mod.ts

// Copyright 2021-Eternity Channelping. All rights reserved. MIT License.

// This is a wrapper for the CLI utility mediainfo.

const MEDIA_INFO_CMD = 'mediainfo';

// HTML and XML are other available formats. Although mediainfo documentation
// does not include JSON as one of the available output formats, it's available.
const DEFAULT_OUTPUT_FORMAT = '--Output=JSON';
const OUTPUT_FORMAT_RX = /^--Output=\w+$/;

interface Info {
  [key: string]: any
}

interface ResultObject {
  exitCode: number,
  info: Info
}

class MediaInfo {

  // Unlike mediainfo behavior, our wrapper has JSON output as the default.
  static setOutputFormat(params: Array<string>) {
    let outputOptionFound = false;
    for (const item of params) {
      if (OUTPUT_FORMAT_RX.test(item)) {
        outputOptionFound = true;
        break;
      }
    }

    if (!outputOptionFound) {
      params.push(DEFAULT_OUTPUT_FORMAT);
    }

    return params;
  }

  // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  // params represents a list of strings.
  //
  // Order is not important.
  //
  // get() returns the following JSON message shape, passed through from
  // getRaw(). The raw nested data structure is simplified to look like:
  //
  //   {
  //     "exitCode": number,
  //     "info": Array<object> | string
  //   }
  //
  // If binary command mediainfo is successful, exitCode = 0 and info is an
  // array of objects or a string.
  //
  // If binary command mediainfo is not successful, exitCode = 1 and info is a
  // string.
  // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  static async get(...params: Array<string>): Promise<ResultObject> {
    const resultTrack: ResultObject = { exitCode: 0, info: [] };
    const resultRaw: ResultObject = await MediaInfo.getRaw(...params);

    resultTrack.exitCode = resultRaw.exitCode;

    if (typeof resultRaw.info === 'object' && 'media' in resultRaw.info) {
      resultTrack.info = resultRaw.info.media.track;
    } else if (typeof resultRaw.info === 'string') {
      resultTrack.info = resultRaw.info;
    } else {
      console.error('unknown data structure returned from getRaw()');
      Deno.exit(1);
    }

    return resultTrack;
  }

  // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  // params represents a list of strings.
  //
  // Order is not important.
  //
  // getRaw() returns the following data structure, derived from mediainfo
  // binary return value:
  //
  //   {
  //     "exitCode": number,
  //     "info": object {
  //       "media": object {
  //         "@ref": string,
  //         "track": Array<object>
  //       }
  //     }
  //   }
  // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  static async getRaw(...params: Array<string>): Promise<ResultObject> {
    const result = { exitCode: 0, info: {} };

    const options = MediaInfo.setOutputFormat(params) ;

    const cmd = Deno.run({
      cmd:[MEDIA_INFO_CMD, ...options],
      stdin: 'piped', stdout: 'piped'
    });

    const rawOutput = await cmd.output();
    const outputString = new TextDecoder().decode(rawOutput);

    // JSON output may have been a specified option, but if there were other
    // options included as well, e.g., --Version, then the mediainfo command
    // returns non-JSON version information instead of getting specified media
    // file's info in JSON format. That's an expected case and is not an error.
    // It is handled as such in the catch block.
    try {
      result.info = JSON.parse(outputString);
    } catch (requiredArgButNotNecessary) {
      result.info = outputString.replace(/\n$/, '');
    }

    const { code } = await cmd.status();
    result.exitCode = code;

    cmd.stdin.close();
    cmd.close();

    return result;
  }

  static async isMediaInfoCommandExist() {
    const cmd = Deno.run({
      cmd:['bash', 'which', MEDIA_INFO_CMD],
      stdout: 'piped'
    });
    try {
      const { code } = await cmd.status();
      cmd.stdout.close();
      cmd.close();
      return code === 0;
    } catch (e) {
      console.info('cmd.status() error:', e);
      Deno.exit(1);
    }
  }
} // end class

// Make sure mediainfo is available on the system
MediaInfo.isMediaInfoCommandExist().then((cmdExists) => {
  if (!cmdExists) {
    console.error(`"${MEDIA_INFO_CMD}" command not found.`);
    Deno.exit(1);
  }
});

export { MediaInfo as mediainfo };