/**

 * Copyright (c) Meta Platforms, Inc. and affiliates.

 *

 * This source code is licensed under the MIT license found in the

 * LICENSE file in the root directory of this source tree.

 *

 * @flow

 */

describe('events', () => {

  let dispatcher;

  beforeEach(() => {

    const EventEmitter = require('../events').default;

    dispatcher = new EventEmitter();

  });

  // @reactVersion >=16

  it('can dispatch an event with no listeners', () => {

    dispatcher.emit('event', 123);

  });

  // @reactVersion >=16

  it('handles a listener being attached multiple times', () => {

    const callback = jest.fn();

    dispatcher.addListener('event', callback);

    dispatcher.addListener('event', callback);

    dispatcher.emit('event', 123);

    expect(callback).toHaveBeenCalledTimes(1);

    expect(callback).toHaveBeenCalledWith(123);

  });

  // @reactVersion >=16

  it('notifies all attached listeners of events', () => {

    const callback1 = jest.fn();

    const callback2 = jest.fn();

    const callback3 = jest.fn();

    dispatcher.addListener('event', callback1);

    dispatcher.addListener('event', callback2);

    dispatcher.addListener('other-event', callback3);

    dispatcher.emit('event', 123);

    expect(callback1).toHaveBeenCalledTimes(1);

    expect(callback1).toHaveBeenCalledWith(123);

    expect(callback2).toHaveBeenCalledTimes(1);

    expect(callback2).toHaveBeenCalledWith(123);

    expect(callback3).not.toHaveBeenCalled();

  });

  // @reactVersion >= 16.0

  it('calls later listeners before re-throwing if an earlier one throws', () => {

    const callbackThatThrows = jest.fn(() => {

      throw Error('expected');

    });

    const callback = jest.fn();

    dispatcher.addListener('event', callbackThatThrows);

    dispatcher.addListener('event', callback);

    expect(() => {

      dispatcher.emit('event', 123);

    }).toThrow('expected');

    expect(callbackThatThrows).toHaveBeenCalledTimes(1);

    expect(callbackThatThrows).toHaveBeenCalledWith(123);

    expect(callback).toHaveBeenCalledTimes(1);

    expect(callback).toHaveBeenCalledWith(123);

  });

  // @reactVersion >= 16.0

  it('removes attached listeners', () => {

    const callback1 = jest.fn();

    const callback2 = jest.fn();

    dispatcher.addListener('event', callback1);

    dispatcher.addListener('other-event', callback2);

    dispatcher.removeListener('event', callback1);

    dispatcher.emit('event', 123);

    expect(callback1).not.toHaveBeenCalled();

    dispatcher.emit('other-event', 123);

    expect(callback2).toHaveBeenCalledTimes(1);

    expect(callback2).toHaveBeenCalledWith(123);

  });

  // @reactVersion >= 16.0

  it('removes all listeners', () => {

    const callback1 = jest.fn();

    const callback2 = jest.fn();

    const callback3 = jest.fn();

    dispatcher.addListener('event', callback1);

    dispatcher.addListener('event', callback2);

    dispatcher.addListener('other-event', callback3);

    dispatcher.removeAllListeners();

    dispatcher.emit('event', 123);

    dispatcher.emit('other-event', 123);

    expect(callback1).not.toHaveBeenCalled();

    expect(callback2).not.toHaveBeenCalled();

    expect(callback3).not.toHaveBeenCalled();

  });

  // @reactVersion >= 16.0

  it('should call the initial listeners even if others are added or removed during a dispatch', () => {

    const callback1 = jest.fn(() => {

      dispatcher.removeListener('event', callback2);

      dispatcher.addListener('event', callback3);

    });

    const callback2 = jest.fn();

    const callback3 = jest.fn();

    dispatcher.addListener('event', callback1);

    dispatcher.addListener('event', callback2);

    dispatcher.emit('event', 123);

    expect(callback1).toHaveBeenCalledTimes(1);

    expect(callback1).toHaveBeenCalledWith(123);

    expect(callback2).toHaveBeenCalledTimes(1);

    expect(callback2).toHaveBeenCalledWith(123);

    expect(callback3).not.toHaveBeenCalled();

    dispatcher.emit('event', 456);

    expect(callback1).toHaveBeenCalledTimes(2);

    expect(callback1).toHaveBeenCalledWith(456);

    expect(callback2).toHaveBeenCalledTimes(1);

    expect(callback3).toHaveBeenCalledTimes(1);

    expect(callback3).toHaveBeenCalledWith(456);

  });

});