var Qs_KeepSession = qs.create();

Qs_KeepSession.prototype = {

    _interval: 300,
    _url: 'keep-session',
    _timestamp: 0,
    _timer: null,
    _obj: null,

    initialize: function (options)
    {
        if (typeof options == 'object') {
            if (typeof options.interval != 'undefined') {
                this.setInterval(options.interval);
            }

            if (typeof options.url != 'undefined') {
                this.setUrl(options.url);
            }
        }

        var d = new Date();
        this._timestamp = d.getTime();
    },

    setInterval: function (interval)
    {
        interval = parseInt(interval);
        if (!isNaN(interval) && interval != 0) {
            this._interval = interval * 1000;
            return true;
        }
        alert('keepSession: time interval is wrong!');
        return false;
    },

    getInterval: function ()
    {
        return this._interval;
    },

    setUrl: function(url)
    {
        this._url = '' + url;
        return true;
    },

    getUrl: function ()
    {
        return this._url;
    },

    start: function ()
    {
        if (this._timer != null) {
            this.stop();
        }
        this.sendRequest();

        return true;
    },

    stop: function ()
    {
        if (this._timer != null) {
            clearTimeout(this._timer);
        }
        this._timer = null;

        return true;
    },

    sendRequest: function ()
    {
        var obj = this;

        $.ajax({
            url:      obj._url + '?' + obj._timestamp,
            type:     'GET',
            complete: function(XMLHttpRequest, textStatus) {
                if (textStatus == 'success') {
                    obj._timer = setTimeout(function(){obj.sendRequest()}, obj._interval);
                }
            }
        });
        obj._timestamp++;

        return true;
    }
}