/**
 * @license
 * Copyright (c) 2016 The Polymer Project Authors. All rights reserved.
 * This code may only be used under the BSD style license found at
 * http://polymer.github.io/LICENSE.txt
 * The complete set of authors may be found at
 * http://polymer.github.io/AUTHORS.txt
 * The complete set of contributors may be found at
 * http://polymer.github.io/CONTRIBUTORS.txt
 * Code distributed by Google as part of the polymer project is also
 * subject to an additional IP rights grant found at
 * http://polymer.github.io/PATENTS.txt
 */


import * as fs from 'fs';
import * as logging from 'plylog';
import {SWConfig} from 'polymer-build';

const logger = logging.getLogger('cli.build.load-config');

export function loadServiceWorkerConfig(configFile: string):
    Promise<SWConfig|null> {
  return new Promise<SWConfig|null>((resolve, _reject) => {
    fs.stat(configFile, (statError) => {
      let config: SWConfig|null = null;
      // only log if the config file exists at all
      if (!statError) {
        try {
          config = require(configFile);
        } catch (loadError) {
          logger.warn(
              `${configFile} file was found but could not be loaded`,
              {loadError});
        }
      }
      resolve(config);
    });
  });
}