/**
 * @license
 * Copyright Google LLC All Rights Reserved.
 *
 * Use of this source code is governed by an MIT-style license that can be
 * found in the LICENSE file at https://angular.io/license
 */

/** Modifier keys that may be held while typing. */
export interface ModifierKeys {
  control?: boolean;
  alt?: boolean;
  shift?: boolean;
  meta?: boolean;
}

/**
 * Creates a browser MouseEvent with the specified options.
 * @docs-private
 */
export function createMouseEvent(type: string, x = 0, y = 0, button = 0) {
  const event = document.createEvent('MouseEvent');
  const originalPreventDefault = event.preventDefault;

  event.initMouseEvent(type,
    true, /* canBubble */
    true, /* cancelable */
    window, /* view */
    0, /* detail */
    x, /* screenX */
    y, /* screenY */
    x, /* clientX */
    y, /* clientY */
    false, /* ctrlKey */
    false, /* altKey */
    false, /* shiftKey */
    false, /* metaKey */
    button, /* button */
    null /* relatedTarget */);

  // `initMouseEvent` doesn't allow us to pass the `buttons` and
  // defaults it to 0 which looks like a fake event.
  Object.defineProperty(event, 'buttons', {get: () => 1});

  // IE won't set `defaultPrevented` on synthetic events so we need to do it manually.
  event.preventDefault = function() {
    Object.defineProperty(event, 'defaultPrevented', { get: () => true });
    return originalPreventDefault.apply(this, arguments);
  };

  return event;
}

/**
 * Creates a browser TouchEvent with the specified pointer coordinates.
 * @docs-private
 */
export function createTouchEvent(type: string, pageX = 0, pageY = 0) {
  // In favor of creating events that work for most of the browsers, the event is created
  // as a basic UI Event. The necessary details for the event will be set manually.
  const event = document.createEvent('UIEvent');
  const touchDetails = {pageX, pageY};

  event.initUIEvent(type, true, true, window, 0);

  // Most of the browsers don't have a "initTouchEvent" method that can be used to define
  // the touch details.
  Object.defineProperties(event, {
    touches: {value: [touchDetails]},
    targetTouches: {value: [touchDetails]},
    changedTouches: {value: [touchDetails]}
  });

  return event;
}

/**
 * Dispatches a keydown event from an element.
 * @docs-private
 */
export function createKeyboardEvent(type: string, keyCode: number = 0, key: string = '',
                                    target?: Element, modifiers: ModifierKeys = {}) {
  const event = document.createEvent('KeyboardEvent') as any;
  const originalPreventDefault = event.preventDefault;

  // Firefox does not support `initKeyboardEvent`, but supports `initKeyEvent`.
  if (event.initKeyEvent) {
    event.initKeyEvent(type, true, true, window, modifiers.control, modifiers.alt, modifiers.shift,
        modifiers.meta, keyCode);
  } else {
    // `initKeyboardEvent` expects to receive modifiers as a whitespace-delimited string
    // See https://developer.mozilla.org/en-US/docs/Web/API/KeyboardEvent/initKeyboardEvent
    const modifiersStr = (modifiers.control ? 'Control ' : '' + modifiers.alt ? 'Alt ' : '' +
        modifiers.shift ? 'Shift ' : '' + modifiers.meta ? 'Meta' : '').trim();
    event.initKeyboardEvent(type,
        true, /* canBubble */
        true, /* cancelable */
        window, /* view */
        0, /* char */
        key, /* key */
        0, /* location */
        modifiersStr, /* modifiersList */
        false /* repeat */);
  }

  // Webkit Browsers don't set the keyCode when calling the init function.
  // See related bug https://bugs.webkit.org/show_bug.cgi?id=16735
  Object.defineProperties(event, {
    keyCode: { get: () => keyCode },
    key: { get: () => key },
    target: { get: () => target },
    ctrlKey: { get: () => !!modifiers.control },
    altKey: { get: () => !!modifiers.alt },
    shiftKey: { get: () => !!modifiers.shift },
    metaKey: { get: () => !!modifiers.meta }
  });

  // IE won't set `defaultPrevented` on synthetic events so we need to do it manually.
  event.preventDefault = function() {
    Object.defineProperty(event, 'defaultPrevented', { get: () => true });
    return originalPreventDefault.apply(this, arguments);
  };

  return event;
}

/**
 * Creates a fake event object with any desired event type.
 * @docs-private
 */
export function createFakeEvent(type: string, canBubble = false, cancelable = true) {
  const event = document.createEvent('Event');
  event.initEvent(type, canBubble, cancelable);
  return event;
}