    /**
     * @author Ed Spencer
     *
     * Proxies are used by {@link Ext.data.Store Stores} to handle the loading and saving of {@link Ext.data.Model Model}
     * data. Usually developers will not need to create or interact with proxies directly.
     *
     * # Types of Proxy
     *
     * There are two main types of Proxy - {@link Ext.data.proxy.Client Client} and {@link Ext.data.proxy.Server Server}.
     * The Client proxies save their data locally and include the following subclasses:
     *
     * - {@link Ext.data.proxy.LocalStorage LocalStorageProxy} - saves its data to localStorage if the browser supports it
     * - {@link Ext.data.proxy.SessionStorage SessionStorageProxy} - saves its data to sessionStorage if the browsers supports it
     * - {@link Ext.data.proxy.Memory MemoryProxy} - holds data in memory only, any data is lost when the page is refreshed
     *
     * The Server proxies save their data by sending requests to some remote server. These proxies include:
     *
     * - {@link Ext.data.proxy.Ajax Ajax} - sends requests to a server on the same domain
     * - {@link Ext.data.proxy.JsonP JsonP} - uses JSON-P to send requests to a server on a different domain
     * - {@link Ext.data.proxy.Rest Rest} - uses RESTful HTTP methods (GET/PUT/POST/DELETE) to communicate with server
     * - {@link Ext.data.proxy.Direct Direct} - uses {@link Ext.direct.Manager} to send requests
     *
     * Proxies operate on the principle that all operations performed are either Create, Read, Update or Delete. These four
     * operations are mapped to the methods {@link #create}, {@link #read}, {@link #update} and {@link #destroy}
     * respectively. Each Proxy subclass implements these functions.
     *
     * The CRUD methods each expect an {@link Ext.data.Operation Operation} object as the sole argument. The Operation
     * encapsulates information about the action the Store wishes to perform, the {@link Ext.data.Model model} instances
     * that are to be modified, etc. See the {@link Ext.data.Operation Operation} documentation for more details. Each CRUD
     * method also accepts a callback function to be called asynchronously on completion.
     *
     * Proxies also support batching of Operations via a {@link Ext.data.Batch batch} object, invoked by the {@link #batch}
     * method.
     */
    Ext.define('Ext.data.proxy.Proxy', {
        alias: 'proxy.proxy',
        alternateClassName: ['Ext.data.DataProxy', 'Ext.data.Proxy'],

        requires: [
            'Ext.data.reader.Json',
            'Ext.data.writer.Json'
        ],

        uses: [
            'Ext.data.Batch',
            'Ext.data.Operation',
            'Ext.data.Model'
        ],

        mixins: {
            observable: 'Ext.util.Observable'
        },

        /**
         * @cfg {String} batchOrder
         * Comma-separated ordering 'create', 'update' and 'destroy' actions when batching. Override this to set a different
         * order for the batched CRUD actions to be executed in. Defaults to 'create,update,destroy'.
         */
        batchOrder: 'create,update,destroy',

        /**
         * @cfg {Boolean} batchActions
         * True to batch actions of a particular type when synchronizing the store. Defaults to true.
         */
        batchActions: true,

        /**
         * @cfg {String} defaultReaderType
         * The default registered reader type. Defaults to 'json'.
         * @private
         */
        defaultReaderType: 'json',

        /**
         * @cfg {String} defaultWriterType
         * The default registered writer type. Defaults to 'json'.
         * @private
         */
        defaultWriterType: 'json',

        /**
         * @cfg {String/Ext.data.Model} model
         * The name of the Model to tie to this Proxy. Can be either the string name of the Model, or a reference to the
         * Model constructor. Required.
         */

        /**
         * @cfg {Object/String/Ext.data.reader.Reader} reader
         * The Ext.data.reader.Reader to use to decode the server's response or data read from client. This can either be a
         * Reader instance, a config object or just a valid Reader type name (e.g. 'json', 'xml').
         */

        /**
         * @cfg {Object/String/Ext.data.writer.Writer} writer
         * The Ext.data.writer.Writer to use to encode any request sent to the server or saved to client. This can either be
         * a Writer instance, a config object or just a valid Writer type name (e.g. 'json', 'xml').
         */

        /**
         * @property {Boolean} isProxy
         * `true` in this class to identify an object as an instantiated Proxy, or subclass thereof.
         */
        isProxy: true,

        /**
         * Creates the Proxy
         * @param {Object} config (optional) Config object.
         */
        constructor: function(config) {
            var me = this;

            config = config || {};

            me.mixins.observable.constructor.call(me, config);

            if (me.model !== undefined && !(me.model instanceof Ext.data.Model)) {
                me.setModel(me.model);
            } else {
                if (me.reader) {
                    me.setReader(me.reader);
                }

                if (me.writer) {
                    me.setWriter(me.writer);
                }
            }

            /**
             * @event metachange
             * Fires when this proxy's reader provides new metadata. Metadata usually consists
             * of new field definitions, but can include any configuration data required by an
             * application, and can be processed as needed in the event handler.
             * This event is currently only fired for JsonReaders. Note that this event is also
             * propagated by {@link Ext.data.Store}, which is typically where it would be handled.
             * @param {Ext.data.proxy.Proxy} this
             * @param {Object} meta The JSON metadata
             */
        },

        /**
         * Sets the model associated with this proxy. This will only usually be called by a Store
         *
         * @param {String/Ext.data.Model} model The new model. Can be either the model name string,
         * or a reference to the model's constructor
         * @param {Boolean} setOnStore Sets the new model on the associated Store, if one is present
         */
        setModel: function(model, setOnStore) {
            var me = this;

            me.model = Ext.ModelManager.getModel(model);

            me.setReader(this.reader);
            me.setWriter(this.writer);

            if (setOnStore && me.store) {
                me.store.setModel(me.model);
            }
        },

        /**
         * Returns the model attached to this Proxy
         * @return {Ext.data.Model} The model
         */
        getModel: function() {
            return this.model;
        },

        /**
         * Sets the Proxy's Reader by string, config object or Reader instance
         *
         * @param {String/Object/Ext.data.reader.Reader} reader The new Reader, which can be either a type string,
         * a configuration object or an Ext.data.reader.Reader instance
         * @return {Ext.data.reader.Reader} The attached Reader object
         */
        setReader: function(reader) {
            var me = this,
                needsCopy = true,
                current = me.reader;

            if (reader === undefined || typeof reader == 'string') {
                reader = {
                    type: reader
                };
                needsCopy = false;
            }

            if (reader.isReader) {
                reader.setModel(me.model);
            } else {
                if (needsCopy) {
                    reader = Ext.apply({}, reader);
                }
                Ext.applyIf(reader, {
                    proxy: me,
                    model: me.model,
                    type : me.defaultReaderType
                });

                reader = Ext.createByAlias('reader.' + reader.type, reader);
            }

            if (reader !== current && reader.onMetaChange) {
                reader.onMetaChange = Ext.Function.createSequence(reader.onMetaChange, this.onMetaChange, this);
            }

            me.reader = reader;
            return me.reader;
        },

        /**
         * Returns the reader currently attached to this proxy instance
         * @return {Ext.data.reader.Reader} The Reader instance
         */
        getReader: function() {
            return this.reader;
        },

        /**
         * @private
         * Called each time the reader's onMetaChange is called so that the proxy can fire the metachange event
         */
        onMetaChange: function(meta) {
            this.fireEvent('metachange', this, meta);
        },

        /**
         * Sets the Proxy's Writer by string, config object or Writer instance
         *
         * @param {String/Object/Ext.data.writer.Writer} writer The new Writer, which can be either a type string,
         * a configuration object or an Ext.data.writer.Writer instance
         * @return {Ext.data.writer.Writer} The attached Writer object
         */
        setWriter: function(writer) {
            var me = this,
                needsCopy = true;

            if (writer === undefined || typeof writer == 'string') {
                writer = {
                    type: writer
                };
                needsCopy = false;
            }

            if (!writer.isWriter) {
                if (needsCopy) {
                    writer = Ext.apply({}, writer);
                }
                Ext.applyIf(writer, {
                    model: me.model,
                    type : me.defaultWriterType
                });

                writer = Ext.createByAlias('writer.' + writer.type, writer);
            }

            me.writer = writer;

            return me.writer;
        },

        /**
         * Returns the writer currently attached to this proxy instance
         * @return {Ext.data.writer.Writer} The Writer instance
         */
        getWriter: function() {
            return this.writer;
        },

        /**
         * Performs the given create operation.
         * @param {Ext.data.Operation} operation The Operation to perform
         * @param {Function} callback Callback function to be called when the Operation has completed (whether
         * successful or not)
         * @param {Object} scope Scope to execute the callback function in
         * @method
         */
        create: Ext.emptyFn,

        /**
         * Performs the given read operation.
         * @param {Ext.data.Operation} operation The Operation to perform
         * @param {Function} callback Callback function to be called when the Operation has completed (whether
         * successful or not)
         * @param {Object} scope Scope to execute the callback function in
         * @method
         */
        read: Ext.emptyFn,

        /**
         * Performs the given update operation.
         * @param {Ext.data.Operation} operation The Operation to perform
         * @param {Function} callback Callback function to be called when the Operation has completed (whether
         * successful or not)
         * @param {Object} scope Scope to execute the callback function in
         * @method
         */
        update: Ext.emptyFn,

        /**
         * Performs the given destroy operation.
         * @param {Ext.data.Operation} operation The Operation to perform
         * @param {Function} callback Callback function to be called when the Operation has completed (whether
         * successful or not)
         * @param {Object} scope Scope to execute the callback function in
         * @method
         */
        destroy: Ext.emptyFn,

        /**
         * Performs a batch of {@link Ext.data.Operation Operations}, in the order specified by {@link #batchOrder}. Used
         * internally by {@link Ext.data.Store}'s {@link Ext.data.Store#sync sync} method. Example usage:
         *
         *     myProxy.batch({
         *         create : [myModel1, myModel2],
         *         update : [myModel3],
         *         destroy: [myModel4, myModel5]
         *     });
         *
         * Where the myModel* above are {@link Ext.data.Model Model} instances - in this case 1 and 2 are new instances and
         * have not been saved before, 3 has been saved previously but needs to be updated, and 4 and 5 have already been
         * saved but should now be destroyed.
         *
         * Note that the previous version of this method took 2 arguments (operations and listeners). While this is still
         * supported for now, the current signature is now a single `options` argument that can contain both operations and
         * listeners, in addition to other options. The multi-argument signature will likely be deprecated in a future release.
         *
         * @param {Object} options Object containing one or more properties supported by the batch method:
         *
         * @param {Object} options.operations Object containing the Model instances to act upon, keyed by action name
         *
         * @param {Object} [options.listeners] Event listeners object passed straight through to the Batch -
         * see {@link Ext.data.Batch} for details
         *
         * @param {Ext.data.Batch/Object} [options.batch] A {@link Ext.data.Batch} object (or batch config to apply
         * to the created batch). If unspecified a default batch will be auto-created.
         *
         * @param {Function} [options.callback] The function to be called upon completion of processing the batch.
         * The callback is called regardless of success or failure and is passed the following parameters:
         * @param {Ext.data.Batch} options.callback.batch The {@link Ext.data.Batch batch} that was processed,
         * containing all operations in their current state after processing
         * @param {Object} options.callback.options The options argument that was originally passed into batch
         *
         * @param {Function} [options.success] The function to be called upon successful completion of the batch. The
         * success function is called only if no exceptions were reported in any operations. If one or more exceptions
         * occurred then the `failure` function will be called instead. The success function is called
         * with the following parameters:
         * @param {Ext.data.Batch} options.success.batch The {@link Ext.data.Batch batch} that was processed,
         * containing all operations in their current state after processing
         * @param {Object} options.success.options The options argument that was originally passed into batch
         *
         * @param {Function} [options.failure] The function to be called upon unsuccessful completion of the batch. The
         * failure function is called when one or more operations returns an exception during processing (even if some
         * operations were also successful). In this case you can check the batch's {@link Ext.data.Batch#exceptions
         * exceptions} array to see exactly which operations had exceptions. The failure function is called with the
         * following parameters:
         * @param {Ext.data.Batch} options.failure.batch The {@link Ext.data.Batch batch} that was processed,
         * containing all operations in their current state after processing
         * @param {Object} options.failure.options The options argument that was originally passed into batch
         *
         * @param {Object} [options.scope] The scope in which to execute any callbacks (i.e. the `this` object inside
         * the callback, success and/or failure functions). Defaults to the proxy.
         *
         * @return {Ext.data.Batch} The newly created Batch
         */
        batch: function(options, /* deprecated */listeners) {
            var me = this,
                useBatch = me.batchActions,
                batch,
                records,
                actions, aLen, action, a, r, rLen, record;

            if (options.operations === undefined) {
                // the old-style (operations, listeners) signature was called
                // so convert to the single options argument syntax
                options = {
                    operations: options,
                    listeners: listeners
                };
            }

            if (options.batch) {
                if (Ext.isDefined(options.batch.runOperation)) {
                    batch = Ext.applyIf(options.batch, {
                        proxy: me,
                        listeners: {}
                    });
                }
            } else {
                options.batch = {
                    proxy: me,
                    listeners: options.listeners || {}
                };
            }

            if (!batch) {
                batch = new Ext.data.Batch(options.batch);
            }

            batch.on('complete', Ext.bind(me.onBatchComplete, me, [options], 0));

            actions = me.batchOrder.split(',');
            aLen    = actions.length;

            for (a = 0; a < aLen; a++) {
                action  = actions[a];
                records = options.operations[action];

                if (records) {
                    if (useBatch) {
                        batch.add(new Ext.data.Operation({
                            action  : action,
                            records : records
                        }));
                    } else {
                        rLen = records.length;

                        for (r = 0; r < rLen; r++) {
                            record = records[r];

                            batch.add(new Ext.data.Operation({
                                action  : action,
                                records : [record]
                            }));
                        }
                    }
                }
            }

            batch.start();
            return batch;
        },

        /**
         * @private
         * The internal callback that the proxy uses to call any specified user callbacks after completion of a batch
         */
        onBatchComplete: function(batchOptions, batch) {
            var scope = batchOptions.scope || this;

            if (batch.hasException) {
                if (Ext.isFunction(batchOptions.failure)) {
                    Ext.callback(batchOptions.failure, scope, [batch, batchOptions]);
                }
            } else if (Ext.isFunction(batchOptions.success)) {
                Ext.callback(batchOptions.success, scope, [batch, batchOptions]);
            }

            if (Ext.isFunction(batchOptions.callback)) {
                Ext.callback(batchOptions.callback, scope, [batch, batchOptions]);
            }
        }
    });