1 files changed, 246 insertions, 0 deletions
diff --git a/lib/epub.js/src/utils/queue.js b/lib/epub.js/src/utils/queue.js
new file mode 100644
index 0000000..1f8a18a
--- /dev/null
+++ b/lib/epub.js/src/utils/queue.js
@@ -0,0 +1,246 @@
+import {defer, requestAnimationFrame} from "./core";
+
+/**
+ * Queue for handling tasks one at a time
+ * @class
+ * @param {scope} context what this will resolve to in the tasks
+ */
+class Queue {
+	constructor(context){
+		this._q = [];
+		this.context = context;
+		this.tick = requestAnimationFrame;
+		this.running = false;
+		this.paused = false;
+	}
+
+	/**
+	 * Add an item to the queue
+	 * @return {Promise}
+	 */
+	enqueue() {
+		var deferred, promise;
+		var queued;
+		var task = [].shift.call(arguments);
+		var args = arguments;
+
+		// Handle single args without context
+		// if(args && !Array.isArray(args)) {
+		//   args = [args];
+		// }
+		if(!task) {
+			throw new Error("No Task Provided");
+		}
+
+		if(typeof task === "function"){
+
+			deferred = new defer();
+			promise = deferred.promise;
+
+			queued = {
+				"task" : task,
+				"args"     : args,
+				//"context"  : context,
+				"deferred" : deferred,
+				"promise" : promise
+			};
+
+		} else {
+			// Task is a promise
+			queued = {
+				"promise" : task
+			};
+
+		}
+
+		this._q.push(queued);
+
+		// Wait to start queue flush
+		if (this.paused == false && !this.running) {
+			// setTimeout(this.flush.bind(this), 0);
+			// this.tick.call(window, this.run.bind(this));
+			this.run();
+		}
+
+		return queued.promise;
+	}
+
+	/**
+	 * Run one item
+	 * @return {Promise}
+	 */
+	dequeue(){
+		var inwait, task, result;
+
+		if(this._q.length && !this.paused) {
+			inwait = this._q.shift();
+			task = inwait.task;
+			if(task){
+				// console.log(task)
+
+				result = task.apply(this.context, inwait.args);
+
+				if(result && typeof result["then"] === "function") {
+					// Task is a function that returns a promise
+					return result.then(function(){
+						inwait.deferred.resolve.apply(this.context, arguments);
+					}.bind(this), function() {
+						inwait.deferred.reject.apply(this.context, arguments);
+					}.bind(this));
+				} else {
+					// Task resolves immediately
+					inwait.deferred.resolve.apply(this.context, result);
+					return inwait.promise;
+				}
+
+
+
+			} else if(inwait.promise) {
+				// Task is a promise
+				return inwait.promise;
+			}
+
+		} else {
+			inwait = new defer();
+			inwait.deferred.resolve();
+			return inwait.promise;
+		}
+
+	}
+
+	// Run All Immediately
+	dump(){
+		while(this._q.length) {
+			this.dequeue();
+		}
+	}
+
+	/**
+	 * Run all tasks sequentially, at convince
+	 * @return {Promise}
+	 */
+	run(){
+
+		if(!this.running){
+			this.running = true;
+			this.defered = new defer();
+		}
+
+		this.tick.call(window, () => {
+
+			if(this._q.length) {
+
+				this.dequeue()
+					.then(function(){
+						this.run();
+					}.bind(this));
+
+			} else {
+				this.defered.resolve();
+				this.running = undefined;
+			}
+
+		});
+
+		// Unpause
+		if(this.paused == true) {
+			this.paused = false;
+		}
+
+		return this.defered.promise;
+	}
+
+	/**
+	 * Flush all, as quickly as possible
+	 * @return {Promise}
+	 */
+	flush(){
+
+		if(this.running){
+			return this.running;
+		}
+
+		if(this._q.length) {
+			this.running = this.dequeue()
+				.then(function(){
+					this.running = undefined;
+					return this.flush();
+				}.bind(this));
+
+			return this.running;
+		}
+
+	}
+
+	/**
+	 * Clear all items in wait
+	 */
+	clear(){
+		this._q = [];
+	}
+
+	/**
+	 * Get the number of tasks in the queue
+	 * @return {number} tasks
+	 */
+	length(){
+		return this._q.length;
+	}
+
+	/**
+	 * Pause a running queue
+	 */
+	pause(){
+		this.paused = true;
+	}
+
+	/**
+	 * End the queue
+	 */
+	stop(){
+		this._q = [];
+		this.running = false;
+		this.paused = true;
+	}
+}
+
+
+/**
+ * Create a new task from a callback
+ * @class
+ * @private
+ * @param {function} task
+ * @param {array} args
+ * @param {scope} context
+ * @return {function} task
+ */
+class Task {
+	constructor(task, args, context){
+
+		return function(){
+			var toApply = arguments || [];
+
+			return new Promise( (resolve, reject) => {
+				var callback = function(value, err){
+					if (!value && err) {
+						reject(err);
+					} else {
+						resolve(value);
+					}
+				};
+				// Add the callback to the arguments list
+				toApply.push(callback);
+
+				// Apply all arguments to the functions
+				task.apply(context || this, toApply);
+
+			});
+
+		};
+
+	}
+}
+
+
+export default Queue;
+export { Task };