function parseRange(rangeHeader, totalLength) {
  if (!rangeHeader) return null;
  const m = /bytes=(\d*)-(\d*)/.exec(rangeHeader);
  if (!m) return null;

  const start = m[1] ? parseInt(m[1], 10) : 0;
  const end = m[2] ? parseInt(m[2], 10) : totalLength - 1;

  if (isNaN(start) || isNaN(end) || start > end || start >= totalLength) {
    return null;
  }

  return { start, end };
}

module.exports = { parseRange };