JS Queue

queue.js

export default class Queue {
  constructor() {
    // All fields should be private
    this.waker = null
    this.kill = false
    this.items = []
    this.killed = this.attend()
  }

  async enqueue_and_wait(async_fn) {
    const promise = new Promise((resolve, reject) => this.items.push(async () => {
      try {
        resolve(await async_fn())
      } catch (e) {
        reject(e)
      }
    }))

    if (this.waker) {
      this.waker()
    }

    return await promise
  }

  async close() {
    // This code path is not tested
    this.kill = true
    if (this.waker) {
      this.waker()
    }
    await this.killed
  }

  // This method should be private
  async sleep() {
    await new Promise(resolve => this.waker = resolve)
    this.waker = null
  }

  // This method should be private
  async attend() {
    while (!this.kill) {
      if (this.items.length > 0) {
        await this.items.shift()()
      } else {
        await this.sleep()
      }
    }
  }
}