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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 () {
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;
}() );
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