/**
 * The XML Reader is used by a Proxy to read a server response that is sent back in XML format. This usually happens as
 * a result of loading a Store - for example we might create something like this:
 *
 *     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.xml',
 *             reader: {
 *                 type: 'xml',
 *                 record: 'user',
 *                 rootProperty: 'users'
 *             }
 *         }
 *     });
 *
 * 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.
 *
 * We created the simplest type of XML Reader possible by simply telling our {@link Ext.data.Store Store}'s {@link
 * Ext.data.proxy.Proxy Proxy} that we want a XML Reader. The Store automatically passes the configured model to the
 * Store, so it is as if we passed this instead:
 *
 *     reader: {
 *         type : 'xml',
 *         model: 'User',
 *         record: 'user',
 *         rootProperty: 'users'
 *     }
 *
 * The reader we set up is ready to read data from our server - at the moment it will accept a response like this:
 *
 *     <?xml version="1.0" encoding="UTF-8"?>
 *     <users>
 *         <user>
 *             <id>1</id>
 *             <name>Ed Spencer</name>
 *             <email>ed@sencha.com</email>
 *         </user>
 *         <user>
 *             <id>2</id>
 *             <name>Abe Elias</name>
 *             <email>abe@sencha.com</email>
 *         </user>
 *     </users>
 *
 * First off there's {@link #rootProperty} option to define the root node `<users>` (there should be only one in a well-formed
 * XML document). Then the XML Reader uses the configured {@link #record} option to pull out the data for each record -
 * in this case we set record to 'user', so each `<user>` above will be converted into a User model.
 *
 * Note that XmlReader doesn't care whether your {@link #rootProperty} and {@link #record} elements are nested deep inside a
 * larger structure, so a response like this will still work:
 *
 *     <?xml version="1.0" encoding="UTF-8"?>
 *     <deeply>
 *         <nested>
 *             <xml>
 *                 <users>
 *                     <user>
 *                         <id>1</id>
 *                         <name>Ed Spencer</name>
 *                         <email>ed@sencha.com</email>
 *                     </user>
 *                     <user>
 *                         <id>2</id>
 *                         <name>Abe Elias</name>
 *                         <email>abe@sencha.com</email>
 *                     </user>
 *                 </users>
 *             </xml>
 *         </nested>
 *     </deeply>
 *
 * If this Reader is being used by a {@link Ext.data.TreeStore TreeStore} to read tree-structured data in which records
 * are nested as descendant nodes of other records, then this lenient behaviour must be overridden by using a more specific
 * child node selector as your {@link #record} selector which will not select all descendants, such as:
 *
 *    record: '>user'
 *
 * # Response metadata
 *
 * 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 XML response like
 * this:
 *
 *     <?xml version="1.0" encoding="UTF-8"?>
 *     <users>
 *         <total>100</total>
 *         <success>true</success>
 *         <user>
 *             <id>1</id>
 *             <name>Ed Spencer</name>
 *             <email>ed@sencha.com</email>
 *         </user>
 *         <user>
 *             <id>2</id>
 *             <name>Abe Elias</name>
 *             <email>abe@sencha.com</email>
 *         </user>
 *     </users>
 *
 * If these properties are present in the XML response they can be parsed out by the XmlReader 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:
 *
 *     reader: {
 *         type: 'xml',
 *         rootProperty: 'users',
 *         totalProperty  : 'total',
 *         successProperty: 'success'
 *     }
 *
 * 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.
 *
 * # Response format
 *
 * **Note:** in order for the browser to parse a returned XML document, the Content-Type header in the HTTP response
 * must be set to "text/xml" or "application/xml". This is very important - the XmlReader will not work correctly
 * otherwise.
 */
Ext.define('Ext.data.reader.Xml', {
    extend: 'Ext.data.reader.Reader',
    requires: [
        'Ext.dom.Query'
    ],
    alternateClassName: 'Ext.data.XmlReader',
    alias : 'reader.xml',

    config: {
        /**
        * @cfg {String} record (required)
        * The DomQuery path to the repeated element which contains record information.
        *
        * By default, the elements which match the selector may be nested at any level
        * below the {@link #rootProperty}
        *
        * If this Reader is being used by a {@link Ext.data.TreeStore TreeStore} to read tree-structured data,
        * then only first generation child nodes of the root element must be selected, so the record selector must be
        * specified with a more specific selector which will not select all descendants. For example:
        *
        *    record: '>node'
        *
        */
        record: '',

        /**
        * @cfg {String} namespace
        * A namespace prefix that will be prepended to the field name when reading a
        * field from an XML node.  Take, for example, the following Model:
        * 
        *     Ext.define('Foo', {
        *         extend: 'Ext.data.Model',
        *         fields: ['bar', 'baz']
        *     });
        *     
        * The reader would need to be configured with a namespace of 'n' in order to read XML
        * data in the following format:
        * 
        *     <foo>
        *         <n:bar>bar</n:bar>
        *         <n:baz>baz</n:baz>
        *     </foo>
        */
        namespace: ''
    },

    /**
     * @private
     * Creates a function to return some particular key of data from a response. The totalProperty and
     * successProperty are treated as special cases for type casting, everything else is just a simple selector.
     * @param {String} key
     * @return {Function}
     */
    createAccessor: function(expr) {
        if (Ext.isEmpty(expr)) {
            return Ext.emptyFn;
        }

        if (Ext.isFunction(expr)) {
            return expr;
        }

        return function(root) {
            return this.getNodeValue(Ext.DomQuery.selectNode(expr, root));
        };
    },

    getNodeValue: function(node) {
        if (node) {
            // overcome a limitation of maximum textnode size
            // http://reference.sitepoint.com/javascript/Node/normalize
            // https://developer.mozilla.org/En/DOM/Node.normalize
            if (typeof node.normalize === 'function') {
                node.normalize();
            }
            node = node.firstChild;
            if (node) {
                return node.nodeValue;
            }
        }
        return undefined;
    },

    getResponseData: function(response) {
        var xml = response.responseXML,
            error = 'XML data not found in the response'; 

        if (!xml) {
            Ext.Logger.warn(error);
            return this.createReadError(error);       
        }

        return xml;
    },

    /**
     * Normalizes the data object.
     * @param {Object} data The raw data object
     * @return {Object} The documentElement property of the data object if present, or the same object if not.
     */
    getData: function(data) {
        return data.documentElement || data;
    },

    /**
     * @private
     * Given an XML object, returns the Element that represents the root as configured by the Reader's meta data.
     * @param {Object} data The XML data object
     * @return {XMLElement} The root node element
     */
    getRoot: function(data) {
        var nodeName = data.nodeName,
            root     = this.getRootProperty();

        if (!root || (nodeName && nodeName == root)) {
            return data;
        } else if (Ext.DomQuery.isXml(data)) {
            // This fix ensures we have XML data
            // Related to TreeStore calling getRoot with the root node, which isn't XML
            // Probably should be resolved in TreeStore at some point
            return Ext.DomQuery.selectNode(root, data);
        }
    },

    /**
     * @private
     * We're just preparing the data for the superclass by pulling out the record nodes we want.
     * @param {XMLElement} root The XML root node
     * @param {Object} [readOptions] See {@link #read} for details.
     * @return {Ext.data.Model[]} The records
     */
    extractData: function(root, readOptions) {
        var recordName = this.getRecord();

        //<debug>
        if (!recordName) {
            Ext.raise('Record is a required parameter');
        }
        //</debug>

        if (recordName !== root.nodeName) {
            root = Ext.DomQuery.select(recordName, root);
        } else {
            root = [root];
        }
        return this.callParent([root, readOptions]);
    },

    /**
     * Parses an XML document and returns a ResultSet containing the model instances.
     * @param {Object} doc Parsed XML document
     * @param {Object} [readOptions] See {@link #read} for details.
     * @return {Ext.data.ResultSet} The parsed result set
     */
    readRecords: function(doc, readOptions, /* private */ internalReadOptions) {
        // it's possible that we get passed an array here by associations.
        // Make sure we strip that out (see Ext.data.reader.Reader#readAssociated)
        if (Ext.isArray(doc)) {
            doc = doc[0];
        }

        return this.callParent([doc, readOptions, internalReadOptions]);
    },

    /**
     * @private
     * Returns an accessor function for the passed Field from an XML element using either the Field's mapping, or
     * its ordinal position in the fields collection as the index.
     * This is used by buildExtractors to create optimized on extractor function which converts raw data into model instances.
     */
    createFieldAccessor: function(field) {
        var me = this,
            namespace = me.getNamespace(),
            selector, result;

        selector = field.mapping || ((namespace ? namespace + '|' : '') + field.name); 

        if (typeof selector === 'function') {
            result = function(raw) {
                return field.mapping(raw, me);
            };
        } else {
            result = function(raw) {
                return me.getNodeValue(Ext.DomQuery.selectNode(selector, raw));
            };
        }
        return result;
    },
    
    deprecated: {
        '5.1.1': {
            properties: {
                /**
                 * @property {Object} xmlData
                 * Copy of {@link #rawData}.
                 * @deprecated 5.1.1 Removed in Ext JS 5.0. Use {@link #rawData} instead.
                 */
                xmlData: null
            }
        }
    }
});
