    /**
     * @author Ed Spencer
     *
     * Associations enable you to express relationships between different {@link Ext.data.Model Models}. Let's say we're
     * writing an ecommerce system where Users can make Orders - there's a relationship between these Models that we can
     * express like this:
     *
     *     Ext.define('User', {
     *         extend: 'Ext.data.Model',
     *         fields: ['id', 'name', 'email'],
     *
     *         hasMany: {model: 'Order', name: 'orders'}
     *     });
     *
     *     Ext.define('Order', {
     *         extend: 'Ext.data.Model',
     *         fields: ['id', 'user_id', 'status', 'price'],
     *
     *         belongsTo: 'User'
     *     });
     *
     * We've set up two models - User and Order - and told them about each other. You can set up as many associations on
     * each Model as you need using the two default types - {@link Ext.data.HasManyAssociation hasMany} and {@link
     * Ext.data.BelongsToAssociation belongsTo}. There's much more detail on the usage of each of those inside their
     * documentation pages. If you're not familiar with Models already, {@link Ext.data.Model there is plenty on those too}.
     *
     * **Further Reading**
     *
     *   - {@link Ext.data.association.HasMany hasMany associations}
     *   - {@link Ext.data.association.BelongsTo belongsTo associations}
     *   - {@link Ext.data.association.HasOne hasOne associations}
     *   - {@link Ext.data.Model using Models}
     *
     * # Self association models
     *
     * We can also have models that create parent/child associations between the same type. Below is an example, where
     * groups can be nested inside other groups:
     *
     *     // Server Data
     *     {
     *         "groups": {
     *             "id": 10,
     *             "parent_id": 100,
     *             "name": "Main Group",
     *             "parent_group": {
     *                 "id": 100,
     *                 "parent_id": null,
     *                 "name": "Parent Group"
     *             },
     *             "child_groups": [{
     *                 "id": 2,
     *                 "parent_id": 10,
     *                 "name": "Child Group 1"
     *             },{
     *                 "id": 3,
     *                 "parent_id": 10,
     *                 "name": "Child Group 2"
     *             },{
     *                 "id": 4,
     *                 "parent_id": 10,
     *                 "name": "Child Group 3"
     *             }]
     *         }
     *     }
     *
     *     // Client code
     *     Ext.define('Group', {
     *         extend: 'Ext.data.Model',
     *         fields: ['id', 'parent_id', 'name'],
     *         proxy: {
     *             type: 'ajax',
     *             url: 'data.json',
     *             reader: {
     *                 type: 'json',
     *                 root: 'groups'
     *             }
     *         },
     *         associations: [{
     *             type: 'hasMany',
     *             model: 'Group',
     *             primaryKey: 'id',
     *             foreignKey: 'parent_id',
     *             autoLoad: true,
     *             associationKey: 'child_groups' // read child data from child_groups
     *         }, {
     *             type: 'belongsTo',
     *             model: 'Group',
     *             primaryKey: 'id',
     *             foreignKey: 'parent_id',
     *             associationKey: 'parent_group' // read parent data from parent_group
     *         }]
     *     });
     *
     *     Ext.onReady(function(){
     *
     *         Group.load(10, {
     *             success: function(group){
     *                 console.log(group.getGroup().get('name'));
     *
     *                 group.groups().each(function(rec){
     *                     console.log(rec.get('name'));
     *                 });
     *             }
     *         });
     *
     *     });
     *
     */
    Ext.define('Ext.data.association.Association', {
        alternateClassName: 'Ext.data.Association',
        /**
         * @cfg {String} ownerModel
         * The string name of the model that owns the association.
         *
         * **NB!** This config is required when instantiating the Association directly.
         * However, it cannot be used at all when defining the association as a config
         * object inside Model, because the name of the model itself will be supplied
         * automatically as the value of this config.
         */

        /**
         * @cfg {String} associatedModel
         * The string name of the model that is being associated with.
         *
         * **NB!** This config is required when instantiating the Association directly.
         * When defining the association as a config object inside Model, the #model
         * configuration will shadow this config.
         */

        /**
         * @cfg {String} model
         * The string name of the model that is being associated with.
         *
         * This config option is to be used when defining the association as a config
         * object within Model.  The value is then mapped to #associatedModel when
         * Association is instantiated inside Model.
         */

        /**
         * @cfg {String} primaryKey
         * The name of the primary key on the associated model. In general this will be the
         * {@link Ext.data.Model#idProperty} of the Model.
         */
        primaryKey: 'id',

        /**
         * @cfg {Ext.data.reader.Reader} reader
         * A special reader to read associated data
         */

        /**
         * @cfg {String} associationKey
         * The name of the property in the data to read the association from. Defaults to the name of the associated model.
         */

        defaultReaderType: 'json',

        isAssociation: true,

        initialConfig: null,

        statics: {
            AUTO_ID: 1000,

            create: function(association){
                if (Ext.isString(association)) {
                    association = {
                        type: association
                    };
                }

                switch (association.type) {
                    case 'belongsTo':
                        return new Ext.data.association.BelongsTo(association);
                    case 'hasMany':
                        return new Ext.data.association.HasMany(association);
                    case 'hasOne':
                        return new Ext.data.association.HasOne(association);
                    //TODO Add this back when it's fixed
    //                    case 'polymorphic':
    //                        return Ext.create('Ext.data.PolymorphicAssociation', association);
                    default:
                        //<debug>
                        Ext.Error.raise('Unknown Association type: "' + association.type + '"');
                        //</debug>
                }
                return association;
            }
        },

        /**
         * Creates the Association object.
         * @param {Object} [config] Config object.
         */
        constructor: function(config) {
            Ext.apply(this, config);

            var me = this,
                types           = Ext.ModelManager.types,
                ownerName       = config.ownerModel,
                associatedName  = config.associatedModel,
                ownerModel      = types[ownerName],
                associatedModel = types[associatedName];

            me.initialConfig = config;

            //<debug>
            if (ownerModel === undefined) {
                Ext.Error.raise("The configured ownerModel was not valid (you tried " + ownerName + ")");
            }
            if (associatedModel === undefined) {
                Ext.Error.raise("The configured associatedModel was not valid (you tried " + associatedName + ")");
            }
            //</debug>

            me.ownerModel = ownerModel;
            me.associatedModel = associatedModel;

            /**
             * @property {String} ownerName
             * The name of the model that 'owns' the association
             */

            /**
             * @property {String} associatedName
             * The name of the model is on the other end of the association (e.g. if a User model hasMany Orders, this is
             * 'Order')
             */

            Ext.applyIf(me, {
                ownerName : ownerName,
                associatedName: associatedName
            });

            me.associationId = 'association' + (++me.statics().AUTO_ID);
        },

        /**
         * Get a specialized reader for reading associated data
         * @return {Ext.data.reader.Reader} The reader, null if not supplied
         */
        getReader: function(){
            var me = this,
                reader = me.reader,
                model = me.associatedModel;

            if (reader) {
                if (Ext.isString(reader)) {
                    reader = {
                        type: reader
                    };
                }
                if (reader.isReader) {
                    reader.setModel(model);
                } else {
                    Ext.applyIf(reader, {
                        model: model,
                        type : me.defaultReaderType
                    });
                }
                me.reader = Ext.createByAlias('reader.' + reader.type, reader);
            }
            return me.reader || null;
        }
    });