    /**
     * 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.
     */
    Ext.define('Ext.data.Connection', {
        mixins: {
            observable: 'Ext.util.Observable'
        },

        statics: {
            requestId: 0
        },

        config: {
            /**
             * @cfg {String} url
             * The default URL to be used for requests to the server.
             * @accessor
             */
            url: null,

            async: true,

            /**
             * @cfg {String} [method=undefined]
             * The default HTTP method to be used for requests. Note that this is case-sensitive and
             * should be all caps.
             *
             * Defaults to undefined; if not set but params are present will use "POST", otherwise "GET".
             */
            method: null,

            username: '',
            password: '',

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

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

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

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

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

            useDefaultHeader : true,
            defaultPostHeader : 'application/x-www-form-urlencoded; charset=UTF-8',
            useDefaultXhrHeader : true,
            defaultXhrHeader : 'XMLHttpRequest',

            autoAbort: false
        },

        constructor : function(config) {
            this.initConfig(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.
             * 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 {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 success 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 {HTMLElement/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.
         *
         * @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 {Boolean} options.disableCaching True to add a unique cache-buster param to GET requests.
         *
         * @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,
                xhr;

            if (me.fireEvent('beforerequest', me, options) !== false) {
                requestOptions = me.setOptions(options, scope);

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

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

                // create a connection object
                xhr = this.getXhrInstance();

                async = options.async !== false ? (options.async || me.getAsync()) : false;

                // open the request
                if (username) {
                    xhr.open(requestOptions.method, requestOptions.url, async, username, password);
                } else {
                    xhr.open(requestOptions.method, requestOptions.url, async);
                }

                headers = me.setupHeaders(xhr, options, requestOptions.data, requestOptions.params);

                // create the transaction object
                request = {
                    id: ++this.self.requestId,
                    xhr: xhr,
                    headers: headers,
                    options: options,
                    async: async,
                    timeout: setTimeout(function() {
                        request.timedout = true;
                        me.abort(request);
                    }, options.timeout || me.getTimeout())
                };
                me.requests[request.id] = request;

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

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

        /**
         * Uploads a form using a hidden iframe.
         * @param {String/HTMLElement/Ext.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;

            /*
             * 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 + 'hide-display',
                src: Ext.SSL_SECURE_URL
            });

            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) {
                Ext.iterate(Ext.Object.fromQueryString(params), function(name, value) {
                    if (Ext.isArray(value)) {
                        Ext.each(value, function(v) {
                            addField(name, v);
                        });
                    } else {
                        addField(name, value);
                    }
                });
            }

            Ext.fly(frame).on('load', Ext.Function.bind(this.onUploadComplete, this, [frame, options]), null, {single: true});
            form.submit();

            Ext.fly(form).set(buf);
            Ext.each(hiddens, function(h) {
                Ext.removeNode(h);
            });
        },

        onUploadComplete: function(frame, options) {
            var me = this,
                // bogus response object
                response = {
                    responseText: '',
                    responseXML: null
                }, doc, firstChild;

            try {
                doc = frame.contentWindow.document || frame.contentDocument || window.frames[id].document;
                if (doc) {
                    if (doc.body) {
                        if (/textarea/i.test((firstChild = doc.body.firstChild || {}).tagName)) { // json response wrapped in textarea
                            response.responseText = firstChild.value;
                        } else {
                            response.responseText = doc.body.innerHTML;
                        }
                    }
                    //in IE the document may still have a body even if returns XML.
                    response.responseXML = doc.XMLDocument || doc;
                }
            } catch (e) {
            }

            me.fireEvent('requestcomplete', me, response, options);

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

            setTimeout(function() {
                Ext.removeNode(frame);
            }, 100);
        },

        /**
         * 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) {
            return Ext.getDom(options.form) || null;
        },

        /**
         * 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(),
                jsonData = options.jsonData,
                method,
                disableCache,
                data;

            // 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.Logger.error('No URL specified');
            }
            //</debug>

            // check for xml or json data, and make sure json data is encoded
            data = options.rawData || options.xmlData || jsonData || null;
            if (jsonData && !Ext.isPrimitive(jsonData)) {
                data = Ext.encode(data);
            }

            // 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
         * @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
         * @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
         * @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,
                key,
                header;

            if (!headers['Content-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['Content-Type'] = contentType;
            }

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

            xhr.withCredentials = options.withCredentials;

            return headers;
        },

        /**
         * Creates the appropriate XHR transport for the browser.
         * @private
         */
        getXhrInstance: (function() {
            var options = [function() {
                return new XMLHttpRequest();
            }, function() {
                return new ActiveXObject('MSXML2.XMLHTTP.3.0');
            }, function() {
                return new ActiveXObject('MSXML2.XMLHTTP');
            }, function() {
                return new ActiveXObject('Microsoft.XMLHTTP');
            }], 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 (Optional) defaults to the last transaction
         * @return {Boolean} True if there is an outstanding request.
         */
        isLoading : function(request) {
            if (!(request && request.xhr)) {
                return false;
            }
            // if there is a connection and readyState is not 0 or 4
            var state = request.xhr.readyState;
            return !(state === 0 || state == 4);
        },

        /**
         * Aborts any outstanding request.
         * @param {Object} request (Optional) defaults to the last request
         */
        abort : function(request) {
            var me = this,
                requests = me.requests,
                id;

            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.
                 */
                request.xhr.onreadystatechange = null;
                request.xhr.abort();
                me.clearTimeout(request);
                if (!request.timedout) {
                    request.aborted = true;
                }
                me.onComplete(request);
                me.cleanup(request);
            } else if (!request) {
                for (id in requests) {
                    if (requests.hasOwnProperty(id)) {
                        me.abort(requests[id]);
                    }
                }
            }
        },

        /**
         * Fires when the state of the xhr changes
         * @private
         * @param {Object} request The request
         */
        onStateChange : function(request) {
            if (request.xhr.readyState == 4) {
                this.clearTimeout(request);
                this.onComplete(request);
                this.cleanup(request);
            }
        },

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

        /**
         * Cleans up any left over information from the request
         * @private
         * @param {Object} 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) {
            var me = this,
                options = request.options,
                result,
                success,
                response;

            try {
                result = me.parseStatus(request.xhr.status);
            } 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 = 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 || status == 0,
                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 xhr = request.xhr,
                headers = {},
                lines = xhr.getAllResponseHeaders().replace(/\r\n/g, '\n').split('\n'),
                count = lines.length,
                line, index, key, value, response;

            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;
                },
                responseText : xhr.responseText,
                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
            };
        }
    });