encodeNevent static method

String encodeNevent({ required String eventId, List<String>? relays, String? author, int? kind, })

Encode nevent (event reference) eventId - 32-byte hex event ID (required) relays - optional list of relay URLs where the event may be found author - optional 32-byte hex public key of the event author kind - optional event kind number

Implementation

static String encodeNevent({
  required String eventId,
  List<String>? relays,
  String? author,
  int? kind,
}) {
  final tlvData = <int>[];

  // Type 0: event ID (special) - 32 bytes
  final eventIdBytes = hex.decode(eventId);
  if (eventIdBytes.length != 32) {
    throw ArgumentError('Event ID must be 32 bytes (64 hex characters)');
  }
  tlvData.add(0); // type
  tlvData.add(32); // length
  tlvData.addAll(eventIdBytes); // value

  // Type 1: relays (optional, can be multiple)
  if (relays != null) {
    for (final relay in relays) {
      final relayBytes = utf8.encode(relay);
      if (relayBytes.length > 255) {
        throw ArgumentError(
            'Relay URL too long: ${relay.length} bytes (max 255)');
      }
      tlvData.add(1); // type
      tlvData.add(relayBytes.length); // length
      tlvData.addAll(relayBytes); // value
    }
  }

  // Type 2: author pubkey (optional, 32 bytes)
  if (author != null) {
    final authorBytes = hex.decode(author);
    if (authorBytes.length != 32) {
      throw ArgumentError(
          'Author pubkey must be 32 bytes (64 hex characters)');
    }
    tlvData.add(2); // type
    tlvData.add(32); // length
    tlvData.addAll(authorBytes); // value
  }

  // Type 3: kind (optional, 32-bit unsigned big-endian)
  if (kind != null) {
    final kindBytes = [
      (kind >> 24) & 0xFF,
      (kind >> 16) & 0xFF,
      (kind >> 8) & 0xFF,
      kind & 0xFF,
    ];
    tlvData.add(3); // type
    tlvData.add(4); // length (32-bit = 4 bytes)
    tlvData.addAll(kindBytes); // value
  }

  // Convert to bech32
  final data = Nip19Utils.convertBits(tlvData, 8, 5, true);
  var encoder = Bech32Encoder();
  Bech32 input = Bech32(Hrps.kNevent, data);
  var encoded = encoder.convert(input, input.hrp.length + data.length + 10);
  return encoded;
}