Chepuhagram/lib/presentation/screens/qr_login_screen.dart

import 'dart:async';
import 'dart:convert';
import 'dart:math';
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:qr_flutter/qr_flutter.dart';
import 'package:web_socket_channel/web_socket_channel.dart';
import 'package:cryptography/cryptography.dart';

import '../../core/constants.dart';
import '../../domain/services/crypto_service.dart';
import '../../domain/services/api_service.dart';
import '../../logic/auth_provider.dart';
import 'contacts_screen.dart';

class QrLoginScreen extends StatefulWidget {
  const QrLoginScreen({super.key});

  @override
  State<QrLoginScreen> createState() => _QrLoginScreenState();
}

class _QrLoginScreenState extends State<QrLoginScreen> {
  final _cryptoService = CryptoService();
  String? _roomId;
  SimpleKeyPair? _tempKeyPair;
  String? _publicKeyBase64;
  String? _deviceName;
  WebSocketChannel? _channel;
  bool _isInitializing = true;
  String? _errorMessage;
  StreamSubscription? _subscription;

  @override
  void initState() {
    super.initState();
    _initQrSession();
  }

  String _generateRandomRoomId() {
    final rand = Random.secure();
    final bytes = List<int>.generate(16, (i) => rand.nextInt(256));
    return bytes.map((b) => b.toRadixString(16).padLeft(2, '0')).join();
  }

  Future<void> _initQrSession() async {
    try {
      setState(() {
        _isInitializing = true;
        _errorMessage = null;
      });

      // 1. Генерируем ID комнаты сопряжения
      final roomId = _generateRandomRoomId();

      // 2. Генерируем временные ключи X25519 для шифрования канала
      final tempKeyPair = await _cryptoService.generateTempKeyPair();
      final publicKey = await tempKeyPair.extractPublicKey();
      final publicKeyBase64 = base64Encode(publicKey.bytes);

      // Получаем имя текущего устройства
      final apiService = ApiService();
      final deviceName = await apiService.getDeviceName();

      setState(() {
        _roomId = roomId;
        _tempKeyPair = tempKeyPair;
        _publicKeyBase64 = publicKeyBase64;
        _deviceName = deviceName;
        _isInitializing = false;
      });

      // 3. Подключаемся к WebSocket серверу сопряжения
      _connectWebSocket(roomId);
    } catch (e) {
      setState(() {
        _isInitializing = false;
        _errorMessage = 'Ошибка инициализации: $e';
      });
    }
  }

  void _connectWebSocket(String roomId) {
    try {
      final wsUri = Uri.parse('${AppConstants.wsUrl}/ws/qr?room_id=$roomId');
      _channel = WebSocketChannel.connect(wsUri);

      _subscription = _channel!.stream.listen(
        (data) {
          _handleWsMessage(data);
        },
        onError: (error) {
          setState(() {
            _errorMessage = 'Сбой подключения: $error. Переподключение...';
          });
          // Попытка переподключения через 3 секунды
          Future.delayed(const Duration(seconds: 3), () {
            if (mounted && _roomId == roomId) {
              _connectWebSocket(roomId);
            }
          });
        },
        onDone: () {
          print('QR WS соединение закрыто');
        },
      );
    } catch (e) {
      setState(() {
        _errorMessage = 'Ошибка WebSocket: $e';
      });
    }
  }

  Future<void> _handleWsMessage(dynamic rawData) async {
    try {
      final data = jsonDecode(rawData) as Map<String, dynamic>;
      if (data['type'] == 'qr_authorized') {
        final accessToken = data['access_token'] as String;
        final refreshToken = data['refresh_token'] as String;
        final userId = data['user_id'].toString();
        final phoneTempPub = data['phone_temp_pub'] as String;
        final encPrivateKeyPayload = data['enc_private_key_payload'] as String;

        if (_tempKeyPair == null) return;

        // Расшифровываем основной E2EE private_key
        final decryptedPrivateKey = await _cryptoService.decryptPrivateKeyWithEcdh(
          tempKeyPair: _tempKeyPair!,
          tempRemotePublicKeyBase64: phoneTempPub,
          encryptedPayloadBase64: encPrivateKeyPayload,
        );

        // Завершаем авторизацию и сохраняем все данные
        final authProvider = context.read<AuthProvider>();
        await authProvider.loginWithQrData(
          accessToken: accessToken,
          refreshToken: refreshToken,
          userId: userId,
          privateKey: decryptedPrivateKey,
        );

        if (mounted) {
          // Запускаем WebSocket клиент мессенджера
          await authProvider.initRealtime();

          // Перенаправляем на главный экран
          Navigator.pushAndRemoveUntil(
            context,
            MaterialPageRoute(builder: (_) => const ContactsScreen()),
            (route) => false,
          );
        }
      }
    } catch (e) {
      setState(() {
        _errorMessage = 'Не удалось завершить авторизацию: $e';
      });
    }
  }

  @override
  void dispose() {
    _subscription?.cancel();
    _channel?.sink.close();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    final colorScheme = Theme.of(context).colorScheme;

    // Содержимое QR-кода
    final encodedPublicKey = Uri.encodeComponent(_publicKeyBase64 ?? '');
    final encodedDeviceName = Uri.encodeComponent(_deviceName ?? 'Новое устройство');
    final qrData = 'chepuhagram:qr_login?room_id=$_roomId&public_key=$encodedPublicKey&device_name=$encodedDeviceName';

    return Scaffold(
      appBar: AppBar(
        title: Text('Вход по QR-коду', style: TextStyle(color: Theme.of(context).colorScheme.onSurface)),
        iconTheme: IconThemeData(color: Theme.of(context).colorScheme.onSurface),
        backgroundColor: Colors.transparent,
        elevation: 0,
      ),
      body: Center(
        child: SingleChildScrollView(
          padding: const EdgeInsets.all(24.0),
          child: ConstrainedBox(
            constraints: const BoxConstraints(maxWidth: 400),
            child: Column(
              mainAxisAlignment: MainAxisAlignment.center,
              children: [
                if (_isInitializing)
                  const Column(
                    children: [
                      CircularProgressIndicator(),
                      SizedBox(height: 16),
                      Text('Генерация сессии авторизации...'),
                    ],
                  )
                else if (_errorMessage != null && _roomId == null)
                  Column(
                    children: [
                      Icon(Icons.error_outline, size: 60, color: colorScheme.error),
                      const SizedBox(height: 16),
                      Text(_errorMessage!, textAlign: TextAlign.center),
                      const SizedBox(height: 24),
                      ElevatedButton(
                        onPressed: _initQrSession,
                        child: const Text('Повторить попытку'),
                      ),
                    ],
                  )
                else
                  Column(
                    children: [
                      Text(
                        'Войти в Чепухаграм',
                        style: TextStyle(
                          fontSize: 24,
                          fontWeight: FontWeight.bold,
                          color: colorScheme.primary,
                        ),
                      ),
                      const SizedBox(height: 12),
                      const Text(
                        'Откройте Чепухаграм на вашем телефоне, зайдите в Настройки -> Устройства -> Подключить устройство и отсканируйте код.',
                        textAlign: TextAlign.center,
                        style: TextStyle(color: Colors.grey, fontSize: 14),
                      ),
                      const SizedBox(height: 36),
                      Container(
                        padding: const EdgeInsets.all(16),
                        decoration: BoxDecoration(
                          color: Colors.white,
                          borderRadius: BorderRadius.circular(24),
                          boxShadow: [
                            BoxShadow(
                              color: Colors.black.withOpacity(0.1),
                              blurRadius: 20,
                              offset: const Offset(0, 10),
                            ),
                          ],
                        ),
                        child: QrImageView(
                          data: qrData,
                          version: QrVersions.auto,
                          size: 260.0,
                          gapless: false,
                        ),
                      ),
                      const SizedBox(height: 36),
                      if (_errorMessage != null)
                        Text(
                          _errorMessage!,
                          style: TextStyle(color: colorScheme.error, fontSize: 13),
                          textAlign: TextAlign.center,
                        )
                      else
                        const Row(
                          mainAxisAlignment: MainAxisAlignment.center,
                          children: [
                            SizedBox(
                              height: 16,
                              width: 16,
                              child: CircularProgressIndicator(strokeWidth: 2),
                            ),
                            SizedBox(width: 12),
                            Text(
                              'Ожидание сканирования...',
                              style: TextStyle(fontSize: 14, fontWeight: FontWeight.w500),
                            ),
                          ],
                        ),
                    ],
                  ),
              ],
            ),
          ),
        ),
      ),
    );
  }
}