/**
 * @author Jacky Nguyen <jacky@sencha.com>
 * @docauthor Jacky Nguyen <jacky@sencha.com>
 * @class Ext.Loader
 *
 * 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.widget('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`, i.e:
 *
 *     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.
 *
 * @singleton
 */

Ext.Loader = new function() {
    var Loader = this,
        Manager = Ext.ClassManager,
        Class = Ext.Class,
        flexSetter = Ext.Function.flexSetter,
        alias = Ext.Function.alias,
        pass = Ext.Function.pass,
        defer = Ext.Function.defer,
        arrayErase = Ext.Array.erase,
        //<if nonBrowser>
        isNonBrowser = typeof window == 'undefined',
        isNodeJS = isNonBrowser && (typeof require == 'function'),
        isJsdb = isNonBrowser && typeof system != 'undefined' && system.program.search(/jsdb/) !== -1,
        isPhantomJS = (typeof phantom != 'undefined' && phantom.fs),
        //</if>
        dependencyProperties = ['extend', 'mixins', 'requires'],
        isInHistory = {},
        history = [],
        slashDotSlashRe = /\/\.\//g,
        dotRe = /\./g;

    Ext.apply(Loader, {

        /**
         * @private
         */
        isInHistory: isInHistory,

        /**
         * 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.
         *
         * @property {Array} history
         */
        history: history,

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

            /**
             * @cfg {Boolean} scriptChainDelay
             * millisecond delay between asynchronous script injection (prevents stack overflow on some user agents)
             * 'false' disables delay but potentially increases stack load.
             */
            scriptChainDelay : 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 {Boolean} garbageCollect
             * True to prepare an asynchronous script tag for garbage collection (effective only
             * if {@link #preserveScripts preserveScripts} is false)
             */
            garbageCollect : false,

            /**
             * @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, <code>Other.awesome.Class</code>
             * will simply be loaded from <code>./Other/awesome/Class.js</code>
             */
            paths: {
                'Ext': '.'
            },

            /**
             * @cfg {Boolean} preserveScripts
             * False to remove and optionally {@link #garbageCollect garbage-collect} asynchronously loaded scripts,
             * True to retain script element for browser debugger compatibility and improved load performance.
             */
            preserveScripts : true,

            /**
             * @cfg {String} scriptCharset
             * Optional charset to specify encoding of dynamic script content.
             */
            scriptCharset : undefined
        },

        /**
         * Set the configuration for the loader. This should be called right after ext-(debug).js
         * is included in the page, and before Ext.onReady. i.e:
         *
         *     <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 {Object} config The config object to override the default values
         * @return {Ext.Loader} this
         */
        setConfig: function(name, value) {
            if (Ext.isObject(name) && arguments.length === 1) {
                Ext.merge(Loader.config, name);
            }
            else {
                Loader.config[name] = (Ext.isObject(value)) ? Ext.merge(Loader.config[name], value) : value;
            }

            return Loader;
        },

        /**
         * 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 Loader.config[name];
            }

            return Loader.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) {
            Loader.config.paths[name] = path;

            return Loader;
        }),

        /**
         * 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 = Loader.config.paths,
                prefix = Loader.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(slashDotSlashRe, '/') + className.replace(dotRe, "/") + '.js';
        },

        /**
         * @private
         * @param {String} className
         */
        getPrefix: function(className) {
            var paths = Loader.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;
        },

        /**
         * @private
         * @param {String} className
         */
        isAClassNameWithAKnownPrefix: function(className) {
            var prefix = Loader.getPrefix(className);

            // we can only say it's really a class if className is not equal to any known namespace
            return prefix !== '' && prefix !== className;
        },

        /**
         * Loads all classes by the given names and all their direct dependencies; optionally executes the given callback function when
         * finishes, within the optional scope. This method is aliased by {@link Ext#require Ext.require} for convenience
         * @param {String/Array} 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/Array} excludes (Optional) Classes to be excluded, useful when being used with expressions
         */
        require: function(expressions, fn, scope, excludes) {
            if (fn) {
                fn.call(scope);
            }
        },

        /**
         * 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. This method is aliased by {@link Ext#syncRequire} for convenience
         * @param {String/Array} 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/Array} excludes (Optional) Classes to be excluded, useful when being used with expressions
         */
        syncRequire: function() {},

        /**
         * 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, eg:
         *
         *     Ext.exclude('Ext.data.*').require('*');
         *
         *     Ext.exclude('widget.button*').require('widget.*');
         *
         * @param {Array} excludes
         * @return {Object} object contains `require` method for chaining
         */
        exclude: function(excludes) {
            return {
                require: function(expressions, fn, scope) {
                    return Loader.require(expressions, fn, scope, excludes);
                },

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

        /**
         * Add a 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 (<code>this</code>) 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);
                };
            }

            fn.call(scope);
        }
    });

    //<feature classSystem.loader>
    var queue = [],
        isClassFileLoaded = {},
        isFileLoaded = {},
        classNameToFilePathMap = {},
        scriptElements = {},
        readyListeners = [],
        usedClasses = [],
        requiresMap = {};

    Ext.apply(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: queue,

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

        /**
         * @private
         */
        isFileLoaded: isFileLoaded,

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

        /**
         * Contains classes referenced in `uses` properties.
         * @private
         */
        optionalRequires: usedClasses,

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

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

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

        /** @private */
        hasFileLoadError: false,

        /**
         * @private
         */
        classNameToFilePathMap: classNameToFilePathMap,

        /**
         * The number of scripts loading via loadScript.
         * @private
         */
        scriptsLoading: 0,

        /**
         * @private
         */
        syncModeEnabled: false,

        scriptElements: scriptElements,

        /**
         * 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 = queue.length,
                i, item, j, requires;

            // When the queue of loading classes reaches zero, trigger readiness

            if (!ln && !Loader.scriptsLoading) {
                return Loader.triggerReady();
            }

            for (i = 0; i < ln; i++) {
                item = 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 > Loader.numLoadedFiles) {
                        continue;
                    }

                    // Remove any required classes that are loaded
                    for (j = 0; j < requires.length; ) {
                        if (Manager.isCreated(requires[j])) {
                            // Take out from the queue
                            arrayErase(requires, j, 1);
                        }
                        else {
                            j++;
                        }
                    }

                    // If we've ended up with no required classes, call the callback
                    if (item.requires.length === 0) {
                        arrayErase(queue, i, 1);
                        item.callback.call(item.scope);
                        Loader.refreshQueue();
                        break;
                    }
                }
            }

            return Loader;
        },

        /**
         * Inject a script element to document's head, call onLoad and onError accordingly
         * @private
         */
        injectScriptElement: function(url, onLoad, onError, scope, charset) {
            var script = document.createElement('script'),
                dispatched = false,
                config = Loader.config,
                onLoadFn = function() {

                    if(!dispatched) {
                        dispatched = true;
                        script.onload = script.onreadystatechange = script.onerror = null;
                        if (typeof config.scriptChainDelay == 'number') {
                            //free the stack (and defer the next script)
                            defer(onLoad, config.scriptChainDelay, scope);
                        } else {
                            onLoad.call(scope);
                        }
                        Loader.cleanupScriptElement(script, config.preserveScripts === false, config.garbageCollect);
                    }

                },
                onErrorFn = function(arg) {
                    defer(onError, 1, scope);   //free the stack
                    Loader.cleanupScriptElement(script, config.preserveScripts === false, config.garbageCollect);
                };

            script.type = 'text/javascript';
            script.onerror = onErrorFn;
            charset = charset || config.scriptCharset;
            if (charset) {
                script.charset = charset;
            }

            /*
             * IE9 Standards mode (and others) SHOULD follow the load event only
             * (Note: IE9 supports both onload AND readystatechange events)
             */
            if ('addEventListener' in script ) {
                script.onload = onLoadFn;
            } else if ('readyState' in script) {   // for <IE9 Compatability
                script.onreadystatechange = function() {
                    if ( this.readyState == 'loaded' || this.readyState == 'complete' ) {
                        onLoadFn();
                    }
                };
            } else {
                 script.onload = onLoadFn;
            }

            script.src = url;
            (Loader.documentHead || document.getElementsByTagName('head')[0]).appendChild(script);

            return script;
        },

        /**
         * @private
         */
        removeScriptElement: function(url) {
            if (scriptElements[url]) {
                Loader.cleanupScriptElement(scriptElements[url], true, !!Loader.getConfig('garbageCollect'));
                delete scriptElements[url];
            }

            return Loader;
        },

        /**
         * @private
         */
        cleanupScriptElement: function(script, remove, collect) {
            var prop;
            script.onload = script.onreadystatechange = script.onerror = null;
            if (remove) {
                Ext.removeNode(script);       // Remove, since its useless now
                if (collect) {
                    for (prop in script) {
                        try {
                            script[prop] = null;
                            delete script[prop];      // and prepare for GC
                        } catch (cleanEx) {
                            //ignore
                        }
                    }
                }
            }

            return Loader;
        },

        /**
         * Loads the specified script URL and calls the supplied callbacks. If this method
         * is called before {@link Ext#isReady}, the script's load will delay the transition
         * to ready. This can be used to load arbitrary scripts that may contain further
         * {@link Ext#require Ext.require} calls.
         *
         * @param {Object/String} options The options object or simply the URL to load.
         * @param {String} options.url The URL from which to load the script.
         * @param {Function} [options.onLoad] The callback to call on successful load.
         * @param {Function} [options.onError] The callback to call on failure to load.
         * @param {Object} [options.scope] The scope (`this`) for the supplied callbacks.
         */
        loadScript: function (options) {
            var config = Loader.getConfig(),
                isString = typeof options == 'string',
                url = isString ? options : options.url,
                onError = !isString && options.onError,
                onLoad = !isString && options.onLoad,
                scope = !isString && options.scope,
                onScriptError = function() {
                    Loader.numPendingFiles--;
                    Loader.scriptsLoading--;

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

                    if (Loader.numPendingFiles + Loader.scriptsLoading === 0) {
                        Loader.refreshQueue();
                    }
                },
                onScriptLoad = function () {
                    Loader.numPendingFiles--;
                    Loader.scriptsLoading--;

                    if (onLoad) {
                        onLoad.call(scope);
                    }

                    if (Loader.numPendingFiles + Loader.scriptsLoading === 0) {
                        Loader.refreshQueue();
                    }
                },
                src;

            Loader.isLoading = true;
            Loader.numPendingFiles++;
            Loader.scriptsLoading++;

            src = config.disableCaching ?
                (url + '?' + config.disableCachingParam + '=' + Ext.Date.now()) : url;

            scriptElements[url] = Loader.injectScriptElement(src, onScriptLoad, onScriptError);
        },

        /**
         * Load a script file, supports both asynchronous and synchronous approaches
         * @private
         */
        loadScriptFile: function(url, onLoad, onError, scope, synchronous) {
            if (isFileLoaded[url]) {
                return Loader;
            }

            var config = Loader.getConfig(),
                noCacheUrl = url + (config.disableCaching ? ('?' + config.disableCachingParam + '=' + Ext.Date.now()) : ''),
                isCrossOriginRestricted = false,
                xhr, status, onScriptError,
                debugSourceURL = "";

            scope = scope || Loader;

            Loader.isLoading = true;

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

                scriptElements[url] = Loader.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 === 0 && (self.location || {}).protocol == 'file:') ? 200 : xhr.status;

                isCrossOriginRestricted = isCrossOriginRestricted || (status === 0);

                if (isCrossOriginRestricted
                    //<if isNonBrowser>
                    && !isPhantomJS
                    //</if>
                ) {
                    //<debug error>
                    onError.call(Loader, "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);
                    //</debug>
                }
                else if ((status >= 200 && status < 300) || (status === 304)
                    //<if isNonBrowser>
                    || isPhantomJS
                    //</if>
                ) {
                    // Debugger friendly, file names are still shown even though they're eval'ed code
                    // Breakpoints work on both Firebug and Chrome's Web Inspector
                    if (!Ext.isIE) {
                        debugSourceURL = "\n//@ sourceURL=" + url;
                    }

                    Ext.globalEval(xhr.responseText + debugSourceURL);

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

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

        // documented above
        syncRequire: function() {
            var syncModeEnabled = Loader.syncModeEnabled;

            if (!syncModeEnabled) {
                Loader.syncModeEnabled = true;
            }

            Loader.require.apply(Loader, arguments);

            if (!syncModeEnabled) {
                Loader.syncModeEnabled = false;
            }

            Loader.refreshQueue();
        },

        // documented above
        require: function(expressions, fn, scope, excludes) {
            var excluded = {},
                included = {},
                excludedClassNames = [],
                possibleClassNames = [],
                classNames = [],
                references = [],
                callback,
                syncModeEnabled,
                filePath, expression, exclude, className,
                possibleClassName, i, j, ln, subLn;

            if (excludes) {
                // Convert possible single string to an array.
                excludes = (typeof excludes === 'string') ? [ excludes ] : excludes;

                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;
                        }
                    }
                }
            }

            // Convert possible single string to an array.
            expressions = (typeof expressions === 'string') ? [ expressions ] : (expressions ? expressions : []);

            if (fn) {
                if (fn.length > 0) {
                    callback = function() {
                        var classes = [],
                            i, ln;

                        for (i = 0,ln = references.length; i < ln; i++) {
                            classes.push(Manager.get(references[i]));
                        }

                        return fn.apply(this, classes);
                    };
                }
                else {
                    callback = fn;
                }
            }
            else {
                callback = Ext.emptyFn;
            }

            scope = scope || Ext.global;

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

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

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

                        if (excluded[possibleClassName] !== true) {
                            references.push(possibleClassName);

                            if (!Manager.isCreated(possibleClassName) && !included[possibleClassName]) {
                                included[possibleClassName] = true;
                                classNames.push(possibleClassName);
                            }
                        }
                    }
                }
            }

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

            syncModeEnabled = Loader.syncModeEnabled;

            if (!syncModeEnabled) {
                queue.push({
                    requires: classNames.slice(), // this array will be modified as the queue is processed,
                                                  // so we need a copy of it
                    callback: callback,
                    scope: scope
                });
            }

            ln = classNames.length;

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

                filePath = Loader.getPath(className);

                // If we are synchronously loading a file that has already been asychronously loaded before
                // we need to destroy the script tag and revert the count
                // This file will then be forced loaded in synchronous
                if (syncModeEnabled && isClassFileLoaded.hasOwnProperty(className)) {
                    Loader.numPendingFiles--;
                    Loader.removeScriptElement(filePath);
                    delete isClassFileLoaded[className];
                }

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

                    classNameToFilePathMap[className] = filePath;

                    Loader.numPendingFiles++;
                    Loader.loadScriptFile(
                        filePath,
                        pass(Loader.onFileLoaded, [className, filePath], Loader),
                        pass(Loader.onFileLoadError, [className, filePath], Loader),
                        Loader,
                        syncModeEnabled
                    );
                }
            }

            if (syncModeEnabled) {
                callback.call(scope);

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

            return Loader;
        },

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

            isClassFileLoaded[className] = true;
            isFileLoaded[filePath] = true;

            Loader.numPendingFiles--;

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

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

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

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

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

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

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

                throw new Error("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) {
            Loader.numPendingFiles--;
            Loader.hasFileLoadError = true;

            //<debug error>
            throw new Error("[Ext.Loader] " + errorMessage);
            //</debug>
        },

        /**
         * @private
         * Ensure that any classes referenced in the `uses` property are loaded.
         */
        addUsedClasses: function (classes) {
            var cls, i, ln;

            if (classes) {
                classes = (typeof classes == 'string') ? [classes] : classes;
                for (i = 0, ln = classes.length; i < ln; i++) {
                    cls = classes[i];
                    if (typeof cls == 'string' && !Ext.Array.contains(usedClasses, cls)) {
                        usedClasses.push(cls);
                    }
                }
            }

            return Loader;
        },

        /**
         * @private
         */
        triggerReady: function() {
            var listener,
                i, refClasses = usedClasses;

            if (Loader.isLoading) {
                Loader.isLoading = false;

                if (refClasses.length !== 0) {
                    // Clone then empty the array to eliminate potential recursive loop issue
                    refClasses = refClasses.slice();
                    usedClasses.length = 0;
                    // this may immediately call us back if all 'uses' classes
                    // have been loaded
                    Loader.require(refClasses, Loader.triggerReady, Loader);
                    return Loader;
                }
            }

            // this method can be called with Loader.isLoading either true or false
            // (can be called with false when all 'uses' classes are already loaded)
            // this may bypass the above if condition
            while (readyListeners.length && !Loader.isLoading) {
                // calls to refreshQueue may re-enter triggerReady
                // so we cannot necessarily iterate the readyListeners array
                listener = readyListeners.shift();
                listener.fn.call(listener.scope);
            }

            return Loader;
        },

        // Documented above already
        onReady: function(fn, scope, withDomReady, options) {
            var oldFn;

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

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

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

        /**
         * @private
         * @param {String} className
         */
        historyPush: function(className) {
            if (className && isClassFileLoaded.hasOwnProperty(className) && !isInHistory[className]) {
                isInHistory[className] = true;
                history.push(className);
            }
            return Loader;
        }
    });

    /**
     * Turns on or off the "cache buster" applied to dynamically loaded scripts. Normally
     * dynamically loaded scripts have an extra query parameter appended to avoid stale
     * cached scripts. This method can be used to disable this mechanism, and is primarily
     * useful for testing. This is done using a cookie.
     * @param {Boolean} disable True to disable the cache buster.
     * @param {String} [path="/"] An optional path to scope the cookie.
     * @private
     */
    Ext.disableCacheBuster = function (disable, path) {
        var date = new Date();
        date.setTime(date.getTime() + (disable ? 10*365 : -1) * 24*60*60*1000);
        date = date.toGMTString();
        document.cookie = 'ext-cache=1; expires=' + date + '; path='+(path || '/');
    };

    //<if nonBrowser>
    if (isNonBrowser) {
        if (isNodeJS) {
            Ext.apply(Loader, {
                syncModeEnabled: true,
                setPath: flexSetter(function(name, path) {
                    path = require('fs').realpathSync(path);
                    Loader.config.paths[name] = path;

                    return Loader;
                }),

                loadScriptFile: function(filePath, onLoad, onError, scope, synchronous) {
                    require(filePath);
                    onLoad.call(scope);
                }
            });
        }
        else if (isJsdb) {
            Ext.apply(Loader, {
                syncModeEnabled: true,
                loadScriptFile: function(filePath, onLoad, onError, scope, synchronous) {
                    load(filePath);
                    onLoad.call(scope);
                }
            });
        }
    }
    //</if>
    //</feature>

    /**
     * Convenient alias of {@link Ext.Loader#require}. Please see the introduction documentation of
     * {@link Ext.Loader} for examples.
     * @member Ext
     * @method require
     */
    Ext.require = alias(Loader, 'require');

    /**
     * Synchronous version of {@link Ext#require}, convenient alias of {@link Ext.Loader#syncRequire}.
     *
     * @member Ext
     * @method syncRequire
     */
    Ext.syncRequire = alias(Loader, 'syncRequire');

    /**
     * Convenient shortcut to {@link Ext.Loader#exclude}
     * @member Ext
     * @method exclude
     */
    Ext.exclude = alias(Loader, 'exclude');

    /**
     * @member Ext
     * @method onReady
     * @ignore
     */
    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, hooks, continueFn) {
        var me = this,
            dependencies = [],
            dependency,
            className = Manager.getName(cls),
            i, j, ln, subLn, value, propertyName, propertyValue,
            requiredMap, requiredDep;

        /*
        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) {
            return;
        }

        //<feature classSystem.loader>
        //<debug error>
        var deadlockPath = [],
            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;
            //<debug>
            requiredMap = Loader.requiredByMap || (Loader.requiredByMap = {});

            for (i = 0,ln = dependencies.length; i < ln; i++) {
                dependency = dependencies[i];
                (requiredMap[dependency] || (requiredMap[dependency] = [])).push(className);
            }
            //</debug>
            detectDeadlock = function(cls) {
                deadlockPath.push(cls);

                if (requiresMap[cls]) {
                    if (Ext.Array.contains(requiresMap[cls], className)) {
                        throw new Error("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>
        //</feature>

        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, hooks);
        });

        return false;
    }, true, 'after', 'className');

    //<feature classSystem.loader>
    /**
     * @cfg {String[]} uses
     * @member Ext.Class
     * List of optional classes to load together with this class. These aren't neccessarily loaded before
     * this class is created, but are guaranteed to be available before Ext.onReady listeners are
     * invoked. 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 = data.uses;
        if (uses) {
            Loader.addUsedClasses(uses);
        }
    });

    Manager.onCreated(Loader.historyPush);
    //</feature>
};
