buzz/mobile/lib/shared/relay/relay_session_auth.dart

part of 'relay_session.dart';

/// Pass the signer's hex [pubkey] when it is already known: deriving it from
/// the key costs about a third of a signature, on the UI isolate.
String buildNip98AuthHeader({
  required String method,
  required String url,
  required List<int> bodyBytes,
  required String? nsec,
  String? pubkey,
}) {
  if (nsec == null || nsec.isEmpty) {
    throw Exception('Cannot query relay: no signing key available');
  }
  final privkeyHex = nostr.Nip19.decode(payload: nsec).data;
  if (privkeyHex.isEmpty) {
    throw Exception('Invalid nsec');
  }
  final payloadHash = SHA256Digest()
      .process(Uint8List.fromList(bodyBytes))
      .map((byte) => byte.toRadixString(16).padLeft(2, '0'))
      .join();
  final event = signEvent(
    kind: 27235,
    content: '',
    tags: [
      ['u', url],
      ['method', method.toUpperCase()],
      ['payload', payloadHash],
      ['nonce', const Uuid().v4()],
    ],
    secretKey: privkeyHex,
    pubkey: pubkey,
    verify: false,
  );
  return 'Nostr ${base64.encode(utf8.encode(event.toJson()))}';
}