}
			}
		}
	}

	return nil
}

func getPrefixForStruct(prefixes []string, fieldStruct *reflect.StructField) []string {
	if fieldStruct.Anonymous && fieldStruct.Tag.Get("anonymous") == "true" {
		return prefixes
	}
	return append(prefixes, fieldStruct.Name)
}

func marshalFile(target interface{}, file string, overWrite bool) error {
	var f *os.File
	var err error
	if exists(file) {
		if !overWrite {
			return fmt.Errorf("Config: File[%s] is exist", file)
		}
		if f, err = os.Open(file); nil != err {
			return err
		}
	} else {
		if f, err = os.Create(file); nil != err {
			return err
		}
	}

	var b []byte
	if b, err = marshal(target, filepath.Ext(file)); nil != err {
		return err
	}

	if _, err = f.Write(b); nil != err {
		return err
	}
	return nil

}

func marshal(target interface{}, ext string) ([]byte, error) {
	switch ext {
	case ".yaml", ".yml":
		return yaml.Marshal(target)
	case ".toml":
		var buf bytes.Buffer
		enc := toml.NewEncoder(&buf)
		if err := enc.Encode(target); nil != err {
			return nil, err
		}
		return buf.Bytes(), nil
	case ".json":
		return json.Marshal(target)
	default:
		return nil, fmt.Errorf("Config: Not supported extention[%s]", ext)
	}
}