crocks/Async/asyncToPromise.js

A collection of well known Algebraic Datatypes for your utter enjoyment.

/** @license ISC License (c) copyright 2018 original and current authors */
/** @author Dale Francis */

var curry = require('../core/curry')
var isSameType = require('../core/isSameType')
var isFunction = require('../core/isFunction')

var Async = require('../core/types').proxy('Async')

var toPromise = function (m) {
  if(!isSameType(Async, m)) {
    throw new TypeError('asyncToPromise: Async or a function returning an Async required')
  }

  return m.toPromise()
}

// asyncToPromise :: m e a -> Promise a e
// asyncToPromise :: (a -> m e b) -> a -> Promise b e
function asyncToPromise(m) {
  return isFunction(m)
    ? function (x) { return toPromise(m(x)); }
    : toPromise(m)
}

module.exports = curry(asyncToPromise)