require("dotenv").config();
const express = require("express");
const couchdbService = require("./services/couchdbService");
const cors = require("cors");
const http = require("http");
const socketio = require("socket.io");
const helmet = require("helmet");
const rateLimit = require("express-rate-limit");
const mongoSanitize = require("express-mongo-sanitize");
const xss = require("xss-clean");
const { errorHandler } = require("./middleware/errorHandler");
const socketAuth = require("./middleware/socketAuth");
const requestLogger = require("./middleware/requestLogger");
const logger = require("./utils/logger");
const { validateEnv, logEnvConfig } = require("./utils/validateEnv");

// Validate environment variables before starting server
try {
  validateEnv();
  logEnvConfig();
} catch (error) {
  logger.error('Environment validation failed:');
  logger.error(error.message);
  process.exit(1);
}

const app = express();
const server = http.createServer(app);
const io = socketio(server, {
  cors: {
    origin: process.env.FRONTEND_URL || "http://localhost:3000",
    methods: ["GET", "POST"],
    credentials: true,
  },
});
const port = process.env.PORT || 5000;

// Trust proxy - required when behind ingress/reverse proxy
app.set('trust proxy', 1);

// Security Headers - Helmet
app.use(helmet());

// CORS Configuration
app.use(
  cors({
    origin: process.env.FRONTEND_URL || "http://localhost:3000",
    credentials: true,
  }),
);

// Body Parser
app.use(express.json());

// Data Sanitization against NoSQL injection
app.use(mongoSanitize());

// Data Sanitization against XSS
app.use(xss());

// Request Logging
app.use(requestLogger);

// Rate Limiting for Auth Routes (5 requests per 15 minutes)
const authLimiter = rateLimit({
  windowMs: 15 * 60 * 1000, // 15 minutes
  max: 5, // 5 requests per windowMs
  message: {
    success: false,
    error: "Too many authentication attempts, please try again later",
  },
  standardHeaders: true,
  legacyHeaders: false,
  // Trust proxy when behind ingress
  validate: { trustProxy: false },
});

// General API Rate Limiting (100 requests per 15 minutes)
const apiLimiter = rateLimit({
  windowMs: 15 * 60 * 1000, // 15 minutes
  max: 100, // 100 requests per windowMs
  message: {
    success: false,
    error: "Too many requests, please try again later",
  },
  standardHeaders: true,
  legacyHeaders: false,
  // Trust proxy when behind ingress
  validate: { trustProxy: false },
});

// Database Connection
// CouchDB (primary database)
// Skip initialization during testing
if (process.env.NODE_ENV !== 'test') {
  couchdbService.initialize()
    .then(() => logger.info("CouchDB initialized successfully"))
    .catch((err) => {
      logger.error("CouchDB initialization failed", err);
      process.exit(1); // Exit if CouchDB fails to initialize since it's the primary database
    });
}

// Socket.IO Authentication Middleware
io.use(socketAuth);

// Socket.IO Setup with Authentication
io.on("connection", (socket) => {
  logger.info(`Socket.IO client connected`, { userId: socket.user.id });

  socket.on("joinEvent", (eventId) => {
    socket.join(`event_${eventId}`);
    logger.debug(`User joined event`, { userId: socket.user.id, eventId });
  });

  socket.on("joinPost", (postId) => {
    socket.join(`post_${postId}`);
    logger.debug(`User joined post`, { userId: socket.user.id, postId });
  });

  socket.on("eventUpdate", (data) => {
    io.to(`event_${data.eventId}`).emit("update", data.message);
  });

  socket.on("disconnect", () => {
    logger.info(`Socket.IO client disconnected`, { userId: socket.user.id });
  });
});

// Make io available to routes
app.set("io", io);

// Routes
const authRoutes = require("./routes/auth");
const streetRoutes = require("./routes/streets");
const taskRoutes = require("./routes/tasks");
const postRoutes = require("./routes/posts");
const commentsRoutes = require("./routes/comments");
const eventRoutes = require("./routes/events");
const rewardRoutes = require("./routes/rewards");
const reportRoutes = require("./routes/reports");
const badgesRoutes = require("./routes/badges");
const aiRoutes = require("./routes/ai");
const paymentRoutes = require("./routes/payments");
const userRoutes = require("./routes/users");
const cacheRoutes = require("./routes/cache");
const profileRoutes = require("./routes/profile");
const analyticsRoutes = require("./routes/analytics");
const leaderboardRoutes = require("./routes/leaderboard");

// Apply rate limiters
app.use("/api/auth/register", authLimiter);
app.use("/api/auth/login", authLimiter);
app.use("/api", apiLimiter);

// Health check endpoint (for Kubernetes liveness/readiness probes)
app.get("/api/health", async (req, res) => {
  try {
    const couchdbStatus = await couchdbService.checkConnection();
    
    // Check Socket.IO status
    const socketIOStatus = {
      engine: io.engine ? "running" : "stopped",
      connectedClients: io.engine ? io.engine.clientsCount : 0,
      // Get number of connected sockets
      sockets: io.sockets ? io.sockets.sockets.size : 0
    };
    
    const isHealthy = couchdbStatus && io.engine;
    
    res.status(isHealthy ? 200 : 503).json({
      status: isHealthy ? "healthy" : "degraded",
      timestamp: new Date().toISOString(),
      uptime: process.uptime(),
      services: {
        couchdb: couchdbStatus ? "connected" : "disconnected",
        socketIO: {
          status: socketIOStatus.engine,
          connectedClients: socketIOStatus.connectedClients,
          activeSockets: socketIOStatus.sockets
        }
      },
      memory: {
        heapUsed: Math.round(process.memoryUsage().heapUsed / 1024 / 1024) + " MB",
        heapTotal: Math.round(process.memoryUsage().heapTotal / 1024 / 1024) + " MB",
        rss: Math.round(process.memoryUsage().rss / 1024 / 1024) + " MB"
      }
    });
  } catch (error) {
    res.status(503).json({
      status: "unhealthy",
      timestamp: new Date().toISOString(),
      uptime: process.uptime(),
      services: {
        couchdb: "disconnected",
        socketIO: "unknown"
      },
      error: error.message,
    });
  }
});

// Detailed Socket.IO health check endpoint
app.get("/api/health/socketio", (req, res) => {
  try {
    const socketIOInfo = {
      status: io.engine ? "running" : "stopped",
      connectedClients: io.engine ? io.engine.clientsCount : 0,
      activeSockets: io.sockets ? io.sockets.sockets.size : 0,
      rooms: [],
      timestamp: new Date().toISOString()
    };

    // Get list of active rooms (excluding auto-generated socket ID rooms)
    if (io.sockets && io.sockets.adapter && io.sockets.adapter.rooms) {
      const rooms = Array.from(io.sockets.adapter.rooms.keys()).filter(room => {
        // Filter out socket ID rooms (they start with socket ID pattern)
        return room.startsWith('event_') || room.startsWith('post_');
      });
      
      socketIOInfo.rooms = rooms.map(room => {
        const roomSize = io.sockets.adapter.rooms.get(room)?.size || 0;
        return { name: room, members: roomSize };
      });
    }

    res.status(200).json(socketIOInfo);
  } catch (error) {
    res.status(500).json({
      status: "error",
      error: error.message,
      timestamp: new Date().toISOString()
    });
  }
});

// Routes
app.use("/api/auth", authRoutes);
app.use("/api/streets", streetRoutes);
app.use("/api/tasks", taskRoutes);
app.use("/api/posts", postRoutes);
app.use("/api/posts", commentsRoutes); // Comments are nested under posts
app.use("/api/events", eventRoutes);
app.use("/api/rewards", rewardRoutes);
app.use("/api/reports", reportRoutes);
app.use("/api/badges", badgesRoutes);
app.use("/api/ai", aiRoutes);
app.use("/api/payments", paymentRoutes);
app.use("/api/users", userRoutes);
app.use("/api/cache", cacheRoutes);
app.use("/api/profile", profileRoutes);
app.use("/api/analytics", analyticsRoutes);
app.use("/api/leaderboard", leaderboardRoutes);

app.get("/", (req, res) => {
  res.send("Street Adoption App Backend");
});

// Error Handler Middleware (must be last)
app.use(errorHandler);

// Only start server if this file is run directly (not when required by tests)
if (require.main === module) {
  server.listen(port, () => {
    logger.info(`Server started`, { port, env: process.env.NODE_ENV || 'development' });
  });
}

// Export app and server for testing
module.exports = { app, server, io };

// Graceful shutdown
process.on("SIGTERM", async () => {
  logger.info("SIGTERM received, shutting down gracefully");
  
  try {
    // Close CouchDB connection
    await couchdbService.shutdown();
    logger.info("CouchDB connection closed");
    
    // Close server
    server.close(() => {
      logger.info("Server closed");
      process.exit(0);
    });
  } catch (error) {
    logger.error("Error during shutdown", error);
    process.exit(1);
  }
});

process.on("SIGINT", async () => {
  logger.info("SIGINT received, shutting down gracefully");
  
  try {
    // Close CouchDB connection
    await couchdbService.shutdown();
    logger.info("CouchDB connection closed");
    
    // Close server
    server.close(() => {
      logger.info("Server closed");
      process.exit(0);
    });
  } catch (error) {
    logger.error("Error during shutdown", error);
    process.exit(1);
  }
});