lib0/promise.js

/**
 * Utility helpers to work with promises.
 *
 * @module promise
 */

import * as time from './time.js'

/**
 * @template T
 * @callback PromiseResolve
 * @param {T|PromiseLike<T>} [result]
 */

/**
 * @template T
 * @param {function(PromiseResolve<T>,function(Error):void):any} f
 * @return {Promise<T>}
 */
export const create = f => /** @type {Promise<T>} */ (new Promise(f))

/**
 * @param {function(function():void,function(Error):void):void} f
 * @return {Promise<void>}
 */
export const createEmpty = f => new Promise(f)

/**
 * `Promise.all` wait for all promises in the array to resolve and return the result
 * @template {unknown[] | []} PS
 *
 * @param {PS} ps
 * @return {Promise<{ -readonly [P in keyof PS]: Awaited<PS[P]> }>}
 */
export const all = Promise.all.bind(Promise)

/**
 * @param {Error} [reason]
 * @return {Promise<never>}
 */
export const reject = reason => Promise.reject(reason)

/**
 * @template T
 * @param {T|void} res
 * @return {Promise<T|void>}
 */
export const resolve = res => Promise.resolve(res)

/**
 * @template T
 * @param {T} res
 * @return {Promise<T>}
 */
export const resolveWith = res => Promise.resolve(res)

/**
 * @todo Next version, reorder parameters: check, [timeout, [intervalResolution]]
 *
 * @param {number} timeout
 * @param {function():boolean} check
 * @param {number} [intervalResolution]
 * @return {Promise<void>}
 */
export const until = (timeout, check, intervalResolution = 10) => create((resolve, reject) => {
  const startTime = time.getUnixTime()
  const hasTimeout = timeout > 0
  const untilInterval = () => {
    if (check()) {
      clearInterval(intervalHandle)
      resolve()
    } else if (hasTimeout) {
      /* c8 ignore else */
      if (time.getUnixTime() - startTime > timeout) {
        clearInterval(intervalHandle)
        reject(new Error('Timeout'))
      }
    }
  }
  const intervalHandle = setInterval(untilInterval, intervalResolution)
})

/**
 * @param {number} timeout
 * @return {Promise<undefined>}
 */
export const wait = timeout => create((resolve, reject) => setTimeout(resolve, timeout))

/**
 * Checks if an object is a promise using ducktyping.
 *
 * Promises are often polyfilled, so it makes sense to add some additional guarantees if the user of this
 * library has some insane environment where global Promise objects are overwritten.
 *
 * @param {any} p
 * @return {boolean}
 */
export const isPromise = p => p instanceof Promise || (p && p.then && p.catch && p.finally)