/**
 * A class which handles loading of data from a server into the Fields of an {@link Ext.form.Basic}.
 *
 * Instances of this class are only created by a {@link Ext.form.Basic Form} when {@link Ext.form.Basic#load load}ing.
 *
 * ## Response Packet Criteria
 *
 * A response packet **must** contain:
 *
 *   - **`success`** property : Boolean
 *   - **`data`** property : Object
 *
 * The `data` property contains the values of Fields to load. The individual value object for each Field is passed to
 * the Field's {@link Ext.form.field.Field#setValue setValue} method.
 *
 * ## JSON Packets
 *
 * By default, response packets are assumed to be JSON, so for the following form load call:
 *
 *     var myFormPanel = new Ext.form.Panel({
 *         title: 'Client and routing info',
 *         renderTo: Ext.getBody(),
 *         defaults: {
 *             xtype: 'textfield'
 *         },
 *         items: [{
 *             fieldLabel: 'Client',
 *             name: 'clientName'
 *         }, {
 *             fieldLabel: 'Port of loading',
 *             name: 'portOfLoading'
 *         }, {
 *             fieldLabel: 'Port of discharge',
 *             name: 'portOfDischarge'
 *         }]
 *     });
 *     myFormPanel.{@link Ext.form.Panel#getForm getForm}().{@link Ext.form.Basic#load load}({
 *         url: '/getRoutingInfo.php',
 *         params: {
 *             consignmentRef: myConsignmentRef
 *         },
 *         failure: function(form, action) {
 *             Ext.Msg.alert("Load failed", action.result.errorMessage);
 *         }
 *     });
 *
 * a **success response** packet may look like this:
 *
 *     {
 *         success: true,
 *         data: {
 *             clientName: "Fred. Olsen Lines",
 *             portOfLoading: "FXT",
 *             portOfDischarge: "OSL"
 *         }
 *     }
 *
 * while a **failure response** packet may look like this:
 *
 *     {
 *         success: false,
 *         errorMessage: "Consignment reference not found"
 *     }
 *
 * Other data may be placed into the response for processing the {@link Ext.form.Basic Form}'s callback or event handler
 * methods. The object decoded from this JSON is available in the {@link Ext.form.action.Action#result result} property.
 */
Ext.define('Ext.form.action.Load', {
    extend:'Ext.form.action.Action',
    requires: ['Ext.data.Connection'],
    alternateClassName: 'Ext.form.Action.Load',
    alias: 'formaction.load',

    type: 'load',

    /**
     * @private
     */
    run: function() {
        Ext.Ajax.request(Ext.apply(
            this.createCallback(),
            {
                method: this.getMethod(),
                url: this.getUrl(),
                headers: this.headers,
                params: this.getParams()
            }
        ));
    },

    /**
     * @private
     */
    onSuccess: function(response){
        var result = this.processResponse(response),
            form = this.form,
            formActive = form && !form.destroying && !form.destroyed;
        
        if (result === true || !result.success || !result.data) {
            this.failureType = Ext.form.action.Action.LOAD_FAILURE;
            
            if (formActive) {
                form.afterAction(this, false);
            }
            
            return;
        }
        
        if (formActive) {
            form.clearInvalid();
            form.setValues(result.data);
            form.afterAction(this, true);
        }
    },

    /**
     * @private
     */
    handleResponse: function(response) {
        var reader = this.form.reader,
            rs, data;
        if (reader) {
            rs = reader.read(response);
            data = rs.records && rs.records[0] ? rs.records[0].data : null;
            return {
                success : rs.success,
                data : data
            };
        }
        return Ext.decode(response.responseText);
    }
});

