locale.js

var Locale = (function() {
	"use strict";

	var Module = {
		setLanguageUrls: setLanguageUrls,
		getMsg: getMsg,

		setCurrentLanguage: setCurrentLanguage,
		// save language in cookie
		saveLanguage: saveLanguage,
		getCurrentLanguage: getCurrentLanguage,
		hasKey: hasKey,
		loadSync: loadSync,
		loadAsync: loadAsync
	};

	function setLanguageUrls(langUrls) {
		this.langUrls = langUrls;
	}

	function getMsg(key) {
		var args, i;

		if (this.map[key]) {
			args = [];
			if (arguments.length == 1) {
				return this.map[key];
			}
			else { // >1
				for (i = 1; i < arguments.length; i++) {
					args.push(arguments[i]);
				}
				return this.map[key].replace(/\{(\d+)\}/g, function(m, i) {
					return args[i];
				});
			}
		}
		return key + '.UNDEFINED';
		// return this.map[key] ? this.map[key] : key + '.undefined';
	}

	function setCurrentLanguage(lang) {
		this.currentLang = lang;
	}

	function getCurrentLanguage() {
		// 0. setCurrentLanguage() 1.url param 2. cookies 3. _guessLanguage 4. default (the first lang)
		var language = this.currentLang || _getQueryParam(location.search, 'lang') || _getCookie('lang') || _guessLanguage();
		return _formatLang(language);
	}

	function saveLanguage(lang) {
		_setCookie('lang', lang);
	}

	function hasKey(key) {
		return this.map[key] !== null;
	}

	function loadSync() {
		_load.call(this, false);
	}

	function loadAsync(callback) {
		_load.call(this, true, callback);
	}

	function _load(async, callback) {
		var me = this,
			xmlhttp,
			lines,
			i,
			first,
			key,
			value,
			lang,
			selectedLangUrl,
			len;
		this.map = {};

		if (!this.langUrls) {
			console.error('You should call setLanguageUrls() before loading lagnuage file.');
		}

		if (window.XMLHttpRequest) {
			// for IE7+, Firefox, Chrome, Opera, Safari
			xmlhttp = new XMLHttpRequest();
		}
		else {
			// for IE6, IE5
			xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
		}
		xmlhttp.onreadystatechange = function() {
			if (xmlhttp.readyState == 4 && xmlhttp.status == 200) {
				lines = xmlhttp.responseText.split(/\r\n|\r|\n/g);
				for (i = 0; i < lines.length; ++i) {
					first = lines[i].indexOf('=');
					key = lines[i].substr(0, first);
					value = lines[i].substr(first + 1);
					if (key && value) {
						value = value.replace(/\r/g, '').replace(/\n/g, '');
						me.map[key] = value;
					}
				}

				if (async) {
					callback();
				}
			}

		};
		// Preventing Open Redirection Attacks
		lang = getCurrentLanguage.call(this);
		for (i = 0, len = this.langUrls.length; i < len; i++) {
			if (this.langUrls[i].indexOf(lang) !== -1) {
				selectedLangUrl = this.langUrls[i];
				break;
			}
		}
		// if preferred language is not listed in langUrls, just use the first one		
		selectedLangUrl = selectedLangUrl || me.langUrls[0];
		xmlhttp.open("GET", selectedLangUrl + '?' + _getRandParam(), async);
		xmlhttp.send();
	}

	function _setCookie(name, value) {
		document.cookie = name + "=" + encodeURIComponent(value);
	}

	function _getCookie(name) {
		var arg = name + "=",
			i = 0,
			j = 0,
			nameIndex;
		while (i < document.cookie.length) {
			j = i + arg.length;
			if (document.cookie.substring(i, j) === arg) {
				return _getCookieVal.call(this, j);
			}
			nameIndex = document.cookie.indexOf(" ", i);
			if (nameIndex === -1) {
				return null;
			}
			i = 1 + nameIndex;
		}
		return null;
	}

	function _getCookieVal(offset) {
		var endstr = document.cookie.indexOf(";", offset);
		if (endstr == -1) {
			endstr = document.cookie.length;
		}
		return encodeURIComponent(document.cookie.substring(offset, endstr));
	}



	function _guessLanguage() {
		return (navigator.language || navigator.browserLanguage || navigator.userLanguage);
	}

	function _getRandParam() {
		return '_rand=' + (new Date()).getTime();
	}

	function _formatLang(lang) {
		lang = lang.split('_');
		if (lang.length == 1) {
			lang = lang[0].split('-');
		}
		return lang[0].toLowerCase() + '_' + lang[1].toUpperCase();
	}

	function _getQueryParam(queryString, target) {
		var params, i, param;
		queryString = location.search.split('?')[1];
		if (queryString) {
			params = queryString.split('&');
			if (params) {
				for (i = 0; i < params.length; ++i) {
					param = params[i].split('=');
					if (param[0] === target) return param[1];
				}
			}
		}
		return null;
	}

	return Module;

})();