shaka-player/lib/polyfill/patchedmediakeys_nop.js

DASH/EME video player library

/*! @license
 * Shaka Player
 * Copyright 2016 Google LLC
 * SPDX-License-Identifier: Apache-2.0
 */

goog.provide('shaka.polyfill.PatchedMediaKeysNop');

goog.require('goog.asserts');
goog.require('shaka.log');
goog.require('shaka.polyfill');


/**
 * @summary A polyfill to stub out
 * {@link https://bit.ly/EmeMar15 EME draft 12 March 2015} on browsers without
 * EME.
 * All methods will fail.
 * @export
 */
shaka.polyfill.PatchedMediaKeysNop = class {
  /**
   * Installs the polyfill if needed.
   * @export
   */
  static install() {
    if (!window.HTMLVideoElement ||
        (navigator.requestMediaKeySystemAccess &&
         // eslint-disable-next-line no-restricted-syntax
         MediaKeySystemAccess.prototype.getConfiguration)) {
      return;
    }
    shaka.log.info('EME not available.');

    // Alias.
    const PatchedMediaKeysNop = shaka.polyfill.PatchedMediaKeysNop;

    // Install patches.
    navigator.requestMediaKeySystemAccess =
        PatchedMediaKeysNop.requestMediaKeySystemAccess;
    // Delete mediaKeys to work around strict mode compatibility issues.
    // eslint-disable-next-line no-restricted-syntax
    delete HTMLMediaElement.prototype['mediaKeys'];
    // Work around read-only declaration for mediaKeys by using a string.
    // eslint-disable-next-line no-restricted-syntax
    HTMLMediaElement.prototype['mediaKeys'] = null;
    // eslint-disable-next-line no-restricted-syntax
    HTMLMediaElement.prototype.setMediaKeys = PatchedMediaKeysNop.setMediaKeys;
    // These are not usable, but allow Player.isBrowserSupported to pass.
    window.MediaKeys = PatchedMediaKeysNop.MediaKeys;
    window.MediaKeySystemAccess = PatchedMediaKeysNop.MediaKeySystemAccess;

    window.shakaMediaKeysPolyfill = true;
  }

  /**
   * An implementation of navigator.requestMediaKeySystemAccess.
   * Retrieves a MediaKeySystemAccess object.
   *
   * @this {!Navigator}
   * @param {string} keySystem
   * @param {!Array.<!MediaKeySystemConfiguration>} supportedConfigurations
   * @return {!Promise.<!MediaKeySystemAccess>}
   */
  static requestMediaKeySystemAccess(keySystem, supportedConfigurations) {
    shaka.log.debug('PatchedMediaKeysNop.requestMediaKeySystemAccess');
    goog.asserts.assert(this == navigator,
        'bad "this" for requestMediaKeySystemAccess');

    return Promise.reject(new Error(
        'The key system specified is not supported.'));
  }

  /**
   * An implementation of HTMLMediaElement.prototype.setMediaKeys.
   * Attaches a MediaKeys object to the media element.
   *
   * @this {!HTMLMediaElement}
   * @param {MediaKeys} mediaKeys
   * @return {!Promise}
   */
  static setMediaKeys(mediaKeys) {
    shaka.log.debug('PatchedMediaKeysNop.setMediaKeys');
    goog.asserts.assert(this instanceof HTMLMediaElement,
        'bad "this" for setMediaKeys');

    if (mediaKeys == null) {
      return Promise.resolve();
    }

    return Promise.reject(new Error('MediaKeys not supported.'));
  }
};


/**
 * An unusable constructor for MediaKeys.
 * @implements {MediaKeys}
 */
shaka.polyfill.PatchedMediaKeysNop.MediaKeys = class {
  /** */
  constructor() {
    throw new TypeError('Illegal constructor.');
  }

  /** @override */
  createSession() {}

  /** @override */
  setServerCertificate() {}

  /** @override */
  getStatusForPolicy(policy) {
    return Promise.resolve('usable');
  }
};


/**
 * An unusable constructor for MediaKeySystemAccess.
 * @implements {MediaKeySystemAccess}
 */
shaka.polyfill.PatchedMediaKeysNop.MediaKeySystemAccess = class {
  /** */
  constructor() {
    /** @override */
    this.keySystem = '';  // For the compiler.

    throw new TypeError('Illegal constructor.');
  }

  /** @override */
  getConfiguration() {}

  /** @override */
  createMediaKeys() {}
};


// A low priority ensures this is the last and acts as a fallback.
shaka.polyfill.register(shaka.polyfill.PatchedMediaKeysNop.install, -10);