import 'dart:math';

/// Random hex id from a cryptographic RNG, e.g. for per-install identifiers.
String randomHexId({int bytes = 16}) {
  final random = Random.secure();
  return List<int>.generate(
    bytes,
    (_) => random.nextInt(256),
  ).map((b) => b.toRadixString(16).padLeft(2, '0')).join();
}

/// Random RFC 4122 version-4 UUID, for ids a server expects in UUID form.
String randomUuidV4() {
  final hex = randomHexId();
  final variant = (int.parse(hex[16], radix: 16) & 0x3 | 0x8).toRadixString(16);
  return '${hex.substring(0, 8)}-${hex.substring(8, 12)}-'
      '4${hex.substring(13, 16)}-$variant${hex.substring(17, 20)}-'
      '${hex.substring(20)}';
}