/**
 * Copyright 2021 Google LLC
 *
 * 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.
 */

/**
 * This application demonstrates how to perform basic operations on buckets with
 * the Google Cloud Storage API.
 *
 * For more information, see the README.md under /storage and the documentation
 * at https://cloud.google.com/storage/docs.
 */
const path = require('path');
const cwd = path.join(__dirname, '..');

function main(
  bucketName = 'my-bucket',
  fileName = 'test.txt',
  startByte = 0,
  endByte = 20,
  destFileName = path.join(cwd, 'downloaded.txt')
) {
  // [START storage_download_byte_range]
  /**
   * TODO(developer): Uncomment the following lines before running the sample.
   */
  // The ID of your GCS bucket
  // const bucketName = 'your-unique-bucket-name';

  // The ID of your GCS file
  // const fileName = 'your-file-name';

  // The starting byte at which to begin the download
  // const startByte = 0;

  // The ending byte at which to end the download
  // const endByte = 20;

  // The path to which the file should be downloaded
  // const destFileName = '/local/path/to/file.txt';

  // Imports the Google Cloud client library
  const {Storage} = require('@google-cloud/storage');

  // Creates a client
  const storage = new Storage();

  async function downloadByteRange() {
    const options = {
      destination: destFileName,
      start: startByte,
      end: endByte,
    };

    // Downloads the file from the starting byte to the ending byte specified in options
    await storage.bucket(bucketName).file(fileName).download(options);

    console.log(
      `gs://${bucketName}/${fileName} downloaded to ${destFileName} from byte ${startByte} to byte ${endByte}.`
    );
  }

  downloadByteRange();
  // [END storage_download_byte_range]
}
process.on('unhandledRejection', err => {
  console.error(err.message);
  process.exitCode = 1;
});
main(...process.argv.slice(2));