/**
 * Copyright (c) 2017-present, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 *
 * @flow
 * @format
 */

// TODO(T17266325): Remove this module when `atom.whenShellEnvironmentLoaded()` lands.

import {ReplaySubject} from 'rxjs';

import UniversalDisposable from './UniversalDisposable';

const emitter = new ReplaySubject(1);

export function loadedShellEnvironment(): void {
  emitter.next();
}

function whenShellEnvironmentLoaded(cb: () => void): IDisposable {
  return new UniversalDisposable(emitter.take(1).subscribe(cb));
}

export default (typeof atom === 'undefined'
  ? null
  : whenShellEnvironmentLoaded);