/**
 * WebSocket Configuration and Connection Management
 * Handles Socket.IO server initialization and connection management
 */

const { Server } = require('socket.io');
const logger = require('../utils/logger');

// Configuration
const WEBSOCKET_CONFIG = {
  cors: {
    origin: process.env.WEBSOCKET_CORS_ORIGIN?.split(',') || ['http://localhost:3000', 'http://localhost:3001'],
    methods: ['GET', 'POST'],
    credentials: true,
  },
  pingTimeout: parseInt(process.env.WEBSOCKET_PING_TIMEOUT) || 20000,
  pingInterval: parseInt(process.env.WEBSOCKET_PING_INTERVAL) || 25000,
  maxHttpBufferSize: parseInt(process.env.WEBSOCKET_MAX_BUFFER_SIZE) || 1e6, // 1MB
  transports: ['websocket', 'polling'],
  allowEIO3: true,
  compression: true,
  httpCompression: true,
};

let io = null;
let connectionCount = 0;
const connectedClients = new Map();

/**
 * Initialize WebSocket server
 * @param {Object} server - HTTP server instance
 * @returns {Promise<Object>} Socket.IO server instance
 */
async function initializeWebSocket(server) {
  try {
    if (io) {
      logger.info('WebSocket server already initialized');
      return io;
    }

    // Create Socket.IO server
    io = new Server(server, WEBSOCKET_CONFIG);

    // Set up middleware for authentication and logging
    io.use(async (socket, next) => {
      const correlationId = socket.handshake.query.correlationId || require('uuid').v4();
      socket.correlationId = correlationId;

      logger.info('WebSocket connection attempt', {
        correlationId,
        socketId: socket.id,
        ip: socket.handshake.address,
        userAgent: socket.handshake.headers['user-agent'],
      });

      next();
    });

    // Connection event handler
    io.on('connection', (socket) => {
      connectionCount++;
      connectedClients.set(socket.id, {
        connectedAt: new Date(),
        ip: socket.handshake.address,
        userAgent: socket.handshake.headers['user-agent'],
        playerId: null, // Will be set after authentication
        rooms: new Set(),
      });

      logger.info('WebSocket client connected', {
        correlationId: socket.correlationId,
        socketId: socket.id,
        totalConnections: connectionCount,
        ip: socket.handshake.address,
      });

      // Set up event handlers
      setupSocketEventHandlers(socket);

      // Handle disconnection
      socket.on('disconnect', (reason) => {
        connectionCount--;
        const clientInfo = connectedClients.get(socket.id);
        connectedClients.delete(socket.id);

        logger.info('WebSocket client disconnected', {
          correlationId: socket.correlationId,
          socketId: socket.id,
          reason,
          totalConnections: connectionCount,
          playerId: clientInfo?.playerId,
          connectionDuration: clientInfo ? Date.now() - clientInfo.connectedAt : 0,
        });
      });

      // Handle connection errors
      socket.on('error', (error) => {
        logger.error('WebSocket connection error', {
          correlationId: socket.correlationId,
          socketId: socket.id,
          error: error.message,
          stack: error.stack,
        });
      });
    });

    // Server-level error handling
    io.engine.on('connection_error', (error) => {
      logger.error('WebSocket connection error:', {
        message: error.message,
        code: error.code,
        context: error.context,
      });
    });

    logger.info('WebSocket server initialized successfully', {
      maxConnections: process.env.WEBSOCKET_MAX_CONNECTIONS || 'unlimited',
      pingTimeout: WEBSOCKET_CONFIG.pingTimeout,
      pingInterval: WEBSOCKET_CONFIG.pingInterval,
    });

    return io;

  } catch (error) {
    logger.error('Failed to initialize WebSocket server:', error);
    throw error;
  }
}

/**
 * Set up event handlers for individual socket connections
 * @param {Object} socket - Socket.IO socket instance
 */
function setupSocketEventHandlers(socket) {
  // Player authentication
  socket.on('authenticate', async (data) => {
    try {
      logger.info('WebSocket authentication attempt', {
        correlationId: socket.correlationId,
        socketId: socket.id,
        playerId: data?.playerId,
      });

      // TODO: Implement JWT token validation
      // For now, just acknowledge
      socket.emit('authenticated', {
        success: true,
        message: 'Authentication successful',
      });

      // Update client information
      if (connectedClients.has(socket.id)) {
        connectedClients.get(socket.id).playerId = data?.playerId;
      }

    } catch (error) {
      logger.error('WebSocket authentication error', {
        correlationId: socket.correlationId,
        socketId: socket.id,
        error: error.message,
      });

      socket.emit('authentication_error', {
        success: false,
        message: 'Authentication failed',
      });
    }
  });

  // Join room (for game features like galaxy regions, player groups, etc.)
  socket.on('join_room', (roomName) => {
    if (typeof roomName !== 'string' || roomName.length > 50) {
      socket.emit('error', { message: 'Invalid room name' });
      return;
    }

    socket.join(roomName);

    const clientInfo = connectedClients.get(socket.id);
    if (clientInfo) {
      clientInfo.rooms.add(roomName);
    }

    logger.info('Client joined room', {
      correlationId: socket.correlationId,
      socketId: socket.id,
      room: roomName,
      playerId: clientInfo?.playerId,
    });

    socket.emit('room_joined', { room: roomName });
  });

  // Leave room
  socket.on('leave_room', (roomName) => {
    socket.leave(roomName);

    const clientInfo = connectedClients.get(socket.id);
    if (clientInfo) {
      clientInfo.rooms.delete(roomName);
    }

    logger.info('Client left room', {
      correlationId: socket.correlationId,
      socketId: socket.id,
      room: roomName,
      playerId: clientInfo?.playerId,
    });

    socket.emit('room_left', { room: roomName });
  });

  // Ping/pong for connection testing
  socket.on('ping', () => {
    socket.emit('pong', { timestamp: Date.now() });
  });

  // Generic message handler (for debugging)
  socket.on('message', (data) => {
    logger.debug('WebSocket message received', {
      correlationId: socket.correlationId,
      socketId: socket.id,
      data: typeof data === 'object' ? JSON.stringify(data) : data,
    });
  });
}

/**
 * Get WebSocket server instance
 * @returns {Object|null} Socket.IO server instance
 */
function getWebSocketServer() {
  return io;
}

/**
 * Get connection statistics
 * @returns {Object} Connection statistics
 */
function getConnectionStats() {
  return {
    totalConnections: connectionCount,
    authenticatedConnections: Array.from(connectedClients.values())
      .filter(client => client.playerId).length,
    anonymousConnections: Array.from(connectedClients.values())
      .filter(client => !client.playerId).length,
    rooms: io ? Array.from(io.sockets.adapter.rooms.keys()) : [],
  };
}

/**
 * Broadcast message to all connected clients
 * @param {string} event - Event name
 * @param {Object} data - Data to broadcast
 */
function broadcastToAll(event, data) {
  if (!io) {
    logger.warn('Attempted to broadcast but WebSocket server not initialized');
    return;
  }

  io.emit(event, data);
  logger.info('Broadcast sent to all clients', {
    event,
    recipientCount: connectionCount,
  });
}

/**
 * Broadcast message to specific room
 * @param {string} room - Room name
 * @param {string} event - Event name
 * @param {Object} data - Data to broadcast
 */
function broadcastToRoom(room, event, data) {
  if (!io) {
    logger.warn('Attempted to broadcast to room but WebSocket server not initialized');
    return;
  }

  io.to(room).emit(event, data);
  logger.info('Broadcast sent to room', {
    room,
    event,
    recipientCount: io.sockets.adapter.rooms.get(room)?.size || 0,
  });
}

/**
 * Close WebSocket server gracefully
 * @returns {Promise<void>}
 */
async function closeWebSocket() {
  if (!io) return;

  try {
    // Disconnect all clients
    io.disconnectSockets();

    // Close server
    io.close();

    io = null;
    connectionCount = 0;
    connectedClients.clear();

    logger.info('WebSocket server closed gracefully');
  } catch (error) {
    logger.error('Error closing WebSocket server:', error);
    throw error;
  }
}

module.exports = {
  initializeWebSocket,
  getWebSocketServer,
  getConnectionStats,
  broadcastToAll,
  broadcastToRoom,
  closeWebSocket,
};