/**
 * @author Ed Spencer
 * @class Ext.data.proxy.Proxy
 * 
 * <p>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.</p>
 * <p><u>Types of Proxy</u></p>
 * 
 * <p>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:</p>
 * 
 * <ul style="list-style-type: disc; padding-left: 25px">
 * <li>{@link Ext.data.proxy.LocalStorage LocalStorageProxy} - saves its data to localStorage if the browser supports it</li>
 * <li>{@link Ext.data.proxy.SessionStorage SessionStorageProxy} - saves its data to sessionStorage if the browsers supports it</li>
 * <li>{@link Ext.data.proxy.Memory MemoryProxy} - holds data in memory only, any data is lost when the page is refreshed</li>
 * </ul>
 * 
 * <p>The Server proxies save their data by sending requests to some remote server. These proxies include:</p>
 * 
 * <ul style="list-style-type: disc; padding-left: 25px">
 * <li>{@link Ext.data.proxy.Ajax Ajax} - sends requests to a server on the same domain</li>
 * <li>{@link Ext.data.proxy.JsonP JsonP} - uses JSON-P to send requests to a server on a different domain</li>
 * <li>{@link Ext.data.proxy.Direct Direct} - uses {@link Ext.direct} to send requests</li>
 * </ul>
 * 
 * <p>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.</p>
 * 
 * <p>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.</p>
 * 
 * <p>Proxies also support batching of Operations via a {@link Ext.data.Batch batch} object, invoked by the {@link #batch} method.</p>
 * 
 * @constructor
 * Creates the Proxy
 * @param {Object} config Optional config object
 */
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 <tt>true</tt>.
     */
    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.
     */
    
    isProxy: true,
    
    constructor: function(config) {
        config = config || {};
        
        if (config.model === undefined) {
            delete config.model;
        }

        this.mixins.observable.constructor.call(this, config);
        
        if (this.model !== undefined && !(this.model instanceof Ext.data.Model)) {
            this.setModel(this.model);
        }
    },
    
    /**
     * 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) {
        this.model = Ext.ModelManager.getModel(model);
        
        var reader = this.reader,
            writer = this.writer;
        
        this.setReader(reader);
        this.setWriter(writer);
        
        if (setOnStore && this.store) {
            this.store.setModel(this.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;
        
        if (reader === undefined || typeof reader == 'string') {
            reader = {
                type: reader
            };
        }

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

            reader = Ext.createByAlias('reader.' + reader.type, reader);
        }
        
        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;
    },
    
    /**
     * 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) {
        if (writer === undefined || typeof writer == 'string') {
            writer = {
                type: writer
            };
        }

        if (!(writer instanceof Ext.data.writer.Writer)) {
            Ext.applyIf(writer, {
                model: this.model,
                type : this.defaultWriterType
            });

            writer = Ext.createByAlias('writer.' + writer.type, writer);
        }
        
        this.writer = writer;
        
        return this.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
     */
    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
     */
    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
     */
    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
     */
    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:
     * <pre><code>
     * myProxy.batch({
     *     create : [myModel1, myModel2],
     *     update : [myModel3],
     *     destroy: [myModel4, myModel5]
     * });
     * </code></pre>
     * 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.
     * @param {Object} operations Object containing the Model instances to act upon, keyed by action name
     * @param {Object} listeners Optional listeners object passed straight through to the Batch - see {@link Ext.data.Batch}
     * @return {Ext.data.Batch} The newly created Ext.data.Batch object
     */
    batch: function(operations, listeners) {
        var me = this,
            batch = Ext.create('Ext.data.Batch', {
                proxy: me,
                listeners: listeners || {}
            }),
            useBatch = me.batchActions, 
            records;
        
        Ext.each(me.batchOrder.split(','), function(action) {
            records = operations[action];
            if (records) {
                if (useBatch) {
                    batch.add(Ext.create('Ext.data.Operation', {
                        action: action,
                        records: records
                    }));
                } else {
                    Ext.each(records, function(record){
                        batch.add(Ext.create('Ext.data.Operation', {
                            action : action, 
                            records: [record]
                        }));
                    });
                }
            }
        }, me);
        
        batch.start();
        return batch;
    }
}, function() {
    // Ext.data.proxy.ProxyMgr.registerType('proxy', this);
    
    //backwards compatibility
    Ext.data.DataProxy = this;
    // Ext.deprecate('platform', '2.0', function() {
    //     Ext.data.DataProxy = this;
    // }, this);
});