i18n.go

package pgo2

import (
	"fmt"
	"strings"

	"github.com/pinguo/pgo2/core"
	"github.com/pinguo/pgo2/util"
)

// I18n the internationalization component,
// language format is ll-CC or ll,
// lower case lang code, upper case area code.
// lang file name format is i18n_{lang}.json,
// and located in conf directory, configuration:
// i18n:
//     sourceLang: "en"
//     targetLang: [ "en", "zh-CN", "zh-TW"]
func NewI18n(config map[string]interface{}) *I18n {
	i18n := &I18n{
		sourceLang: "en",
		targetLang: make(map[string]bool),
	}

	core.Configure(i18n, config)

	return i18n
}

type I18n struct {
	sourceLang string
	targetLang map[string]bool
}

// SetSourceLang set language of source
func (i *I18n) SetSourceLang(lang string) {
	i.sourceLang = lang
}

// SetTargetLang set language of target
func (i *I18n) SetTargetLang(targets []interface{}) {
	for _, v := range targets {
		lang := util.ToString(v)
		i.targetLang[lang] = true
	}
}

// Translate message to target lang, lang format is one of the following:
// 1. accept-language header value: zh-CN,zh;q=0.9,en;q=0.8,zh-TW;q=0.7
// 2. ll-CC: lower case lang code and upper case area code, zh-CN
// 3. ll: lower case of lang code without area code, zh
func (i *I18n) Translate(message, lang string, params ...interface{}) string {
	translation := i.loadMessage(message, i.detectLang(lang))
	if len(params) > 0 {
		return fmt.Sprintf(translation, params...)
	}

	return translation
}

// detect support lang, lang can be accept-language header
func (i *I18n) detectLang(lang string) string {
	// use first part of accept-language
	if pos := strings.IndexByte(lang, ','); pos > 0 {
		lang = lang[:pos]
	}

	// omit q weight
	if pos := strings.IndexByte(lang, ';'); pos > 0 {
		lang = lang[:pos]
	}

	// format lang to ll-CC format
	lang = util.FormatLanguage(lang)

	if i.targetLang[lang] {
		return lang
	}

	if pos := strings.IndexByte(lang, '-'); pos > 0 {
		if lang = lang[:pos]; i.targetLang[lang] {
			return lang
		}
	}

	return i.sourceLang
}

// load message from lang file i18n_{lang}.json
func (i *I18n) loadMessage(message, lang string) string {
	if !i.targetLang[lang] {
		return message
	}

	key := fmt.Sprintf("i18n_%s.%s", lang, message)
	return App().Config().GetString(key, message)
}