import 'dart:convert';
import 'dart:math';

import 'package:actors/actors.dart';
import 'package:bip340/bip340.dart' as bip340;
import 'package:crypto/crypto.dart';

sealed class SignerMessage {
  const SignerMessage();
}

final class SignEvent extends SignerMessage {
  final int kind;
  final List<List<String>> tags;
  final String content;
  final int? createdAt;
  const SignEvent({
    required this.kind,
    this.tags = const [],
    required this.content,
    this.createdAt,
  });
}

final class GetPublicKey extends SignerMessage {
  const GetPublicKey();
}

sealed class SignerResult {
  const SignerResult();
}

final class EventSigned extends SignerResult {
  final String event;
  const EventSigned(this.event);
}

final class PublicKeyResult extends SignerResult {
  final String publicKey;
  const PublicKeyResult(this.publicKey);
}

class NostrSignerActor with Handler<SignerMessage, SignerResult> {
  final String _privateKey;
  final String _publicKey;

  NostrSignerActor(String privateKey)
      : _privateKey = privateKey,
        _publicKey = bip340.getPublicKey(privateKey);

  @override
  Future<SignerResult> handle(SignerMessage message) => switch (message) {
        SignEvent(:final kind, :final tags, :final content, :final createdAt) =>
          Future.value(_signEvent(kind, tags, content, createdAt)),
        GetPublicKey() => Future.value(PublicKeyResult(_publicKey)),
      };

  EventSigned _signEvent(
    int kind,
    List<List<String>> tags,
    String content,
    int? createdAt,
  ) {
    final ts = createdAt ?? DateTime.now().millisecondsSinceEpoch ~/ 1000;
    final ser = jsonEncode([0, _publicKey, ts, kind, tags, content]);
    final idBytes = sha256.convert(utf8.encode(ser)).bytes;
    final id = idBytes.map((b) => b.toRadixString(16).padLeft(2, '0')).join();

    final rng = Random.secure();
    final auxBytes = List.generate(32, (_) => rng.nextInt(256));
    final aux = auxBytes.map((b) => b.toRadixString(16).padLeft(2, '0')).join();

    final sig = bip340.sign(_privateKey, id, aux);

    return EventSigned(jsonEncode({
      'id': id,
      'pubkey': _publicKey,
      'created_at': ts,
      'kind': kind,
      'tags': tags,
      'content': content,
      'sig': sig,
    }));
  }
}