text: // Copyright 2013 The Closure Library Authors. All Rights Reserved.
  //
  // 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.
  
  /**
   * @fileoverview Closure user agent detection.
   * @see http://en.wikipedia.org/wiki/User_agent
   * For more information on browser brand, platform, or device see the other
   * sub-namespaces in goog.labs.userAgent (browser, platform, and device).
   */
  
  goog.provide('goog.labs.userAgent.engine');
  
  goog.require('goog.array');
  goog.require('goog.labs.userAgent.util');
  goog.require('goog.string');
  
  
  /**
   * @return {boolean} Whether the rendering engine is Presto.
   */
  goog.labs.userAgent.engine.isPresto = function() {
    return goog.labs.userAgent.util.matchUserAgent('Presto');
  };
  
  
  /**
   * @return {boolean} Whether the rendering engine is Trident.
   */
  goog.labs.userAgent.engine.isTrident = function() {
    // IE only started including the Trident token in IE8.
    return goog.labs.userAgent.util.matchUserAgent('Trident') ||
        goog.labs.userAgent.util.matchUserAgent('MSIE');
  };
  
  
  /**
   * @return {boolean} Whether the rendering engine is EdgeHTML.
   */
  goog.labs.userAgent.engine.isEdge = function() {
    return goog.labs.userAgent.util.matchUserAgent('Edge');
  };
  
  
  /**
   * @return {boolean} Whether the rendering engine is WebKit. This will return
   * true for Chrome, Blink-based Opera (15+), Edge Chromium and Safari.
   */
  goog.labs.userAgent.engine.isWebKit = function() {
    return goog.labs.userAgent.util.matchUserAgentIgnoreCase('WebKit') &&
        !goog.labs.userAgent.engine.isEdge();
  };
  
  
  /**
   * @return {boolean} Whether the rendering engine is Gecko.
   */
  goog.labs.userAgent.engine.isGecko = function() {
    return goog.labs.userAgent.util.matchUserAgent('Gecko') &&
        !goog.labs.userAgent.engine.isWebKit() &&
        !goog.labs.userAgent.engine.isTrident() &&
        !goog.labs.userAgent.engine.isEdge();
  };
  
  
  /**
   * @return {string} The rendering engine's version or empty string if version
   *     can't be determined.
   */
  goog.labs.userAgent.engine.getVersion = function() {
    var userAgentString = goog.labs.userAgent.util.getUserAgent();
    if (userAgentString) {
      var tuples = goog.labs.userAgent.util.extractVersionTuples(userAgentString);
  
      var engineTuple = goog.labs.userAgent.engine.getEngineTuple_(tuples);
      if (engineTuple) {
        // In Gecko, the version string is either in the browser info or the
        // Firefox version.  See Gecko user agent string reference:
        // http://goo.gl/mULqa
        if (engineTuple[0] == 'Gecko') {
          return goog.labs.userAgent.engine.getVersionForKey_(tuples, 'Firefox');
        }
  
        return engineTuple[1];
      }
  
      // MSIE has only one version identifier, and the Trident version is
      // specified in the parenthetical. IE Edge is covered in the engine tuple
      // detection.
      var browserTuple = tuples[0];
      var info;
      if (browserTuple && (info = browserTuple[2])) {
        var match = /Trident\/([^\s;]+)/.exec(info);
        if (match) {
          return match[1];
        }
      }
    }
    return '';
  };
  
  
  /**
   * @param {!Array<!Array<string>>} tuples Extracted version tuples.
   * @return {!Array<string>|undefined} The engine tuple or undefined if not
   *     found.
   * @private
   */
  goog.labs.userAgent.engine.getEngineTuple_ = function(tuples) {
    if (!goog.labs.userAgent.engine.isEdge()) {
      return tuples[1];
    }
    for (var i = 0; i < tuples.length; i++) {
      var tuple = tuples[i];
      if (tuple[0] == 'Edge') {
        return tuple;
      }
    }
  };
  
  
  /**
   * @param {string|number} version The version to check.
   * @return {boolean} Whether the rendering engine version is higher or the same
   *     as the given version.
   */
  goog.labs.userAgent.engine.isVersionOrHigher = function(version) {
    return goog.string.compareVersions(
               goog.labs.userAgent.engine.getVersion(), version) >= 0;
  };
  
  
  /**
   * @param {!Array<!Array<string>>} tuples Version tuples.
   * @param {string} key The key to look for.
   * @return {string} The version string of the given key, if present.
   *     Otherwise, the empty string.
   * @private
   */
  goog.labs.userAgent.engine.getVersionForKey_ = function(tuples, key) {
    // TODO(user): Move to util if useful elsewhere.
  
    var pair = goog.array.find(tuples, function(pair) { return key == pair[0]; });
  
    return pair && pair[1] || '';
  };
  