Merge "Don't purge thumbs for old versions of an image during ?action=purge"

[lhc/web/wiklou.git] / resources / mediawiki / mediawiki.js

/*
 * Core MediaWiki JavaScript Library
 */

var mw = ( function ( $, undefined ) {
        'use strict';

        /* Private Members */

        var hasOwn = Object.prototype.hasOwnProperty,
                slice = Array.prototype.slice;

        /* Object constructors */

        /**
         * Creates an object that can be read from or written to from prototype functions
         * that allow both single and multiple variables at once.
         *
         *     @example
         *
         *     var addies, wanted, results;
         *
         *     // Create your address book
         *     addies = new mw.Map();
         *
         *     // This data could be coming from an external source (eg. API/AJAX)
         *     addies.set( {
         *         'John Doe' : '10 Wall Street, New York, USA',
         *         'Jane Jackson' : '21 Oxford St, London, UK',
         *         'Dominique van Halen' : 'Kalverstraat 7, Amsterdam, NL'
         *     } );
         *
         *     wanted = ['Dominique van Halen', 'George Johnson', 'Jane Jackson'];
         *
         *     // You can detect missing keys first
         *     if ( !addies.exists( wanted ) ) {
         *         // One or more are missing (in this case: "George Johnson")
         *         mw.log( 'One or more names were not found in your address book' );
         *     }
         *
         *     // Or just let it give you what it can
         *     results = addies.get( wanted, 'Middle of Nowhere, Alaska, US' );
         *     mw.log( results['Jane Jackson'] ); // "21 Oxford St, London, UK"
         *     mw.log( results['George Johnson'] ); // "Middle of Nowhere, Alaska, US"
         *
         * @class mw.Map
         *
         * @constructor
         * @param {boolean} [global=false] Whether to store the values in the global window
         *  object or a exclusively in the object property 'values'.
         */
        function Map( global ) {
                this.values = global === true ? window : {};
                return this;
        }

        Map.prototype = {
                /**
                 * Get the value of one or multiple a keys.
                 *
                 * If called with no arguments, all values will be returned.
                 *
                 * @param {string|Array} selection String key or array of keys to get values for.
                 * @param {Mixed} [fallback] Value to use in case key(s) do not exist.
                 * @return mixed If selection was a string returns the value or null,
                 *  If selection was an array, returns an object of key/values (value is null if not found),
                 *  If selection was not passed or invalid, will return the 'values' object member (be careful as
                 *  objects are always passed by reference in JavaScript!).
                 * @return {string|Object|null} Values as a string or object, null if invalid/inexistant.
                 */
                get: function ( selection, fallback ) {
                        var results, i;
                        // If we only do this in the `return` block, it'll fail for the
                        // call to get() from the mutli-selection block.
                        fallback = arguments.length > 1 ? fallback : null;

                        if ( $.isArray( selection ) ) {
                                selection = slice.call( selection );
                                results = {};
                                for ( i = 0; i < selection.length; i++ ) {
                                        results[selection[i]] = this.get( selection[i], fallback );
                                }
                                return results;
                        }

                        if ( typeof selection === 'string' ) {
                                if ( !hasOwn.call( this.values, selection ) ) {
                                        return fallback;
                                }
                                return this.values[selection];
                        }

                        if ( selection === undefined ) {
                                return this.values;
                        }

                        // invalid selection key
                        return null;
                },

                /**
                 * Sets one or multiple key/value pairs.
                 *
                 * @param {string|Object} selection String key to set value for, or object mapping keys to values.
                 * @param {Mixed} [value] Value to set (optional, only in use when key is a string)
                 * @return {Boolean} This returns true on success, false on failure.
                 */
                set: function ( selection, value ) {
                        var s;

                        if ( $.isPlainObject( selection ) ) {
                                for ( s in selection ) {
                                        this.values[s] = selection[s];
                                }
                                return true;
                        }
                        if ( typeof selection === 'string' && arguments.length > 1 ) {
                                this.values[selection] = value;
                                return true;
                        }
                        return false;
                },

                /**
                 * Checks if one or multiple keys exist.
                 *
                 * @param {Mixed} selection String key or array of keys to check
                 * @return {boolean} Existence of key(s)
                 */
                exists: function ( selection ) {
                        var s;

                        if ( $.isArray( selection ) ) {
                                for ( s = 0; s < selection.length; s++ ) {
                                        if ( typeof selection[s] !== 'string' || !hasOwn.call( this.values, selection[s] ) ) {
                                                return false;
                                        }
                                }
                                return true;
                        }
                        return typeof selection === 'string' && hasOwn.call( this.values, selection );
                }
        };

        /**
         * Object constructor for messages,
         * similar to the Message class in MediaWiki PHP.
         * @class mw.Message
         *
         * @constructor
         * @param {mw.Map} map Message storage
         * @param {string} key
         * @param {Array} [parameters]
         */
        function Message( map, key, parameters ) {
                this.format = 'text';
                this.map = map;
                this.key = key;
                this.parameters = parameters === undefined ? [] : slice.call( parameters );
                return this;
        }

        Message.prototype = {
                /**
                 * Simple message parser, does $N replacement and nothing else.
                 *
                 * This may be overridden to provide a more complex message parser.
                 *
                 * The primary override is in mediawiki.jqueryMsg.
                 *
                 * This function will not be called for nonexistent messages.
                 */
                parser: function () {
                        var parameters = this.parameters;
                        return this.map.get( this.key ).replace( /\$(\d+)/g, function ( str, match ) {
                                var index = parseInt( match, 10 ) - 1;
                                return parameters[index] !== undefined ? parameters[index] : '$' + match;
                        } );
                },

                /**
                 * Appends (does not replace) parameters for replacement to the .parameters property.
                 *
                 * @param {Array} parameters
                 * @chainable
                 */
                params: function ( parameters ) {
                        var i;
                        for ( i = 0; i < parameters.length; i += 1 ) {
                                this.parameters.push( parameters[i] );
                        }
                        return this;
                },

                /**
                 * Converts message object to it's string form based on the state of format.
                 *
                 * @return {string} Message as a string in the current form or `<key>` if key does not exist.
                 */
                toString: function () {
                        var text;

                        if ( !this.exists() ) {
                                // Use <key> as text if key does not exist
                                if ( this.format === 'escaped' || this.format === 'parse' ) {
                                        // format 'escaped' and 'parse' need to have the brackets and key html escaped
                                        return mw.html.escape( '<' + this.key + '>' );
                                }
                                return '<' + this.key + '>';
                        }

                        if ( this.format === 'plain' || this.format === 'text' || this.format === 'parse' ) {
                                text = this.parser();
                        }

                        if ( this.format === 'escaped' ) {
                                text = this.parser();
                                text = mw.html.escape( text );
                        }

                        return text;
                },

                /**
                 * Changes format to 'parse' and converts message to string
                 *
                 * If jqueryMsg is loaded, this parses the message text from wikitext
                 * (where supported) to HTML
                 *
                 * Otherwise, it is equivalent to plain.
                 *
                 * @return {string} String form of parsed message
                 */
                parse: function () {
                        this.format = 'parse';
                        return this.toString();
                },

                /**
                 * Changes format to 'plain' and converts message to string
                 *
                 * This substitutes parameters, but otherwise does not change the
                 * message text.
                 *
                 * @return {string} String form of plain message
                 */
                plain: function () {
                        this.format = 'plain';
                        return this.toString();
                },

                /**
                 * Changes format to 'text' and converts message to string
                 *
                 * If jqueryMsg is loaded, {{-transformation is done where supported
                 * (such as {{plural:}}, {{gender:}}, {{int:}}).
                 *
                 * Otherwise, it is equivalent to plain.
                 */
                text: function () {
                        this.format = 'text';
                        return this.toString();
                },

                /**
                 * Changes the format to 'escaped' and converts message to string
                 *
                 * This is equivalent to using the 'text' format (see text method), then
                 * HTML-escaping the output.
                 *
                 * @return {string} String form of html escaped message
                 */
                escaped: function () {
                        this.format = 'escaped';
                        return this.toString();
                },

                /**
                 * Checks if message exists
                 *
                 * @see mw.Map#exists
                 * @return {boolean}
                 */
                exists: function () {
                        return this.map.exists( this.key );
                }
        };

        /**
         * Base library for MediaWiki.
         *
         * @class mw
         * @alternateClassName mediaWiki
         * @singleton
         */
        return {
                /* Public Members */

                /**
                 * Dummy placeholder for {@link mw.log}
                 * @method
                 */
                log: ( function () {
                        var log = function () {};
                        log.warn = function () {};
                        log.deprecate = function ( obj, key, val ) {
                                obj[key] = val;
                        };
                        return log;
                }() ),

                // Make the Map constructor publicly available.
                Map: Map,

                // Make the Message constructor publicly available.
                Message: Message,

                /**
                 * Map of configuration values
                 *
                 * Check out [the complete list of configuration values](https://www.mediawiki.org/wiki/Manual:Interface/JavaScript#mw.config)
                 * on MediaWiki.org.
                 *
                 * If `$wgLegacyJavaScriptGlobals` is true, this Map will put its values in the
                 * global window object.
                 *
                 * @property {mw.Map} config
                 */
                // Dummy placeholder. Re-assigned in ResourceLoaderStartupModule with an instance of `mw.Map`.
                config: null,

                /**
                 * Empty object that plugins can be installed in.
                 * @property
                 */
                libs: {},

                /**
                 * Access container for deprecated functionality that can be moved from
                 * from their legacy location and attached to this object (e.g. a global
                 * function that is deprecated and as stop-gap can be exposed through here).
                 *
                 * This was reserved for future use but never ended up being used.
                 *
                 * @deprecated since 1.22: Let deprecated identifiers keep their original name
                 * and use mw.log#deprecate to create an access container for tracking.
                 * @property
                 */
                legacy: {},

                /**
                 * Localization system
                 * @property {mw.Map}
                 */
                messages: new Map(),

                /* Public Methods */

                /**
                 * Gets a message object, similar to wfMessage().
                 *
                 * @param {string} key Key of message to get
                 * @param {Mixed...} parameters Parameters for the $N replacements in messages.
                 * @return {mw.Message}
                 */
                message: function ( key ) {
                        // Variadic arguments
                        var parameters = slice.call( arguments, 1 );
                        return new Message( mw.messages, key, parameters );
                },

                /**
                 * Gets a message string, similar to wfMessage()
                 *
                 * @see mw.Message#toString
                 * @param {string} key Key of message to get
                 * @param {Mixed...} parameters Parameters for the $N replacements in messages.
                 * @return {string}
                 */
                msg: function ( /* key, parameters... */ ) {
                        return mw.message.apply( mw.message, arguments ).toString();
                },

                /**
                 * Client-side module loader which integrates with the MediaWiki ResourceLoader
                 * @class mw.loader
                 * @singleton
                 */
                loader: ( function () {

                        /* Private Members */

                        /**
                         * Mapping of registered modules
                         *
                         * The jquery module is pre-registered, because it must have already
                         * been provided for this object to have been built, and in debug mode
                         * jquery would have been provided through a unique loader request,
                         * making it impossible to hold back registration of jquery until after
                         * mediawiki.
                         *
                         * For exact details on support for script, style and messages, look at
                         * mw.loader.implement.
                         *
                         * Format:
                         *     {
                         *         'moduleName': {
                         *             'version': ############## (unix timestamp),
                         *             'dependencies': ['required.foo', 'bar.also', ...], (or) function () {}
                         *             'group': 'somegroup', (or) null,
                         *             'source': 'local', 'someforeignwiki', (or) null
                         *             'state': 'registered', 'loaded', 'loading', 'ready', 'error' or 'missing'
                         *             'script': ...,
                         *             'style': ...,
                         *             'messages': { 'key': 'value' },
                         *         }
                         *     }
                         *
                         * @property
                         * @private
                         */
                        var registry = {},
                                //
                                // Mapping of sources, keyed by source-id, values are objects.
                                // Format:
                                //      {
                                //              'sourceId': {
                                //                      'loadScript': 'http://foo.bar/w/load.php'
                                //              }
                                //      }
                                //
                                sources = {},
                                // List of modules which will be loaded as when ready
                                batch = [],
                                // List of modules to be loaded
                                queue = [],
                                // List of callback functions waiting for modules to be ready to be called
                                jobs = [],
                                // Selector cache for the marker element. Use getMarker() to get/use the marker!
                                $marker = null,
                                // Buffer for addEmbeddedCSS.
                                cssBuffer = '',
                                // Callbacks for addEmbeddedCSS.
                                cssCallbacks = $.Callbacks();

                        /* Private methods */

                        function getMarker() {
                                // Cached ?
                                if ( $marker ) {
                                        return $marker;
                                }

                                $marker = $( 'meta[name="ResourceLoaderDynamicStyles"]' );
                                if ( $marker.length ) {
                                        return $marker;
                                }
                                mw.log( 'getMarker> No <meta name="ResourceLoaderDynamicStyles"> found, inserting dynamically.' );
                                $marker = $( '<meta>' ).attr( 'name', 'ResourceLoaderDynamicStyles' ).appendTo( 'head' );

                                return $marker;
                        }

                        /**
                         * Create a new style tag and add it to the DOM.
                         *
                         * @private
                         * @param {string} text CSS text
                         * @param {HTMLElement|jQuery} [nextnode=document.head] The element where the style tag should be
                         *  inserted before. Otherwise it will be appended to `<head>`.
                         * @return {HTMLElement} Reference to the created `<style>` element.
                         */
                        function newStyleTag( text, nextnode ) {
                                var s = document.createElement( 'style' );
                                // Insert into document before setting cssText (bug 33305)
                                if ( nextnode ) {
                                        // Must be inserted with native insertBefore, not $.fn.before.
                                        // When using jQuery to insert it, like $nextnode.before( s ),
                                        // then IE6 will throw "Access is denied" when trying to append
                                        // to .cssText later. Some kind of weird security measure.
                                        // http://stackoverflow.com/q/12586482/319266
                                        // Works: jsfiddle.net/zJzMy/1
                                        // Fails: jsfiddle.net/uJTQz
                                        // Works again: http://jsfiddle.net/Azr4w/ (diff: the next 3 lines)
                                        if ( nextnode.jquery ) {
                                                nextnode = nextnode.get( 0 );
                                        }
                                        nextnode.parentNode.insertBefore( s, nextnode );
                                } else {
                                        document.getElementsByTagName( 'head' )[0].appendChild( s );
                                }
                                if ( s.styleSheet ) {
                                        // IE
                                        s.styleSheet.cssText = text;
                                } else {
                                        // Other browsers.
                                        // (Safari sometimes borks on non-string values,
                                        // play safe by casting to a string, just in case.)
                                        s.appendChild( document.createTextNode( String( text ) ) );
                                }
                                return s;
                        }

                        /**
                         * Checks whether it is safe to add this css to a stylesheet.
                         *
                         * @private
                         * @param {string} cssText
                         * @return {boolean} False if a new one must be created.
                         */
                        function canExpandStylesheetWith( cssText ) {
                                // Makes sure that cssText containing `@import`
                                // rules will end up in a new stylesheet (as those only work when
                                // placed at the start of a stylesheet; bug 35562).
                                return cssText.indexOf( '@import' ) === -1;
                        }

                        /**
                         * Add a bit of CSS text to the current browser page.
                         *
                         * The CSS will be appended to an existing ResourceLoader-created `<style>` tag
                         * or create a new one based on whether the given `cssText` is safe for extension.
                         *
                         * @param {string} [cssText=cssBuffer] If called without cssText,
                         *  the internal buffer will be inserted instead.
                         * @param {Function} [callback]
                         */
                        function addEmbeddedCSS( cssText, callback ) {
                                var $style, styleEl;

                                if ( callback ) {
                                        cssCallbacks.add( callback );
                                }

                                // Yield once before inserting the <style> tag. There are likely
                                // more calls coming up which we can combine this way.
                                // Appending a stylesheet and waiting for the browser to repaint
                                // is fairly expensive, this reduces it (bug 45810)
                                if ( cssText ) {
                                        // Be careful not to extend the buffer with css that needs a new stylesheet
                                        if ( !cssBuffer || canExpandStylesheetWith( cssText ) ) {
                                                // Linebreak for somewhat distinguishable sections
                                                // (the rl-cachekey comment separating each)
                                                cssBuffer += '\n' + cssText;
                                                // TODO: Use requestAnimationFrame in the future which will
                                                // perform even better by not injecting styles while the browser
                                                // is paiting.
                                                setTimeout( function () {
                                                        // Can't pass addEmbeddedCSS to setTimeout directly because Firefox
                                                        // (below version 13) has the non-standard behaviour of passing a
                                                        // numerical "lateness" value as first argument to this callback
                                                        // http://benalman.com/news/2009/07/the-mysterious-firefox-settime/
                                                        addEmbeddedCSS();
                                                } );
                                                return;
                                        }

                                // This is a delayed call and we got a buffer still
                                } else if ( cssBuffer ) {
                                        cssText = cssBuffer;
                                        cssBuffer = '';
                                } else {
                                        // This is a delayed call, but buffer is already cleared by
                                        // another delayed call.
                                        return;
                                }

                                // By default, always create a new <style>. Appending text
                                // to a <style> tag means the contents have to be re-parsed (bug 45810).
                                // Except, of course, in IE below 9, in there we default to
                                // re-using and appending to a <style> tag due to the
                                // IE stylesheet limit (bug 31676).
                                if ( 'documentMode' in document && document.documentMode <= 9 ) {

                                        $style = getMarker().prev();
                                        // Verify that the the element before Marker actually is a
                                        // <style> tag and one that came from ResourceLoader
                                        // (not some other style tag or even a `<meta>` or `<script>`).
                                        if ( $style.data( 'ResourceLoaderDynamicStyleTag' ) === true ) {
                                                // There's already a dynamic <style> tag present and
                                                // canExpandStylesheetWith() gave a green light to append more to it.
                                                styleEl = $style.get( 0 );
                                                if ( styleEl.styleSheet ) {
                                                        try {
                                                                styleEl.styleSheet.cssText += cssText; // IE
                                                        } catch ( e ) {
                                                                log( 'addEmbeddedCSS fail\ne.message: ' + e.message, e );
                                                        }
                                                } else {
                                                        styleEl.appendChild( document.createTextNode( String( cssText ) ) );
                                                }
                                                cssCallbacks.fire().empty();
                                                return;
                                        }
                                }

                                $( newStyleTag( cssText, getMarker() ) ).data( 'ResourceLoaderDynamicStyleTag', true );

                                cssCallbacks.fire().empty();
                        }

                        /**
                         * Generates an ISO8601 "basic" string from a UNIX timestamp
                         * @private
                         */
                        function formatVersionNumber( timestamp ) {
                                var     d = new Date();
                                function pad( a, b, c ) {
                                        return [a < 10 ? '0' + a : a, b < 10 ? '0' + b : b, c < 10 ? '0' + c : c].join( '' );
                                }
                                d.setTime( timestamp * 1000 );
                                return [
                                        pad( d.getUTCFullYear(), d.getUTCMonth() + 1, d.getUTCDate() ), 'T',
                                        pad( d.getUTCHours(), d.getUTCMinutes(), d.getUTCSeconds() ), 'Z'
                                ].join( '' );
                        }

                        /**
                         * Resolves dependencies and detects circular references.
                         *
                         * @private
                         * @param {string} module Name of the top-level module whose dependencies shall be
                         *   resolved and sorted.
                         * @param {Array} resolved Returns a topological sort of the given module and its
                         *   dependencies, such that later modules depend on earlier modules. The array
                         *   contains the module names. If the array contains already some module names,
                         *   this function appends its result to the pre-existing array.
                         * @param {Object} [unresolved] Hash used to track the current dependency
                         *   chain; used to report loops in the dependency graph.
                         * @throws {Error} If any unregistered module or a dependency loop is encountered
                         */
                        function sortDependencies( module, resolved, unresolved ) {
                                var n, deps, len;

                                if ( registry[module] === undefined ) {
                                        throw new Error( 'Unknown dependency: ' + module );
                                }
                                // Resolves dynamic loader function and replaces it with its own results
                                if ( $.isFunction( registry[module].dependencies ) ) {
                                        registry[module].dependencies = registry[module].dependencies();
                                        // Ensures the module's dependencies are always in an array
                                        if ( typeof registry[module].dependencies !== 'object' ) {
                                                registry[module].dependencies = [registry[module].dependencies];
                                        }
                                }
                                if ( $.inArray( module, resolved ) !== -1 ) {
                                        // Module already resolved; nothing to do.
                                        return;
                                }
                                // unresolved is optional, supply it if not passed in
                                if ( !unresolved ) {
                                        unresolved = {};
                                }
                                // Tracks down dependencies
                                deps = registry[module].dependencies;
                                len = deps.length;
                                for ( n = 0; n < len; n += 1 ) {
                                        if ( $.inArray( deps[n], resolved ) === -1 ) {
                                                if ( unresolved[deps[n]] ) {
                                                        throw new Error(
                                                                'Circular reference detected: ' + module +
                                                                ' -> ' + deps[n]
                                                        );
                                                }

                                                // Add to unresolved
                                                unresolved[module] = true;
                                                sortDependencies( deps[n], resolved, unresolved );
                                                delete unresolved[module];
                                        }
                                }
                                resolved[resolved.length] = module;
                        }

                        /**
                         * Gets a list of module names that a module depends on in their proper dependency
                         * order.
                         *
                         * @private
                         * @param {string} module Module name or array of string module names
                         * @return {Array} list of dependencies, including 'module'.
                         * @throws {Error} If circular reference is detected
                         */
                        function resolve( module ) {
                                var m, resolved;

                                // Allow calling with an array of module names
                                if ( $.isArray( module ) ) {
                                        resolved = [];
                                        for ( m = 0; m < module.length; m += 1 ) {
                                                sortDependencies( module[m], resolved );
                                        }
                                        return resolved;
                                }

                                if ( typeof module === 'string' ) {
                                        resolved = [];
                                        sortDependencies( module, resolved );
                                        return resolved;
                                }

                                throw new Error( 'Invalid module argument: ' + module );
                        }

                        /**
                         * Narrows a list of module names down to those matching a specific
                         * state (see comment on top of this scope for a list of valid states).
                         * One can also filter for 'unregistered', which will return the
                         * modules names that don't have a registry entry.
                         *
                         * @private
                         * @param {string|string[]} states Module states to filter by
                         * @param {Array} [modules] List of module names to filter (optional, by default the entire
                         * registry is used)
                         * @return {Array} List of filtered module names
                         */
                        function filter( states, modules ) {
                                var list, module, s, m;

                                // Allow states to be given as a string
                                if ( typeof states === 'string' ) {
                                        states = [states];
                                }
                                // If called without a list of modules, build and use a list of all modules
                                list = [];
                                if ( modules === undefined ) {
                                        modules = [];
                                        for ( module in registry ) {
                                                modules[modules.length] = module;
                                        }
                                }
                                // Build a list of modules which are in one of the specified states
                                for ( s = 0; s < states.length; s += 1 ) {
                                        for ( m = 0; m < modules.length; m += 1 ) {
                                                if ( registry[modules[m]] === undefined ) {
                                                        // Module does not exist
                                                        if ( states[s] === 'unregistered' ) {
                                                                // OK, undefined
                                                                list[list.length] = modules[m];
                                                        }
                                                } else {
                                                        // Module exists, check state
                                                        if ( registry[modules[m]].state === states[s] ) {
                                                                // OK, correct state
                                                                list[list.length] = modules[m];
                                                        }
                                                }
                                        }
                                }
                                return list;
                        }

                        /**
                         * Determine whether all dependencies are in state 'ready', which means we may
                         * execute the module or job now.
                         *
                         * @private
                         * @param {Array} dependencies Dependencies (module names) to be checked.
                         * @return {boolean} True if all dependencies are in state 'ready', false otherwise
                         */
                        function allReady( dependencies ) {
                                return filter( 'ready', dependencies ).length === dependencies.length;
                        }

                        /**
                         * Log a message to window.console, if possible. Useful to force logging of some
                         * errors that are otherwise hard to detect (I.e., this logs also in production mode).
                         * Gets console references in each invocation, so that delayed debugging tools work
                         * fine. No need for optimization here, which would only result in losing logs.
                         *
                         * @private
                         * @param {string} msg text for the log entry.
                         * @param {Error} [e]
                         */
                        function log( msg, e ) {
                                var console = window.console;
                                if ( console && console.log ) {
                                        console.log( msg );
                                        // If we have an exception object, log it through .error() to trigger
                                        // proper stacktraces in browsers that support it. There are no (known)
                                        // browsers that don't support .error(), that do support .log() and
                                        // have useful exception handling through .log().
                                        if ( e && console.error ) {
                                                console.error( e );
                                        }
                                }
                        }

                        /**
                         * A module has entered state 'ready', 'error', or 'missing'. Automatically update pending jobs
                         * and modules that depend upon this module. if the given module failed, propagate the 'error'
                         * state up the dependency tree; otherwise, execute all jobs/modules that now have all their
                         * dependencies satisfied. On jobs depending on a failed module, run the error callback, if any.
                         *
                         * @private
                         * @param {string} module Name of module that entered one of the states 'ready', 'error', or 'missing'.
                         */
                        function handlePending( module ) {
                                var j, job, hasErrors, m, stateChange;

                                // Modules.
                                if ( $.inArray( registry[module].state, ['error', 'missing'] ) !== -1 ) {
                                        // If the current module failed, mark all dependent modules also as failed.
                                        // Iterate until steady-state to propagate the error state upwards in the
                                        // dependency tree.
                                        do {
                                                stateChange = false;
                                                for ( m in registry ) {
                                                        if ( $.inArray( registry[m].state, ['error', 'missing'] ) === -1 ) {
                                                                if ( filter( ['error', 'missing'], registry[m].dependencies ).length > 0 ) {
                                                                        registry[m].state = 'error';
                                                                        stateChange = true;
                                                                }
                                                        }
                                                }
                                        } while ( stateChange );
                                }

                                // Execute all jobs whose dependencies are either all satisfied or contain at least one failed module.
                                for ( j = 0; j < jobs.length; j += 1 ) {
                                        hasErrors = filter( ['error', 'missing'], jobs[j].dependencies ).length > 0;
                                        if ( hasErrors || allReady( jobs[j].dependencies ) ) {
                                                // All dependencies satisfied, or some have errors
                                                job = jobs[j];
                                                jobs.splice( j, 1 );
                                                j -= 1;
                                                try {
                                                        if ( hasErrors ) {
                                                                throw new Error( 'Module ' + module + ' failed.');
                                                        } else {
                                                                if ( $.isFunction( job.ready ) ) {
                                                                        job.ready();
                                                                }
                                                        }
                                                } catch ( e ) {
                                                        if ( $.isFunction( job.error ) ) {
                                                                try {
                                                                        job.error( e, [module] );
                                                                } catch ( ex ) {
                                                                        // A user-defined operation raised an exception. Swallow to protect
                                                                        // our state machine!
                                                                        log( 'Exception thrown by job.error()', ex );
                                                                }
                                                        }
                                                }
                                        }
                                }

                                if ( registry[module].state === 'ready' ) {
                                        // The current module became 'ready'. Recursively execute all dependent modules that are loaded
                                        // and now have all dependencies satisfied.
                                        for ( m in registry ) {
                                                if ( registry[m].state === 'loaded' && allReady( registry[m].dependencies ) ) {
                                                        execute( m );
                                                }
                                        }
                                }
                        }

                        /**
                         * Adds a script tag to the DOM, either using document.write or low-level DOM manipulation,
                         * depending on whether document-ready has occurred yet and whether we are in async mode.
                         *
                         * @private
                         * @param {string} src URL to script, will be used as the src attribute in the script tag
                         * @param {Function} [callback] Callback which will be run when the script is done
                         */
                        function addScript( src, callback, async ) {
                                /*jshint evil:true */
                                var script, head, done;

                                // Using isReady directly instead of storing it locally from
                                // a $.fn.ready callback (bug 31895).
                                if ( $.isReady || async ) {
                                        // Can't use jQuery.getScript because that only uses <script> for cross-domain,
                                        // it uses XHR and eval for same-domain scripts, which we don't want because it
                                        // messes up line numbers.
                                        // The below is based on jQuery ([jquery@1.8.2]/src/ajax/script.js)

                                        // IE-safe way of getting the <head>. document.head isn't supported
                                        // in old IE, and doesn't work when in the <head>.
                                        done = false;
                                        head = document.getElementsByTagName( 'head' )[0] || document.body;

                                        script = document.createElement( 'script' );
                                        script.async = true;
                                        script.src = src;
                                        if ( $.isFunction( callback ) ) {
                                                script.onload = script.onreadystatechange = function () {
                                                        if (
                                                                !done
                                                                && (
                                                                        !script.readyState
                                                                        || /loaded|complete/.test( script.readyState )
                                                                )
                                                        ) {
                                                                done = true;

                                                                // Handle memory leak in IE
                                                                script.onload = script.onreadystatechange = null;

                                                                // Detach the element from the document
                                                                if ( script.parentNode ) {
                                                                        script.parentNode.removeChild( script );
                                                                }

                                                                // Dereference the element from javascript
                                                                script = undefined;

                                                                callback();
                                                        }
                                                };
                                        }

                                        if ( window.opera ) {
                                                // Appending to the <head> blocks rendering completely in Opera,
                                                // so append to the <body> after document ready. This means the
                                                // scripts only start loading after the document has been rendered,
                                                // but so be it. Opera users don't deserve faster web pages if their
                                                // browser makes it impossible.
                                                $( function () {
                                                        document.body.appendChild( script );
                                                } );
                                        } else {
                                                head.appendChild( script );
                                        }
                                } else {
                                        document.write( mw.html.element( 'script', { 'src': src }, '' ) );
                                        if ( $.isFunction( callback ) ) {
                                                // Document.write is synchronous, so this is called when it's done
                                                // FIXME: that's a lie. doc.write isn't actually synchronous
                                                callback();
                                        }
                                }
                        }

                        /**
                         * Executes a loaded module, making it ready to use
                         *
                         * @private
                         * @param {string} module Module name to execute
                         */
                        function execute( module ) {
                                var key, value, media, i, urls, cssHandle, checkCssHandles,
                                        cssHandlesRegistered = false;

                                if ( registry[module] === undefined ) {
                                        throw new Error( 'Module has not been registered yet: ' + module );
                                } else if ( registry[module].state === 'registered' ) {
                                        throw new Error( 'Module has not been requested from the server yet: ' + module );
                                } else if ( registry[module].state === 'loading' ) {
                                        throw new Error( 'Module has not completed loading yet: ' + module );
                                } else if ( registry[module].state === 'ready' ) {
                                        throw new Error( 'Module has already been executed: ' + module );
                                }

                                /**
                                 * Define loop-function here for efficiency
                                 * and to avoid re-using badly scoped variables.
                                 * @ignore
                                 */
                                function addLink( media, url ) {
                                        var el = document.createElement( 'link' );
                                        getMarker().before( el ); // IE: Insert in dom before setting href
                                        el.rel = 'stylesheet';
                                        if ( media && media !== 'all' ) {
                                                el.media = media;
                                        }
                                        el.href = url;
                                }

                                function runScript() {
                                        var script, markModuleReady, nestedAddScript;
                                        try {
                                                script = registry[module].script;
                                                markModuleReady = function () {
                                                        registry[module].state = 'ready';
                                                        handlePending( module );
                                                };
                                                nestedAddScript = function ( arr, callback, async, i ) {
                                                        // Recursively call addScript() in its own callback
                                                        // for each element of arr.
                                                        if ( i >= arr.length ) {
                                                                // We're at the end of the array
                                                                callback();
                                                                return;
                                                        }

                                                        addScript( arr[i], function () {
                                                                nestedAddScript( arr, callback, async, i + 1 );
                                                        }, async );
                                                };

                                                if ( $.isArray( script ) ) {
                                                        nestedAddScript( script, markModuleReady, registry[module].async, 0 );
                                                } else if ( $.isFunction( script ) ) {
                                                        registry[module].state = 'ready';
                                                        script( $ );
                                                        handlePending( module );
                                                }
                                        } catch ( e ) {
                                                // This needs to NOT use mw.log because these errors are common in production mode
                                                // and not in debug mode, such as when a symbol that should be global isn't exported
                                                log( 'Exception thrown by ' + module + ': ' + e.message, e );
                                                registry[module].state = 'error';
                                                handlePending( module );
                                        }
                                }

                                // This used to be inside runScript, but since that is now fired asychronously
                                // (after CSS is loaded) we need to set it here right away. It is crucial that
                                // when execute() is called this is set synchronously, otherwise modules will get
                                // executed multiple times as the registry will state that it isn't loading yet.
                                registry[module].state = 'loading';

                                // Add localizations to message system
                                if ( $.isPlainObject( registry[module].messages ) ) {
                                        mw.messages.set( registry[module].messages );
                                }

                                // Make sure we don't run the scripts until all (potentially asynchronous)
                                // stylesheet insertions have completed.
                                ( function () {
                                        var pending = 0;
                                        checkCssHandles = function () {
                                                // cssHandlesRegistered ensures we don't take off too soon, e.g. when
                                                // one of the cssHandles is fired while we're still creating more handles.
                                                if ( cssHandlesRegistered && pending === 0 && runScript ) {
                                                        runScript();
                                                        runScript = undefined; // Revoke
                                                }
                                        };
                                        cssHandle = function () {
                                                var check = checkCssHandles;
                                                pending++;
                                                return function () {
                                                        if (check) {
                                                                pending--;
                                                                check();
                                                                check = undefined; // Revoke
                                                        }
                                                };
                                        };
                                }() );

                                // Process styles (see also mw.loader.implement)
                                // * back-compat: { <media>: css }
                                // * back-compat: { <media>: [url, ..] }
                                // * { "css": [css, ..] }
                                // * { "url": { <media>: [url, ..] } }
                                if ( $.isPlainObject( registry[module].style ) ) {
                                        for ( key in registry[module].style ) {
                                                value = registry[module].style[key];
                                                media = undefined;

                                                if ( key !== 'url' && key !== 'css' ) {
                                                        // Backwards compatibility, key is a media-type
                                                        if ( typeof value === 'string' ) {
                                                                // back-compat: { <media>: css }
                                                                // Ignore 'media' because it isn't supported (nor was it used).
                                                                // Strings are pre-wrapped in "@media". The media-type was just ""
                                                                // (because it had to be set to something).
                                                                // This is one of the reasons why this format is no longer used.
                                                                addEmbeddedCSS( value, cssHandle() );
                                                        } else {
                                                                // back-compat: { <media>: [url, ..] }
                                                                media = key;
                                                                key = 'bc-url';
                                                        }
                                                }

                                                // Array of css strings in key 'css',
                                                // or back-compat array of urls from media-type
                                                if ( $.isArray( value ) ) {
                                                        for ( i = 0; i < value.length; i += 1 ) {
                                                                if ( key === 'bc-url' ) {
                                                                        // back-compat: { <media>: [url, ..] }
                                                                        addLink( media, value[i] );
                                                                } else if ( key === 'css' ) {
                                                                        // { "css": [css, ..] }
                                                                        addEmbeddedCSS( value[i], cssHandle() );
                                                                }
                                                        }
                                                // Not an array, but a regular object
                                                // Array of urls inside media-type key
                                                } else if ( typeof value === 'object' ) {
                                                        // { "url": { <media>: [url, ..] } }
                                                        for ( media in value ) {
                                                                urls = value[media];
                                                                for ( i = 0; i < urls.length; i += 1 ) {
                                                                        addLink( media, urls[i] );
                                                                }
                                                        }
                                                }
                                        }
                                }

                                // Kick off.
                                cssHandlesRegistered = true;
                                checkCssHandles();
                        }

                        /**
                         * Adds a dependencies to the queue with optional callbacks to be run
                         * when the dependencies are ready or fail
                         *
                         * @private
                         * @param {string|string[]} dependencies Module name or array of string module names
                         * @param {Function} [ready] Callback to execute when all dependencies are ready
                         * @param {Function} [error] Callback to execute when any dependency fails
                         * @param {boolean} [async] If true, load modules asynchronously even if
                         *  document ready has not yet occurred.
                         */
                        function request( dependencies, ready, error, async ) {
                                var n;

                                // Allow calling by single module name
                                if ( typeof dependencies === 'string' ) {
                                        dependencies = [dependencies];
                                }

                                // Add ready and error callbacks if they were given
                                if ( ready !== undefined || error !== undefined ) {
                                        jobs[jobs.length] = {
                                                'dependencies': filter(
                                                        ['registered', 'loading', 'loaded'],
                                                        dependencies
                                                ),
                                                'ready': ready,
                                                'error': error
                                        };
                                }

                                // Queue up any dependencies that are registered
                                dependencies = filter( ['registered'], dependencies );
                                for ( n = 0; n < dependencies.length; n += 1 ) {
                                        if ( $.inArray( dependencies[n], queue ) === -1 ) {
                                                queue[queue.length] = dependencies[n];
                                                if ( async ) {
                                                        // Mark this module as async in the registry
                                                        registry[dependencies[n]].async = true;
                                                }
                                        }
                                }

                                // Work the queue
                                mw.loader.work();
                        }

                        function sortQuery(o) {
                                var sorted = {}, key, a = [];
                                for ( key in o ) {
                                        if ( hasOwn.call( o, key ) ) {
                                                a.push( key );
                                        }
                                }
                                a.sort();
                                for ( key = 0; key < a.length; key += 1 ) {
                                        sorted[a[key]] = o[a[key]];
                                }
                                return sorted;
                        }

                        /**
                         * Converts a module map of the form { foo: [ 'bar', 'baz' ], bar: [ 'baz, 'quux' ] }
                         * to a query string of the form foo.bar,baz|bar.baz,quux
                         * @private
                         */
                        function buildModulesString( moduleMap ) {
                                var arr = [], p, prefix;
                                for ( prefix in moduleMap ) {
                                        p = prefix === '' ? '' : prefix + '.';
                                        arr.push( p + moduleMap[prefix].join( ',' ) );
                                }
                                return arr.join( '|' );
                        }

                        /**
                         * Asynchronously append a script tag to the end of the body
                         * that invokes load.php
                         * @private
                         * @param {Object} moduleMap Module map, see #buildModulesString
                         * @param {Object} currReqBase Object with other parameters (other than 'modules') to use in the request
                         * @param {string} sourceLoadScript URL of load.php
                         * @param {boolean} async If true, use an asynchrounous request even if document ready has not yet occurred
                         */
                        function doRequest( moduleMap, currReqBase, sourceLoadScript, async ) {
                                var request = $.extend(
                                        { modules: buildModulesString( moduleMap ) },
                                        currReqBase
                                );
                                request = sortQuery( request );
                                // Asynchronously append a script tag to the end of the body
                                // Append &* to avoid triggering the IE6 extension check
                                addScript( sourceLoadScript + '?' + $.param( request ) + '&*', null, async );
                        }

                        /* Public Methods */
                        return {
                                /**
                                 * @inheritdoc #newStyleTag
                                 * @method
                                 */
                                addStyleTag: newStyleTag,

                                /**
                                 * Batch-request queued dependencies from the server.
                                 */
                                work: function () {
                                        var     reqBase, splits, maxQueryLength, q, b, bSource, bGroup, bSourceGroup,
                                                source, group, g, i, modules, maxVersion, sourceLoadScript,
                                                currReqBase, currReqBaseLength, moduleMap, l,
                                                lastDotIndex, prefix, suffix, bytesAdded, async;

                                        // Build a list of request parameters common to all requests.
                                        reqBase = {
                                                skin: mw.config.get( 'skin' ),
                                                lang: mw.config.get( 'wgUserLanguage' ),
                                                debug: mw.config.get( 'debug' )
                                        };
                                        // Split module batch by source and by group.
                                        splits = {};
                                        maxQueryLength = mw.config.get( 'wgResourceLoaderMaxQueryLength', -1 );

                                        // Appends a list of modules from the queue to the batch
                                        for ( q = 0; q < queue.length; q += 1 ) {
                                                // Only request modules which are registered
                                                if ( registry[queue[q]] !== undefined && registry[queue[q]].state === 'registered' ) {
                                                        // Prevent duplicate entries
                                                        if ( $.inArray( queue[q], batch ) === -1 ) {
                                                                batch[batch.length] = queue[q];
                                                                // Mark registered modules as loading
                                                                registry[queue[q]].state = 'loading';
                                                        }
                                                }
                                        }
                                        // Early exit if there's nothing to load...
                                        if ( !batch.length ) {
                                                return;
                                        }

                                        // The queue has been processed into the batch, clear up the queue.
                                        queue = [];

                                        // Always order modules alphabetically to help reduce cache
                                        // misses for otherwise identical content.
                                        batch.sort();

                                        // Split batch by source and by group.
                                        for ( b = 0; b < batch.length; b += 1 ) {
                                                bSource = registry[batch[b]].source;
                                                bGroup = registry[batch[b]].group;
                                                if ( splits[bSource] === undefined ) {
                                                        splits[bSource] = {};
                                                }
                                                if ( splits[bSource][bGroup] === undefined ) {
                                                        splits[bSource][bGroup] = [];
                                                }
                                                bSourceGroup = splits[bSource][bGroup];
                                                bSourceGroup[bSourceGroup.length] = batch[b];
                                        }

                                        // Clear the batch - this MUST happen before we append any
                                        // script elements to the body or it's possible that a script
                                        // will be locally cached, instantly load, and work the batch
                                        // again, all before we've cleared it causing each request to
                                        // include modules which are already loaded.
                                        batch = [];

                                        for ( source in splits ) {

                                                sourceLoadScript = sources[source].loadScript;

                                                for ( group in splits[source] ) {

                                                        // Cache access to currently selected list of
                                                        // modules for this group from this source.
                                                        modules = splits[source][group];

                                                        // Calculate the highest timestamp
                                                        maxVersion = 0;
                                                        for ( g = 0; g < modules.length; g += 1 ) {
                                                                if ( registry[modules[g]].version > maxVersion ) {
                                                                        maxVersion = registry[modules[g]].version;
                                                                }
                                                        }

                                                        currReqBase = $.extend( { version: formatVersionNumber( maxVersion ) }, reqBase );
                                                        // For user modules append a user name to the request.
                                                        if ( group === 'user' && mw.config.get( 'wgUserName' ) !== null ) {
                                                                currReqBase.user = mw.config.get( 'wgUserName' );
                                                        }
                                                        currReqBaseLength = $.param( currReqBase ).length;
                                                        async = true;
                                                        // We may need to split up the request to honor the query string length limit,
                                                        // so build it piece by piece.
                                                        l = currReqBaseLength + 9; // '&modules='.length == 9

                                                        moduleMap = {}; // { prefix: [ suffixes ] }

                                                        for ( i = 0; i < modules.length; i += 1 ) {
                                                                // Determine how many bytes this module would add to the query string
                                                                lastDotIndex = modules[i].lastIndexOf( '.' );
                                                                // Note that these substr() calls work even if lastDotIndex == -1
                                                                prefix = modules[i].substr( 0, lastDotIndex );
                                                                suffix = modules[i].substr( lastDotIndex + 1 );
                                                                bytesAdded = moduleMap[prefix] !== undefined
                                                                        ? suffix.length + 3 // '%2C'.length == 3
                                                                        : modules[i].length + 3; // '%7C'.length == 3

                                                                // If the request would become too long, create a new one,
                                                                // but don't create empty requests
                                                                if ( maxQueryLength > 0 && !$.isEmptyObject( moduleMap ) && l + bytesAdded > maxQueryLength ) {
                                                                        // This request would become too long, create a new one
                                                                        // and fire off the old one
                                                                        doRequest( moduleMap, currReqBase, sourceLoadScript, async );
                                                                        moduleMap = {};
                                                                        async = true;
                                                                        l = currReqBaseLength + 9;
                                                                }
                                                                if ( moduleMap[prefix] === undefined ) {
                                                                        moduleMap[prefix] = [];
                                                                }
                                                                moduleMap[prefix].push( suffix );
                                                                if ( !registry[modules[i]].async ) {
                                                                        // If this module is blocking, make the entire request blocking
                                                                        // This is slightly suboptimal, but in practice mixing of blocking
                                                                        // and async modules will only occur in debug mode.
                                                                        async = false;
                                                                }
                                                                l += bytesAdded;
                                                        }
                                                        // If there's anything left in moduleMap, request that too
                                                        if ( !$.isEmptyObject( moduleMap ) ) {
                                                                doRequest( moduleMap, currReqBase, sourceLoadScript, async );
                                                        }
                                                }
                                        }
                                },

                                /**
                                 * Register a source.
                                 *
                                 * @param {string} id Short lowercase a-Z string representing a source, only used internally.
                                 * @param {Object} props Object containing only the loadScript property which is a url to
                                 *  the load.php location of the source.
                                 * @return {boolean}
                                 */
                                addSource: function ( id, props ) {
                                        var source;
                                        // Allow multiple additions
                                        if ( typeof id === 'object' ) {
                                                for ( source in id ) {
                                                        mw.loader.addSource( source, id[source] );
                                                }
                                                return true;
                                        }

                                        if ( sources[id] !== undefined ) {
                                                throw new Error( 'source already registered: ' + id );
                                        }

                                        sources[id] = props;

                                        return true;
                                },

                                /**
                                 * Register a module, letting the system know about it and its
                                 * properties. Startup modules contain calls to this function.
                                 *
                                 * @param {string} module Module name
                                 * @param {number} version Module version number as a timestamp (falls backs to 0)
                                 * @param {string|Array|Function} dependencies One string or array of strings of module
                                 *  names on which this module depends, or a function that returns that array.
                                 * @param {string} [group=null] Group which the module is in
                                 * @param {string} [source='local'] Name of the source
                                 */
                                register: function ( module, version, dependencies, group, source ) {
                                        var m;
                                        // Allow multiple registration
                                        if ( typeof module === 'object' ) {
                                                for ( m = 0; m < module.length; m += 1 ) {
                                                        // module is an array of module names
                                                        if ( typeof module[m] === 'string' ) {
                                                                mw.loader.register( module[m] );
                                                        // module is an array of arrays
                                                        } else if ( typeof module[m] === 'object' ) {
                                                                mw.loader.register.apply( mw.loader, module[m] );
                                                        }
                                                }
                                                return;
                                        }
                                        // Validate input
                                        if ( typeof module !== 'string' ) {
                                                throw new Error( 'module must be a string, not a ' + typeof module );
                                        }
                                        if ( registry[module] !== undefined ) {
                                                throw new Error( 'module already registered: ' + module );
                                        }
                                        // List the module as registered
                                        registry[module] = {
                                                version: version !== undefined ? parseInt( version, 10 ) : 0,
                                                dependencies: [],
                                                group: typeof group === 'string' ? group : null,
                                                source: typeof source === 'string' ? source: 'local',
                                                state: 'registered'
                                        };
                                        if ( typeof dependencies === 'string' ) {
                                                // Allow dependencies to be given as a single module name
                                                registry[module].dependencies = [ dependencies ];
                                        } else if ( typeof dependencies === 'object' || $.isFunction( dependencies ) ) {
                                                // Allow dependencies to be given as an array of module names
                                                // or a function which returns an array
                                                registry[module].dependencies = dependencies;
                                        }
                                },

                                /**
                                 * Implement a module given the components that make up the module.
                                 *
                                 * When #load or #using requests one or more modules, the server
                                 * response contain calls to this function.
                                 *
                                 * All arguments are required.
                                 *
                                 * @param {string} module Name of module
                                 * @param {Function|Array} script Function with module code or Array of URLs to
                                 *  be used as the src attribute of a new `<script>` tag.
                                 * @param {Object} style Should follow one of the following patterns:
                                 *     { "css": [css, ..] }
                                 *     { "url": { <media>: [url, ..] } }
                                 * And for backwards compatibility (needs to be supported forever due to caching):
                                 *     { <media>: css }
                                 *     { <media>: [url, ..] }
                                 *
                                 * The reason css strings are not concatenated anymore is bug 31676. We now check
                                 * whether it's safe to extend the stylesheet (see #canExpandStylesheetWith).
                                 *
                                 * @param {Object} msgs List of key/value pairs to be added to {@link mw#messages}.
                                 */
                                implement: function ( module, script, style, msgs ) {
                                        // Validate input
                                        if ( typeof module !== 'string' ) {
                                                throw new Error( 'module must be a string, not a ' + typeof module );
                                        }
                                        if ( !$.isFunction( script ) && !$.isArray( script ) ) {
                                                throw new Error( 'script must be a function or an array, not a ' + typeof script );
                                        }
                                        if ( !$.isPlainObject( style ) ) {
                                                throw new Error( 'style must be an object, not a ' + typeof style );
                                        }
                                        if ( !$.isPlainObject( msgs ) ) {
                                                throw new Error( 'msgs must be an object, not a ' + typeof msgs );
                                        }
                                        // Automatically register module
                                        if ( registry[module] === undefined ) {
                                                mw.loader.register( module );
                                        }
                                        // Check for duplicate implementation
                                        if ( registry[module] !== undefined && registry[module].script !== undefined ) {
                                                throw new Error( 'module already implemented: ' + module );
                                        }
                                        // Attach components
                                        registry[module].script = script;
                                        registry[module].style = style;
                                        registry[module].messages = msgs;
                                        // The module may already have been marked as erroneous
                                        if ( $.inArray( registry[module].state, ['error', 'missing'] ) === -1 ) {
                                                registry[module].state = 'loaded';
                                                if ( allReady( registry[module].dependencies ) ) {
                                                        execute( module );
                                                }
                                        }
                                },

                                /**
                                 * Execute a function as soon as one or more required modules are ready.
                                 *
                                 * @param {string|Array} dependencies Module name or array of modules names the callback
                                 *  dependends on to be ready before executing
                                 * @param {Function} [ready] callback to execute when all dependencies are ready
                                 * @param {Function} [error] callback to execute when if dependencies have a errors
                                 */
                                using: function ( dependencies, ready, error ) {
                                        var tod = typeof dependencies;
                                        // Validate input
                                        if ( tod !== 'object' && tod !== 'string' ) {
                                                throw new Error( 'dependencies must be a string or an array, not a ' + tod );
                                        }
                                        // Allow calling with a single dependency as a string
                                        if ( tod === 'string' ) {
                                                dependencies = [ dependencies ];
                                        }
                                        // Resolve entire dependency map
                                        dependencies = resolve( dependencies );
                                        if ( allReady( dependencies ) ) {
                                                // Run ready immediately
                                                if ( $.isFunction( ready ) ) {
                                                        ready();
                                                }
                                        } else if ( filter( ['error', 'missing'], dependencies ).length ) {
                                                // Execute error immediately if any dependencies have errors
                                                if ( $.isFunction( error ) ) {
                                                        error( new Error( 'one or more dependencies have state "error" or "missing"' ),
                                                                dependencies );
                                                }
                                        } else {
                                                // Not all dependencies are ready: queue up a request
                                                request( dependencies, ready, error );
                                        }
                                },

                                /**
                                 * Load an external script or one or more modules.
                                 *
                                 * @param {string|Array} modules Either the name of a module, array of modules,
                                 *  or a URL of an external script or style
                                 * @param {string} [type='text/javascript'] mime-type to use if calling with a URL of an
                                 *  external script or style; acceptable values are "text/css" and
                                 *  "text/javascript"; if no type is provided, text/javascript is assumed.
                                 * @param {boolean} [async] If true, load modules asynchronously
                                 *  even if document ready has not yet occurred. If false, block before
                                 *  document ready and load async after. If not set, true will be
                                 *  assumed if loading a URL, and false will be assumed otherwise.
                                 */
                                load: function ( modules, type, async ) {
                                        var filtered, m, module, l;

                                        // Validate input
                                        if ( typeof modules !== 'object' && typeof modules !== 'string' ) {
                                                throw new Error( 'modules must be a string or an array, not a ' + typeof modules );
                                        }
                                        // Allow calling with an external url or single dependency as a string
                                        if ( typeof modules === 'string' ) {
                                                // Support adding arbitrary external scripts
                                                if ( /^(https?:)?\/\//.test( modules ) ) {
                                                        if ( async === undefined ) {
                                                                // Assume async for bug 34542
                                                                async = true;
                                                        }
                                                        if ( type === 'text/css' ) {
                                                                // IE7-8 throws security warnings when inserting a <link> tag
                                                                // with a protocol-relative URL set though attributes (instead of
                                                                // properties) - when on HTTPS. See also bug #.
                                                                l = document.createElement( 'link' );
                                                                l.rel = 'stylesheet';
                                                                l.href = modules;
                                                                $( 'head' ).append( l );
                                                                return;
                                                        }
                                                        if ( type === 'text/javascript' || type === undefined ) {
                                                                addScript( modules, null, async );
                                                                return;
                                                        }
                                                        // Unknown type
                                                        throw new Error( 'invalid type for external url, must be text/css or text/javascript. not ' + type );
                                                }
                                                // Called with single module
                                                modules = [ modules ];
                                        }

                                        // Filter out undefined modules, otherwise resolve() will throw
                                        // an exception for trying to load an undefined module.
                                        // Undefined modules are acceptable here in load(), because load() takes
                                        // an array of unrelated modules, whereas the modules passed to
                                        // using() are related and must all be loaded.
                                        for ( filtered = [], m = 0; m < modules.length; m += 1 ) {
                                                module = registry[modules[m]];
                                                if ( module !== undefined ) {
                                                        if ( $.inArray( module.state, ['error', 'missing'] ) === -1 ) {
                                                                filtered[filtered.length] = modules[m];
                                                        }
                                                }
                                        }

                                        if ( filtered.length === 0 ) {
                                                return;
                                        }
                                        // Resolve entire dependency map
                                        filtered = resolve( filtered );
                                        // If all modules are ready, nothing to be done
                                        if ( allReady( filtered ) ) {
                                                return;
                                        }
                                        // If any modules have errors: also quit.
                                        if ( filter( ['error', 'missing'], filtered ).length ) {
                                                return;
                                        }
                                        // Since some modules are not yet ready, queue up a request.
                                        request( filtered, undefined, undefined, async );
                                },

                                /**
                                 * Change the state of one or more modules.
                                 *
                                 * @param {string|Object} module module name or object of module name/state pairs
                                 * @param {string} state state name
                                 */
                                state: function ( module, state ) {
                                        var m;

                                        if ( typeof module === 'object' ) {
                                                for ( m in module ) {
                                                        mw.loader.state( m, module[m] );
                                                }
                                                return;
                                        }
                                        if ( registry[module] === undefined ) {
                                                mw.loader.register( module );
                                        }
                                        if ( $.inArray( state, ['ready', 'error', 'missing'] ) !== -1
                                                && registry[module].state !== state ) {
                                                // Make sure pending modules depending on this one get executed if their
                                                // dependencies are now fulfilled!
                                                registry[module].state = state;
                                                handlePending( module );
                                        } else {
                                                registry[module].state = state;
                                        }
                                },

                                /**
                                 * Get the version of a module.
                                 *
                                 * @param {string} module Name of module to get version for
                                 */
                                getVersion: function ( module ) {
                                        if ( registry[module] !== undefined && registry[module].version !== undefined ) {
                                                return formatVersionNumber( registry[module].version );
                                        }
                                        return null;
                                },

                                /**
                                 * @inheritdoc #getVersion
                                 * @deprecated since 1.18 use #getVersion instead
                                 */
                                version: function () {
                                        return mw.loader.getVersion.apply( mw.loader, arguments );
                                },

                                /**
                                 * Get the state of a module.
                                 *
                                 * @param {string} module name of module to get state for
                                 */
                                getState: function ( module ) {
                                        if ( registry[module] !== undefined && registry[module].state !== undefined ) {
                                                return registry[module].state;
                                        }
                                        return null;
                                },

                                /**
                                 * Get names of all registered modules.
                                 *
                                 * @return {Array}
                                 */
                                getModuleNames: function () {
                                        return $.map( registry, function ( i, key ) {
                                                return key;
                                        } );
                                },

                                /**
                                 * Load the `mediawiki.user` module.
                                 *
                                 * For backwards-compatibility with cached pages from before 2013 where:
                                 *
                                 * - the `mediawiki.user` module didn't exist yet
                                 * - `mw.user` was still part of mediawiki.js
                                 * - `mw.loader.go` still existed and called after `mw.loader.load()`
                                 */
                                go: function () {
                                        mw.loader.load( 'mediawiki.user' );
                                }
                        };
                }() ),

                /**
                 * HTML construction helper functions
                 *
                 *     @example
                 *
                 *     var Html, output;
                 *
                 *     Html = mw.html;
                 *     output = Html.element( 'div', {}, new Html.Raw(
                 *         Html.element( 'img', { src: '<' } )
                 *     ) );
                 *     mw.log( output ); // <div><img src="&lt;"/></div>
                 *
                 * @class mw.html
                 * @singleton
                 */
                html: ( function () {
                        function escapeCallback( s ) {
                                switch ( s ) {
                                        case '\'':
                                                return '&#039;';
                                        case '"':
                                                return '&quot;';
                                        case '<':
                                                return '&lt;';
                                        case '>':
                                                return '&gt;';
                                        case '&':
                                                return '&amp;';
                                }
                        }

                        return {
                                /**
                                 * Escape a string for HTML. Converts special characters to HTML entities.
                                 * @param {string} s The string to escape
                                 */
                                escape: function ( s ) {
                                        return s.replace( /['"<>&]/g, escapeCallback );
                                },

                                /**
                                 * Create an HTML element string, with safe escaping.
                                 *
                                 * @param {string} name The tag name.
                                 * @param {Object} attrs An object with members mapping element names to values
                                 * @param {Mixed} contents The contents of the element. May be either:
                                 *  - string: The string is escaped.
                                 *  - null or undefined: The short closing form is used, e.g. <br/>.
                                 *  - this.Raw: The value attribute is included without escaping.
                                 *  - this.Cdata: The value attribute is included, and an exception is
                                 *   thrown if it contains an illegal ETAGO delimiter.
                                 *   See http://www.w3.org/TR/1999/REC-html401-19991224/appendix/notes.html#h-B.3.2
                                 */
                                element: function ( name, attrs, contents ) {
                                        var v, attrName, s = '<' + name;

                                        for ( attrName in attrs ) {
                                                v = attrs[attrName];
                                                // Convert name=true, to name=name
                                                if ( v === true ) {
                                                        v = attrName;
                                                // Skip name=false
                                                } else if ( v === false ) {
                                                        continue;
                                                }
                                                s += ' ' + attrName + '="' + this.escape( String( v ) ) + '"';
                                        }
                                        if ( contents === undefined || contents === null ) {
                                                // Self close tag
                                                s += '/>';
                                                return s;
                                        }
                                        // Regular open tag
                                        s += '>';
                                        switch ( typeof contents ) {
                                                case 'string':
                                                        // Escaped
                                                        s += this.escape( contents );
                                                        break;
                                                case 'number':
                                                case 'boolean':
                                                        // Convert to string
                                                        s += String( contents );
                                                        break;
                                                default:
                                                        if ( contents instanceof this.Raw ) {
                                                                // Raw HTML inclusion
                                                                s += contents.value;
                                                        } else if ( contents instanceof this.Cdata ) {
                                                                // CDATA
                                                                if ( /<\/[a-zA-z]/.test( contents.value ) ) {
                                                                        throw new Error( 'mw.html.element: Illegal end tag found in CDATA' );
                                                                }
                                                                s += contents.value;
                                                        } else {
                                                                throw new Error( 'mw.html.element: Invalid type of contents' );
                                                        }
                                        }
                                        s += '</' + name + '>';
                                        return s;
                                },

                                /**
                                 * Wrapper object for raw HTML passed to mw.html.element().
                                 * @class mw.html.Raw
                                 */
                                Raw: function ( value ) {
                                        this.value = value;
                                },

                                /**
                                 * Wrapper object for CDATA element contents passed to mw.html.element()
                                 * @class mw.html.Cdata
                                 */
                                Cdata: function ( value ) {
                                        this.value = value;
                                }
                        };
                }() ),

                // Skeleton user object. mediawiki.user.js extends this
                user: {
                        options: new Map(),
                        tokens: new Map()
                },

                /**
                 * Registry and firing of events.
                 *
                 * MediaWiki has various interface components that are extended, enhanced
                 * or manipulated in some other way by extensions, gadgets and even
                 * in core itself.
                 *
                 * This framework helps streamlining the timing of when these other
                 * code paths fire their plugins (instead of using document-ready,
                 * which can and should be limited to firing only once).
                 *
                 * Features like navigating to other wiki pages, previewing an edit
                 * and editing itself – without a refresh – can then retrigger these
                 * hooks accordingly to ensure everything still works as expected.
                 *
                 * Example usage:
                 *
                 *     mw.hook( 'wikipage.content' ).add( fn ).remove( fn );
                 *     mw.hook( 'wikipage.content' ).fire( $content );
                 *
                 * Handlers can be added and fired for arbitrary event names at any time. The same
                 * event can be fired multiple times. The last run of an event is memorized
                 * (similar to `$(document).ready` and `$.Deferred().done`).
                 * This means if an event is fired, and a handler added afterwards, the added
                 * function will be fired right away with the last given event data.
                 *
                 * Like Deferreds and Promises, the mw.hook object is both detachable and chainable.
                 * Thus allowing flexible use and optimal maintainability and authority control.
                 * You can pass around the `add` and/or `fire` method to another piece of code
                 * without it having to know the event name (or `mw.hook` for that matter).
                 *
                 *     var h = mw.hook( 'bar.ready' );
                 *     new mw.Foo( .. ).fetch( { callback: h.fire } );
                 *
                 * @class mw.hook
                 */
                hook: ( function () {
                        var lists = {};

                        /**
                         * Create an instance of mw.hook.
                         *
                         * @method hook
                         * @member mw
                         * @param {string} name Name of hook.
                         * @return {mw.hook}
                         */
                        return function ( name ) {
                                var list = lists[name] || ( lists[name] = $.Callbacks( 'memory' ) );

                                return {
                                        /**
                                         * Register a hook handler
                                         * @param {Function...} handler Function to bind.
                                         * @chainable
                                         */
                                        add: list.add,

                                        /**
                                         * Unregister a hook handler
                                         * @param {Function...} handler Function to unbind.
                                         * @chainable
                                         */
                                        remove: list.remove,

                                        /**
                                         * Run a hook.
                                         * @param {Mixed...} data
                                         * @chainable
                                         */
                                        fire: function () {
                                                return list.fireWith( null, slice.call( arguments ) );
                                        }
                                };
                        };
                }() )
        };

}( jQuery ) );

// Alias $j to jQuery for backwards compatibility
window.$j = jQuery;

// Attach to window and globally alias
window.mw = window.mediaWiki = mw;

// Auto-register from pre-loaded startup scripts
if ( jQuery.isFunction( window.startUp ) ) {
        window.startUp();
        window.startUp = undefined;
}