promise-magic

promise-magic.js

const sleep = (n, ...args) => new Promise((resolve) => { setTimeout(resolve, n, ...args) })

const sleepError = (n, error) => ({
  timeout: null,
  prom: null,
  clearMyTimeout () {
    clearTimeout(this.timeout)
    this.prom && this.prom.resolve()
  },
  get promise () {
    this.prom = new Promise((resolve, reject) => {
      // potentially avoiding memory leaks
      setImmediate(() => { this.prom.resolve = resolve })

      this.timeout = setTimeout(reject, n, error)
    })

    return this.prom
  }
})

class PM {
  #thePromise = null

  constructor () {
    this.preparePromise()
  }

  async waitForThatThingToHappenOrTimesOut (timeout = 15_000 ) {
    const sleepingBeauty = sleepError(timeout, new Error('thisHasTimedout'))
    return Promise.race([
      this.#thePromise,
      sleepingBeauty.promise
    ]).finally(() => {
      sleepingBeauty.clearMyTimeout()
    })
  }

  async preparePromise () {
  //   let innerResolve = 
    this.#thePromise = new Promise((resolve) => process.nextTick(() => {
    this.#thePromise.resolve = resolve
    }))
  //   this.#thePromise = new Promise((resolve) => {
  //   innerResolve = resolve
  //   })

  //   this.#thePromise.resolve = innerResolve
  }

  resolveFromOutside (v) {
    this.#thePromise.resolve(v)
  }
}

async function resolveExample () {
  const pm = new PM()

  pm.waitForThatThingToHappenOrTimesOut()
  .then(console.log.bind(0, 'SUCESS'))
  .catch(console.error.bind(0, 'Shit Man!'))

  await sleep(100)
  pm.resolveFromOutside('Nothing')
}

async function rejectExample (timeout = 10_000) {
  const pm = new PM()

  await pm.waitForThatThingToHappenOrTimesOut(timeout)
  .then(console.log.bind(0, 'SUCESS'))
  .catch(console.error.bind(0, 'Shit Man!'))
}

module.exports = {
  PM,
  sleep,
  sleepError,
  resolveExample,
  rejectExample
}