/**
 * The Connection class encapsulates a connection to the page's originating domain, allowing requests to be made either
 * to a configured URL, or to a URL specified at request time.
 *
 * Requests made by this class are asynchronous, and will return immediately. No data from the server will be available
 * to the statement immediately following the {@link #request} call. To process returned data, use a success callback
 * in the request options object, or an {@link #requestcomplete event listener}.
 *
 * # File Uploads
 *
 * File uploads are not performed using normal "Ajax" techniques, that is they are not performed using XMLHttpRequests.
 * Instead the form is submitted in the standard manner with the DOM &lt;form&gt; element temporarily modified to have its
 * target set to refer to a dynamically generated, hidden &lt;iframe&gt; which is inserted into the document but removed
 * after the return data has been gathered.
 *
 * The server response is parsed by the browser to create the document for the IFRAME. If the server is using JSON to
 * send the return object, then the Content-Type header must be set to "text/html" in order to tell the browser to
 * insert the text unchanged into the document body.
 *
 * Characters which are significant to an HTML parser must be sent as HTML entities, so encode `<` as `&lt;`, `&` as
 * `&amp;` etc.
 *
 * The response text is retrieved from the document, and a fake XMLHttpRequest object is created containing a
 * responseText property in order to conform to the requirements of event handlers and callbacks.
 *
 * Be aware that file upload packets are sent with the content type multipart/form and some server technologies
 * (notably JEE) may require some custom processing in order to retrieve parameter names and parameter values from the
 * packet content.
 *
 * Also note that it's not possible to check the response code of the hidden iframe, so the success handler will ALWAYS fire.
 *
 * # Binary Posts
 *
 * The class supports posting binary data to the server by using native browser capabilities, or a flash polyfill plugin in browsers that do not support native binary posting (e.g. Internet Explorer version 9 or less). A number of limitations exist when the polyfill is used:
 *
 * - Only asynchronous connections are supported.
 * - Only the POST method can be used.
 * - The return data can only be binary for now. Set the {@link Ext.data.Connection#binary binary} parameter to <tt>true</tt>.
 * - Only the 0, 1 and 4 (complete) readyState values will be reported to listeners.
 * - The flash object will be injected at the bottom of the document and should be invisible.
 * - Important: See note about packaing the flash plugin with the app in the documenetation of {@link Ext.data.flash.BinaryXhr BinaryXhr}.
 *
 */
Ext.define('Ext.data.Connection', {
    mixins: {
        observable: 'Ext.mixin.Observable'
    },

    requires: [
        'Ext.data.flash.BinaryXhr'
    ],

    statics: {
        requestId: 0
    },

    config: {
        /**
         * @cfg {String} url
         * The URL for this connection.
         */
        url: null,

        /**
         * @cfg {Boolean} async
         * `true` if this request should run asynchronously. Setting this to `false` should generally
         * be avoided, since it will cause the UI to be blocked, the user won't be able to interact
         * with the browser until the request completes.
         */
        async: true,

        /**
         * @cfg {String} username
         * The username to pass when using {@link #withCredentials}.
         */
        username: '',

        /**
         * @cfg {String} password
         * The password to pass when using {@link #withCredentials}.
         */
        password: '',

        /**
        * @cfg {Boolean} disableCaching
        * True to add a unique cache-buster param to GET requests.
        */
        disableCaching: true,

        /**
        * @cfg {Boolean} withCredentials
        * True to set `withCredentials = true` on the XHR object
        */
        withCredentials: false,

        /**
        * @cfg {Boolean} binary
        * True if the response should be treated as binary data.  If true, the binary
        * data will be accessible as a "responseBytes" property on the response object.
        */
        binary: false,

        /**
        * @cfg {Boolean} cors
        * True to enable CORS support on the XHR object. Currently the only effect of this option
        * is to use the XDomainRequest object instead of XMLHttpRequest if the browser is IE8 or above.
        */
        cors: false,

        isXdr: false,

        defaultXdrContentType: 'text/plain',

        /**
        * @cfg {String} disableCachingParam
        * Change the parameter which is sent went disabling caching through a cache buster.
        */
        disableCachingParam: '_dc',

        /**
        * @cfg {Number} timeout
        * The timeout in milliseconds to be used for requests.
        */
        timeout : 30000,

        /**
        * @cfg {Object} extraParams
        * Any parameters to be appended to the request.
        */
       extraParams: null,

        /**
        * @cfg {Boolean} [autoAbort=false]
        * Whether this request should abort any pending requests.
        */
       autoAbort: false,

        /**
        * @cfg {String} method
        * The default HTTP method to be used for requests.
        *
        * If not set, but {@link #request} params are present, POST will be used;
        * otherwise, GET will be used.
        */
       method: null,

        /**
        * @cfg {Object} defaultHeaders
        * An object containing request headers which are added to each request made by this object.
        */
       defaultHeaders: null,

        /**
         * @cfg {String} defaultPostHeader
         * The default header to be sent out with any post request.
         */
        defaultPostHeader : 'application/x-www-form-urlencoded; charset=UTF-8',

        /**
         * @cfg {Boolean} useDefaultXhrHeader
         * `true` to send the {@link #defaultXhrHeader} along with any request.
         */
        useDefaultXhrHeader : true,

        /**
         * @cfg {String}
         * The header to send with Ajax requests. Also see {@link #useDefaultXhrHeader}.
         */
        defaultXhrHeader : 'XMLHttpRequest'
    },

    constructor : function(config) {
        // Will call initConfig
        this.mixins.observable.constructor.call(this, config);

        /**
         * @event beforerequest
         * Fires before a network request is made to retrieve a data object.
         * @param {Ext.data.Connection} conn This Connection object.
         * @param {Object} options The options config object passed to the {@link #request} method.
         */
        /**
         * @event requestcomplete
         * Fires if the request was successfully completed.
         * @param {Ext.data.Connection} conn This Connection object.
         * @param {Object} response The XHR object containing the response data.
         * See [The XMLHttpRequest Object](http://www.w3.org/TR/XMLHttpRequest/) for details.
         * @param {Object} options The options config object passed to the {@link #request} method.
         */
        /**
         * @event requestexception
         * Fires if an error HTTP status was returned from the server. This event may also
         * be listened to in the event that a request has timed out or has been aborted.
         * See [HTTP Status Code Definitions](http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html)
         * for details of HTTP status codes.
         * @param {Ext.data.Connection} conn This Connection object.
         * @param {Object} response The XHR object containing the response data.
         * See [The XMLHttpRequest Object](http://www.w3.org/TR/XMLHttpRequest/) for details.
         * @param {Object} options The options config object passed to the {@link #request} method.
         */
        this.requests = {};
    },

    /**
     * Sends an HTTP request to a remote server.
     *
     * **Important:** Ajax server requests are asynchronous, and this call will
     * return before the response has been received. Process any returned data
     * in a callback function.
     *
     *     Ext.Ajax.request({
     *         url: 'ajax_demo/sample.json',
     *         success: function(response, opts) {
     *             var obj = Ext.decode(response.responseText);
     *             console.dir(obj);
     *         },
     *         failure: function(response, opts) {
     *             console.log('server-side failure with status code ' + response.status);
     *         }
     *     });
     *
     * To execute a callback function in the correct scope, use the `scope` option.
     *
     * @param {Object} options An object which may contain the following properties:
     *
     * (The options object may also contain any other property which might be needed to perform
     * postprocessing in a callback because it is passed to callback functions.)
     *
     * @param {String/Function} options.url The URL to which to send the request, or a function
     * to call which returns a URL string. The scope of the function is specified by the `scope` option.
     * Defaults to the configured `url`.
     *
     * @param {Boolean} options.async `true` if this request should run asynchronously.
     * Setting this to `false` should generally be avoided, since it will cause the UI to be
     * blocked, the user won't be able to interact with the browser until the request completes.
     * Defaults to `true`.
     *
     * @param {Object/String/Function} options.params An object containing properties which are
     * used as parameters to the request, a url encoded string or a function to call to get either. The scope
     * of the function is specified by the `scope` option.
     *
     * @param {String} options.method The HTTP method to use
     * for the request. Defaults to the configured method, or if no method was configured,
     * "GET" if no parameters are being sent, and "POST" if parameters are being sent.  Note that
     * the method name is case-sensitive and should be all caps.
     *
     * @param {Function} options.callback The function to be called upon receipt of the HTTP response.
     * The callback is called regardless of success or failure and is passed the following parameters:
     * @param {Object} options.callback.options The parameter to the request call.
     * @param {Boolean} options.callback.success True if the request succeeded.
     * @param {Object} options.callback.response The XMLHttpRequest object containing the response data.
     * See [www.w3.org/TR/XMLHttpRequest/](http://www.w3.org/TR/XMLHttpRequest/) for details about
     * accessing elements of the response.
     *
     * @param {Function} options.success The function to be called upon success of the request.
     * The callback is passed the following parameters:
     * @param {Object} options.success.response The XMLHttpRequest object containing the response data.
     * @param {Object} options.success.options The parameter to the request call.
     *
     * @param {Function} options.failure The function to be called upon failure of the request.
     * The callback is passed the following parameters:
     * @param {Object} options.failure.response The XMLHttpRequest object containing the response data.
     * @param {Object} options.failure.options The parameter to the request call.
     *
     * @param {Object} options.scope The scope in which to execute the callbacks: The "this" object for
     * the callback function. If the `url`, or `params` options were specified as functions from which to
     * draw values, then this also serves as the scope for those function calls. Defaults to the browser
     * window.
     *
     * @param {Number} options.timeout The timeout in milliseconds to be used for this request.
     * Defaults to 30 seconds.
     *
     * @param {Ext.Element/HTMLElement/String} options.form The `<form>` Element or the id of the `<form>`
     * to pull parameters from.
     *
     * @param {Boolean} options.isUpload **Only meaningful when used with the `form` option.**
     *
     * True if the form object is a file upload (will be set automatically if the form was configured
     * with **`enctype`** `"multipart/form-data"`).
     *
     * File uploads are not performed using normal "Ajax" techniques, that is they are **not**
     * performed using XMLHttpRequests. Instead the form is submitted in the standard manner with the
     * DOM `<form>` element temporarily modified to have its [target][] set to refer to a dynamically
     * generated, hidden `<iframe>` which is inserted into the document but removed after the return data
     * has been gathered.
     *
     * The server response is parsed by the browser to create the document for the IFRAME. If the
     * server is using JSON to send the return object, then the [Content-Type][] header must be set to
     * "text/html" in order to tell the browser to insert the text unchanged into the document body.
     *
     * The response text is retrieved from the document, and a fake XMLHttpRequest object is created
     * containing a `responseText` property in order to conform to the requirements of event handlers
     * and callbacks.
     *
     * Be aware that file upload packets are sent with the content type [multipart/form][] and some server
     * technologies (notably JEE) may require some custom processing in order to retrieve parameter names
     * and parameter values from the packet content.
     *
     * [target]: http://www.w3.org/TR/REC-html40/present/frames.html#adef-target
     * [Content-Type]: http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.17
     * [multipart/form]: http://www.faqs.org/rfcs/rfc2388.html
     *
     * @param {Object} options.headers Request headers to set for the request.
     * The XHR will attempt to set an appropriate Content-Type based on the params/data passed
     * to the request. To prevent this, setting the Content-Type header to `null` or `undefined`
     * will not attempt to set any Content-Type and it will be left to the browser.
     *
     * @param {Object} options.xmlData XML document to use for the post. Note: This will be used instead
     * of params for the post data. Any params will be appended to the URL.
     *
     * @param {Object/String} options.jsonData JSON data to use as the post. Note: This will be used
     * instead of params for the post data. Any params will be appended to the URL.
     *
     * @param {String} options.rawData A raw string to use as the post. Note: This will be used
     * instead of params for the post data. Any params will be appended to the URL.
     *
     * @param {Array} options.binaryData An array of bytes to submit in binary form. Any params will be appended to the URL. If binaryData is present, you must set {@link Ext.data.Connection#binary binary} to <tt>true</tt> and options.method to <tt>POST</tt>.
     *
     * @param {Boolean} options.disableCaching True to add a unique cache-buster param to GET requests.
     *
     * @param {Boolean} options.withCredentials True to add the withCredentials property to the XHR object
     *
     * @param {String} options.username The username to pass when using `withCredentials`.
     *
     * @param {String} options.password The password to pass when using `withCredentials`.
     *
     * @param {Boolean} options.binary True if the response should be treated as binary data.  If true, the binary
     * data will be accessible as a "responseBytes" property on the response object.
     *
     * @return {Object} The request object. This may be used to cancel the request.
     */
    request : function(options) {
        options = options || {};
        var me = this,
            scope = options.scope || window,
            username = options.username || me.getUsername(),
            password = options.password || me.getPassword() || '',
            async, requestOptions, request, headers, xdr, xhr;

        if (me.fireEvent('beforerequest', me, options) !== false) {

            requestOptions = me.setOptions(options, scope);

            if (me.isFormUpload(options)) {
                me.upload(options.form, requestOptions.url, requestOptions.data, options);
                return null;
            }

            // if autoabort is set, cancel the current transactions
            if (options.autoAbort || me.getAutoAbort()) {
                me.abort();
            }

            // create a connection object
            async = options.async !== false ? (options.async || me.getAsync()) : false;
            xhr = me.openRequest(options, requestOptions, async, username, password);

            // XDR doesn't support setting any headers
            xdr = me.getIsXdr();
            if (!xdr) {
                headers = me.setupHeaders(xhr, options, requestOptions.data, requestOptions.params);
            }

            // create the transaction object
            request = {
                id: ++Ext.data.Connection.requestId,
                xhr: xhr,
                headers: headers,
                options: options,
                async: async,
                binary: options.binary || me.getBinary(),
                timeout: Ext.defer(function() {
                    request.timedout = true;
                    me.abort(request);
                }, options.timeout || me.getTimeout())
            };

            me.requests[request.id] = request;
            me.latestId = request.id;
            // bind our statechange listener
            if (async) {
                if (!xdr) {
                    xhr.onreadystatechange = Ext.Function.bind(me.onStateChange, me, [request]);
                }
            }

            if (xdr) {
                me.processXdrRequest(request, xhr);
            }

            // start the request!
            xhr.send(requestOptions.data);
            if (!async) {
                return me.onComplete(request);
            }
            return request;
        } else {
            Ext.callback(options.callback, options.scope, [options, undefined, undefined]);
            return null;
        }
    },

    processXdrRequest: function(request, xhr) {
        var me = this;

        // Mutate the request object as per XDR spec.
        delete request.headers;

        request.contentType = request.options.contentType || me.getDefaultXdrContentType();

        xhr.onload = Ext.Function.bind(me.onStateChange, me, [request, true]);
        xhr.onerror = xhr.ontimeout = Ext.Function.bind(me.onStateChange, me, [request, false]);
    },

    processXdrResponse: function(response, xhr) {
        // Mutate the response object as per XDR spec.
        response.getAllResponseHeaders = function () {
            return [];
        };
        response.getResponseHeader = function () {
            return '';
        };
        response.contentType = xhr.contentType || this.getDefaultXdrContentType();
    },

    /**
     * Uploads a form using a hidden iframe.
     * @param {String/HTMLElement/Ext.dom.Element} form The form to upload
     * @param {String} url The url to post to
     * @param {String} params Any extra parameters to pass
     * @param {Object} options The initial options
     */
    upload: function(form, url, params, options) {
        form = Ext.getDom(form);
        options = options || {};

        var id = Ext.id(),
            frame = document.createElement('iframe'),
            hiddens = [],
            encoding = 'multipart/form-data',
            buf = {
                target: form.target,
                method: form.method,
                encoding: form.encoding,
                enctype: form.enctype,
                action: form.action
            },
            addField = function(name, value) {
                hiddenItem = document.createElement('input');
                Ext.fly(hiddenItem).set({
                    type: 'hidden',
                    value: value,
                    name: name
                });
                form.appendChild(hiddenItem);
                hiddens.push(hiddenItem);
            },
            hiddenItem, obj, value, name, vLen, v, hLen, h;

        /*
         * Originally this behaviour was modified for Opera 10 to apply the secure URL after
         * the frame had been added to the document. It seems this has since been corrected in
         * Opera so the behaviour has been reverted, the URL will be set before being added.
         */
        Ext.fly(frame).set({
            id: id,
            name: id,
            cls: Ext.baseCSSPrefix + 'hidden-display',
            src: Ext.SSL_SECURE_URL,
            tabIndex: -1
        });

        document.body.appendChild(frame);

        // This is required so that IE doesn't pop the response up in a new window.
        if (document.frames) {
            document.frames[id].name = id;
        }

        Ext.fly(form).set({
            target: id,
            method: 'POST',
            enctype: encoding,
            encoding: encoding,
            action: url || buf.action
        });

        // add dynamic params
        if (params) {
            obj = Ext.Object.fromQueryString(params) || {};

            for (name in obj) {
                if (obj.hasOwnProperty(name)) {
                    value = obj[name];
                    if (Ext.isArray(value)) {
                        vLen = value.length;
                        for (v = 0; v < vLen; v++) {
                            addField(name, value[v]);
                        }
                    } else {
                        addField(name, value);
                    }
                }
            }
        }

        // Bind the frame's load event
        Ext.get(frame).on({
            load        : Ext.Function.bind(this.onUploadComplete, this, [frame, options]),
            single      : !Ext.isOpera    // Opera introduces multiple 'load' events, so account for extras as well with {single: ? }.
        });

        form.submit();

        // Restore form to previous settings
        Ext.fly(form).set(buf);

        for (hLen = hiddens.length, h = 0; h < hLen; h++) {
            Ext.removeNode(hiddens[h]);
        }
    },

    /**
     * @private
     * Callback handler for the upload function. After we've submitted the form via the iframe this creates a bogus
     * response object to simulate an XHR and populates its responseText from the now-loaded iframe's document body
     * (or a textarea inside the body). We then clean up by removing the iframe
     */
    onUploadComplete: function(frame, options) {
        var me = this,
            // bogus response object
            response = {
                responseText: '',
                responseXML: null
            }, callback, success, doc, contentNode;

        try {
            doc = (frame && (frame.contentWindow.document || frame.contentDocument)) || (window.frames[frame.id] || {}).document;
            // Opera will fire an extraneous load event on about:blank
            // We want to ignore this since the load event will be fired twice
            if (doc) {
                //TODO: See if this still applies vs Current opera-webkit releases
                if (Ext.isOpera && doc.location == Ext.SSL_SECURE_URL) {
                    return;
                }

                if (doc.body) {

                    // Response sent as Content-Type: text/json or text/plain. Browser will embed in a <pre> element
                    // Note: The statement below tests the result of an assignment.
                    if ((contentNode = doc.body.firstChild) && /pre/i.test(contentNode.tagName)) {
                        response.responseText = contentNode.textContent || contentNode.innerText;
                    }

                    // Response sent as Content-Type: text/html. We must still support JSON response wrapped in textarea.
                    // Note: The statement below tests the result of an assignment.
                    else if ((contentNode = doc.getElementsByTagName('textarea')[0])) {
                        response.responseText = contentNode.value;
                    }
                    // Response sent as Content-Type: text/html with no wrapping. Scrape JSON response out of text
                    else {
                        response.responseText = doc.body.textContent || doc.body.innerText;
                    }
                }

                //in IE the document may still have a body even if returns XML.
                response.responseXML = doc.XMLDocument || doc;
                callback = options.success;
                success = true;

            } else {
                Ext.Error.raise("Could not acquire a suitable connection for the file upload service.");
            }
        } catch (e) {
            // Report any error in the message property
            response.responseText = '{success:false,message:"' + Ext.String.trim(e.message || e.description) + '"}';
            callback = options.failure;
            success = false;
        }

        me.fireEvent(success ? 'requestcomplete' : 'requestexception', me, response, options);

        Ext.callback(callback, options.scope, [response, options]);
        Ext.callback(options.callback, options.scope, [options, success, response]);

        // Must defer slightly to permit full exit from load event before destruction
        Ext.defer(Ext.removeNode, 100, Ext, [frame]);

    },

    /**
     * Detects whether the form is intended to be used for an upload.
     * @private
     */
    isFormUpload: function(options) {
        var form = this.getForm(options);
        if (form) {
            return (options.isUpload || (/multipart\/form-data/i).test(form.getAttribute('enctype')));
        }
        return false;
    },

    /**
     * Gets the form object from options.
     * @private
     * @param {Object} options The request options
     * @return {HTMLElement} The form, null if not passed
     */
    getForm: function(options) {
        var form = options.form || null;
        if (form) {
            form = Ext.getDom(form);
        }
        return form;
    },

    /**
     * Sets various options such as the url, params for the request
     * @param {Object} options The initial options
     * @param {Object} scope The scope to execute in
     * @return {Object} The params for the request
     */
    setOptions: function(options, scope) {
        var me = this,
            params = options.params || {},
            extraParams = me.getExtraParams(),
            urlParams = options.urlParams,
            url = options.url || me.getUrl(),
            cors = options.cors,
            jsonData = options.jsonData,
            method,
            disableCache,
            data;

        if (cors !== undefined) {
            me.setCors(cors);
        }

        // allow params to be a method that returns the params object
        if (Ext.isFunction(params)) {
            params = params.call(scope, options);
        }

        // allow url to be a method that returns the actual url
        if (Ext.isFunction(url)) {
            url = url.call(scope, options);
        }

        url = this.setupUrl(options, url);

        //<debug>
        if (!url) {
            Ext.Error.raise({
                options: options,
                msg: 'No URL specified'
            });
        }
        //</debug>

        // check for xml or json data, and make sure json data is encoded
        data = options.rawData || options.binaryData || options.xmlData || jsonData || null;
        if (jsonData && !Ext.isPrimitive(jsonData)) {
            data = Ext.encode(data);
        }
        // Check for binary data. Transform if needed
        if (options.binaryData) {
            //<debug>
            if (!Ext.isArray(options.binaryData)) {
                Ext.log.warn("Binary submission data must be an array of byte values! Instead got " + typeof(options.binaryData));
            }
            //</debug>
            if (me.nativeBinaryPostSupport()) {
                data = (new Uint8Array(options.binaryData));
                if ((Ext.isChrome && Ext.chromeVersion < 22) || Ext.isSafari || Ext.isGecko) {
                    data = data.buffer; //  send the underlying buffer, not the view, since that's not supported on versions of chrome older than 22
                }
            }
        }

        // make sure params are a url encoded string and include any extraParams if specified
        if (Ext.isObject(params)) {
            params = Ext.Object.toQueryString(params);
        }

        if (Ext.isObject(extraParams)) {
            extraParams = Ext.Object.toQueryString(extraParams);
        }

        params = params + ((extraParams) ? ((params) ? '&' : '') + extraParams : '');

        urlParams = Ext.isObject(urlParams) ? Ext.Object.toQueryString(urlParams) : urlParams;

        params = this.setupParams(options, params);

        // decide the proper method for this request
        method = (options.method || me.getMethod() || ((params || data) ? 'POST' : 'GET')).toUpperCase();
        this.setupMethod(options, method);


        disableCache = options.disableCaching !== false ? (options.disableCaching || me.getDisableCaching()) : false;
        // if the method is get append date to prevent caching
        if (method === 'GET' && disableCache) {
            url = Ext.urlAppend(url, (options.disableCachingParam || me.getDisableCachingParam()) + '=' + (new Date().getTime()));
        }

        // if the method is get or there is json/xml data append the params to the url
        if ((method == 'GET' || data) && params) {
            url = Ext.urlAppend(url, params);
            params = null;
        }

        // allow params to be forced into the url
        if (urlParams) {
            url = Ext.urlAppend(url, urlParams);
        }

        return {
            url: url,
            method: method,
            data: data || params || null
        };
    },

    /**
     * Template method for overriding url
     * @template
     * @private
     * @param {Object} options
     * @param {String} url
     * @return {String} The modified url
     */
    setupUrl: function(options, url) {
        var form = this.getForm(options);
        if (form) {
            url = url || form.action;
        }
        return url;
    },


    /**
     * Template method for overriding params
     * @template
     * @private
     * @param {Object} options
     * @param {String} params
     * @return {String} The modified params
     */
    setupParams: function(options, params) {
        var form = this.getForm(options),
            serializedForm;
        if (form && !this.isFormUpload(options)) {
            serializedForm = Ext.Element.serializeForm(form);
            params = params ? (params + '&' + serializedForm) : serializedForm;
        }
        return params;
    },

    /**
     * Template method for overriding method
     * @template
     * @private
     * @param {Object} options
     * @param {String} method
     * @return {String} The modified method
     */
    setupMethod: function(options, method) {
        if (this.isFormUpload(options)) {
            return 'POST';
        }
        return method;
    },

    /**
     * Setup all the headers for the request
     * @private
     * @param {Object} xhr The xhr object
     * @param {Object} options The options for the request
     * @param {Object} data The data for the request
     * @param {Object} params The params for the request
     */
    setupHeaders: function(xhr, options, data, params) {
        var me = this,
            headers = Ext.apply({}, options.headers || {}, me.getDefaultHeaders() || {}),
            contentType = me.getDefaultPostHeader(),
            jsonData = options.jsonData,
            xmlData = options.xmlData,
            type = 'Content-Type',
            useHeader = Ext.isDefined(options.useDefaultXhrHeader) ? options.useDefaultXhrHeader : me.getUseDefaultXhrHeader(),
            key,
            header;

        if (!headers.hasOwnProperty(type) && (data || params)) {
            if (data) {
                if (options.rawData) {
                    contentType = 'text/plain';
                } else {
                    if (xmlData && Ext.isDefined(xmlData)) {
                        contentType = 'text/xml';
                    } else if (jsonData && Ext.isDefined(jsonData)) {
                        contentType = 'application/json';
                    }
                }
            }
            headers[type] = contentType;
        }

        if (useHeader && !headers['X-Requested-With']) {
            headers['X-Requested-With'] = me.getDefaultXhrHeader();
        }

        // If undefined/null, remove it and don't set the header.
        // Allow the browser to do so.
        if (headers[type] === undefined || headers[type] === null) {
            delete headers[type];
        }

        // set up all the request headers on the xhr object
        try {
            for (key in headers) {
                if (headers.hasOwnProperty(key)) {
                    header = headers[key];
                    xhr.setRequestHeader(key, header);
                }
            }
        } catch(e) {
            me.fireEvent('exception', key, header);
        }
        return headers;
    },

    /**
     * Creates the appropriate XHR transport for a given request on this browser. On IE
     * this may be an `XDomainRequest` rather than an `XMLHttpRequest`.
     * @private
     */
    newRequest: function (options) {
        var me = this,
            xhr;

        if (options.binaryData) {
            // This is a binary data request. Handle submission differently for differnet browsers
            if (me.nativeBinaryPostSupport()) {
                xhr = me.getXhrInstance(); // On browsers that support this, use the native XHR object
            } else {
                // catch all for all other browser types
                xhr = new Ext.data.flash.BinaryXhr();
            }
        } else  if (me.getCors() && Ext.isIE && Ext.ieVersion <= 9) {
            xhr = me.getXdrInstance();
            me.setIsXdr(true);
        } else {
            xhr = me.getXhrInstance();
            me.setIsXdr(false);
        }

        return xhr;
    },

    /**
     * Creates and opens an appropriate XHR transport for a given request on this browser.
     * This logic is contained in an individual method to allow for overrides to process all
     * of the parameters and options and return a suitable, open connection.
     * @private
     */
    openRequest: function (options, requestOptions, async, username, password) {
        var me = this,
            xhr = me.newRequest(options);

        if (username) {
            xhr.open(requestOptions.method, requestOptions.url, async, username, password);
        } else {
            if (me.getIsXdr()) {
                xhr.open(requestOptions.method, requestOptions.url);
            } else {
                xhr.open(requestOptions.method, requestOptions.url, async);
            }
        }

        if (options.binary || me.getBinary()) {
            if (window.Uint8Array) {
                xhr.responseType = 'arraybuffer';
            } else if (xhr.overrideMimeType) {
                // In some older non-IE browsers, e.g. ff 3.6, that do not
                // support Uint8Array, a mime type override is required so that
                // the unprocessed binary data can be read from the responseText
                // (see createResponse())
                xhr.overrideMimeType('text\/plain; charset=x-user-defined');
            //<debug>
            } else if (!Ext.isIE) {
                Ext.log.warn("Your browser does not support loading binary data using Ajax.");
            //</debug>
            }
        }

        if (options.withCredentials || me.getWithCredentials()) {
            xhr.withCredentials = true;
        }

        return xhr;
    },

    /**
     * Creates the appropriate XDR transport for this browser.
     * - IE 7 and below don't support CORS
     * - IE 8 and 9 support CORS with native XDomainRequest object
     * - IE 10 (and above?) supports CORS with native XMLHttpRequest object
     * @private
     */
    getXdrInstance: function() {
        var xdr;

        if (Ext.ieVersion >= 8) {
            xdr = new XDomainRequest();
        } else {
            Ext.Error.raise({
                msg: 'Your browser does not support CORS'
            });
        }

        return xdr;
    },

    /**
     * Creates the appropriate XHR transport for this browser.
     * @private
     */
    getXhrInstance: (function() {
        var options = [function() {
            return new XMLHttpRequest();
        }, function() {
            return new ActiveXObject('MSXML2.XMLHTTP.3.0'); // jshint ignore:line
        }, function() {
            return new ActiveXObject('MSXML2.XMLHTTP'); // jshint ignore:line
        }, function() {
            return new ActiveXObject('Microsoft.XMLHTTP'); // jshint ignore:line
        }], i = 0,
            len = options.length,
            xhr;

        for (; i < len; ++i) {
            try {
                xhr = options[i];
                xhr();
                break;
            } catch(e) {
            }
        }
        return xhr;
    }()),

    /**
     * Determines whether this object has a request outstanding.
     * @param {Object} [request] Defaults to the last transaction
     * @return {Boolean} True if there is an outstanding request.
     */
    isLoading : function(request) {
        if (!request) {
            request = this.getLatest();
        }
        if (!(request && request.xhr)) {
            return false;
        }
        // if there is a connection and readyState is not 0 or 4, or in case of BinaryXHR, not 4
        var state = request.xhr.readyState,
            Cls = Ext.data.flash && Ext.data.flash.BinaryXhr;

        return ((request.xhr instanceof Cls) && state != 4) || !(state === 0 || state == 4);
    },

    /**
     * Aborts an active request.
     * @param {Object} [request] Defaults to the last request
     */
    abort : function(request) {
        var me = this,
            xhr;

        if (!request) {
            request = me.getLatest();
        }

        if (request && me.isLoading(request)) {
            /*
             * Clear out the onreadystatechange here, this allows us
             * greater control, the browser may/may not fire the function
             * depending on a series of conditions.
             */
            xhr = request.xhr;
            try {
                xhr.onreadystatechange = null;
            } catch (e) {
                // Setting onreadystatechange to null can cause problems in IE, see
                // http://www.quirksmode.org/blog/archives/2005/09/xmlhttp_notes_a_1.html
                xhr.onreadystatechange = Ext.emptyFn;
            }
            xhr.abort();
            me.clearTimeout(request);
            if (!request.timedout) {
                request.aborted = true;
            }
            me.onComplete(request);
            me.cleanup(request);
        }
    },

    /**
     * Aborts all active requests
     */
    abortAll: function(){
        var requests = this.requests,
            id;

        for (id in requests) {
            if (requests.hasOwnProperty(id)) {
                this.abort(requests[id]);
            }
        }
    },

    /**
     * Gets the most recent request
     * @private
     * @return {Object} The request. Null if there is no recent request
     */
    getLatest: function(){
        var id = this.latestId,
            request;

        if (id) {
            request = this.requests[id];
        }
        return request || null;
    },

    /**
     * Fires when the state of the xhr changes
     * @private
     * @param {Object} request The request
     */
    onStateChange : function(request, xdrResult) {
        var me = this,
            globalEvents = Ext.GlobalEvents;

        // Using CORS with IE doesn't support readyState so we fake it.
        if ((request.xhr && request.xhr.readyState == 4) || me.getIsXdr()) {
            me.clearTimeout(request);
            me.onComplete(request, xdrResult);
            me.cleanup(request);
            if (globalEvents.hasListeners.idle) {
                globalEvents.fireEvent('idle');
            }
        }
    },

    /**
     * Clears the timeout on the request
     * @private
     * @param {Object} request The request
     */
    clearTimeout: function(request) {
        clearTimeout(request.timeout);
        delete request.timeout;
    },

    /**
     * Cleans up any left over information from the request
     * @private
     * @param {Object} request The request
     */
    cleanup: function(request) {
        request.xhr = null;
        delete request.xhr;
    },

    /**
     * To be called when the request has come back from the server
     * @private
     * @param {Object} request
     * @return {Object} The response
     */
    onComplete : function(request, xdrResult) {
        var me = this,
            options = request.options,
            xhr,
            result,
            success,
            response;

        try {
            xhr = request.xhr;
            result = me.parseStatus(xhr.status);
            if (result.success) {
                // This is quite difficult to reproduce, however if we abort a request just before
                // it returns from the server, occasionally the status will be returned correctly
                // but the request is still yet to be complete.
                result.success = xhr.readyState === 4;
            }
        } catch (e) {
            // in some browsers we can't access the status if the readyState is not 4, so the request has failed
            result = {
                success : false,
                isException : false
            };

        }
        success = me.getIsXdr() ? xdrResult : result.success;

        if (success) {
            response = me.createResponse(request);
            me.fireEvent('requestcomplete', me, response, options);
            Ext.callback(options.success, options.scope, [response, options]);
        } else {
            if (result.isException || request.aborted || request.timedout) {
                response = me.createException(request);
            } else {
                response = me.createResponse(request);
            }
            me.fireEvent('requestexception', me, response, options);
            Ext.callback(options.failure, options.scope, [response, options]);
        }
        Ext.callback(options.callback, options.scope, [options, success, response]);
        delete me.requests[request.id];
        return response;
    },

    /**
     * Checks if the response status was successful
     * @param {Number} status The status code
     * @return {Object} An object containing success/status state
     */
    parseStatus: function(status) {
        // see: https://prototype.lighthouseapp.com/projects/8886/tickets/129-ie-mangles-http-response-status-code-204-to-1223
        status = status == 1223 ? 204 : status;

        var success = (status >= 200 && status < 300) || status == 304,
            isException = false;

        if (!success) {
            switch (status) {
                case 12002:
                case 12029:
                case 12030:
                case 12031:
                case 12152:
                case 13030:
                    isException = true;
                    break;
            }
        }
        return {
            success: success,
            isException: isException
        };
    },

    /**
     * Creates the response object
     * @private
     * @param {Object} request
     */
    createResponse : function(request) {
        var me = this,
            xhr = request.xhr,
            isXdr = me.getIsXdr(),
            headers = {},
            lines = isXdr ? [] : xhr.getAllResponseHeaders().replace(/\r\n/g, '\n').split('\n'),
            count = lines.length,
            line, index, key, response, byteArray;

        while (count--) {
            line = lines[count];
            index = line.indexOf(':');
            if (index >= 0) {
                key = line.substr(0, index).toLowerCase();
                if (line.charAt(index + 1) == ' ') {
                    ++index;
                }
                headers[key] = line.substr(index + 1);
            }
        }

        request.xhr = null;
        delete request.xhr;

        response = {
            request: request,
            requestId: request.id,
            status: xhr.status,
            statusText: xhr.statusText,
            getResponseHeader: function(header) {
                return headers[header.toLowerCase()];
            },
            getAllResponseHeaders: function() {
                return headers;
            }
        };

        if (isXdr) {
            me.processXdrResponse(response, xhr);
        }

        if (request.binary) {
            response.responseBytes = me.getByteArray(xhr);
        } else {
            // an error is thrown when trying to access responseText or responseXML
            // on an xhr object with responseType of 'arraybuffer', so only attempt
            // to set these properties in the response if we're not dealing with
            // binary data
            response.responseText = xhr.responseText;
            response.responseXML = xhr.responseXML;
        }

        // If we don't explicitly tear down the xhr reference, IE6/IE7 will hold this in the closure of the
        // functions created with getResponseHeader/getAllResponseHeaders
        xhr = null;
        return response;
    },

    /**
     * Creates the exception object
     * @private
     * @param {Object} request
     */
    createException : function(request) {
        return {
            request : request,
            requestId : request.id,
            status : request.aborted ? -1 : 0,
            statusText : request.aborted ? 'transaction aborted' : 'communication failure',
            aborted: request.aborted,
            timedout: request.timedout
        };
    },

    /**
     * Gets binary data from the xhr response object and returns it as a byte array
     * @private
     * @param {Object} xhr the xhr response object
     * @return {Uint8Array/Array}
     */
    getByteArray: function(xhr) {
        var response = xhr.response,
            responseBody = xhr.responseBody,
            Cls = Ext.data.flash && Ext.data.flash.BinaryXhr,
            byteArray, responseText, len, i;

        if (xhr instanceof Cls) {
            // If this was a BinaryXHR request via flash, we already have the bytes ready
            byteArray = xhr.responseBytes;
        } else if (window.Uint8Array) {
            // Modern browsers (including IE10) have a native byte array
            // which can be created by passing the ArrayBuffer (returned as
            // the xhr.response property) to the Uint8Array constructor.
            byteArray = response ? new Uint8Array(response) : [];
        } else if (Ext.isIE9p) {
            // In IE9 and below the responseBody property contains a byte array
            // but it is not directly accessible using javascript.
            // In IE9p we can get the bytes by constructing a VBArray
            // using the responseBody and then converting it to an Array.
            try {
                byteArray = new VBArray(responseBody).toArray(); // jshint ignore:line
            } catch(e) {
                // If the binary response is empty, the VBArray constructor will
                // choke on the responseBody.  We can't simply do a null check
                // on responseBody because responseBody is always falsy when it
                // contains binary data.
                byteArray = [];
            }
        } else if (Ext.isIE) {
            // IE8 and below also have a VBArray constructor, but throw a
            // "VBArray Expected" error if you try to pass the responseBody to
            // the VBArray constructor.
            // http://msdn.microsoft.com/en-us/library/ye3x9by3%28v=vs.71%29.aspx
            // so we have to use vbscript injection to access the bytes
            if (!this.self.vbScriptInjected) {
                this.injectVBScript();
            }
            getIEByteArray(xhr.responseBody, byteArray = []); // jshint ignore:line
        } else {
            // in other older browsers make a best-effort attempt to read the
            // bytes from responseText
            byteArray = [];
            responseText = xhr.responseText;
            len = responseText.length;
            for (i = 0; i < len; i++) {
                // Some characters have an extra byte 0xF7 in the high order
                // position. Throw away the high order byte and then push the
                // result onto the byteArray.
                byteArray.push(responseText.charCodeAt(i) & 0xFF);
            }
        }

        return byteArray;
    },

    /**
     * Injects a vbscript tag containing a 'getIEByteArray' method for reading
     * binary data from an xhr response in IE8 and below.
     * @private
     */
    injectVBScript: function() {
        var scriptTag = document.createElement('script');
        scriptTag.type = 'text/vbscript';
        scriptTag.text = [
            'Function getIEByteArray(byteArray, out)',
                'Dim len, i',
                'len = LenB(byteArray)',
                'For i = 1 to len',
                    'out.push(AscB(MidB(byteArray, i, 1)))',
                'Next',
            'End Function'
        ].join('\n');
        Ext.getHead().dom.appendChild(scriptTag);
        this.self.vbScriptInjected = true;
    },

    /**
     * @private
     * @return {boolean} <tt>true</tt> if the browser can natively post binary data.
     */
    nativeBinaryPostSupport: function() {
        return Ext.isChrome ||
            (Ext.isSafari && Ext.isDefined(window.Uint8Array)) ||
            (Ext.isGecko && Ext.isDefined(window.Uint8Array));
    }


});
