/**
+ * @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 = new 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 and defaults to undefined.
+ */
+
+ /**
+ * @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 jsonData
+ * @type Mixed
+ */
+ this.jsonData = data;
+ return this.callParent([data]);
+ },
+
+ //inherit docs
+ getResponseData: function(response) {
+ try {
+ var 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 {Array} The records
+ */
+ extractData: function(root) {
+ var recordName = this.record,
+ data = [],
+ length, i;
+
+ if (recordName) {
+ length = root.length;
+
+ 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];
+ };
+ };
+ }()
+});