/**
 * @class Ext.Loader
 * @singleton
 * @author Jacky Nguyen <jacky@sencha.com>
 * @docauthor Jacky Nguyen <jacky@sencha.com>
 *
 * Ext.Loader is the heart of the new dynamic dependency loading capability in Ext JS 4+. It is most commonly used
 * via the {@link Ext#require} shorthand. Ext.Loader supports both asynchronous and synchronous loading
 * approaches, and leverage their advantages for the best development flow. We'll discuss about the pros and cons
 * of each approach:
 *
 * # Asynchronous Loading
 *
 * - Advantages:
 * 	 + Cross-domain
 * 	 + No web server needed: you can run the application via the file system protocol
 *     (i.e: `file://path/to/your/index.html`)
 * 	 + Best possible debugging experience: error messages come with the exact file name and line number
 *
 * - Disadvantages:
 * 	 + Dependencies need to be specified before-hand
 *
 * ### Method 1: Explicitly include what you need:
 *
 *     // Syntax
 *     Ext.require({String/Array} expressions);
 *
 *     // Example: Single alias
 *     Ext.require('widget.window');
 *
 *     // Example: Single class name
 *     Ext.require('Ext.window.Window');
 *
 *     // Example: Multiple aliases / class names mix
 *     Ext.require(['widget.window', 'layout.border', 'Ext.data.Connection']);
 *
 *     // Wildcards
 *     Ext.require(['widget.*', 'layout.*', 'Ext.data.*']);
 *
 * ### Method 2: Explicitly exclude what you don't need:
 *
 *     // Syntax: Note that it must be in this chaining format.
 *     Ext.exclude({String/Array} expressions)
 *        .require({String/Array} expressions);
 *
 *     // Include everything except Ext.data.*
 *     Ext.exclude('Ext.data.*').require('*'); 
 *
 *     // Include all widgets except widget.checkbox*,
 *     // which will match widget.checkbox, widget.checkboxfield, widget.checkboxgroup, etc.
 *     Ext.exclude('widget.checkbox*').require('widget.*');
 *
 * # Synchronous Loading on Demand
 *
 * - Advantages:
 * 	 + There's no need to specify dependencies before-hand, which is always the convenience of including
 *     ext-all.js before
 *
 * - Disadvantages:
 * 	 + Not as good debugging experience since file name won't be shown (except in Firebug at the moment)
 * 	 + Must be from the same domain due to XHR restriction
 * 	 + Need a web server, same reason as above
 *
 * There's one simple rule to follow: Instantiate everything with Ext.create instead of the `new` keyword
 *
 *     Ext.create('widget.window', { ... }); // Instead of new Ext.window.Window({...});
 *
 *     Ext.create('Ext.window.Window', {}); // Same as above, using full class name instead of alias
 *
 *     Ext.widget('window', {}); // Same as above, all you need is the traditional `xtype`
 *
 * Behind the scene, {@link Ext.ClassManager} will automatically check whether the given class name / alias has already
 * existed on the page. If it's not, Ext.Loader will immediately switch itself to synchronous mode and automatic load
 * the given class and all its dependencies.
 *
 * # Hybrid Loading - The Best of Both Worlds
 *
 * It has all the advantages combined from asynchronous and synchronous loading. The development flow is simple:
 *
 * ### Step 1: Start writing your application using synchronous approach.
 *
 * Ext.Loader will automatically fetch all dependencies on demand as they're needed during run-time. For example:
 *
 *     Ext.onReady(function(){
 *         var window = Ext.createWidget('window', {
 *             width: 500,
 *             height: 300,
 *             layout: {
 *                 type: 'border',
 *                 padding: 5
 *             },
 *             title: 'Hello Dialog',
 *             items: [{
 *                 title: 'Navigation',
 *                 collapsible: true,
 *                 region: 'west',
 *                 width: 200,
 *                 html: 'Hello',
 *                 split: true
 *             }, {
 *                 title: 'TabPanel',
 *                 region: 'center'
 *             }]
 *         });
 *
 *         window.show();
 *     })
 *
 * ### Step 2: Along the way, when you need better debugging ability, watch the console for warnings like these:
 *
 *     [Ext.Loader] Synchronously loading 'Ext.window.Window'; consider adding Ext.require('Ext.window.Window') before your application's code ClassManager.js:432
 *     [Ext.Loader] Synchronously loading 'Ext.layout.container.Border'; consider adding Ext.require('Ext.layout.container.Border') before your application's code
 *
 * Simply copy and paste the suggested code above `Ext.onReady`, e.g.:
 *
 *     Ext.require('Ext.window.Window');
 *     Ext.require('Ext.layout.container.Border');
 *
 *     Ext.onReady(...);
 *
 * Everything should now load via asynchronous mode.
 *
 * # Deployment
 *
 * It's important to note that dynamic loading should only be used during development on your local machines.
 * During production, all dependencies should be combined into one single JavaScript file. Ext.Loader makes
 * the whole process of transitioning from / to between development / maintenance and production as easy as
 * possible. Internally {@link Ext.Loader#history Ext.Loader.history} maintains the list of all dependencies
 * your application needs in the exact loading sequence. It's as simple as concatenating all files in this
 * array into one, then include it on top of your application.
 *
 * This process will be automated with Sencha Command, to be released and documented towards Ext JS 4 Final.
 */
(function(Manager, Class, flexSetter, alias) {

    var
        //<if nonBrowser>
        isNonBrowser = typeof window === 'undefined',
        isNodeJS = isNonBrowser && (typeof require === 'function'),
        isPhantomJS = (typeof phantom !== 'undefined' && phantom.fs),
        //</if>
        dependencyProperties = ['extend', 'mixins', 'requires'],
        Loader;

    Loader = Ext.Loader = {
        /**
         * @private
         */
        documentHead: typeof document !== 'undefined' && (document.head || document.getElementsByTagName('head')[0]),

        /**
         * Flag indicating whether there are still files being loaded
         * @private
         */
        isLoading: false,

        /**
         * Maintain the queue for all dependencies. Each item in the array is an object of the format:
         * {
         *      requires: [...], // The required classes for this queue item
         *      callback: function() { ... } // The function to execute when all classes specified in requires exist
         * }
         * @private
         */
        queue: [],

        /**
         * Maintain the list of files that have already been handled so that they never get double-loaded
         * @private
         */
        isFileLoaded: {},

        /**
         * Maintain the list of listeners to execute when all required scripts are fully loaded
         * @private
         */
        readyListeners: [],

        /**
         * Contains optional dependencies to be loaded last
         * @private
         */
        optionalRequires: [],

        /**
         * Map of fully qualified class names to an array of dependent classes.
         * @private
         */
        requiresMap: {},

        /**
         * @private
         */
        numPendingFiles: 0,

        /**
         * @private
         */
        numLoadedFiles: 0,

        /** @private */
        hasFileLoadError: false,

        /**
         * @private
         */
        classNameToFilePathMap: {},

        /**
         * @property {String[]} history
         * An array of class names to keep track of the dependency loading order.
         * This is not guaranteed to be the same everytime due to the asynchronous nature of the Loader.
         */
        history: [],

        /**
         * Configuration
         * @private
         */
        config: {
            /**
             * @cfg {Boolean} enabled
             * Whether or not to enable the dynamic dependency loading feature.
             */
            enabled: false,

            /**
             * @cfg {Boolean} disableCaching
             * Appends current timestamp to script files to prevent caching.
             */
            disableCaching: true,

            /**
             * @cfg {String} disableCachingParam
             * The get parameter name for the cache buster's timestamp.
             */
            disableCachingParam: '_dc',

            /**
             * @cfg {Object} paths
             * The mapping from namespaces to file paths
             *
             *     {
             *         'Ext': '.', // This is set by default, Ext.layout.container.Container will be
             *                     // loaded from ./layout/Container.js
             *
             *         'My': './src/my_own_folder' // My.layout.Container will be loaded from
             *                                     // ./src/my_own_folder/layout/Container.js
             *     }
             *
             * Note that all relative paths are relative to the current HTML document.
             * If not being specified, for example, `Other.awesome.Class`
             * will simply be loaded from `./Other/awesome/Class.js`
             */
            paths: {
                'Ext': '.'
            }
        },

        /**
         * Set the configuration for the loader. This should be called right after ext-core.js
         * (or ext-core-debug.js) is included in the page, e.g.:
         *
         *     <script type="text/javascript" src="ext-core-debug.js"></script>
         *     <script type="text/javascript">
         *       Ext.Loader.setConfig({
         *           enabled: true,
         *           paths: {
         *               'My': 'my_own_path'
         *           }
         *       });
         *     <script>
         *     <script type="text/javascript">
         *       Ext.require(...);
         *
         *       Ext.onReady(function() {
         *           // application code here
         *       });
         *     </script>
         *
         * Refer to config options of {@link Ext.Loader} for the list of possible properties.
         *
         * @param {String/Object} name  Name of the value to override, or a config object to override multiple values.
         * @param {Object} value  (optional) The new value to set, needed if first parameter is String.
         * @return {Ext.Loader} this
         */
        setConfig: function(name, value) {
            if (Ext.isObject(name) && arguments.length === 1) {
                Ext.Object.merge(this.config, name);
            }
            else {
                this.config[name] = (Ext.isObject(value)) ? Ext.Object.merge(this.config[name], value) : value;
            }

            return this;
        },

        /**
         * Get the config value corresponding to the specified name.
         * If no name is given, will return the config object.
         * @param {String} name The config property name
         * @return {Object}
         */
        getConfig: function(name) {
            if (name) {
                return this.config[name];
            }

            return this.config;
        },

        /**
         * Sets the path of a namespace. For Example:
         *
         *     Ext.Loader.setPath('Ext', '.');
         *
         * @param {String/Object} name See {@link Ext.Function#flexSetter flexSetter}
         * @param {String} path See {@link Ext.Function#flexSetter flexSetter}
         * @return {Ext.Loader} this
         * @method
         */
        setPath: flexSetter(function(name, path) {
            //<if nonBrowser>
            if (isNonBrowser) {
                if (isNodeJS) {
                    path = require('fs').realpathSync(path);
                }
            }
            //</if>
            this.config.paths[name] = path;

            return this;
        }),

        /**
         * Translates a className to a file path by adding the the proper prefix and converting the .'s to /'s.
         * For example:
         *
         *     Ext.Loader.setPath('My', '/path/to/My');
         *
         *     alert(Ext.Loader.getPath('My.awesome.Class')); // alerts '/path/to/My/awesome/Class.js'
         *
         * Note that the deeper namespace levels, if explicitly set, are always resolved first. For example:
         *
         *     Ext.Loader.setPath({
         *         'My': '/path/to/lib',
         *         'My.awesome': '/other/path/for/awesome/stuff',
         *         'My.awesome.more': '/more/awesome/path'
         *     });
         *
         *     alert(Ext.Loader.getPath('My.awesome.Class')); // alerts '/other/path/for/awesome/stuff/Class.js'
         *
         *     alert(Ext.Loader.getPath('My.awesome.more.Class')); // alerts '/more/awesome/path/Class.js'
         *
         *     alert(Ext.Loader.getPath('My.cool.Class')); // alerts '/path/to/lib/cool/Class.js'
         *
         *     alert(Ext.Loader.getPath('Unknown.strange.Stuff')); // alerts 'Unknown/strange/Stuff.js'
         *
         * @param {String} className
         * @return {String} path
         */
        getPath: function(className) {
            var path = '',
                paths = this.config.paths,
                prefix = this.getPrefix(className);

            if (prefix.length > 0) {
                if (prefix === className) {
                    return paths[prefix];
                }

                path = paths[prefix];
                className = className.substring(prefix.length + 1);
            }

            if (path.length > 0) {
                path += '/';
            }

            return path.replace(/\/\.\//g, '/') + className.replace(/\./g, "/") + '.js';
        },

        /**
         * @private
         * @param {String} className
         */
        getPrefix: function(className) {
            var paths = this.config.paths,
                prefix, deepestPrefix = '';

            if (paths.hasOwnProperty(className)) {
                return className;
            }

            for (prefix in paths) {
                if (paths.hasOwnProperty(prefix) && prefix + '.' === className.substring(0, prefix.length + 1)) {
                    if (prefix.length > deepestPrefix.length) {
                        deepestPrefix = prefix;
                    }
                }
            }

            return deepestPrefix;
        },

        /**
         * Refresh all items in the queue. If all dependencies for an item exist during looping,
         * it will execute the callback and call refreshQueue again. Triggers onReady when the queue is
         * empty
         * @private
         */
        refreshQueue: function() {
            var ln = this.queue.length,
                i, item, j, requires;

            if (ln === 0) {
                this.triggerReady();
                return;
            }

            for (i = 0; i < ln; i++) {
                item = this.queue[i];

                if (item) {
                    requires = item.requires;

                    // Don't bother checking when the number of files loaded
                    // is still less than the array length
                    if (requires.length > this.numLoadedFiles) {
                        continue;
                    }

                    j = 0;

                    do {
                        if (Manager.isCreated(requires[j])) {
                            // Take out from the queue
                            Ext.Array.erase(requires, j, 1);
                        }
                        else {
                            j++;
                        }
                    } while (j < requires.length);

                    if (item.requires.length === 0) {
                        Ext.Array.erase(this.queue, i, 1);
                        item.callback.call(item.scope);
                        this.refreshQueue();
                        break;
                    }
                }
            }

            return this;
        },

        /**
         * Inject a script element to document's head, call onLoad and onError accordingly
         * @private
         */
        injectScriptElement: function(url, onLoad, onError, scope) {
            var script = document.createElement('script'),
                me = this,
                onLoadFn = function() {
                    me.cleanupScriptElement(script);
                    onLoad.call(scope);
                },
                onErrorFn = function() {
                    me.cleanupScriptElement(script);
                    onError.call(scope);
                };

            script.type = 'text/javascript';
            script.src = url;
            script.onload = onLoadFn;
            script.onerror = onErrorFn;
            script.onreadystatechange = function() {
                if (this.readyState === 'loaded' || this.readyState === 'complete') {
                    onLoadFn();
                }
            };

            this.documentHead.appendChild(script);

            return script;
        },

        /**
         * @private
         */
        cleanupScriptElement: function(script) {
            script.onload = null;
            script.onreadystatechange = null;
            script.onerror = null;

            return this;
        },

        /**
         * Load a script file, supports both asynchronous and synchronous approaches
         *
         * @param {String} url
         * @param {Function} onLoad
         * @param {Object} scope
         * @param {Boolean} synchronous
         * @private
         */
        loadScriptFile: function(url, onLoad, onError, scope, synchronous) {
            var me = this,
                noCacheUrl = url + (this.getConfig('disableCaching') ? ('?' + this.getConfig('disableCachingParam') + '=' + Ext.Date.now()) : ''),
                fileName = url.split('/').pop(),
                isCrossOriginRestricted = false,
                xhr, status, onScriptError;

            scope = scope || this;

            this.isLoading = true;

            if (!synchronous) {
                onScriptError = function() {
                    onError.call(scope, "Failed loading '" + url + "', please verify that the file exists", synchronous);
                };

                if (!Ext.isReady && Ext.onDocumentReady) {
                    Ext.onDocumentReady(function() {
                        me.injectScriptElement(noCacheUrl, onLoad, onScriptError, scope);
                    });
                }
                else {
                    this.injectScriptElement(noCacheUrl, onLoad, onScriptError, scope);
                }
            }
            else {
                if (typeof XMLHttpRequest !== 'undefined') {
                    xhr = new XMLHttpRequest();
                } else {
                    xhr = new ActiveXObject('Microsoft.XMLHTTP');
                }

                try {
                    xhr.open('GET', noCacheUrl, false);
                    xhr.send(null);
                } catch (e) {
                    isCrossOriginRestricted = true;
                }

                status = (xhr.status === 1223) ? 204 : xhr.status;

                if (!isCrossOriginRestricted) {
                    isCrossOriginRestricted = (status === 0);
                }

                if (isCrossOriginRestricted
                //<if isNonBrowser>
                && !isPhantomJS
                //</if>
                ) {
                    onError.call(this, "Failed loading synchronously via XHR: '" + url + "'; It's likely that the file is either " +
                                       "being loaded from a different domain or from the local file system whereby cross origin " +
                                       "requests are not allowed due to security reasons. Use asynchronous loading with " +
                                       "Ext.require instead.", synchronous);
                }
                else if (status >= 200 && status < 300
                //<if isNonBrowser>
                || isPhantomJS
                //</if>
                ) {
                    // Firebug friendly, file names are still shown even though they're eval'ed code
                    new Function(xhr.responseText + "\n//@ sourceURL=" + fileName)();

                    onLoad.call(scope);
                }
                else {
                    onError.call(this, "Failed loading synchronously via XHR: '" + url + "'; please " +
                                       "verify that the file exists. " +
                                       "XHR status code: " + status, synchronous);
                }

                // Prevent potential IE memory leak
                xhr = null;
            }
        },

        /**
         * Explicitly exclude files from being loaded. Useful when used in conjunction with a broad include expression.
         * Can be chained with more `require` and `exclude` methods, e.g.:
         *
         *     Ext.exclude('Ext.data.*').require('*');
         *
         *     Ext.exclude('widget.button*').require('widget.*');
         *
         * {@link Ext#exclude Ext.exclude} is alias for {@link Ext.Loader#exclude Ext.Loader.exclude} for convenience.
         *
         * @param {String/String[]} excludes
         * @return {Object} object contains `require` method for chaining
         */
        exclude: function(excludes) {
            var me = this;

            return {
                require: function(expressions, fn, scope) {
                    return me.require(expressions, fn, scope, excludes);
                },

                syncRequire: function(expressions, fn, scope) {
                    return me.syncRequire(expressions, fn, scope, excludes);
                }
            };
        },

        /**
         * Synchronously loads all classes by the given names and all their direct dependencies;
         * optionally executes the given callback function when finishes, within the optional scope.
         *
         * {@link Ext#syncRequire Ext.syncRequire} is alias for {@link Ext.Loader#syncRequire Ext.Loader.syncRequire} for convenience.
         *
         * @param {String/String[]} expressions Can either be a string or an array of string
         * @param {Function} fn (Optional) The callback function
         * @param {Object} scope (Optional) The execution scope (`this`) of the callback function
         * @param {String/String[]} excludes (Optional) Classes to be excluded, useful when being used with expressions
         */
        syncRequire: function() {
            this.syncModeEnabled = true;
            this.require.apply(this, arguments);
            this.refreshQueue();
            this.syncModeEnabled = false;
        },

        /**
         * Loads all classes by the given names and all their direct dependencies;
         * optionally executes the given callback function when finishes, within the optional scope.
         *
         * {@link Ext#require Ext.require} is alias for {@link Ext.Loader#require Ext.Loader.require} for convenience.
         *
         * @param {String/String[]} expressions Can either be a string or an array of string
         * @param {Function} fn (Optional) The callback function
         * @param {Object} scope (Optional) The execution scope (`this`) of the callback function
         * @param {String/String[]} excludes (Optional) Classes to be excluded, useful when being used with expressions
         */
        require: function(expressions, fn, scope, excludes) {
            var filePath, expression, exclude, className, excluded = {},
                excludedClassNames = [],
                possibleClassNames = [],
                possibleClassName, classNames = [],
                i, j, ln, subLn;

            expressions = Ext.Array.from(expressions);
            excludes = Ext.Array.from(excludes);

            fn = fn || Ext.emptyFn;

            scope = scope || Ext.global;

            for (i = 0, ln = excludes.length; i < ln; i++) {
                exclude = excludes[i];

                if (typeof exclude === 'string' && exclude.length > 0) {
                    excludedClassNames = Manager.getNamesByExpression(exclude);

                    for (j = 0, subLn = excludedClassNames.length; j < subLn; j++) {
                        excluded[excludedClassNames[j]] = true;
                    }
                }
            }

            for (i = 0, ln = expressions.length; i < ln; i++) {
                expression = expressions[i];

                if (typeof expression === 'string' && expression.length > 0) {
                    possibleClassNames = Manager.getNamesByExpression(expression);

                    for (j = 0, subLn = possibleClassNames.length; j < subLn; j++) {
                        possibleClassName = possibleClassNames[j];

                        if (!excluded.hasOwnProperty(possibleClassName) && !Manager.isCreated(possibleClassName)) {
                            Ext.Array.include(classNames, possibleClassName);
                        }
                    }
                }
            }

            // If the dynamic dependency feature is not being used, throw an error
            // if the dependencies are not defined
            if (!this.config.enabled) {
                if (classNames.length > 0) {
                    Ext.Error.raise({
                        sourceClass: "Ext.Loader",
                        sourceMethod: "require",
                        msg: "Ext.Loader is not enabled, so dependencies cannot be resolved dynamically. " +
                             "Missing required class" + ((classNames.length > 1) ? "es" : "") + ": " + classNames.join(', ')
                    });
                }
            }

            if (classNames.length === 0) {
                fn.call(scope);
                return this;
            }

            this.queue.push({
                requires: classNames,
                callback: fn,
                scope: scope
            });

            classNames = classNames.slice();

            for (i = 0, ln = classNames.length; i < ln; i++) {
                className = classNames[i];

                if (!this.isFileLoaded.hasOwnProperty(className)) {
                    this.isFileLoaded[className] = false;

                    filePath = this.getPath(className);

                    this.classNameToFilePathMap[className] = filePath;

                    this.numPendingFiles++;

                    //<if nonBrowser>
                    if (isNonBrowser) {
                        if (isNodeJS) {
                            require(filePath);
                        }
                        // Temporary support for hammerjs
                        else {
                            var f = fs.open(filePath),
                                content = '',
                                line;

                            while (true) {
                                line = f.readLine();
                                if (line.length === 0) {
                                    break;
                                }
                                content += line;
                            }

                            f.close();
                            eval(content);
                        }

                        this.onFileLoaded(className, filePath);

                        if (ln === 1) {
                            return Manager.get(className);
                        }

                        continue;
                    }
                    //</if>
                    this.loadScriptFile(
                        filePath,
                        Ext.Function.pass(this.onFileLoaded, [className, filePath], this),
                        Ext.Function.pass(this.onFileLoadError, [className, filePath]),
                        this,
                        this.syncModeEnabled
                    );
                }
            }

            return this;
        },

        /**
         * @private
         * @param {String} className
         * @param {String} filePath
         */
        onFileLoaded: function(className, filePath) {
            this.numLoadedFiles++;

            this.isFileLoaded[className] = true;

            this.numPendingFiles--;

            if (this.numPendingFiles === 0) {
                this.refreshQueue();
            }

            //<debug>
            if (this.numPendingFiles <= 1) {
                window.status = "Finished loading all dependencies, onReady fired!";
            }
            else {
                window.status = "Loading dependencies, " + this.numPendingFiles + " files left...";
            }
            //</debug>

            //<debug>
            if (!this.syncModeEnabled && this.numPendingFiles === 0 && this.isLoading && !this.hasFileLoadError) {
                var queue = this.queue,
                    requires,
                    i, ln, j, subLn, missingClasses = [], missingPaths = [];

                for (i = 0, ln = queue.length; i < ln; i++) {
                    requires = queue[i].requires;

                    for (j = 0, subLn = requires.length; j < ln; j++) {
                        if (this.isFileLoaded[requires[j]]) {
                            missingClasses.push(requires[j]);
                        }
                    }
                }

                if (missingClasses.length < 1) {
                    return;
                }

                missingClasses = Ext.Array.filter(missingClasses, function(item) {
                    return !this.requiresMap.hasOwnProperty(item);
                }, this);

                for (i = 0,ln = missingClasses.length; i < ln; i++) {
                    missingPaths.push(this.classNameToFilePathMap[missingClasses[i]]);
                }

                Ext.Error.raise({
                    sourceClass: "Ext.Loader",
                    sourceMethod: "onFileLoaded",
                    msg: "The following classes are not declared even if their files have been " +
                            "loaded: '" + missingClasses.join("', '") + "'. Please check the source code of their " +
                            "corresponding files for possible typos: '" + missingPaths.join("', '") + "'"
                });
            }
            //</debug>
        },

        /**
         * @private
         */
        onFileLoadError: function(className, filePath, errorMessage, isSynchronous) {
            this.numPendingFiles--;
            this.hasFileLoadError = true;

            //<debug error>
            Ext.Error.raise({
                sourceClass: "Ext.Loader",
                classToLoad: className,
                loadPath: filePath,
                loadingType: isSynchronous ? 'synchronous' : 'async',
                msg: errorMessage
            });
            //</debug>
        },

        /**
         * @private
         */
        addOptionalRequires: function(requires) {
            var optionalRequires = this.optionalRequires,
                i, ln, require;

            requires = Ext.Array.from(requires);

            for (i = 0, ln = requires.length; i < ln; i++) {
                require = requires[i];

                Ext.Array.include(optionalRequires, require);
            }

            return this;
        },

        /**
         * @private
         */
        triggerReady: function(force) {
            var readyListeners = this.readyListeners,
                optionalRequires, listener;

            if (this.isLoading || force) {
                this.isLoading = false;

                if (this.optionalRequires.length) {
                    // Clone then empty the array to eliminate potential recursive loop issue
                    optionalRequires = Ext.Array.clone(this.optionalRequires);

                    // Empty the original array
                    this.optionalRequires.length = 0;

                    this.require(optionalRequires, Ext.Function.pass(this.triggerReady, [true], this), this);
                    return this;
                }

                while (readyListeners.length) {
                    listener = readyListeners.shift();
                    listener.fn.call(listener.scope);

                    if (this.isLoading) {
                        return this;
                    }
                }
            }

            return this;
        },

        /**
         * Adds new listener to be executed when all required scripts are fully loaded.
         *
         * @param {Function} fn The function callback to be executed
         * @param {Object} scope The execution scope (`this`) of the callback function
         * @param {Boolean} withDomReady Whether or not to wait for document dom ready as well
         */
        onReady: function(fn, scope, withDomReady, options) {
            var oldFn;

            if (withDomReady !== false && Ext.onDocumentReady) {
                oldFn = fn;

                fn = function() {
                    Ext.onDocumentReady(oldFn, scope, options);
                };
            }

            if (!this.isLoading) {
                fn.call(scope);
            }
            else {
                this.readyListeners.push({
                    fn: fn,
                    scope: scope
                });
            }
        },

        /**
         * @private
         * @param {String} className
         */
        historyPush: function(className) {
            if (className && this.isFileLoaded.hasOwnProperty(className)) {
                Ext.Array.include(this.history, className);
            }

            return this;
        }
    };

    /**
     * @member Ext
     * @method require
     * @alias Ext.Loader#require
     */
    Ext.require = alias(Loader, 'require');

    /**
     * @member Ext
     * @method syncRequire
     * @alias Ext.Loader#syncRequire
     */
    Ext.syncRequire = alias(Loader, 'syncRequire');

    /**
     * @member Ext
     * @method exclude
     * @alias Ext.Loader#exclude
     */
    Ext.exclude = alias(Loader, 'exclude');

    /**
     * @member Ext
     * @method onReady
     * @alias Ext.Loader#onReady
     */
    Ext.onReady = function(fn, scope, options) {
        Loader.onReady(fn, scope, true, options);
    };

    /**
     * @cfg {String[]} requires
     * @member Ext.Class
     * List of classes that have to be loaded before instantiating this class.
     * For example:
     *
     *     Ext.define('Mother', {
     *         requires: ['Child'],
     *         giveBirth: function() {
     *             // we can be sure that child class is available.
     *             return new Child();
     *         }
     *     });
     */
    Class.registerPreprocessor('loader', function(cls, data, continueFn) {
        var me = this,
            dependencies = [],
            className = Manager.getName(cls),
            i, j, ln, subLn, value, propertyName, propertyValue;

        /*
        Basically loop through the dependencyProperties, look for string class names and push
        them into a stack, regardless of whether the property's value is a string, array or object. For example:
        {
              extend: 'Ext.MyClass',
              requires: ['Ext.some.OtherClass'],
              mixins: {
                  observable: 'Ext.util.Observable';
              }
        }
        which will later be transformed into:
        {
              extend: Ext.MyClass,
              requires: [Ext.some.OtherClass],
              mixins: {
                  observable: Ext.util.Observable;
              }
        }
        */

        for (i = 0, ln = dependencyProperties.length; i < ln; i++) {
            propertyName = dependencyProperties[i];

            if (data.hasOwnProperty(propertyName)) {
                propertyValue = data[propertyName];

                if (typeof propertyValue === 'string') {
                    dependencies.push(propertyValue);
                }
                else if (propertyValue instanceof Array) {
                    for (j = 0, subLn = propertyValue.length; j < subLn; j++) {
                        value = propertyValue[j];

                        if (typeof value === 'string') {
                            dependencies.push(value);
                        }
                    }
                }
                else if (typeof propertyValue != 'function') {
                    for (j in propertyValue) {
                        if (propertyValue.hasOwnProperty(j)) {
                            value = propertyValue[j];

                            if (typeof value === 'string') {
                                dependencies.push(value);
                            }
                        }
                    }
                }
            }
        }

        if (dependencies.length === 0) {
//            Loader.historyPush(className);
            return;
        }

        //<debug error>
        var deadlockPath = [],
            requiresMap = Loader.requiresMap,
            detectDeadlock;

        /*
        Automatically detect deadlocks before-hand,
        will throw an error with detailed path for ease of debugging. Examples of deadlock cases:

        - A extends B, then B extends A
        - A requires B, B requires C, then C requires A

        The detectDeadlock function will recursively transverse till the leaf, hence it can detect deadlocks
        no matter how deep the path is.
        */

        if (className) {
            requiresMap[className] = dependencies;

            detectDeadlock = function(cls) {
                deadlockPath.push(cls);

                if (requiresMap[cls]) {
                    if (Ext.Array.contains(requiresMap[cls], className)) {
                        Ext.Error.raise({
                            sourceClass: "Ext.Loader",
                            msg: "Deadlock detected while loading dependencies! '" + className + "' and '" +
                                deadlockPath[1] + "' " + "mutually require each other. Path: " +
                                deadlockPath.join(' -> ') + " -> " + deadlockPath[0]
                        });
                    }

                    for (i = 0, ln = requiresMap[cls].length; i < ln; i++) {
                        detectDeadlock(requiresMap[cls][i]);
                    }
                }
            };

            detectDeadlock(className);
        }

        //</debug>

        Loader.require(dependencies, function() {
            for (i = 0, ln = dependencyProperties.length; i < ln; i++) {
                propertyName = dependencyProperties[i];

                if (data.hasOwnProperty(propertyName)) {
                    propertyValue = data[propertyName];

                    if (typeof propertyValue === 'string') {
                        data[propertyName] = Manager.get(propertyValue);
                    }
                    else if (propertyValue instanceof Array) {
                        for (j = 0, subLn = propertyValue.length; j < subLn; j++) {
                            value = propertyValue[j];

                            if (typeof value === 'string') {
                                data[propertyName][j] = Manager.get(value);
                            }
                        }
                    }
                    else if (typeof propertyValue != 'function') {
                        for (var k in propertyValue) {
                            if (propertyValue.hasOwnProperty(k)) {
                                value = propertyValue[k];

                                if (typeof value === 'string') {
                                    data[propertyName][k] = Manager.get(value);
                                }
                            }
                        }
                    }
                }
            }

            continueFn.call(me, cls, data);
        });

        return false;
    }, true);

    Class.setDefaultPreprocessorPosition('loader', 'after', 'className');

    /**
     * @cfg {String[]} uses
     * @member Ext.Class
     * List of classes to load together with this class.  These aren't neccessarily loaded before
     * this class is instantiated. For example:
     *
     *     Ext.define('Mother', {
     *         uses: ['Child'],
     *         giveBirth: function() {
     *             // This code might, or might not work:
     *             // return new Child();
     *
     *             // Instead use Ext.create() to load the class at the spot if not loaded already:
     *             return Ext.create('Child');
     *         }
     *     });
     */
    Manager.registerPostprocessor('uses', function(name, cls, data) {
        var uses = Ext.Array.from(data.uses),
            items = [],
            i, ln, item;

        for (i = 0, ln = uses.length; i < ln; i++) {
            item = uses[i];

            if (typeof item === 'string') {
                items.push(item);
            }
        }

        Loader.addOptionalRequires(items);
    });

    Manager.setDefaultPostprocessorPosition('uses', 'last');

})(Ext.ClassManager, Ext.Class, Ext.Function.flexSetter, Ext.Function.alias);