import fs from 'fs';

export function setCommonNoCacheHeaders(res) {
  res.setHeader('Cache-Control', 'no-store');
  res.setHeader('Accept-Ranges', 'bytes');
}

export function headFile(res, { size, mime }) {
  setCommonNoCacheHeaders(res);
  res.setHeader('Content-Type', mime);
  res.setHeader('Content-Length', size);
  res.status(200).end();
}

export function streamFile(req, res, { filePath, mime }) {
  const stat = fs.statSync(filePath);
  const size = stat.size;
  const range = req.headers.range;
  setCommonNoCacheHeaders(res);
  if (range) {
    const match = /bytes=(\d+)-(\d+)?/.exec(range);
    let start = match?.[1] ? parseInt(match[1], 10) : 0;
    let end = match?.[2] ? parseInt(match[2], 10) : size - 1;
    if (Number.isNaN(start)) start = 0;
    if (Number.isNaN(end)) end = size - 1;
    start = Math.min(Math.max(0, start), Math.max(0, size - 1));
    end = Math.min(Math.max(start, end), Math.max(0, size - 1));
    if (start > end || start >= size) {
      res.setHeader('Content-Range', `bytes */${size}`);
      return res.status(416).end();
    }
    const chunkSize = end - start + 1;
    res.writeHead(206, {
      'Content-Range': `bytes ${start}-${end}/${size}`,
      'Content-Length': chunkSize,
      'Content-Type': mime,
    });
    fs.createReadStream(filePath, { start, end }).pipe(res);
  } else {
    res.writeHead(200, {
      'Content-Length': size,
      'Content-Type': mime,
    });
    fs.createReadStream(filePath).pipe(res);
  }
}