W3C Traceparent Header Parser

const HEX = { trace: 32, span: 16 };

export function parseTraceparent(value) {
  if (typeof value !== 'string') throw new TypeError('traceparent must be a string');
  const parts = value.trim().split('-');
  if (parts.length !== 4) throw new SyntaxError('traceparent must have 4 fields');
  const [version, traceId, spanId, flags] = parts;
  if (!/^[0-9a-f]{2}$/.test(version)) throw new SyntaxError('invalid version: ' + version);
  if (version === 'ff') throw new SyntaxError('version ff is invalid');
  if (!new RegExp('^[0-9a-f]{' + HEX.trace + '}$').test(traceId)) {
    throw new SyntaxError('invalid trace id: ' + traceId);
  }
  if (traceId === '0'.repeat(HEX.trace)) throw new SyntaxError('trace id must not be all zeros');
  if (!new RegExp('^[0-9a-f]{' + HEX.span + '}$').test(spanId)) {
    throw new SyntaxError('invalid span id: ' + spanId);
  }
  if (spanId === '0'.repeat(HEX.span)) throw new SyntaxError('span id must not be all zeros');
  if (!/^[0-9a-f]{2}$/.test(flags)) throw new SyntaxError('invalid flags: ' + flags);
  return { version, traceId, spanId, sampled: (parseInt(flags, 16) & 1) === 1 };
}