webvideo-clip-core/src/video-types/youtube/downloader.ts

import { spawnSync } from 'child_process';
import { convertDurationToSeconds, convertSecondsToDuration } from '../../duration';

const normalizeStartSeconds = (start?: number | string) => {
  if (typeof start === 'undefined') {
    return 0;
  }
  if (typeof start === 'string') {
    return convertDurationToSeconds(start);
  }

  return start;
};

const FORMAT_DEFAULT_ARGS = [
  '--youtube-skip-dash-manifest',
  '-f', 'bestvideo+bestaudio',
];

const constructDownloadSectionsRegex = (start?: number | string, end?: number | string) => {
  const startSeconds = normalizeStartSeconds(start);
  if (typeof end !== 'undefined') {
    const endSeconds = (
      typeof end === 'string'
        ? convertDurationToSeconds(end)
        : end
    );

    return `*${convertSecondsToDuration(startSeconds)}-${convertSecondsToDuration(endSeconds)}`;
  }

  if (startSeconds > 0) {
    return `*${convertSecondsToDuration(startSeconds)}-inf`;
  }

  return null;
};

export const getFileExtension = (downloaderExecutablePath: string, url: string) => {
  const result = spawnSync(
    downloaderExecutablePath,
    [
      ...FORMAT_DEFAULT_ARGS,
      '--print', 'filename',
      '-o', '%(ext)s',
      url,
    ],
  );

  if (result.error) {
    throw result.error;
  }

  const errorMessage = result.stderr.toString('utf-8').trim();

  if (errorMessage.length > 0) {
    throw new Error(errorMessage);
  }

  return result.stdout.toString('utf-8').trim();
};

export const constructDefaultDownloadArgs = (
  outputFilename: string,
  url: string,
  start?: number | string,
  end?: number | string,
) => {
  const defaultDownloadArgs = [
    ...FORMAT_DEFAULT_ARGS,
    '-o', outputFilename,
  ];

  const downloadSectionsRegex = constructDownloadSectionsRegex(start, end);
  if (typeof downloadSectionsRegex === 'string') {
    return [
      ...defaultDownloadArgs,
      '--force-keyframes-at-cuts',
      '--download-sections', downloadSectionsRegex,
      url,
    ];
  }

  return [
    ...defaultDownloadArgs,
    url,
  ];
};