* @license Copyright 2016 Google Inc. 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
 * 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 Audit a page to see if it is using Mutation Events (and suggest
 *     MutationObservers instead).

'use strict';

const URL = require('../../lib/url-shim');
const Audit = require('../audit');
const EventHelpers = require('../../lib/event-helpers');

class NoMutationEventsAudit extends Audit {
  static get MUTATION_EVENTS() {
    return [

   * @return {!AuditMeta}
  static get meta() {
    return {
      name: 'no-mutation-events',
      description: 'Avoids Mutation Events in its own scripts',
      failureDescription: 'Uses Mutation Events in its own scripts',
      helpText: 'Mutation Events are deprecated and harm performance. Consider using Mutation ' +
          'Observers instead. [Learn more](',
      requiredArtifacts: ['URL', 'EventListeners'],

   * @param {!Artifacts} artifacts
   * @return {!AuditResult}
  static audit(artifacts) {
    let debugString;
    const listeners = artifacts.EventListeners;

    const results = listeners.filter(loc => {
      const isMutationEvent = this.MUTATION_EVENTS.includes(loc.type);
      let sameHost = URL.hostsMatch(artifacts.URL.finalUrl, loc.url);

      if (!URL.isValid(loc.url) && isMutationEvent) {
        sameHost = true;
        debugString = URL.INVALID_URL_DEBUG_STRING;

      return sameHost && isMutationEvent;

    const groupedResults = EventHelpers.groupCodeSnippetsByLocation(results);

    const headings = [
      {key: 'url', itemType: 'url', text: 'URL'},
      {key: 'type', itemType: 'code', text: 'Event'},
      {key: 'line', itemType: 'text', text: 'Line'},
      {key: 'col', itemType: 'text', text: 'Col'},
      {key: 'pre', itemType: 'code', text: 'Snippet'},
    const details = NoMutationEventsAudit.makeTableDetails(headings, groupedResults);

    return {
      rawValue: groupedResults.length === 0,
      extendedInfo: {
        value: {
          results: groupedResults,

module.exports = NoMutationEventsAudit;