/*
  Copyright 2018 Google LLC

  Use of this source code is governed by an MIT-style
  license that can be found in the LICENSE file or at
  https://opensource.org/licenses/MIT.
*/

const fse = require('fs-extra');
const path = require('path');
const errors = require('./errors');


// Used to filter the libraries to copy based on our package.json dependencies.
const WORKBOX_PREFIX = 'workbox-';

/**
 * This copies over a set of runtime libraries used by Workbox into a
 * local directory, which should be deployed alongside your service worker file.
 *
 * As an alternative to deploying these local copies, you could instead use
 * Workbox from its official CDN URL.
 *
 * This method is exposed for the benefit of developers using
 * [injectManifest()]{@link module:workbox-build.injectManifest} who would
 * prefer not to use the CDN copies of Workbox. Developers using
 * [generateSW()]{@link module:workbox-build.generateSW} don't need to
 * explicitly call this method, as it's called automatically when
 * `importWorkboxFrom` is set to `local`.
 *
 * @param {string} destDirectory The path to the parent directory under which
 * the new directory of libraries will be created.
 * @return {Promise<string>} The name of the newly created directory.
 *
 * @alias module:workbox-build.copyWorkboxLibraries
 */
module.exports = async (destDirectory) => {
  const thisPkg = require('../../package.json');
  // Use the version string from workbox-build in the name of the parent
  // directory. This should be safe, because lerna will bump workbox-build's
  // pkg.version whenever one of the dependent libraries gets bumped, and we
  // care about versioning the dependent libraries.
  const workboxDirectoryName = `workbox-v${thisPkg.version}`;
  const workboxDirectoryPath = path.join(destDirectory, workboxDirectoryName);
  await fse.ensureDir(workboxDirectoryPath);

  const copyPromises = [];
  const librariesToCopy = Object.keys(thisPkg.dependencies).filter(
      (dependency) => dependency.startsWith(WORKBOX_PREFIX));
  for (const library of librariesToCopy) {
    const mainFilePath = require.resolve(library);
    const srcPath = path.dirname(mainFilePath);

    // fse.copy() copies all the files in a directory, not the directory itself.
    // See https://github.com/jprichardson/node-fs-extra/blob/master/docs/copy.md#copysrc-dest-options-callback
    copyPromises.push(fse.copy(srcPath, workboxDirectoryPath));
  }

  try {
    await Promise.all(copyPromises);
    return workboxDirectoryName;
  } catch (error) {
    throw Error(`${errors['unable-to-copy-workbox-libraries']} ${error}`);
  }
};