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diff --git a/www/wiki/extensions/MultimediaViewer/resources/mmv/model/mmv.model.TaskQueue.js b/www/wiki/extensions/MultimediaViewer/resources/mmv/model/mmv.model.TaskQueue.js
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+/*
+ * This file is part of the MediaWiki extension MultimediaViewer.
+ *
+ * MultimediaViewer is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * MultimediaViewer is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with MultimediaViewer.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+( function ( mw, $ ) {
+	var tqp;
+
+	/**
+	 * A queue which holds a list of tasks (functions). The tasks will be executed in order,
+	 * each starting when the previous one has finished (or failed).
+	 *
+	 * @class mw.mmv.model.TaskQueue
+	 * @constructor
+	 */
+	function TaskQueue() {
+		/**
+		 * The list of functions to execute.
+		 * @protected
+		 * @property {Array.<function()>}
+		 */
+		this.queue = [];
+
+		/**
+		 * State of the task queue (running, finished etc)
+		 * @protected
+		 * @property {mw.mmv.model.TaskQueue.State}
+		 */
+		this.state = TaskQueue.State.NOT_STARTED;
+
+		/**
+		 * A deferred which shows the state of the queue.
+		 * @protected
+		 * @property {jQuery.Deferred}
+		 */
+		this.deferred = $.Deferred();
+	}
+
+	tqp = TaskQueue.prototype;
+
+	/**
+	 * Adds a task. The task should be a function which returns a promise. (Other return values are
+	 * permitted, and will be taken to mean that the task has finished already.) The next task will
+	 * start when the promise resolves (or rejects).
+	 *
+	 * Tasks can only be added before the queue is first executed.
+	 *
+	 * @param {function()} task
+	 */
+	tqp.push = function ( task ) {
+		if ( this.state !== TaskQueue.State.NOT_STARTED ) {
+			throw new Error( 'Task queue already started!' );
+		}
+		this.queue.push( task );
+	};
+
+	/**
+	 * Execute the queue. The tasks will be performed in order. No more tasks can be added to the
+	 * queue.
+	 *
+	 * @return {jQuery.Promise} a promise which will resolve when the queue execution is finished,
+	 *     or reject when it is cancelled.
+	 */
+	tqp.execute = function () {
+		if ( this.state === TaskQueue.State.NOT_STARTED ) {
+			this.state = TaskQueue.State.RUNNING;
+			this.runNextTask( 0, $.Deferred().resolve() );
+		}
+
+		return this.deferred;
+	};
+
+	/**
+	 * Runs the next task once the current one has finished.
+	 *
+	 * @param {number} index
+	 * @param {jQuery.Promise} currentTask
+	 */
+	tqp.runNextTask = function ( index, currentTask ) {
+		var taskQueue = this;
+
+		function handleThen() {
+			if ( !taskQueue.queue[ index ] ) {
+				taskQueue.state = TaskQueue.State.FINISHED;
+				taskQueue.queue = []; // just to be sure there are no memory leaks
+				taskQueue.deferred.resolve();
+				return;
+			}
+
+			taskQueue.runNextTask( index + 1, $.when( taskQueue.queue[ index ]() ) );
+		}
+
+		if ( this.state !== TaskQueue.State.RUNNING ) {
+			return;
+		}
+
+		currentTask.then( handleThen, handleThen );
+	};
+
+	/**
+	 * Cancel the queue. No more tasks will be executed.
+	 */
+	tqp.cancel = function () {
+		this.state = TaskQueue.State.CANCELLED;
+		this.queue = []; // just to be sure there are no memory leaks
+		this.deferred.reject();
+	};
+
+	/**
+	 * State of the task queue (running, finished etc)
+	 *
+	 * @enum {string} mw.mmv.model.TaskQueue.State
+	 */
+	TaskQueue.State = {
+		/** not executed yet, tasks can still be added */
+		NOT_STARTED: 'not_started',
+
+		/** some task is being executed */
+		RUNNING: 'running',
+
+		/** all tasks finished, queue can be discarded */
+		FINISHED: 'finished',
+
+		/** cancel() function has been called, queue can be discarded */
+		CANCELLED: 'cancelled'
+	};
+
+	mw.mmv.model.TaskQueue = TaskQueue;
+}( mediaWiki, jQuery ) );