window.Messenger = (function(){

    // 消息前缀, 避免多项目之间的冲突
    var prefix = "[SHOPEX_ECSTORE]",
        supportPostMessage = 'postMessage' in window;

    // Target 类, 消息对象
    function Target(target, name){
        var errMsg = '';
        if(arguments.length < 2){
            errMsg = 'ERROR: target and name are both requied';
        } else if (typeof target != 'object'){
            errMsg = 'ERROR: target itself must be window object';
        } else if (typeof name != 'string'){
            errMsg = 'ERROR: target name must be string type';
        }
        if(errMsg){
            throw new Error(errMsg);
        }
        this.target = target;
        this.name = name;
    }

    // 往 target 发送消息, 出于安全考虑, 发送消息会带上前缀
    if ( supportPostMessage ){
        // IE8+ 以及现代浏览器支持
        Target.prototype.send = function(msg){
            this.target.postMessage(prefix + msg, '*');
        };
    } else {
        // 兼容IE 6/7
        Target.prototype.send = function(msg){
            var targetFunc = window.navigator[prefix + this.name];
            if (typeof targetFunc == 'function') {
                targetFunc(prefix + msg, window);
            } else {
                throw new Error("target callback function is not defined");
            }
        };
    }

    // 信使类
    // 创建Messenger实例时指定, 必须指定Messenger的名字, (可选)指定项目名, 以避免Mashup类应用中的冲突
    // !注意: 父子页面中projectName必须保持一致, 否则无法匹配
    function Messenger(messengerName, projectName){
        this.targets = {};
        this.name = messengerName;
        this.listenFunc = [];
        prefix = projectName || prefix;
        this.initListen();
    }

    // 添加一个消息对象
    Messenger.prototype.addTarget = function(target, name){
        var targetObj = new Target(target, name);
        this.targets[name] = targetObj;
    };

    // 初始化消息监听
    Messenger.prototype.initListen = function(){
        var self = this;
        var generalCallback = function(msg){
            if(typeof msg == 'object' && msg.data){
                msg = msg.data;
            }
            // 剥离消息前缀
            msg = msg.slice(prefix.length);
            for(var i = 0; i < self.listenFunc.length; i++){
                self.listenFunc[i](msg);
            }
        };

        if (supportPostMessage){
            if ('addEventListener' in document) {
                window.addEventListener('message', generalCallback, false);
            } else if ('attachEvent' in document) {
                window.attachEvent('onmessage', generalCallback);
            }
        } else {
            // 兼容IE 6/7
            window.navigator[prefix + this.name] = generalCallback;
        }
    };

    // 监听消息
    Messenger.prototype.listen = function(callback){
        this.listenFunc.push(callback);
    };
    // 注销监听
    Messenger.prototype.clear = function(){
        this.listenFunc = [];
    };
    // 广播消息
    Messenger.prototype.send = function(msg){
        var targets = this.targets,
            target;
        for(target in targets){
            if(targets.hasOwnProperty(target)){
                targets[target].send(msg);
            }
        }
    };

    return Messenger;
})();
