(function($){
    var cookieExpireTime = 1209600; // cookie项过期时间 2周
    $.session = {
        _id: null,

        _cookieCache: undefined,


        _init: function()
        {
            //if (!window.name) {
            //    window.name = Math.random();
            //}
            //this._id = window.name;
            // 如果id设置为动态，会导致浏览器不断生成cookie，进而导致取值有问题
            this._id = 'sessionID';
            this._initCache();

            // See if we've changed protcols
			var matches = (new RegExp(this._generatePrefix() + "=([^;]+);")).exec(document.cookie);
            if (matches && document.location.protocol !== matches[1]) {
               this._clearSession();
               for (var key in this._cookieCache) {
                   try {
                       window.sessionStorage.setItem(key, this._cookieCache[key]);
                   } catch (e) {};
               }
            }

            document.cookie = this._generatePrefix() + "=" + document.location.protocol + ';path=/;expires=' + (new Date((new Date).getTime() + 28800000 + cookieExpireTime)).toUTCString(); // 28800000 含义：世界时间+8天=北京时间

        },

        _generatePrefix: function()
        {
            return '__session:' + this._id + ':';
        },

        _initCache: function()
        {
            var cookies = document.cookie.split(';');
            this._cookieCache = {};
            for (var i in cookies) {
                var kv = cookies[i].split('=');
                if ((new RegExp(this._generatePrefix() + '.+')).test(kv[0]) && kv[1]) {
                    this._cookieCache[kv[0].split(':', 3)[2]] = kv[1];
                }
            }
        },

        _setFallback: function(key, value, onceOnly)
        {
            var cookie = this._generatePrefix() + key + "=" + value + ";path=/";
            if (onceOnly) { // 只一次设置项，为其添加过期时间，过期自动删除
                cookie += ";expires=" + (new Date(Date.now() + 28800000 + cookieExpireTime)).toUTCString();
            }
            document.cookie = cookie;
            this._cookieCache[key] = value;
            return this;
        },

        _getFallback: function(key)
        {
            if (!this._cookieCache) {
                this._initCache();
            }
            return this._cookieCache[key];
        },

        _clearFallback: function()
        {
            for (var i in this._cookieCache) {
                document.cookie = this._generatePrefix() + i + '=;path=/;expires=Thu, 01 Jan 1970 00:00:01 GMT;';
            }
            this._cookieCache = {};
        },

        _deleteFallback: function(key)
        {
            document.cookie = this._generatePrefix() + key + '=;path=/;expires=Thu, 01 Jan 1970 00:00:01 GMT;'; // 把有效时间设置为过期
            delete this._cookieCache[key];
        },

        get: function(key)
        {
            return window.sessionStorage.getItem(key) || this._getFallback(key);
        },

        set: function(key, value, onceOnly)
        {
            try {
                window.sessionStorage.setItem(key, value);
            } catch (e) {}
            this._setFallback(key, value, onceOnly || false);
            return this;
        },
        
        'delete': function(key){
            return this.remove(key);
        },

        remove: function(key)
        {
            try {
            window.sessionStorage.removeItem(key);
            } catch (e) {};
            this._deleteFallback(key);
            return this;
        },

        _clearSession: function()
        {
          try {
                window.sessionStorage.clear();
            } catch (e) {
                for (var i in window.sessionStorage) {
                    window.sessionStorage.removeItem(i);
                }
            }
        },

        clear: function()
        {
            this._clearSession();
            this._clearFallback();
            return this;
        }

    };

    $.session._init();

})(jQuery);