import {defer} from "./utils.js";
/**
* 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} enqueued
*/
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) {
this.run();
}
return queued.promise;
}
/**
* Run one item
* @return {Promise} dequeued
*/
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} all run
*/
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} ran
*/
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
* @return {void}
*/
clear(){
this._q = [];
}
/**
* Get the number of tasks in the queue
* @return {number} tasks
*/
length(){
return this._q.length;
}
/**
* Pause a running queue
* @return {void}
*/
pause(){
this.paused = true;
}
/**
* End the queue
* @return {void}
*/
stop(){
this._q = [];
this.running = false;
this.paused = true;
}
}
/**
* Create a new task from a callback
* @class
* @private
* @param {function} task task to complete
* @param {array} args arguments for the task
* @param {scope} context scope of the task
* @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 };