const express = require('express');
const http = require('http');
const socketIo = require('socket.io');
const mongoose = require('mongoose');
const cors = require('cors');
const bcrypt = require('bcryptjs');
const jwt = require('jsonwebtoken');
const path = require('path');
const fs = require('fs');
const helmet = require('helmet');
const rateLimit = require('express-rate-limit');
require('dotenv').config();

const app = express();
const server = http.createServer(app);

// Security middleware
app.use(helmet());

// Rate limiting
const limiter = rateLimit({
  windowMs: 15 * 60 * 1000,
  max: 1000,
  message: 'Too many requests from this IP, please try again later.'
});
app.use('/api/', limiter);

// CORS configuration
app.use(cors({
  origin: process.env.CLIENT_URL || "http://localhost:3000",
  credentials: true,
  methods: ["GET", "POST", "PUT", "DELETE", "PATCH"],
  allowedHeaders: ["Content-Type", "Authorization", "X-Requested-With"]
}));

app.use(express.json({ limit: '50mb' }));
app.use(express.urlencoded({ extended: true, limit: '50mb' }));

// Ensure uploads directory exists
const uploadsDir = path.join(__dirname, 'uploads');
if (!fs.existsSync(uploadsDir)) {
  fs.mkdirSync(uploadsDir, { recursive: true });
  console.log('📁 Created uploads directory');
}
app.use('/uploads', express.static(uploadsDir));

// Database connection
const connectDB = async () => {
  try {
    const conn = await mongoose.connect(process.env.MONGODB_URI || 'mongodb://localhost:27017/ysnrfd-messenger', {
      useNewUrlParser: true,
      useUnifiedTopology: true,
    });
    console.log(`✅ MongoDB Connected: ${conn.connection.host}`);
  } catch (error) {
    console.error('❌ Database connection error:', error);
    process.exit(1);
  }
};

// Import models
const User = require('./src/models/User');
const Conversation = require('./src/models/Conversation');
const Message = require('./src/models/Message');

// Import routes
const authRoutes = require('./src/routes/auth');
const userRoutes = require('./src/routes/users');
const conversationRoutes = require('./src/routes/conversations');
const messageRoutes = require('./src/routes/messages');
const uploadRoutes = require('./src/routes/upload');

// Use routes
app.use('/api/auth', authRoutes);
app.use('/api/users', userRoutes);
app.use('/api/conversations', conversationRoutes);
app.use('/api/messages', messageRoutes);
app.use('/api/upload', uploadRoutes);

// Socket.io configuration
const io = socketIo(server, {
  cors: {
    origin: process.env.CLIENT_URL || "http://localhost:3000",
    methods: ["GET", "POST"],
    credentials: true
  }
});

// Socket.io authentication middleware
io.use(async (socket, next) => {
  try {
    const token = socket.handshake.auth.token || socket.handshake.headers.token;
    if (!token) {
      return next(new Error('Authentication error: No token provided'));
    }
    
    const decoded = jwt.verify(token, process.env.JWT_SECRET || 'fallback-secret');
    const user = await User.findById(decoded.userId);
    
    if (!user) {
      return next(new Error('Authentication error: User not found'));
    }
    
    socket.userId = user._id;
    socket.user = user;
    next();
  } catch (error) {
    console.error('Socket authentication error:', error);
    next(new Error('Authentication error: Invalid token'));
  }
});

// Socket event handlers
io.on('connection', (socket) => {
  console.log(`🔗 User ${socket.userId} connected via WebSocket: ${socket.id}`);

  // Join user to their conversation rooms
  const joinConversationRooms = async () => {
    try {
      const conversations = await Conversation.find({
        'participants.user': socket.userId
      });
      
      conversations.forEach(conversation => {
        socket.join(conversation._id.toString());
        console.log(`👥 User ${socket.userId} joined room ${conversation._id}`);
      });
      
      // Update user status to online
      await User.findByIdAndUpdate(socket.userId, {
        status: 'online',
        lastSeen: new Date()
      });

      // Notify others that user is online
      socket.broadcast.emit('user:status', {
        userId: socket.userId,
        status: 'online',
        lastSeen: new Date()
      });
    } catch (error) {
      console.error('❌ Error joining conversation rooms:', error);
    }
  };

  // Handle new message
  socket.on('message:send', async (data) => {
    try {
      const { conversationId, content, type, attachment, replyTo } = data;

      // Validate conversation membership
      const conversation = await Conversation.findOne({
        _id: conversationId,
        'participants.user': socket.userId
      });

      if (!conversation) {
        socket.emit('message:error', { error: 'Not a member of this conversation' });
        return;
      }

      // Create message
      const message = new Message({
        conversation: conversationId,
        sender: socket.userId,
        content,
        type: type || 'text',
        attachment,
        replyTo,
        status: 'sent'
      });

      await message.save();
      await message.populate('sender', 'username displayName avatar status');
      if (message.replyTo) {
        await message.populate('replyTo');
      }

      // Update conversation last activity
      conversation.updatedAt = new Date();
      conversation.lastMessage = message._id;
      await conversation.save();

      // Emit to all users in conversation
      io.to(conversationId).emit('message:receive', message);

      // Emit conversation update
      io.to(conversationId).emit('conversation:updated', {
        conversationId,
        lastMessage: message,
        updatedAt: conversation.updatedAt
      });

      console.log(`💬 Message sent in conversation ${conversationId} by user ${socket.userId}`);

    } catch (error) {
      console.error('❌ Error sending message:', error);
      socket.emit('message:error', { error: 'Failed to send message' });
    }
  });

  // Handle typing indicators
  socket.on('typing:start', (data) => {
    const { conversationId } = data;
    socket.to(conversationId).emit('typing:start', {
      userId: socket.userId,
      conversationId
    });
  });

  socket.on('typing:stop', (data) => {
    const { conversationId } = data;
    socket.to(conversationId).emit('typing:stop', {
      userId: socket.userId,
      conversationId
    });
  });

  // Handle message read receipts
  socket.on('message:read', async (data) => {
    try {
      const { messageId, conversationId } = data;

      const message = await Message.findByIdAndUpdate(
        messageId,
        {
          $addToSet: { 
            readBy: { 
              user: socket.userId, 
              readAt: new Date() 
            } 
          }
        },
        { new: true }
      );

      if (!message) {
        return;
      }

      // Update user's last read in conversation
      await Conversation.updateOne(
        {
          _id: conversationId,
          'participants.user': socket.userId
        },
        {
          $set: {
            'participants.$.lastRead': new Date()
          }
        }
      );

      // Notify others in conversation
      socket.to(conversationId).emit('message:read', {
        messageId,
        userId: socket.userId,
        readAt: new Date()
      });

    } catch (error) {
      console.error('❌ Error updating read receipt:', error);
    }
  });

  // Handle disconnect
  socket.on('disconnect', async () => {
    try {
      console.log(`🔌 User ${socket.userId} disconnected`);

      // Update user status to offline
      await User.findByIdAndUpdate(socket.userId, {
        status: 'offline',
        lastSeen: new Date()
      });

      // Notify others that user is offline
      socket.broadcast.emit('user:status', {
        userId: socket.userId,
        status: 'offline',
        lastSeen: new Date()
      });
    } catch (error) {
      console.error('❌ Error handling disconnect:', error);
    }
  });

  // Initialize socket connection
  joinConversationRooms();
});

// Health check endpoint
app.get('/api/health', (req, res) => {
  res.json({ 
    status: 'OK', 
    message: 'YSNRFD Messenger Backend is running!',
    timestamp: new Date().toISOString(),
    environment: process.env.NODE_ENV || 'development'
  });
});

// Test CORS endpoint
app.get('/api/test-cors', (req, res) => {
  res.json({ 
    message: 'CORS is working correctly!',
    timestamp: new Date().toISOString()
  });
});

// Error handling middleware
app.use((err, req, res, next) => {
  console.error('❌ Error:', err.stack);
  res.status(500).json({
    error: process.env.NODE_ENV === 'production' 
      ? 'Internal server error' 
      : err.message
  });
});

// 404 handler
app.use('*', (req, res) => {
  res.status(404).json({ error: 'Route not found' });
});

// اضافه کردن کانفیگ CORS
app.use(cors({
  origin: process.env.CLIENT_URL || "http://localhost:3000",
  credentials: true,
  methods: ["GET", "POST", "PUT", "DELETE", "PATCH"],
  allowedHeaders: ["Content-Type", "Authorization", "X-Requested-With"]
}));

// پیش‌پردازش درخواست‌های OPTIONS
app.options('*', cors());

// Start server
const PORT = process.env.PORT || 5000;

const startServer = async () => {
  try {
    await connectDB();
    
    server.listen(PORT, () => {
      console.log(`\n🚀 YSNRFD Messenger backend running on port ${PORT}`);
      console.log(`🔧 Environment: ${process.env.NODE_ENV || 'development'}`);
      console.log(`🌍 Frontend URL: ${process.env.CLIENT_URL || 'http://localhost:3000'}`);
      console.log(`📊 MongoDB: ${process.env.MONGODB_URI || 'mongodb://localhost:27017/ysnrfd-messenger'}`);
      console.log(`🔍 Health check: http://localhost:${PORT}/api/health`);
      console.log(`🔍 CORS test: http://localhost:${PORT}/api/test-cors\n`);
    });
  } catch (error) {
    console.error('❌ Failed to start server:', error);
    process.exit(1);
  }
};

startServer();