all files / lighthouse-core/formatters/ formatter.js

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/**
 * @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
 *
 *     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.
 */
 
'use strict';
 
class Formatter {
 
  static get CAPITAL_LETTERS() {
    return /([A-Z])/g;
  }
 
  static get SUPPORTED_FORMATS() {
    // Get the available formatters if they don't already exist.
    if (!this._formatters) {
      this._getFormatters();
    }
 
    // From the formatters we can establish a master list of supported format names.
    if (!this._supportedFormatsNames) {
      this._generateSupportedFormats();
    }
 
    return this._supportedFormatsNames;
  }
 
  static _getFormatters() {
    this._formatters = {
      accessibility: require('./accessibility'),
      criticalRequestChains: require('./critical-request-chains'),
      null: require('./null-formatter'),
      speedline: require('./speedline-formatter'),
      userTimings: require('./user-timings')
    };
  }
 
  static _generateSupportedFormats() {
    const formatNames = Object.keys(this._formatters);
    this._supportedFormatsNames = formatNames.reduce((prev, format) => {
      // Reformulates names like criticalNetworkChains to CRITICAL_NETWORK_CHAINS so they appear
      // like a bunch of constants.
      const formatName = format.replace(Formatter.CAPITAL_LETTERS, '_$1').toUpperCase();
      prev[formatName] = format;
      return prev;
    }, {});
  }
 
  static getByName(name) {
    if (!this._formatters) {
      this._getFormatters();
    }
 
    if (!this._formatters[name]) {
      throw new Error(`Unknown formatter: ${name}`);
    }
 
    return this._formatters[name];
  }
 
  static getFormatter() {
    throw new Error('Formatter must implement getPrettyFormatter()');
  }
 
  /**
   * Optional function to get any Handlebars helpers this formatter expects to need.
   */
  static getHelpers() {}
}
 
module.exports = Formatter;