promise_utils.js

import { isObject, isFunction, curry } from 'lodash/fp';

export function isThenable(promise) {
  return isObject(promise) && isFunction(promise.then);
}

export function isCancellable(promise) {
  return isThenable(promise) && isFunction(promise.cancel);
}

export function isCancelled(promise) {
  return isCancellable(promise) && isFunction(promise.isCancelled) && promise.isCancelled();
}

export function hasFinallyInterface(promise) {
  return isThenable(promise) && isFunction(promise.finally);
}

export function cancel(promise) {
  if (!isCancellable(promise)) { return false }

  promise.cancel();
  return true;
}

export const onFinally = curry((callback, promise) => {
  if (!hasFinallyInterface(promise)) { return promise }

  return promise.finally(callback);
});

export const onCancel = curry((callback, promise) => {
  if (!isCancellable(promise)) { return promise }

  return onFinally(() => {
    if (isCancelled(promise)) { callback() }
  })(promise);
});