'use strict';

const threads = require('node:worker_threads');

const { Worker, isMainThread } = threads;

const LOCKED = 0;

const UNLOCKED = 1;

class Mutex {

constructor(shared, offset = 0, initial = false) {

this.lock = new Int32Array(shared, offset, 1);

if (initial) Atomics.store(this.lock, 0, UNLOCKED);

this.owner = false;

}

enter() {

let prev = Atomics.exchange(this.lock, 0, LOCKED);

while (prev !== UNLOCKED) {

Atomics.wait(this.lock, 0, LOCKED);

prev = Atomics.exchange(this.lock, 0, LOCKED);

}

this.owner = true;

}

leave() {

if (!this.owner) return;

Atomics.store(this.lock, 0, UNLOCKED);

Atomics.notify(this.lock, 0, 1);

this.owner = false;

}

}

class Point {

constructor(data, x, y) {

this.data = data;

if (typeof x === 'number') data[0] = x;

if (typeof y === 'number') data[1] = y;

}

get x() {

return this.data[0];

}

set x(value) {

this.data[0] = value;

}

get y() {

return this.data[1];

}

set y(value) {

this.data[1] = value;

}

move(x, y) {

this.x += x;

this.y += y;

}

}

// Usage

if (isMainThread) {

const buffer = new SharedArrayBuffer(12);

const mutex = new Mutex(buffer, 0, true);

const array = new Int32Array(buffer, 4, 2);

const point = new Point(array, 0, 0);

console.dir({ mutex, point });

new Worker(__filename, { workerData: buffer });

new Worker(__filename, { workerData: buffer });

} else {

const { threadId, workerData } = threads;

const mutex = new Mutex(workerData);

const array = new Int32Array(workerData, 4, 2);

const point = new Point(array);

if (threadId === 1) {

for (let i = 0; i < 1000000; i++) {

mutex.enter();

point.move(1, 1);

mutex.leave();

}

mutex.enter();

console.dir({ point });

mutex.leave();

} else {

for (let i = 0; i < 1000000; i++) {

mutex.enter();

point.move(-1, -1);

mutex.leave();

}

mutex.enter();

console.dir({ point });

mutex.leave();

}

}