import 'dart:async';
import 'dart:developer';
import 'package:flutter/foundation.dart';
import 'package:signalr_netcore/hub_connection.dart';
import 'package:signalr_netcore/signalr_client.dart';
import 'package:test_sa/controllers/api_routes/urls.dart';

class SignalRService {
  // Singleton instance - DO NOT instantiate directly, use DI (Provider)
  static final SignalRService _instance = SignalRService._internal();
  factory SignalRService() => _instance;
  SignalRService._internal() {
    log('🏗️ [SIGNALR] SignalRService singleton created (hashCode: ${hashCode})', name: 'SignalRService');
  }

  // Single HubConnection instance - ONLY created and managed by this service
  HubConnection? _hubConnection;

  // Connection state management
  bool _isInitializing = false;
  Completer<bool>? _initializationCompleter;

  // Authentication data
  String? _userId;
  String? _authToken;
  String? _currentConversationId;

  // Event handler registrations for re-registration after reconnect
  final Map<String, List<Function(List<Object?>?)>> _eventHandlers = {};

  // Connection state stream for reactive updates
  final StreamController<HubConnectionState> _connectionStateController =
      StreamController<HubConnectionState>.broadcast();

  /// Stream of connection state changes for consumers to listen
  Stream<HubConnectionState> get connectionStateStream => _connectionStateController.stream;

  /// Get the current HubConnection (read-only access)
  HubConnection? get hubConnection => _hubConnection;

  /// Check if connected
  bool get isConnected => _hubConnection?.state == HubConnectionState.Connected;

  /// Get current connection state
  HubConnectionState? get connectionState => _hubConnection?.state;

  /// Get connection ID (for debugging and verification)
  String? get connectionId => _hubConnection?.connectionId;

  /// Initialize SignalR connection with authentication
  /// Thread-safe: Multiple callers will wait for the same connection task
  Future<bool> initialize({
    required String userId,
    required String authToken,
    String? conversationId,
  }) async {
    log('═══════════════════════════════════════════', name: 'SignalRService');
    log('🔌 [SIGNALR] initialize() called', name: 'SignalRService');
    log('   Instance hashCode: ${hashCode}', name: 'SignalRService');
    log('   User ID: $userId', name: 'SignalRService');
    log('   Conversation ID: ${conversationId ?? "none"}', name: 'SignalRService');

    // THREAD SAFETY: If already initializing, wait for current initialization
    if (_isInitializing && _initializationCompleter != null) {
      log('⏳ [SIGNALR] Already initializing, waiting for completion...', name: 'SignalRService');
      return await _initializationCompleter!.future;
    }

    // If already connected with same credentials, reuse connection
    if (isConnected && _userId == userId && _authToken == authToken) {
      log('✅ [SIGNALR] Already connected with same credentials', name: 'SignalRService');
      log('   Connection ID: ${_hubConnection?.connectionId}', name: 'SignalRService');

      // Join new conversation if provided and different
      if (conversationId != null && conversationId != _currentConversationId) {
        await _joinConversation(conversationId);
      }

      log('═══════════════════════════════════════════', name: 'SignalRService');
      return true;
    }

    // Start new initialization
    _isInitializing = true;
    _initializationCompleter = Completer<bool>();

    try {
      // Store credentials
      _userId = userId;
      _authToken = authToken;
      _currentConversationId = conversationId;

      // Dispose existing connection if any
      await _disposeConnection();

      // Create new connection
      log('🔧 [SIGNALR] Creating new HubConnection...', name: 'SignalRService');
      log('   URL: ${URLs.chatHubUrlChat}', name: 'SignalRService');

      final httpOp = HttpConnectionOptions(
        skipNegotiation: false,
        logMessageContent: kDebugMode,
        transport: HttpTransportType.WebSockets, // Use WebSockets
        requestTimeout: 30000, // 30 seconds timeout
      );

      _hubConnection = HubConnectionBuilder()
          .withUrl(
            "${URLs.chatHubUrlChat}?UserId=$userId&source=Desktop&access_token=$authToken",
            options: httpOp,
          )
          .withAutomaticReconnect(retryDelays: <int>[2000, 5000, 10000, 20000])
          .build();

      log('✅ [SIGNALR] HubConnection created (hashCode: ${_hubConnection.hashCode})', name: 'SignalRService');

      // Setup reconnection handlers BEFORE starting connection
      _setupReconnectionHandlers();

      // Start connection with timeout
      log('🔌 [SIGNALR] Starting connection...', name: 'SignalRService');

      try {
        final startFuture = _hubConnection!.start();
        if (startFuture != null) {
          await startFuture.timeout(
            const Duration(seconds: 30),
            onTimeout: () {
              throw TimeoutException('SignalR connection timeout after 30 seconds');
            },
          );
        } else {
          log('⚠️ [SIGNALR] start() returned null, checking state...', name: 'SignalRService');
        }
      } catch (e) {
        log('❌ [SIGNALR] Connection start failed: $e', name: 'SignalRService');
        rethrow;
      }

      // Verify connection state
      if (_hubConnection!.state != HubConnectionState.Connected) {
        throw Exception('SignalR failed to connect. State: ${_hubConnection!.state}');
      }

      log('✅ [SIGNALR] Connection established', name: 'SignalRService');
      log('   Connection ID: ${_hubConnection!.connectionId}', name: 'SignalRService');
      log('   Connection State: ${_hubConnection!.state}', name: 'SignalRService');

      // Emit connected state
      _connectionStateController.add(HubConnectionState.Connected);

      // Join conversation if provided
      if (conversationId != null) {
        await _joinConversation(conversationId);
      }

      // Re-register all event handlers
      _reregisterAllHandlers();

      _isInitializing = false;
      _initializationCompleter?.complete(true);
      log('═══════════════════════════════════════════', name: 'SignalRService');

      return true;

    } catch (e, stackTrace) {
      log('❌ [SIGNALR] Error initializing connection: $e',
          name: 'SignalRService', error: e, stackTrace: stackTrace);
      log('   User ID: $userId', name: 'SignalRService');
      log('   URL: ${URLs.chatHubUrlChat}', name: 'SignalRService');

      _isInitializing = false;
      _initializationCompleter?.complete(false);
      log('═══════════════════════════════════════════', name: 'SignalRService');

      return false;
    }
  }

  /// Setup reconnection handlers
  void _setupReconnectionHandlers() {
    if (_hubConnection == null) return;

    _hubConnection!.onclose(({Exception? error}) {
      log('🔴 [SIGNALR] Connection closed: $error', name: 'SignalRService');
      _connectionStateController.add(HubConnectionState.Disconnected);
    });

    _hubConnection!.onreconnecting(({Exception? error}) {
      log('🟡 [SIGNALR] Reconnecting: $error', name: 'SignalRService');
      _connectionStateController.add(HubConnectionState.Reconnecting);
    });

    _hubConnection!.onreconnected(({String? connectionId}) async {
      log('🟢 [SIGNALR] Reconnected: $connectionId', name: 'SignalRService');
      _connectionStateController.add(HubConnectionState.Connected);

      // Rejoin conversation if we had one
      if (_currentConversationId != null) {
        await _joinConversation(_currentConversationId!);
      }

      // Re-register all event handlers
      _reregisterAllHandlers();

      log('✅ [SIGNALR] Reconnection complete', name: 'SignalRService');
    });
  }

  /// Join a conversation
  Future<void> _joinConversation(String conversationId) async {
    try {
      if (_hubConnection?.state != HubConnectionState.Connected) {
        log('⚠️ [SIGNALR] Cannot join conversation - not connected', name: 'SignalRService');
        return;
      }

      await _hubConnection!.invoke("JoinConversation", args: [conversationId]);
      _currentConversationId = conversationId;
      log('✅ [SIGNALR] Joined conversation: $conversationId', name: 'SignalRService');
    } catch (e) {
      log('❌ [SIGNALR] Error joining conversation: $e', name: 'SignalRService');
    }
  }

  /// Register an event handler
  /// Events are stored and automatically re-registered after reconnect
  void on(String eventName, Function(List<Object?>?) handler) {
    log('🔧 [SIGNALR] Registering handler for: $eventName', name: 'SignalRService');

    // Store handler for re-registration after reconnect
    if (!_eventHandlers.containsKey(eventName)) {
      _eventHandlers[eventName] = [];
    }

    // Check for duplicate handler
    if (_eventHandlers[eventName]!.contains(handler)) {
      log('⚠️ [SIGNALR] Handler already registered for: $eventName', name: 'SignalRService');
      return;
    }

    _eventHandlers[eventName]!.add(handler);

    // Register with SignalR if connected
    if (_hubConnection != null) {
      _hubConnection!.on(eventName, handler);
      log('✅ [SIGNALR] Handler registered for: $eventName', name: 'SignalRService');
    } else {
      log('⚠️ [SIGNALR] Handler stored but not registered (not connected): $eventName', name: 'SignalRService');
    }
  }

  /// Unregister an event handler
  void off(String eventName, [Function(List<Object?>?)? handler]) {
    log('🔧 [SIGNALR] Unregistering handler for: $eventName', name: 'SignalRService');

    if (handler != null) {
      _eventHandlers[eventName]?.remove(handler);
      if (_eventHandlers[eventName]?.isEmpty ?? false) {
        _eventHandlers.remove(eventName);
      }
    } else {
      _eventHandlers.remove(eventName);
    }

    // Unregister from SignalR if connected
    if (_hubConnection != null) {
      _hubConnection!.off(eventName, method: handler);
    }
  }

  /// Re-register all event handlers (after reconnection)
  void _reregisterAllHandlers() {
    if (_hubConnection == null) return;

    log('🔄 [SIGNALR] Re-registering ${_eventHandlers.length} event types...', name: 'SignalRService');

    int totalHandlers = 0;
    for (final entry in _eventHandlers.entries) {
      final eventName = entry.key;
      final handlers = entry.value;

      for (final handler in handlers) {
        _hubConnection!.on(eventName, handler);
        totalHandlers++;
      }
    }

    log('✅ [SIGNALR] $totalHandlers event handlers re-registered', name: 'SignalRService');
  }

  /// Invoke a SignalR method
  Future<Object?> invoke(String methodName, {List<Object>? args}) async {
    if (_hubConnection?.state != HubConnectionState.Connected) {
      throw Exception('SignalR not connected. Current state: ${_hubConnection?.state}');
    }

    log('📤 [SIGNALR] Invoking: $methodName', name: 'SignalRService');
    if (kDebugMode && args != null && args.isNotEmpty) {
      log('   Args: ${args.take(3)}${args.length > 3 ? "..." : ""}', name: 'SignalRService');
    }

    return await _hubConnection!.invoke(methodName, args: args);
  }

  /// Ensure connection is ready (connect if needed)
  /// Thread-safe: Multiple callers will wait for the same connection task
  Future<bool> ensureConnected() async {
    if (isConnected) {
      return true;
    }

    if (_userId != null && _authToken != null) {
      log('🔄 [SIGNALR] Not connected, attempting to reconnect...', name: 'SignalRService');
      return await initialize(
        userId: _userId!,
        authToken: _authToken!,
        conversationId: _currentConversationId,
      );
    }

    log('❌ [SIGNALR] Cannot reconnect - no credentials stored', name: 'SignalRService');
    return false;
  }

  /// Dispose connection
  Future<void> _disposeConnection() async {
    try {
      if (_hubConnection != null) {
        log('🔌 [SIGNALR] Disposing existing connection...', name: 'SignalRService');
        await _hubConnection!.stop();
        _hubConnection = null;
        log('✅ [SIGNALR] Connection disposed', name: 'SignalRService');
      }
    } catch (e) {
      log('⚠️ [SIGNALR] Error disposing connection: $e', name: 'SignalRService');
    }
  }

  /// Reset service (for logout)
  Future<void> reset() async {
    log('═══════════════════════════════════════════', name: 'SignalRService');
    log('🔄 [SIGNALR] Resetting service...', name: 'SignalRService');

    await _disposeConnection();

    _eventHandlers.clear();
    _userId = null;
    _authToken = null;
    _currentConversationId = null;
    _isInitializing = false;
    _initializationCompleter = null;

    log('✅ [SIGNALR] Service reset complete', name: 'SignalRService');
    log('═══════════════════════════════════════════', name: 'SignalRService');
  }

  /// Disconnect from SignalR (alias for reset)
  Future<void> disconnect() async {
    await reset();
  }

  /// Dispose stream controller (called when app is terminating)
  void dispose() {
    _connectionStateController.close();
  }
}