/*
This file is part of Ext JS 4.2

Copyright (c) 2011-2013 Sencha Inc

Contact:  http://www.sencha.com/contact

Commercial Usage
Licensees holding valid commercial licenses may use this file in accordance with the Commercial
Software License Agreement provided with the Software or, alternatively, in accordance with the
terms contained in a written agreement between you and Sencha.

If you are unsure which license is appropriate for your use, please contact the sales department
at http://www.sencha.com/contact.

Build date: 2013-09-18 17:18:59 (940c324ac822b840618a3a8b2b4b873f83a1a9b1)
*/
/**
 * @author Ed Spencer
 *
 * AjaxProxy is one of the most widely-used ways of getting data into your application. It uses AJAX requests to load
 * data from the server, usually to be placed into a {@link Ext.data.Store Store}. Let's take a look at a typical setup.
 * Here we're going to set up a Store that has an AjaxProxy. To prepare, we'll also set up a {@link Ext.data.Model
 * Model}:
 *
 *     Ext.define('User', {
 *         extend: 'Ext.data.Model',
 *         fields: ['id', 'name', 'email']
 *     });
 *
 *     //The Store contains the AjaxProxy as an inline configuration
 *     var store = Ext.create('Ext.data.Store', {
 *         model: 'User',
 *         proxy: {
 *             type: 'ajax',
 *             url : 'users.json'
 *         }
 *     });
 *
 *     store.load();
 *
 * Our example is going to load user data into a Store, so we start off by defining a {@link Ext.data.Model Model} with
 * the fields that we expect the server to return. Next we set up the Store itself, along with a
 * {@link Ext.data.Store#proxy proxy} configuration. This configuration was automatically turned into an
 * Ext.data.proxy.Ajax instance, with the url we specified being passed into AjaxProxy's constructor.
 * It's as if we'd done this:
 *
 *     new Ext.data.proxy.Ajax({
 *         url: 'users.json',
 *         model: 'User',
 *         reader: 'json'
 *     });
 *
 * A couple of extra configurations appeared here - {@link #model} and {@link #reader}. These are set by default when we
 * create the proxy via the Store - the Store already knows about the Model, and Proxy's default {@link
 * Ext.data.reader.Reader Reader} is {@link Ext.data.reader.Json JsonReader}.
 *
 * Now when we call store.load(), the AjaxProxy springs into action, making a request to the url we configured
 * ('users.json' in this case). As we're performing a read, it sends a GET request to that url (see
 * {@link #actionMethods} to customize this - by default any kind of read will be sent as a GET request and any kind of write
 * will be sent as a POST request).
 *
 * # Limitations
 *
 * AjaxProxy cannot be used to retrieve data from other domains. If your application is running on http://domainA.com it
 * cannot load data from http://domainB.com because browsers have a built-in security policy that prohibits domains
 * talking to each other via AJAX.
 *
 * If you need to read data from another domain and can't set up a proxy server (some software that runs on your own
 * domain's web server and transparently forwards requests to http://domainB.com, making it look like they actually came
 * from http://domainA.com), you can use {@link Ext.data.proxy.JsonP} and a technique known as JSON-P (JSON with
 * Padding), which can help you get around the problem so long as the server on http://domainB.com is set up to support
 * JSON-P responses. See {@link Ext.data.proxy.JsonP JsonPProxy}'s introduction docs for more details.
 *
 * # Readers and Writers
 *
 * AjaxProxy can be configured to use any type of {@link Ext.data.reader.Reader Reader} to decode the server's response.
 * If no Reader is supplied, AjaxProxy will default to using a {@link Ext.data.reader.Json JsonReader}. Reader
 * configuration can be passed in as a simple object, which the Proxy automatically turns into a {@link
 * Ext.data.reader.Reader Reader} instance:
 *
 *     var proxy = new Ext.data.proxy.Ajax({
 *         model: 'User',
 *         reader: {
 *             type: 'xml',
 *             root: 'users'
 *         }
 *     });
 *
 *     proxy.getReader(); //returns an {@link Ext.data.reader.Xml XmlReader} instance based on the config we supplied
 *
 * # Url generation
 *
 * AjaxProxy automatically inserts any sorting, filtering, paging and grouping options into the url it generates for
 * each request. These are controlled with the following configuration options:
 *
 * - {@link #pageParam} - controls how the page number is sent to the server (see also {@link #startParam} and {@link #limitParam})
 * - {@link #sortParam} - controls how sort information is sent to the server
 * - {@link #groupParam} - controls how grouping information is sent to the server
 * - {@link #filterParam} - controls how filter information is sent to the server
 *
 * Each request sent by AjaxProxy is described by an {@link Ext.data.Operation Operation}. To see how we can customize
 * the generated urls, let's say we're loading the Proxy with the following Operation:
 *
 *     var operation = new Ext.data.Operation({
 *         action: 'read',
 *         page  : 2
 *     });
 *
 * Now we'll issue the request for this Operation by calling {@link #read}:
 *
 *     var proxy = new Ext.data.proxy.Ajax({
 *         url: '/users'
 *     });
 *
 *     proxy.read(operation); //GET /users?page=2
 *
 * Easy enough - the Proxy just copied the page property from the Operation. We can customize how this page data is sent
 * to the server:
 *
 *     var proxy = new Ext.data.proxy.Ajax({
 *         url: '/users',
 *         pageParam: 'pageNumber'
 *     });
 *
 *     proxy.read(operation); //GET /users?pageNumber=2
 *
 * Alternatively, our Operation could have been configured to send start and limit parameters instead of page:
 *
 *     var operation = new Ext.data.Operation({
 *         action: 'read',
 *         start : 50,
 *         limit : 25
 *     });
 *
 *     var proxy = new Ext.data.proxy.Ajax({
 *         url: '/users'
 *     });
 *
 *     proxy.read(operation); //GET /users?start=50&limit;=25
 *
 * Again we can customize this url:
 *
 *     var proxy = new Ext.data.proxy.Ajax({
 *         url: '/users',
 *         startParam: 'startIndex',
 *         limitParam: 'limitIndex'
 *     });
 *
 *     proxy.read(operation); //GET /users?startIndex=50&limitIndex;=25
 *
 * AjaxProxy will also send sort and filter information to the server. Let's take a look at how this looks with a more
 * expressive Operation object:
 *
 *     var operation = new Ext.data.Operation({
 *         action: 'read',
 *         sorters: [
 *             new Ext.util.Sorter({
 *                 property : 'name',
 *                 direction: 'ASC'
 *             }),
 *             new Ext.util.Sorter({
 *                 property : 'age',
 *                 direction: 'DESC'
 *             })
 *         ],
 *         filters: [
 *             new Ext.util.Filter({
 *                 property: 'eyeColor',
 *                 value   : 'brown'
 *             })
 *         ]
 *     });
 *
 * This is the type of object that is generated internally when loading a {@link Ext.data.Store Store} with sorters and
 * filters defined. By default the AjaxProxy will JSON encode the sorters and filters, resulting in something like this
 * (note that the url is escaped before sending the request, but is left unescaped here for clarity):
 *
 *     var proxy = new Ext.data.proxy.Ajax({
 *         url: '/users'
 *     });
 *
 *     proxy.read(operation); //GET /users?sort=[{"property":"name","direction":"ASC"},{"property":"age","direction":"DESC"}]&filter;=[{"property":"eyeColor","value":"brown"}]
 *
 * We can again customize how this is created by supplying a few configuration options. Let's say our server is set up
 * to receive sorting information is a format like "sortBy=name#ASC,age#DESC". We can configure AjaxProxy to provide
 * that format like this:
 *
 *      var proxy = new Ext.data.proxy.Ajax({
 *          url: '/users',
 *          sortParam: 'sortBy',
 *          filterParam: 'filterBy',
 *
 *          //our custom implementation of sorter encoding - turns our sorters into "name#ASC,age#DESC"
 *          encodeSorters: function(sorters) {
 *              var length   = sorters.length,
 *                  sortStrs = [],
 *                  sorter, i;
 *
 *              for (i = 0; i < length; i++) {
 *                  sorter = sorters[i];
 *
 *                  sortStrs[i] = sorter.property + '#' + sorter.direction
 *              }
 *
 *              return sortStrs.join(",");
 *          }
 *      });
 *
 *      proxy.read(operation); //GET /users?sortBy=name#ASC,age#DESC&filterBy;=[{"property":"eyeColor","value":"brown"}]
 *
 * We can also provide a custom {@link #encodeFilters} function to encode our filters.
 *
 * @constructor
 * Note that if this HttpProxy is being used by a {@link Ext.data.Store Store}, then the Store's call to
 * {@link Ext.data.Store#method-load load} will override any specified callback and params options. In this case, use the
 * {@link Ext.data.Store Store}'s events to modify parameters, or react to loading events.
 *
 * @param {Object} config (optional) Config object.
 * If an options parameter is passed, the singleton {@link Ext.Ajax} object will be used to make the request.
 */
Ext.define('Ext.data.proxy.Ajax', {
    requires: ['Ext.Ajax'],
    extend: 'Ext.data.proxy.Server',
    alias: 'proxy.ajax',
    alternateClassName: ['Ext.data.HttpProxy', 'Ext.data.AjaxProxy'],
    
    /**
     * @property {Object} actionMethods
     * Mapping of action name to HTTP request method. In the basic AjaxProxy these are set to 'GET' for 'read' actions
     * and 'POST' for 'create', 'update' and 'destroy' actions. The {@link Ext.data.proxy.Rest} maps these to the
     * correct RESTful methods.
     */
    actionMethods: {
        create : 'POST',
        read   : 'GET',
        update : 'POST',
        destroy: 'POST'
    },
    
    // Keep a default copy of the action methods here. Ideally could just null
    // out actionMethods and just check if it exists & has a property, otherwise
    // fallback to the default. But at the moment it's defined as a public property,
    // so we need to be able to maintain the ability to modify/access it. 
    defaultActionMethods: {
        create : 'POST',
        read   : 'GET',
        update : 'POST',
        destroy: 'POST'    
    },

    /**
     * @cfg {Boolean} binary
     * True to request binary data from the server.  This feature requires
     * the use of a binary reader such as {@link Ext.data.amf.Reader AMF Reader}
     */
    binary: false,
    
    /**
     * @cfg {Object} headers
     * Any headers to add to the Ajax request. Defaults to undefined.
     */
    
    /**
     * @cfg {Boolean} paramsAsJson `true` to have any request parameters sent as {@link Ext.data.Connection#jsonData} 
     * where they can be parsed from the raw request. By default, parameters are sent via the 
     * {@link Ext.data.Connection#params} property. **Note**: This setting does not apply when the
     * request is sent as a 'GET' request. See {@link #actionMethods} for controlling the HTTP verb
     * that is used when sending requests.
     */
    paramsAsJson: false,
    
    doRequest: function(operation, callback, scope) {
        var me = this,
            writer  = me.getWriter(),
            request = me.buildRequest(operation),
            method  = me.getMethod(request);
            
        if (operation.allowWrite()) {
            request = writer.write(request);
        }
        
        Ext.apply(request, {
            binary        : me.binary,
            headers       : me.headers,
            timeout       : me.timeout,
            scope         : me,
            callback      : me.createRequestCallback(request, operation, callback, scope),
            method        : method,
            disableCaching: false // explicitly set it to false, ServerProxy handles caching
        });
        
        if (method.toUpperCase() !== 'GET' && me.paramsAsJson) {
            // We need to copy the request here, because the params object is attached to
            // the request and may be accessed by other callers, since it doesn't really care how the
            // information is encoded, so we can't mutate it here.
            request = Ext.apply({
                jsonData: request.params
            }, request);
            delete request.params;
        }
        
        Ext.Ajax.request(request);
        
        return request;
    },
    
    /**
     * Returns the HTTP method name for a given request. By default this returns based on a lookup on
     * {@link #actionMethods}.
     * @param {Ext.data.Request} request The request object
     * @return {String} The HTTP method to use (should be one of 'GET', 'POST', 'PUT' or 'DELETE')
     */
    getMethod: function(request) {
        var actions = this.actionMethods,
            action = request.action,
            method;
            
        if (actions) {
            method = actions[action];
        }
        return method || this.defaultActionMethods[action];
    },
    
    /**
     * @private
     * TODO: This is currently identical to the JsonPProxy version except for the return function's signature. There is a lot
     * of code duplication inside the returned function so we need to find a way to DRY this up.
     * @param {Ext.data.Request} request The Request object
     * @param {Ext.data.Operation} operation The Operation being executed
     * @param {Function} callback The callback function to be called when the request completes. This is usually the callback
     * passed to doRequest
     * @param {Object} scope The scope in which to execute the callback function
     * @return {Function} The callback function
     */
    createRequestCallback: function(request, operation, callback, scope) {
        var me = this;
        
        return function(options, success, response) {
            me.processResponse(success, operation, request, response, callback, scope);
        };
    }
});
