text: // Copyright 2010 WebDriver committers
  // Copyright 2010 Google Inc.
  //
  // 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.
  
  goog.provide('bot.locators.className');
  
  goog.require('bot.Error');
  goog.require('bot.ErrorCode');
  goog.require('goog.array');
  goog.require('goog.dom');
  goog.require('goog.dom.DomHelper');
  goog.require('goog.string');
  
  
  /**
   * Tests whether the standardized W3C Selectors API are available on an
   * element.
   * @param {!(Document|Element)} root The document or element to test for CSS
   *     selector support.
   * @return {boolean} Whether or not the root supports query selector APIs.
   * @see http://www.w3.org/TR/selectors-api/
   * @private
   */
  bot.locators.className.canUseQuerySelector_ = function(root) {
    return !!(root.querySelectorAll && root.querySelector);
  };
  
  
  /**
   * Find an element by its class name.
   * @param {string} target The class name to search for.
   * @param {!(Document|Element)} root The document or element to perform the
   *     search under.
   * @return {Element} The first matching element found in the DOM, or null if no
   *     such element could be found.
   */
  bot.locators.className.single = function(target, root) {
    if (!target) {
      throw new bot.Error(bot.ErrorCode.INVALID_SELECTOR_ERROR,
                          'No class name specified');
    }
  
    target = goog.string.trim(target);
    if (target.indexOf(' ') !== -1) {
      throw new bot.Error(bot.ErrorCode.INVALID_SELECTOR_ERROR,
                          'Compound class names not permitted');
    }
  
    // Closure will not properly escape class names that contain a '.' when using
    // the native selectors API, so we have to handle this ourselves.
    if (bot.locators.className.canUseQuerySelector_(root)) {
      try {
        return root.querySelector('.' + target.replace(/\./g, '\\.')) || null;
      } catch (e) {
        throw new bot.Error(bot.ErrorCode.INVALID_SELECTOR_ERROR,
                            'An invalid or illegal class name was specified');
      }
    }
    var elements = goog.dom.getDomHelper(root).getElementsByTagNameAndClass(
        /*tagName=*/'*', /*className=*/target, root);
    return elements.length ? elements[0] : null;
  };
  
  
  /**
   * Find an element by its class name.
   * @param {string} target The class name to search for.
   * @param {!(Document|Element)} root The document or element to perform the
   *     search under.
   * @return {!goog.array.ArrayLike} All matching elements, or an empty list.
   */
  bot.locators.className.many = function(target, root) {
    if (!target) {
      throw new bot.Error(bot.ErrorCode.INVALID_SELECTOR_ERROR,
                          'No class name specified');
    }
  
    target = goog.string.trim(target);
    if (target.indexOf(' ') !== -1) {
      throw new bot.Error(bot.ErrorCode.INVALID_SELECTOR_ERROR,
                          'Compound class names not permitted');
    }
  
    // Closure will not properly escape class names that contain a '.' when using
    // the native selectors API, so we have to handle this ourselves.
    if (bot.locators.className.canUseQuerySelector_(root)) {
      try {
        return root.querySelectorAll('.' + target.replace(/\./g, '\\.'));
      } catch (e) {
        throw new bot.Error(bot.ErrorCode.INVALID_SELECTOR_ERROR,
                            'An invalid or illegal class name was specified');
      }
    }
    return goog.dom.getDomHelper(root).getElementsByTagNameAndClass(
        /*tagName=*/'*', /*className=*/target, root);
  };
  