/**
 * Copyright 2017 Google Inc. All rights reserved.
 * Modifications copyright (c) Microsoft Corporation.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

type EventEmitterLike = {
  on(eventName: string | symbol, handler: (...args: any[]) => unknown): unknown;
  removeListener(eventName: string | symbol, handler: (...args: any[]) => unknown): unknown;
};

export type RegisteredListener = {
  emitter: EventEmitterLike;
  eventName: (string | symbol);
  handler: (...args: any[]) => void;
  dispose: () => Promise<void>;
};

class EventsHelper {
  static addEventListener(
    emitter: EventEmitterLike,
    eventName: (string | symbol),
    handler: (...args: any[]) => void): RegisteredListener {
    emitter.on(eventName, handler);
    return { emitter, eventName, handler, dispose: async () => { emitter.removeListener(eventName, handler); } };
  }

  static removeEventListeners(listeners: Array<{
    emitter: EventEmitterLike;
    eventName: (string | symbol);
    handler: (...args: any[]) => void;
  }>) {
    for (const listener of listeners)
      listener.emitter.removeListener(listener.eventName, listener.handler);
    listeners.splice(0, listeners.length);
  }
}

export const eventsHelper = EventsHelper;