/**
 * @license
 * Copyright (c) 2016 The Polymer Project Authors. All rights reserved.
 * This code may only be used under the BSD style license found at http://polymer.github.io/LICENSE.txt
 * The complete set of authors may be found at http://polymer.github.io/AUTHORS.txt
 * The complete set of contributors may be found at http://polymer.github.io/CONTRIBUTORS.txt
 * Code distributed by Google as part of the polymer project is also
 * subject to an additional IP rights grant found at http://polymer.github.io/PATENTS.txt
 */

/**
 * This shim allows elements written in, or compiled to, ES5 to work on native
 * implementations of Custom Elements v1. It sets new.target to the value of
 * this.constructor so that the native HTMLElement constructor can access the
 * current under-construction element's definition.
 */
export function shim () {
    const _window = <any>window;
    if (
      // No Reflect, no classes, no need for shim because native custom elements
      // require ES2015 classes or Reflect.
      _window.Reflect === undefined ||
      _window.customElements === undefined ||
      // The webcomponentsjs custom elements polyfill doesn't require
      // ES2015-compatible construction (`super()` or `Reflect.construct`).
      _window.customElements.polyfillWrapFlushCallback
    ) {
      return;
    }
    const BuiltInHTMLElement = HTMLElement;
    _window.HTMLElement = /** @this {!Object} */ function HTMLElement() {
      return Reflect.construct(
          BuiltInHTMLElement, [], /** @type {!Function} */ (this.constructor));
    };
    HTMLElement.prototype = BuiltInHTMLElement.prototype;
    HTMLElement.prototype.constructor = HTMLElement;
    Object.setPrototypeOf(HTMLElement, BuiltInHTMLElement);
  }