/*

This file is part of Ext JS 4

Copyright (c) 2011 Sencha Inc

Contact:  http://www.sencha.com/contact

Commercial Usage
Licensees holding valid commercial licenses may use this file in accordance with the Commercial Software License Agreement provided with the Software or, alternatively, in accordance with the terms contained in a written agreement between you and Sencha.

If you are unsure which license is appropriate for your use, please contact the sales department at http://www.sencha.com/contact.

*/
/**
 * @class Ext.direct.PollingProvider
 * @extends Ext.direct.JsonProvider
 *
 * <p>Provides for repetitive polling of the server at distinct {@link #interval intervals}.
 * The initial request for data originates from the client, and then is responded to by the
 * server.</p>
 * 
 * <p>All configurations for the PollingProvider should be generated by the server-side
 * API portion of the Ext.Direct stack.</p>
 *
 * <p>An instance of PollingProvider may be created directly via the new keyword or by simply
 * specifying <tt>type = 'polling'</tt>.  For example:</p>
 * <pre><code>
var pollA = new Ext.direct.PollingProvider({
    type:'polling',
    url: 'php/pollA.php',
});
Ext.direct.Manager.addProvider(pollA);
pollA.disconnect();

Ext.direct.Manager.addProvider(
    {
        type:'polling',
        url: 'php/pollB.php',
        id: 'pollB-provider'
    }
);
var pollB = Ext.direct.Manager.getProvider('pollB-provider');
 * </code></pre>
 */
Ext.define('Ext.direct.PollingProvider', {
    
    /* Begin Definitions */
    
    extend: 'Ext.direct.JsonProvider',
    
    alias: 'direct.pollingprovider',
    
    uses: ['Ext.direct.ExceptionEvent'],
    
    requires: ['Ext.Ajax', 'Ext.util.DelayedTask'],
    
    /* End Definitions */
    
    /**
     * @cfg {Number} interval
     * How often to poll the server-side in milliseconds. Defaults to every 3 seconds.
     */
    interval: 3000,

    /**
     * @cfg {Object} baseParams
     * An object containing properties which are to be sent as parameters on every polling request
     */
    
    /**
     * @cfg {String/Function} url
     * The url which the PollingProvider should contact with each request. This can also be
     * an imported Ext.Direct method which will accept the baseParams as its only argument.
     */

    // private
    constructor : function(config){
        this.callParent(arguments);
        this.addEvents(
            /**
             * @event beforepoll
             * Fired immediately before a poll takes place, an event handler can return false
             * in order to cancel the poll.
             * @param {Ext.direct.PollingProvider} this
             */
            'beforepoll',            
            /**
             * @event poll
             * This event has not yet been implemented.
             * @param {Ext.direct.PollingProvider} this
             */
            'poll'
        );
    },

    // inherited
    isConnected: function(){
        return !!this.pollTask;
    },

    /**
     * Connect to the server-side and begin the polling process. To handle each
     * response subscribe to the data event.
     */
    connect: function(){
        var me = this, url = me.url;
        
        if (url && !me.pollTask) {
            me.pollTask = Ext.TaskManager.start({
                run: function(){
                    if (me.fireEvent('beforepoll', me) !== false) {
                        if (Ext.isFunction(url)) {
                            url(me.baseParams);
                        } else {
                            Ext.Ajax.request({
                                url: url,
                                callback: me.onData,
                                scope: me,
                                params: me.baseParams
                            });
                        }
                    }
                },
                interval: me.interval,
                scope: me
            });
            me.fireEvent('connect', me);
        } else if (!url) {
            //<debug>
            Ext.Error.raise('Error initializing PollingProvider, no url configured.');
            //</debug>
        }
    },

    /**
     * Disconnect from the server-side and stop the polling process. The disconnect
     * event will be fired on a successful disconnect.
     */
    disconnect: function(){
        var me = this;
        
        if (me.pollTask) {
            Ext.TaskManager.stop(me.pollTask);
            delete me.pollTask;
            me.fireEvent('disconnect', me);
        }
    },

    // private
    onData: function(opt, success, response){
        var me = this, 
            i = 0, 
            len,
            events;
        
        if (success) {
            events = me.createEvents(response);
            for (len = events.length; i < len; ++i) {
                me.fireEvent('data', me, events[i]);
            }
        } else {
            me.fireEvent('data', me, Ext.create('Ext.direct.ExceptionEvent', {
                data: null,
                code: Ext.direct.Manager.self.exceptions.TRANSPORT,
                message: 'Unable to connect to the server.',
                xhr: response
            }));
        }
    }
});