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index.js
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index.js
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'use strict';
// Port of lower_bound from http://en.cppreference.com/w/cpp/algorithm/lower_bound
// Used to compute insertion index to keep queue sorted after insertion
function lowerBound(array, value, comp) {
let first = 0;
let count = array.length;
while (count > 0) {
const step = (count / 2) | 0;
let it = first + step;
if (comp(array[it], value) <= 0) {
first = ++it;
count -= step + 1;
} else {
count = step;
}
}
return first;
}
class PriorityQueue {
constructor() {
this._queue = [];
}
enqueue(run, options) {
options = Object.assign({
priority: 0
}, options);
const element = {priority: options.priority, run};
if (this.size && this._queue[this.size - 1].priority >= options.priority) {
this._queue.push(element);
return;
}
const index = lowerBound(this._queue, element, (a, b) => b.priority - a.priority);
this._queue.splice(index, 0, element);
}
dequeue() {
return this._queue.shift().run;
}
get size() {
return this._queue.length;
}
}
class PQueue {
constructor(options) {
options = Object.assign({
carryoverConcurrencyCount: false,
intervalCap: Infinity,
interval: 0,
concurrency: Infinity,
autoStart: true,
queueClass: PriorityQueue
}, options);
if (!(typeof options.concurrency === 'number' && options.concurrency >= 1)) {
throw new TypeError(`Expected \`concurrency\` to be a number from 1 and up, got \`${options.concurrency}\` (${typeof options.concurrency})`);
}
if (!(typeof options.intervalCap === 'number' && options.intervalCap >= 1)) {
throw new TypeError(`Expected \`intervalCap\` to be a number from 1 and up, got \`${options.intervalCap}\` (${typeof options.intervalCap})`);
}
if (!(Number.isFinite(options.interval) && options.interval >= 0)) {
throw new TypeError(`Expected \`interval\` to be a finite number >= 0, got \`${options.interval}\` (${typeof options.interval})`);
}
this._carryoverConcurrencyCount = options.carryoverConcurrencyCount;
this._isIntervalIgnored = options.intervalCap === Infinity || options.interval === 0;
this._intervalCount = 0;
this._intervalCap = options.intervalCap;
this._interval = options.interval;
this._intervalId = null;
this._intervalEnd = 0;
this._timeoutId = null;
this.queue = new options.queueClass(); // eslint-disable-line new-cap
this._queueClass = options.queueClass;
this._pendingCount = 0;
this._concurrency = options.concurrency;
this._isPaused = options.autoStart === false;
this._resolveEmpty = () => {};
this._resolveIdle = () => {};
}
get _doesIntervalAllowAnother() {
return this._isIntervalIgnored || this._intervalCount < this._intervalCap;
}
get _doesConcurrentAllowAnother() {
return this._pendingCount < this._concurrency;
}
_next() {
this._pendingCount--;
this._tryToStartAnother();
}
_resolvePromises() {
this._resolveEmpty();
this._resolveEmpty = () => {};
if (this._pendingCount === 0) {
this._resolveIdle();
this._resolveIdle = () => {};
}
}
_onResumeInterval() {
this._onInterval();
this._initializeIntervalIfNeeded();
this._timeoutId = null;
}
_intervalPaused() {
const now = Date.now();
if (this._intervalId === null) {
const delay = this._intervalEnd - now;
if (delay < 0) {
// Act as the interval was done
// We don't need to resume it here,
// because it'll be resumed on line 160
this._intervalCount = (this._carryoverConcurrencyCount) ? this._pendingCount : 0;
} else {
// Act as the interval is pending
if (this._timeoutId === null) {
this._timeoutId = setTimeout(() => this._onResumeInterval(), delay);
}
return true;
}
}
return false;
}
_tryToStartAnother() {
if (this.queue.size === 0) {
// We can clear the interval ("pause")
// because we can redo it later ("resume")
clearInterval(this._intervalId);
this._intervalId = null;
this._resolvePromises();
return false;
}
if (!this._isPaused) {
const canInitializeInterval = !this._intervalPaused();
if (this._doesIntervalAllowAnother && this._doesConcurrentAllowAnother) {
this.queue.dequeue()();
if (canInitializeInterval) {
this._initializeIntervalIfNeeded();
}
return true;
}
}
return false;
}
_initializeIntervalIfNeeded() {
if (this._isIntervalIgnored || this._intervalId !== null) {
return;
}
this._intervalId = setInterval(() => this._onInterval(), this._interval);
this._intervalEnd = Date.now() + this._interval;
}
_onInterval() {
if (this._intervalCount === 0 && this._pendingCount === 0) {
clearInterval(this._intervalId);
this._intervalId = null;
}
this._intervalCount = (this._carryoverConcurrencyCount) ? this._pendingCount : 0;
while (this._tryToStartAnother()) {} // eslint-disable-line no-empty
}
add(fn, options) {
return new Promise((resolve, reject) => {
const run = () => {
this._pendingCount++;
this._intervalCount++;
try {
Promise.resolve(fn()).then(
val => {
resolve(val);
this._next();
},
err => {
reject(err);
this._next();
}
);
} catch (err) {
reject(err);
this._next();
}
};
this.queue.enqueue(run, options);
this._tryToStartAnother();
});
}
addAll(fns, options) {
return Promise.all(fns.map(fn => this.add(fn, options)));
}
start() {
if (!this._isPaused) {
return;
}
this._isPaused = false;
while (this._tryToStartAnother()) {} // eslint-disable-line no-empty
}
pause() {
this._isPaused = true;
}
clear() {
this.queue = new this._queueClass(); // eslint-disable-line new-cap
}
onEmpty() {
// Instantly resolve if the queue is empty
if (this.queue.size === 0) {
return Promise.resolve();
}
return new Promise(resolve => {
const existingResolve = this._resolveEmpty;
this._resolveEmpty = () => {
existingResolve();
resolve();
};
});
}
onIdle() {
// Instantly resolve if none pending and if nothing else is queued
if (this._pendingCount === 0 && this.queue.size === 0) {
return Promise.resolve();
}
return new Promise(resolve => {
const existingResolve = this._resolveIdle;
this._resolveIdle = () => {
existingResolve();
resolve();
};
});
}
get size() {
return this.queue.size;
}
get pending() {
return this._pendingCount;
}
get isPaused() {
return this._isPaused;
}
}
module.exports = PQueue;