import 'dart:async';
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:chepuhagram/logic/auth_provider.dart';
import 'package:chepuhagram/logic/contact_provider.dart';
import 'package:chepuhagram/presentation/screens/login_screen.dart';
import 'package:chepuhagram/presentation/screens/contacts_screen.dart';
import 'package:chepuhagram/presentation/screens/account_setup_screen.dart';
import 'package:chepuhagram/presentation/screens/key_recovery_screen.dart';
import 'package:chepuhagram/presentation/screens/chat_screen.dart';
import 'package:firebase_messaging/firebase_messaging.dart';
import 'package:chepuhagram/main.dart';
import 'package:shared_preferences/shared_preferences.dart';
import 'dart:convert';
import 'package:chepuhagram/domain/services/crypto_service.dart';
import 'package:cryptography/cryptography.dart';
import 'package:flutter/foundation.dart';
import 'package:chepuhagram/core/theme_manager.dart';
import 'dart:ui';
import 'dart:io';

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

  @override
  State<SplashScreen> createState() => _SplashScreenState();
}

class _SplashScreenState extends State<SplashScreen>
    with TickerProviderStateMixin {
  int? _targetChatId;
  String? _statusMessage;

  late AnimationController _fadeController;
  late AnimationController _pulseController;
  late Animation<double> _fadeAnimation;
  late Animation<double> _pulseAnimation;

  static const String _notificationLaunchKey = 'notification_launch_data';
  static const String _contactPublicKey = 'contact_public_key_';
  static const String _contactSharedKey = 'contact_shared_key_';

  @override
  void initState() {
    super.initState();
    _fadeController = AnimationController(
        vsync: this, duration: const Duration(milliseconds: 800));
    _pulseController = AnimationController(
        vsync: this, duration: const Duration(milliseconds: 1200));

    _fadeAnimation =
        Tween<double>(begin: 0.0, end: 1.0).animate(CurvedAnimation(
      parent: _fadeController,
      curve: Curves.easeIn,
    ));

    _pulseAnimation = Tween<double>(begin: 1.0, end: 1.15)
        .animate(CurvedAnimation(
      parent: _pulseController,
      curve: Curves.easeInOut,
    ));

    _pulseController.repeat(reverse: true);
    _fadeController.forward();

    _setupNotificationHandler();
    _initializeApp();
  }

  void _setupNotificationHandler() {
    FirebaseMessaging.onMessageOpenedApp.listen((RemoteMessage message) {
      if (message.data['type'] == 'enc_message') {
        final senderId = int.tryParse(message.data['sender_id']?.toString() ?? '');
        if (senderId != null) {
          setState(() => _targetChatId = senderId);
        }
      }
    });
  }

  Future<void> _initializeApp() async {
    if (!mounted) return;
    setState(() => _statusMessage = "Подключение...");

    final authProvider = context.read<AuthProvider>();
    bool? isLoggedIn;
    try {
      isLoggedIn = await authProvider.tryAutoLogin();
    } catch (e) {
      setState(() => _statusMessage = 'Ошибка входа: ${e.toString().replaceAll('Exception: ', '')}');
      await Future.delayed(const Duration(seconds: 3));
      if (mounted) _navigateTo(const LoginScreen());
      return;
    }

    if (!mounted) return;

    if (isLoggedIn) {
      setState(() => _statusMessage = "Аутентификация...");
      bool connected = false;
      int connectAttempt = 1;
      while (!connected) {
        try {
          await authProvider.initRealtime();
          connected = true;
        } catch (e) {
          setState(() => _statusMessage = 'Соединение... (попытка $connectAttempt)');
          connectAttempt++;
          await Future.delayed(const Duration(seconds: 2));
        }
      }
      
      setState(() => _statusMessage = "Загрузка профиля...");
      await authProvider.refreshMe();

      if (authProvider.needsSetup) {
        _navigateTo(const AccountSetupScreen());
      } else if (authProvider.needsKeyRecovery) {
        _navigateTo(const KeyRecoveryScreen());
      } else {
        setState(() => _statusMessage = "Загрузка контактов...");
        _loadContactsAndNavigate(authProvider.currentUserId);
      }
    } else {
      _navigateTo(const LoginScreen());
    }
  }

  Future<void> _loadContactsAndNavigate(int? currentUserId) async {
    // Navigate to ContactsScreen while contacts are loading in the background
    _navigateTo(ContactsScreen(targetChatId: await _getTargetChatId()));

    try {
      final contactProvider = context.read<ContactProvider>();
      contactProvider.setCurrentUserId(currentUserId);
      await contactProvider.loadContacts(enrichContacts: false);

      final prefs = await SharedPreferences.getInstance();
      final myPrivKeyBase64 = await context.read<CryptoService>().getPrivateKey();

      if (myPrivKeyBase64 != null) {
        final Map<int, String> keysToCompute = {};
        for (var c in contactProvider.contacts) {
          final savedKeyHex = prefs.getString('$_contactSharedKey${c.id}');
          final savedPubKey = prefs.getString('$_contactPublicKey${c.id}');
          if (savedKeyHex != null && savedPubKey == c.publicKey) {
            contactProvider.setSharedKey(c.id, SecretKey(base64Decode(savedKeyHex)));
          } else if (c.publicKey != null) {
            keysToCompute[c.id] = c.publicKey!;
          }
        }
        
        final computedKeys = await compute(
          CryptoService.computeSharedKeysTask,
          {'keysMap': keysToCompute, 'privKey': myPrivKeyBase64},
        );

        computedKeys.forEach((id, bytes) {
          contactProvider.setSharedKey(id, SecretKey(bytes));
          prefs.setString('$_contactSharedKey$id', base64Encode(bytes));
          prefs.setString('$_contactPublicKey$id', keysToCompute[id]!);
        });
      }
    } catch (e) {
      print("Ошибка при фоновой загрузке контактов или ключей: $e");
    }
  }

  Future<int?> _getTargetChatId() async {
    int? targetChatId = _targetChatId;
    final prefs = await SharedPreferences.getInstance();
    
    if (targetChatId == null) {
      final savedData = prefs.getString(_notificationLaunchKey);
      if (savedData != null) {
        try {
          final data = jsonDecode(savedData) as Map<String, dynamic>;
          targetChatId = int.tryParse(data['sender_id']?.toString() ?? '');
        } catch (e) {
          print('Error parsing saved notification data: $e');
        }
      }
    }

    if (targetChatId == null && initialMessage != null) {
      if (initialMessage!.data['type'] == 'enc_message') {
        targetChatId = int.tryParse(initialMessage!.data['sender_id']?.toString() ?? '');
      }
    }

    await prefs.remove(_notificationLaunchKey);
    return targetChatId;
  }

  void _navigateTo(Widget screen) {
    if (mounted) {
      Navigator.pushReplacement(
        context,
        MaterialPageRoute(builder: (_) => screen),
      );
    }
  }

  @override
  void dispose() {
    _fadeController.dispose();
    _pulseController.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    final themeProv = context.watch<ThemeProvider>();
    final colorScheme = Theme.of(context).colorScheme;

    return Scaffold(
      body: Stack(
        children: [
          if (themeProv.wallpaperPath != null)
            Container(
              decoration: BoxDecoration(
                image: DecorationImage(
                  image: FileImage(File(themeProv.wallpaperPath!)),
                  fit: BoxFit.cover,
                ),
              ),
            ),
          if (themeProv.wallpaperPath != null)
            BackdropFilter(
              filter: ImageFilter.blur(sigmaX: 15, sigmaY: 15),
              child: Container(color: Colors.black.withOpacity(0.1)),
            ),

          Center(
            child: FadeTransition(
              opacity: _fadeAnimation,
              child: Column(
                mainAxisAlignment: MainAxisAlignment.center,
                children: [
                  const Spacer(),
                  ScaleTransition(
                    scale: _pulseAnimation,
                    child: Icon(
                      Icons.messenger_outline,
                      size: 80,
                      color: colorScheme.primary,
                    ),
                  ),
                  const SizedBox(height: 24),
                  Text(
                    "Chepuhagram",
                    style: TextStyle(
                      color: colorScheme.primary,
                      fontSize: 32,
                      fontWeight: FontWeight.bold,
                      letterSpacing: 1.2,
                    ),
                  ),
                  const SizedBox(height: 80),
                  SizedBox(
                    height: 40,
                    child: AnimatedSwitcher(
                      duration: const Duration(milliseconds: 300),
                      child: _statusMessage != null
                        ? Text(
                            _statusMessage!,
                            key: ValueKey(_statusMessage),
                            style: TextStyle(
                              color: colorScheme.outline,
                              fontSize: 14,
                            ),
                            textAlign: TextAlign.center,
                          )
                        : const SizedBox.shrink(),
                    ),
                  ),
                  const CircularProgressIndicator(),
                  const Spacer(),
                  Text(
                    'Made by ArturKarasevich',
                    style: TextStyle(
                      color: colorScheme.outline,
                      fontSize: 12,
                    ),
                  ),
                  const SizedBox(height: 40),
                ],
              ),
            ),
          ),
        ],
      ),
    );
  }
}