const path = require('path');
const fs = require('fs');
const spawn = require('cross-spawn');
const logger = require('./logger');

const sendError = (res, code) => {
  res.writeHeader(code);
  res.write(code === 400 ? 'Bad Request' : 'Internal Server Error');
  res.end();
};

module.exports = async function server(req, res) {
  let sent = false;
  let filename;
  const { url, format } = req.queryParams;

  logger.info(`Request: ${req.url}`);

  if (!url) {
    sendError(res, 400);
    return;
  }

  const dataPath = path.resolve(__dirname, '../data');

  const params = [url];

  if (format) {
    params.unshift(format);
    params.unshift('--format');
  }

  logger.info(`Downloading ${url}`);
  const proc = spawn('youtube-dl', params, {
    stdio: 'pipe',
    cwd: dataPath,
  });

  proc.stdout.on('data', data => {
    const match = data.toString().match(/\[download\] Destination: (.+)/i);
    const existsMatch = data.toString().match(/\[download\] (.+) has already been downloaded/i);

    if (match !== null) {
      // eslint-disable-next-line prefer-destructuring
      filename = match[1];
    } else if (existsMatch !== null) {
      // eslint-disable-next-line prefer-destructuring
      filename = existsMatch[1];
    }
  });

  proc.on('error', err => {
    logger.error(err);
    logger.info(`child process exited with code ${err.code}`);
    if (!sent) {
      sendError(res, 500);
      sent = true;
    }
  });

  proc.on('close', code => {
    logger.info(`child process exited with code ${code}`);

    if (!filename) {
      logger.error('Failed to capture download filename');
      sendError(res, 500);
      sent = true;
      return;
    }

    const dlFilepath = path.join(__dirname, '../data', filename);
    logger.info(`Downloaded file is ${dlFilepath}`);

    if (!sent) {
      fs.readFile(dlFilepath, (err, fileBuffer) => {
        if (err) {
          sendError(res, 500);
          sent = true;
          return;
        }

        res.writeHead(200, {
          'Content-Type': 'application/octet-stream',
          'Content-Length': fileBuffer.length,
          'Content-disposition': `attachment; filename=${filename}`,
        });
        res.write(fileBuffer);
        res.end();
        sent = true;
      });
    }

    sent = true;

    // clean up the download if told to
    res.on('finish', () => {
      const { REMOVE_DOWNLOAD } = process.env;
      if (!REMOVE_DOWNLOAD) return;

      const shouldRemove = REMOVE_DOWNLOAD === '1' || REMOVE_DOWNLOAD.toLowerCase() === 'true';
      if (shouldRemove) {
        logger.info('Removing local file:', dlFilepath);
        fs.unlinkSync(dlFilepath);
      }
    });
  });
};