/*
This file is part of Ext JS 3.4

Copyright (c) 2011-2013 Sencha Inc

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

GNU General Public License Usage
This file may be used under the terms of the GNU General Public License version 3.0 as
published by the Free Software Foundation and appearing in the file LICENSE included in the
packaging of this file.

Please review the following information to ensure the GNU General Public License version 3.0
requirements will be met: http://www.gnu.org/copyleft/gpl.html.

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

Build date: 2013-04-03 15:07:25
*/
/**
 * @class Ext.data.ScriptTagProxy
 * @extends Ext.data.DataProxy
 * An implementation of Ext.data.DataProxy that reads a data object from a URL which may be in a domain
 * other than the originating domain of the running page.<br>
 * <p>
 * <b>Note that if you are retrieving data from a page that is in a domain that is NOT the same as the originating domain
 * of the running page, you must use this class, rather than HttpProxy.</b><br>
 * <p>
 * The content passed back from a server resource requested by a ScriptTagProxy <b>must</b> be executable JavaScript
 * source code because it is used as the source inside a &lt;script> tag.<br>
 * <p>
 * In order for the browser to process the returned data, the server must wrap the data object
 * with a call to a callback function, the name of which is passed as a parameter by the ScriptTagProxy.
 * Below is a Java example for a servlet which returns data for either a ScriptTagProxy, or an HttpProxy
 * depending on whether the callback name was passed:
 * <p>
 * <pre><code>
boolean scriptTag = false;
String cb = request.getParameter("callback");
if (cb != null) {
    scriptTag = true;
    response.setContentType("text/javascript");
} else {
    response.setContentType("application/x-json");
}
Writer out = response.getWriter();
if (scriptTag) {
    out.write(cb + "(");
}
out.print(dataBlock.toJsonString());
if (scriptTag) {
    out.write(");");
}
</code></pre>
 * <p>Below is a PHP example to do the same thing:</p><pre><code>
$callback = $_REQUEST['callback'];

// Create the output object.
$output = array('a' => 'Apple', 'b' => 'Banana');

//start output
if ($callback) {
    header('Content-Type: text/javascript');
    echo $callback . '(' . json_encode($output) . ');';
} else {
    header('Content-Type: application/x-json');
    echo json_encode($output);
}
</code></pre>
 * <p>Below is the ASP.Net code to do the same thing:</p><pre><code>
String jsonString = "{success: true}";
String cb = Request.Params.Get("callback");
String responseString = "";
if (!String.IsNullOrEmpty(cb)) {
    responseString = cb + "(" + jsonString + ")";
} else {
    responseString = jsonString;
}
Response.Write(responseString);
</code></pre>
 *
 * @constructor
 * @param {Object} config A configuration object.
 */
Ext.data.ScriptTagProxy = function(config){
    Ext.apply(this, config);

    Ext.data.ScriptTagProxy.superclass.constructor.call(this, config);

    this.head = document.getElementsByTagName("head")[0];

    /**
     * @event loadexception
     * <b>Deprecated</b> in favor of 'exception' event.
     * Fires if an exception occurs in the Proxy during data loading.  This event can be fired for one of two reasons:
     * <ul><li><b>The load call timed out.</b>  This means the load callback did not execute within the time limit
     * specified by {@link #timeout}.  In this case, this event will be raised and the
     * fourth parameter (read error) will be null.</li>
     * <li><b>The load succeeded but the reader could not read the response.</b>  This means the server returned
     * data, but the configured Reader threw an error while reading the data.  In this case, this event will be
     * raised and the caught error will be passed along as the fourth parameter of this event.</li></ul>
     * Note that this event is also relayed through {@link Ext.data.Store}, so you can listen for it directly
     * on any Store instance.
     * @param {Object} this
     * @param {Object} options The loading options that were specified (see {@link #load} for details).  If the load
     * call timed out, this parameter will be null.
     * @param {Object} arg The callback's arg object passed to the {@link #load} function
     * @param {Error} e The JavaScript Error object caught if the configured Reader could not read the data.
     * If the remote request returns success: false, this parameter will be null.
     */
};

Ext.data.ScriptTagProxy.TRANS_ID = 1000;

Ext.extend(Ext.data.ScriptTagProxy, Ext.data.DataProxy, {
    /**
     * @cfg {String} url The URL from which to request the data object.
     */
    /**
     * @cfg {Number} timeout (optional) The number of milliseconds to wait for a response. Defaults to 30 seconds.
     */
    timeout : 30000,
    /**
     * @cfg {String} callbackParam (Optional) The name of the parameter to pass to the server which tells
     * the server the name of the callback function set up by the load call to process the returned data object.
     * Defaults to "callback".<p>The server-side processing must read this parameter value, and generate
     * javascript output which calls this named function passing the data object as its only parameter.
     */
    callbackParam : "callback",
    /**
     *  @cfg {Boolean} nocache (optional) Defaults to true. Disable caching by adding a unique parameter
     * name to the request.
     */
    nocache : true,

    /**
     * HttpProxy implementation of DataProxy#doRequest
     * @param {String} action
     * @param {Ext.data.Record/Ext.data.Record[]} rs If action is <tt>read</tt>, rs will be null
     * @param {Object} params An object containing properties which are to be used as HTTP parameters
     * for the request to the remote server.
     * @param {Ext.data.DataReader} reader The Reader object which converts the data
     * object into a block of Ext.data.Records.
     * @param {Function} callback The function into which to pass the block of Ext.data.Records.
     * The function must be passed <ul>
     * <li>The Record block object</li>
     * <li>The "arg" argument from the load function</li>
     * <li>A boolean success indicator</li>
     * </ul>
     * @param {Object} scope The scope (<code>this</code> reference) in which the callback function is executed. Defaults to the browser window.
     * @param {Object} arg An optional argument which is passed to the callback as its second parameter.
     */
    doRequest : function(action, rs, params, reader, callback, scope, arg) {
        var p = Ext.urlEncode(Ext.apply(params, this.extraParams));

        var url = this.buildUrl(action, rs);
        if (!url) {
            throw new Ext.data.Api.Error('invalid-url', url);
        }
        url = Ext.urlAppend(url, p);

        if(this.nocache){
            url = Ext.urlAppend(url, '_dc=' + (new Date().getTime()));
        }
        var transId = ++Ext.data.ScriptTagProxy.TRANS_ID;
        var trans = {
            id : transId,
            action: action,
            cb : "stcCallback"+transId,
            scriptId : "stcScript"+transId,
            params : params,
            arg : arg,
            url : url,
            callback : callback,
            scope : scope,
            reader : reader
        };
        window[trans.cb] = this.createCallback(action, rs, trans);
        url += String.format("&{0}={1}", this.callbackParam, trans.cb);
        if(this.autoAbort !== false){
            this.abort();
        }

        trans.timeoutId = this.handleFailure.defer(this.timeout, this, [trans]);

        var script = document.createElement("script");
        script.setAttribute("src", url);
        script.setAttribute("type", "text/javascript");
        script.setAttribute("id", trans.scriptId);
        this.head.appendChild(script);

        this.trans = trans;
    },

    // @private createCallback
    createCallback : function(action, rs, trans) {
        var self = this;
        return function(res) {
            self.trans = false;
            self.destroyTrans(trans, true);
            if (action === Ext.data.Api.actions.read) {
                self.onRead.call(self, action, trans, res);
            } else {
                self.onWrite.call(self, action, trans, res, rs);
            }
        };
    },
    /**
     * Callback for read actions
     * @param {String} action [Ext.data.Api.actions.create|read|update|destroy]
     * @param {Object} trans The request transaction object
     * @param {Object} res The server response
     * @protected
     */
    onRead : function(action, trans, res) {
        var result;
        try {
            result = trans.reader.readRecords(res);
        }catch(e){
            // @deprecated: fire loadexception
            this.fireEvent("loadexception", this, trans, res, e);

            this.fireEvent('exception', this, 'response', action, trans, res, e);
            trans.callback.call(trans.scope||window, null, trans.arg, false);
            return;
        }
        if (result.success === false) {
            // @deprecated: fire old loadexception for backwards-compat.
            this.fireEvent('loadexception', this, trans, res);

            this.fireEvent('exception', this, 'remote', action, trans, res, null);
        } else {
            this.fireEvent("load", this, res, trans.arg);
        }
        trans.callback.call(trans.scope||window, result, trans.arg, result.success);
    },
    /**
     * Callback for write actions
     * @param {String} action [Ext.data.Api.actions.create|read|update|destroy]
     * @param {Object} trans The request transaction object
     * @param {Object} res The server response
     * @protected
     */
    onWrite : function(action, trans, response, rs) {
        var reader = trans.reader;
        try {
            // though we already have a response object here in STP, run through readResponse to catch any meta-data exceptions.
            var res = reader.readResponse(action, response);
        } catch (e) {
            this.fireEvent('exception', this, 'response', action, trans, res, e);
            trans.callback.call(trans.scope||window, null, res, false);
            return;
        }
        if(!res.success === true){
            this.fireEvent('exception', this, 'remote', action, trans, res, rs);
            trans.callback.call(trans.scope||window, null, res, false);
            return;
        }
        this.fireEvent("write", this, action, res.data, res, rs, trans.arg );
        trans.callback.call(trans.scope||window, res.data, res, true);
    },

    // private
    isLoading : function(){
        return this.trans ? true : false;
    },

    /**
     * Abort the current server request.
     */
    abort : function(){
        if(this.isLoading()){
            this.destroyTrans(this.trans);
        }
    },

    // private
    destroyTrans : function(trans, isLoaded){
        this.head.removeChild(document.getElementById(trans.scriptId));
        clearTimeout(trans.timeoutId);
        if(isLoaded){
            window[trans.cb] = undefined;
            try{
                delete window[trans.cb];
            }catch(e){}
        }else{
            // if hasn't been loaded, wait for load to remove it to prevent script error
            window[trans.cb] = function(){
                window[trans.cb] = undefined;
                try{
                    delete window[trans.cb];
                }catch(e){}
            };
        }
    },

    // private
    handleFailure : function(trans){
        this.trans = false;
        this.destroyTrans(trans, false);
        if (trans.action === Ext.data.Api.actions.read) {
            // @deprecated firing loadexception
            this.fireEvent("loadexception", this, null, trans.arg);
        }

        this.fireEvent('exception', this, 'response', trans.action, {
            response: null,
            options: trans.arg
        });
        trans.callback.call(trans.scope||window, null, trans.arg, false);
    },

    // inherit docs
    destroy: function(){
        this.abort();
        Ext.data.ScriptTagProxy.superclass.destroy.call(this);
    }
});