import 'dart:math';

final Random _rng = Random.secure();

String randomHex(int bytes) {
  final sb = StringBuffer();
  for (var i = 0; i < bytes; i++) {
    sb.write(_rng.nextInt(256).toRadixString(16).padLeft(2, '0'));
  }
  return sb.toString();
}

String uuidV4() {
  final b = List<int>.generate(16, (_) => _rng.nextInt(256));
  b[6] = (b[6] & 0x0f) | 0x40;
  b[8] = (b[8] & 0x3f) | 0x80;
  String h(int i) => b[i].toRadixString(16).padLeft(2, '0');
  return '${h(0)}${h(1)}${h(2)}${h(3)}-${h(4)}${h(5)}-${h(6)}${h(7)}-'
      '${h(8)}${h(9)}-${h(10)}${h(11)}${h(12)}${h(13)}${h(14)}${h(15)}';
}