    /**
     * @author Ed Spencer
     * @class Ext.data.reader.Json
     * @extends Ext.data.reader.Reader
     *
     * <p>The JSON Reader is used by a Proxy to read a server response that is sent back in JSON format. This usually
     * happens as a result of loading a Store - for example we might create something like this:</p>
     *
    <pre><code>
    Ext.define('User', {
        extend: 'Ext.data.Model',
        fields: ['id', 'name', 'email']
    });

    var store = Ext.create('Ext.data.Store', {
        model: 'User',
        proxy: {
            type: 'ajax',
            url : 'users.json',
            reader: {
                type: 'json'
            }
        }
    });
    </code></pre>
     *
     * <p>The example above creates a 'User' model. Models are explained in the {@link Ext.data.Model Model} docs if you're
     * not already familiar with them.</p>
     *
     * <p>We created the simplest type of JSON Reader possible by simply telling our {@link Ext.data.Store Store}'s
     * {@link Ext.data.proxy.Proxy Proxy} that we want a JSON Reader. The Store automatically passes the configured model to the
     * Store, so it is as if we passed this instead:
     *
    <pre><code>
    reader: {
        type : 'json',
        model: 'User'
    }
    </code></pre>
     *
     * <p>The reader we set up is ready to read data from our server - at the moment it will accept a response like this:</p>
     *
    <pre><code>
    [
        {
            "id": 1,
            "name": "Ed Spencer",
            "email": "ed@sencha.com"
        },
        {
            "id": 2,
            "name": "Abe Elias",
            "email": "abe@sencha.com"
        }
    ]
    </code></pre>
     *
     * <p><u>Reading other JSON formats</u></p>
     *
     * <p>If you already have your JSON format defined and it doesn't look quite like what we have above, you can usually
     * pass JsonReader a couple of configuration options to make it parse your format. For example, we can use the
     * {@link #root} configuration to parse data that comes back like this:</p>
     *
    <pre><code>
    {
        "users": [
           {
               "id": 1,
               "name": "Ed Spencer",
               "email": "ed@sencha.com"
           },
           {
               "id": 2,
               "name": "Abe Elias",
               "email": "abe@sencha.com"
           }
        ]
    }
    </code></pre>
     *
     * <p>To parse this we just pass in a {@link #root} configuration that matches the 'users' above:</p>
     *
    <pre><code>
    reader: {
        type: 'json',
        root: 'users'
    }
    </code></pre>
     *
     * <p>Sometimes the JSON structure is even more complicated. Document databases like CouchDB often provide metadata
     * around each record inside a nested structure like this:</p>
     *
    <pre><code>
    {
        "total": 122,
        "offset": 0,
        "users": [
            {
                "id": "ed-spencer-1",
                "value": 1,
                "user": {
                    "id": 1,
                    "name": "Ed Spencer",
                    "email": "ed@sencha.com"
                }
            }
        ]
    }
    </code></pre>
     *
     * <p>In the case above the record data is nested an additional level inside the "users" array as each "user" item has
     * additional metadata surrounding it ('id' and 'value' in this case). To parse data out of each "user" item in the
     * JSON above we need to specify the {@link #record} configuration like this:</p>
     *
    <pre><code>
    reader: {
        type  : 'json',
        root  : 'users',
        record: 'user'
    }
    </code></pre>
     *
     * <p><u>Response metadata</u></p>
     *
     * <p>The server can return additional data in its response, such as the {@link #totalProperty total number of records}
     * and the {@link #successProperty success status of the response}. These are typically included in the JSON response
     * like this:</p>
     *
    <pre><code>
    {
        "total": 100,
        "success": true,
        "users": [
            {
                "id": 1,
                "name": "Ed Spencer",
                "email": "ed@sencha.com"
            }
        ]
    }
    </code></pre>
     *
     * <p>If these properties are present in the JSON response they can be parsed out by the JsonReader and used by the
     * Store that loaded it. We can set up the names of these properties by specifying a final pair of configuration
     * options:</p>
     *
    <pre><code>
    reader: {
        type : 'json',
        root : 'users',
        totalProperty  : 'total',
        successProperty: 'success'
    }
    </code></pre>
     *
     * <p>These final options are not necessary to make the Reader work, but can be useful when the server needs to report
     * an error or if it needs to indicate that there is a lot of data available of which only a subset is currently being
     * returned.</p>
     */
    Ext.define('Ext.data.reader.Json', {
        extend: 'Ext.data.reader.Reader',
        alternateClassName: 'Ext.data.JsonReader',
        alias : 'reader.json',

        root: '',

        /**
         * @cfg {String} record The optional location within the JSON response that the record data itself can be found at.
         * See the JsonReader intro docs for more details. This is not often needed.
         */

        /**
         * @cfg {Boolean} useSimpleAccessors True to ensure that field names/mappings are treated as literals when
         * reading values. Defalts to <tt>false</tt>.
         * For example, by default, using the mapping "foo.bar.baz" will try and read a property foo from the root, then a property bar
         * from foo, then a property baz from bar. Setting the simple accessors to true will read the property with the name
         * "foo.bar.baz" direct from the root object.
         */
        useSimpleAccessors: false,

        /**
         * Reads a JSON object and returns a ResultSet. Uses the internal getTotal and getSuccess extractors to
         * retrieve meta data from the response, and extractData to turn the JSON data into model instances.
         * @param {Object} data The raw JSON data
         * @return {Ext.data.ResultSet} A ResultSet containing model instances and meta data about the results
         */
        readRecords: function(data) {
            //this has to be before the call to super because we use the meta data in the superclass readRecords
            if (data.metaData) {
                this.onMetaChange(data.metaData);
            }

            /**
             * @deprecated will be removed in Ext JS 5.0. This is just a copy of this.rawData - use that instead
             * @property {Object} jsonData
             */
            this.jsonData = data;
            return this.callParent([data]);
        },

        //inherit docs
        getResponseData: function(response) {
            var data;
            try {
                data = Ext.decode(response.responseText);
            }
            catch (ex) {
                Ext.Error.raise({
                    response: response,
                    json: response.responseText,
                    parseError: ex,
                    msg: 'Unable to parse the JSON returned by the server: ' + ex.toString()
                });
            }
            //<debug>
            if (!data) {
                Ext.Error.raise('JSON object not found');
            }
            //</debug>

            return data;
        },

        //inherit docs
        buildExtractors : function() {
            var me = this;

            me.callParent(arguments);

            if (me.root) {
                me.getRoot = me.createAccessor(me.root);
            } else {
                me.getRoot = function(root) {
                    return root;
                };
            }
        },

        /**
         * @private
         * We're just preparing the data for the superclass by pulling out the record objects we want. If a {@link #record}
         * was specified we have to pull those out of the larger JSON object, which is most of what this function is doing
         * @param {Object} root The JSON root node
         * @return {Ext.data.Model[]} The records
         */
        extractData: function(root) {
            var recordName = this.record,
                data = [],
                length, i;

            if (recordName) {
                length = root.length;

                if (!length && Ext.isObject(root)) {
                    length = 1;
                    root = [root];
                }

                for (i = 0; i < length; i++) {
                    data[i] = root[i][recordName];
                }
            } else {
                data = root;
            }
            return this.callParent([data]);
        },

        /**
         * @private
         * Returns an accessor function for the given property string. Gives support for properties such as the following:
         * 'someProperty'
         * 'some.property'
         * 'some["property"]'
         * This is used by buildExtractors to create optimized extractor functions when casting raw data into model instances.
         */
        createAccessor: function() {
            var re = /[\[\.]/;

            return function(expr) {
                if (Ext.isEmpty(expr)) {
                    return Ext.emptyFn;
                }
                if (Ext.isFunction(expr)) {
                    return expr;
                }
                if (this.useSimpleAccessors !== true) {
                    var i = String(expr).search(re);
                    if (i >= 0) {
                        return Ext.functionFactory('obj', 'return obj' + (i > 0 ? '.' : '') + expr);
                    }
                }
                return function(obj) {
                    return obj[expr];
                };
            };
        }()
    });