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

import 'package:nostr/nostr.dart' as nostr;

import 'nostr_models.dart';
import 'relay_session.dart';

/// Signs and submits Nostr events through the relay WebSocket connection.
class SignedEventRelay {
  final RelaySessionNotifier _session;
  final String? _nsec;

  SignedEventRelay({
    required RelaySessionNotifier session,
    required String? nsec,
  }) : _session = session,
       _nsec = nsec;

  /// The hex pubkey derived from the signing key, or null if no key.
  String? get pubkey {
    final nsec = _nsec;
    if (nsec == null || nsec.isEmpty) return null;
    final privkeyHex = nostr.Nip19.decode(payload: nsec).data;
    if (privkeyHex.isEmpty) return null;
    return nostr.Keys(privkeyHex).public;
  }

  /// Sign and submit an event. Returns the relay's OK response as a [NostrEvent]
  /// whose `content` field contains the OK message (e.g. `"response:{...}"`
  /// for command kinds).
  Future<NostrEvent> submit({
    required int kind,
    required String content,
    required List<List<String>> tags,
    int? createdAt,
  }) async {
    final nsec = _nsec;
    if (nsec == null || nsec.isEmpty) {
      throw Exception('Cannot submit event: no signing key available');
    }

    final privkeyHex = nostr.Nip19.decode(payload: nsec).data;
    if (privkeyHex.isEmpty) {
      throw Exception('Invalid nsec');
    }

    final event = nostr.Event.from(
      kind: kind,
      content: content,
      tags: tags,
      secretKey: privkeyHex,
      createdAt: createdAt,
      verify: false,
    );

    final nostrEvent = NostrEvent.fromJson(event.toMap());
    return _session.publish(nostrEvent);
  }
}