    /**
     * @author Ed Spencer
     *
     * ServerProxy is a superclass of {@link Ext.data.proxy.JsonP JsonPProxy} and {@link Ext.data.proxy.Ajax AjaxProxy}, and
     * would not usually be used directly.
     *
     * ServerProxy should ideally be named HttpProxy as it is a superclass for all HTTP proxies - for Ext JS 4.x it has been
     * called ServerProxy to enable any 3.x applications that reference the HttpProxy to continue to work (HttpProxy is now
     * an alias of AjaxProxy).
     * @private
     */
    Ext.define('Ext.data.proxy.Server', {
        extend: 'Ext.data.proxy.Proxy',
        alias : 'proxy.server',
        alternateClassName: 'Ext.data.ServerProxy',
        uses  : ['Ext.data.Request'],

        /**
         * @cfg {String} url
         * The URL from which to request the data object.
         */

        /**
         * @cfg {String} pageParam
         * The name of the 'page' parameter to send in a request. Defaults to 'page'. Set this to undefined if you don't
         * want to send a page parameter.
         */
        pageParam: 'page',

        /**
         * @cfg {String} startParam
         * The name of the 'start' parameter to send in a request. Defaults to 'start'. Set this to undefined if you don't
         * want to send a start parameter.
         */
        startParam: 'start',

        /**
         * @cfg {String} limitParam
         * The name of the 'limit' parameter to send in a request. Defaults to 'limit'. Set this to undefined if you don't
         * want to send a limit parameter.
         */
        limitParam: 'limit',

        /**
         * @cfg {String} groupParam
         * The name of the 'group' parameter to send in a request. Defaults to 'group'. Set this to undefined if you don't
         * want to send a group parameter.
         */
        groupParam: 'group',

        /**
         * @cfg {String} sortParam
         * The name of the 'sort' parameter to send in a request. Defaults to 'sort'. Set this to undefined if you don't
         * want to send a sort parameter.
         */
        sortParam: 'sort',

        /**
         * @cfg {String} filterParam
         * The name of the 'filter' parameter to send in a request. Defaults to 'filter'. Set this to undefined if you don't
         * want to send a filter parameter.
         */
        filterParam: 'filter',

        /**
         * @cfg {String} directionParam
         * The name of the direction parameter to send in a request. **This is only used when simpleSortMode is set to
         * true.** Defaults to 'dir'.
         */
        directionParam: 'dir',

        /**
         * @cfg {Boolean} simpleSortMode
         * Enabling simpleSortMode in conjunction with remoteSort will only send one sort property and a direction when a
         * remote sort is requested. The directionParam and sortParam will be sent with the property name and either 'ASC'
         * or 'DESC'.
         */
        simpleSortMode: false,

        /**
         * @cfg {Boolean} noCache
         * Disable caching by adding a unique parameter name to the request. Set to false to allow caching. Defaults to true.
         */
        noCache : true,

        /**
         * @cfg {String} cacheString
         * The name of the cache param added to the url when using noCache. Defaults to "_dc".
         */
        cacheString: "_dc",

        /**
         * @cfg {Number} timeout
         * The number of milliseconds to wait for a response. Defaults to 30000 milliseconds (30 seconds).
         */
        timeout : 30000,

        /**
         * @cfg {Object} api
         * Specific urls to call on CRUD action methods "create", "read", "update" and "destroy". Defaults to:
         *
         *     api: {
         *         create  : undefined,
         *         read    : undefined,
         *         update  : undefined,
         *         destroy : undefined
         *     }
         *
         * The url is built based upon the action being executed [create|read|update|destroy] using the commensurate
         * {@link #api} property, or if undefined default to the configured
         * {@link Ext.data.Store}.{@link Ext.data.proxy.Server#url url}.
         *
         * For example:
         *
         *     api: {
         *         create  : '/controller/new',
         *         read    : '/controller/load',
         *         update  : '/controller/update',
         *         destroy : '/controller/destroy_action'
         *     }
         *
         * If the specific URL for a given CRUD action is undefined, the CRUD action request will be directed to the
         * configured {@link Ext.data.proxy.Server#url url}.
         */

        constructor: function(config) {
            var me = this;

            config = config || {};
            /**
             * @event exception
             * Fires when the server returns an exception
             * @param {Ext.data.proxy.Proxy} this
             * @param {Object} response The response from the AJAX request
             * @param {Ext.data.Operation} operation The operation that triggered request
             */
            me.callParent([config]);

            /**
             * @cfg {Object} extraParams
             * Extra parameters that will be included on every request. Individual requests with params of the same name
             * will override these params when they are in conflict.
             */
            me.extraParams = config.extraParams || {};

            me.api = Ext.apply({}, config.api || me.api);

            //backwards compatibility, will be deprecated in 5.0
            me.nocache = me.noCache;
        },

        //in a ServerProxy all four CRUD operations are executed in the same manner, so we delegate to doRequest in each case
        create: function() {
            return this.doRequest.apply(this, arguments);
        },

        read: function() {
            return this.doRequest.apply(this, arguments);
        },

        update: function() {
            return this.doRequest.apply(this, arguments);
        },

        destroy: function() {
            return this.doRequest.apply(this, arguments);
        },

        /**
         * Sets a value in the underlying {@link #extraParams}.
         * @param {String} name The key for the new value
         * @param {Object} value The value
         */
        setExtraParam: function(name, value) {
            this.extraParams[name] = value;
        },

        /**
         * Creates and returns an Ext.data.Request object based on the options passed by the {@link Ext.data.Store Store}
         * that this Proxy is attached to.
         * @param {Ext.data.Operation} operation The {@link Ext.data.Operation Operation} object to execute
         * @return {Ext.data.Request} The request object
         */
        buildRequest: function(operation) {
            var me = this,
                params = Ext.applyIf(operation.params || {}, me.extraParams || {}),
                request;

            //copy any sorters, filters etc into the params so they can be sent over the wire
            params = Ext.applyIf(params, me.getParams(operation));

            if (operation.id && !params.id) {
                params.id = operation.id;
            }

            request = new Ext.data.Request({
                params   : params,
                action   : operation.action,
                records  : operation.records,
                operation: operation,
                url      : operation.url,

                // this is needed by JsonSimlet in order to properly construct responses for
                // requests from this proxy
                proxy: me
            });

            request.url = me.buildUrl(request);

            /*
             * Save the request on the Operation. Operations don't usually care about Request and Response data, but in the
             * ServerProxy and any of its subclasses we add both request and response as they may be useful for further processing
             */
            operation.request = request;

            return request;
        },

        // Should this be documented as protected method?
        processResponse: function(success, operation, request, response, callback, scope) {
            var me = this,
                reader,
                result;

            if (success === true) {
                reader = me.getReader();

                // Apply defaults to incoming data only for read operations.
                // For create and update, there will already be a client-side record
                // to match with which will contain any defaulted in values.
                reader.applyDefaults = operation.action === 'read';

                result = reader.read(me.extractResponseData(response));

                if (result.success !== false) {
                    //see comment in buildRequest for why we include the response object here
                    Ext.apply(operation, {
                        response: response,
                        resultSet: result
                    });

                    operation.commitRecords(result.records);
                    operation.setCompleted();
                    operation.setSuccessful();
                } else {
                    operation.setException(result.message);
                    me.fireEvent('exception', this, response, operation);
                }
            } else {
                me.setException(operation, response);
                me.fireEvent('exception', this, response, operation);
            }

            //this callback is the one that was passed to the 'read' or 'write' function above
            if (typeof callback == 'function') {
                callback.call(scope || me, operation);
            }

            me.afterRequest(request, success);
        },

        /**
         * Sets up an exception on the operation
         * @private
         * @param {Ext.data.Operation} operation The operation
         * @param {Object} response The response
         */
        setException: function(operation, response) {
            operation.setException({
                status: response.status,
                statusText: response.statusText
            });
        },

        /**
         * Template method to allow subclasses to specify how to get the response for the reader.
         * @template
         * @private
         * @param {Object} response The server response
         * @return {Object} The response data to be used by the reader
         */
        extractResponseData: function(response) {
            return response;
        },

        /**
         * Encode any values being sent to the server. Can be overridden in subclasses.
         * @private
         * @param {Array} An array of sorters/filters.
         * @return {Object} The encoded value
         */
        applyEncoding: function(value) {
            return Ext.encode(value);
        },

        /**
         * Encodes the array of {@link Ext.util.Sorter} objects into a string to be sent in the request url. By default,
         * this simply JSON-encodes the sorter data
         * @param {Ext.util.Sorter[]} sorters The array of {@link Ext.util.Sorter Sorter} objects
         * @return {String} The encoded sorters
         */
        encodeSorters: function(sorters) {
            var min = [],
                length = sorters.length,
                i = 0;

            for (; i < length; i++) {
                min[i] = {
                    property : sorters[i].property,
                    direction: sorters[i].direction
                };
            }
            return this.applyEncoding(min);

        },

        /**
         * Encodes the array of {@link Ext.util.Filter} objects into a string to be sent in the request url. By default,
         * this simply JSON-encodes the filter data
         * @param {Ext.util.Filter[]} filters The array of {@link Ext.util.Filter Filter} objects
         * @return {String} The encoded filters
         */
        encodeFilters: function(filters) {
            var min = [],
                length = filters.length,
                i = 0;

            for (; i < length; i++) {
                min[i] = {
                    property: filters[i].property,
                    value   : filters[i].value
                };
            }
            return this.applyEncoding(min);
        },

        /**
         * @private
         * Copy any sorters, filters etc into the params so they can be sent over the wire
         */
        getParams: function(operation) {
            var me = this,
                params = {},
                isDef = Ext.isDefined,
                groupers = operation.groupers,
                sorters = operation.sorters,
                filters = operation.filters,
                page = operation.page,
                start = operation.start,
                limit = operation.limit,

                simpleSortMode = me.simpleSortMode,

                pageParam = me.pageParam,
                startParam = me.startParam,
                limitParam = me.limitParam,
                groupParam = me.groupParam,
                sortParam = me.sortParam,
                filterParam = me.filterParam,
                directionParam = me.directionParam;

            if (pageParam && isDef(page)) {
                params[pageParam] = page;
            }

            if (startParam && isDef(start)) {
                params[startParam] = start;
            }

            if (limitParam && isDef(limit)) {
                params[limitParam] = limit;
            }

            if (groupParam && groupers && groupers.length > 0) {
                // Grouper is a subclass of sorter, so we can just use the sorter method
                params[groupParam] = me.encodeSorters(groupers);
            }

            if (sortParam && sorters && sorters.length > 0) {
                if (simpleSortMode) {
                    params[sortParam] = sorters[0].property;
                    params[directionParam] = sorters[0].direction;
                } else {
                    params[sortParam] = me.encodeSorters(sorters);
                }

            }

            if (filterParam && filters && filters.length > 0) {
                params[filterParam] = me.encodeFilters(filters);
            }

            return params;
        },

        /**
         * Generates a url based on a given Ext.data.Request object. By default, ServerProxy's buildUrl will add the
         * cache-buster param to the end of the url. Subclasses may need to perform additional modifications to the url.
         * @param {Ext.data.Request} request The request object
         * @return {String} The url
         */
        buildUrl: function(request) {
            var me = this,
                url = me.getUrl(request);

            //<debug>
            if (!url) {
                Ext.Error.raise("You are using a ServerProxy but have not supplied it with a url.");
            }
            //</debug>

            if (me.noCache) {
                url = Ext.urlAppend(url, Ext.String.format("{0}={1}", me.cacheString, Ext.Date.now()));
            }

            return url;
        },

        /**
         * Get the url for the request taking into account the order of priority,
         * - The request
         * - The api
         * - The url
         * @private
         * @param {Ext.data.Request} request The request
         * @return {String} The url
         */
        getUrl: function(request) {
            return request.url || this.api[request.action] || this.url;
        },

        /**
         * In ServerProxy subclasses, the {@link #create}, {@link #read}, {@link #update} and {@link #destroy} methods all
         * pass through to doRequest. Each ServerProxy subclass must implement the doRequest method - see {@link
         * Ext.data.proxy.JsonP} and {@link Ext.data.proxy.Ajax} for examples. This method carries the same signature as
         * each of the methods that delegate to it.
         *
         * @param {Ext.data.Operation} operation The Ext.data.Operation object
         * @param {Function} callback The callback function to call when the Operation has completed
         * @param {Object} scope The scope in which to execute the callback
         */
        doRequest: function(operation, callback, scope) {
            //<debug>
            Ext.Error.raise("The doRequest function has not been implemented on your Ext.data.proxy.Server subclass. See src/data/ServerProxy.js for details");
            //</debug>
        },

        /**
         * Optional callback function which can be used to clean up after a request has been completed.
         * @param {Ext.data.Request} request The Request object
         * @param {Boolean} success True if the request was successful
         * @method
         */
        afterRequest: Ext.emptyFn,

        onDestroy: function() {
            Ext.destroy(this.reader, this.writer);
        }
    });