const { Server } = require('socket.io');
const express = require('express');
const cors = require('cors');
const http = require('http');
const dotenv = require('dotenv');
const helmet = require('helmet');
const rateLimit = require('express-rate-limit');
const Joi = require('joi');
const validator = require('validator');
const { v4: uuidv4 } = require('uuid');

dotenv.config();

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

// Security middlewares
app.use(helmet({
    contentSecurityPolicy: {
        directives: {
            defaultSrc: ["'self'"],
            styleSrc: ["'self'", "'unsafe-inline'"],
            scriptSrc: ["'self'"],
            imgSrc: ["'self'", "data:", "https:"],
            connectSrc: ["'self'", "wss:", "ws:"],
            fontSrc: ["'self'"],
            objectSrc: ["'none'"],
            mediaSrc: ["'self'"],
            frameSrc: ["'none'"],
        },
    },
    crossOriginEmbedderPolicy: false
}));

// Rate limiting
const limiter = rateLimit({
    windowMs: 15 * 60 * 1000, // 15 minutos
    max: 100, // Límite de 100 requests por ventana de tiempo por IP
    message: 'Too many requests from this IP, please try again later.',
    standardHeaders: true,
    legacyHeaders: false,
});

app.use(limiter);

// CORS configuration
const corsOptions = {
    origin: process.env.CLIENT_URL || ["http://localhost:3000", "https://localhost:3000"],
    methods: ["GET", "POST"],
    credentials: true
};

app.use(cors(corsOptions));
app.use(express.json({ limit: '10mb' }));

const io = new Server(server, {
    cors: corsOptions,
    transports: ['websocket', 'polling'],
    allowEIO3: true
});

// Validation schemas
const roomJoinSchema = Joi.object({
    email: Joi.string().email().required(),
    room: Joi.string().pattern(/^[a-zA-Z0-9-_]+$/).min(3).max(50).required()
});

const callSchema = Joi.object({
    to: Joi.string().required(),
    offer: Joi.object().required()
});

const callAcceptedSchema = Joi.object({
    to: Joi.string().required(),
    ans: Joi.object().required()
});

app.get("/", (req, res) => {
    res.json({ 
        message: `${process.env.APP_NAME || 'VideoPeersJS'} Server`, 
        status: "running",
        timestamp: new Date().toISOString()
    });
});

app.get("/health", (req, res) => {
    res.status(200).json({ status: "healthy" });
});

const emailToSocket = new Map();
const socketToEmail = new Map();
const rooms = new Map();

// Helper function to sanitize input
function sanitizeInput(input) {
    if (typeof input === 'string') {
        return validator.escape(input.trim());
    }
    return input;
}

// Helper function to validate room access
function validateRoomAccess(socket, room) {
    const userEmail = socketToEmail.get(socket.id);
    if (!userEmail) return false;
    
    const roomData = rooms.get(room);
    return roomData && roomData.participants.has(userEmail);
}

io.on("connection", (socket) => {
    console.log(`Socket Connected: ${socket.id} at ${new Date().toISOString()}`);
    
    // Set a timeout for socket connection
    const connectionTimeout = setTimeout(() => {
        socket.disconnect(true);
    }, 30000); // 30 segundos

    socket.on("room:join", (data) => {
        try {
            // Validate input
            const { error, value } = roomJoinSchema.validate(data);
            if (error) {
                let errorMessage = "Invalid room join data";
                if (error.details[0]?.context?.key === 'room') {
                    errorMessage = "Room ID must contain only letters, numbers, hyphens, and underscores (3-50 characters)";
                } else if (error.details[0]?.context?.key === 'email') {
                    errorMessage = "Please provide a valid email address";
                }
                socket.emit("error", { message: errorMessage });
                return;
            }

            const { email, room } = value;
            
            // Sanitize inputs
            const sanitizedEmail = sanitizeInput(email);
            const sanitizedRoom = sanitizeInput(room);

            // Additional email validation
            if (!validator.isEmail(sanitizedEmail)) {
                socket.emit("error", { message: "Invalid email format" });
                return;
            }

            // Clear connection timeout
            clearTimeout(connectionTimeout);

            // Remove old socket mapping if exists
            const oldSocketId = emailToSocket.get(sanitizedEmail);
            if (oldSocketId && oldSocketId !== socket.id) {
                socketToEmail.delete(oldSocketId);
                io.sockets.sockets.get(oldSocketId)?.leave(sanitizedRoom);
            }

            emailToSocket.set(sanitizedEmail, socket.id);
            socketToEmail.set(socket.id, sanitizedEmail);

            // Manage room data
            if (!rooms.has(sanitizedRoom)) {
                rooms.set(sanitizedRoom, {
                    id: uuidv4(),
                    participants: new Set(),
                    createdAt: new Date()
                });
            }
            
            const roomData = rooms.get(sanitizedRoom);
            roomData.participants.add(sanitizedEmail);

            socket.join(sanitizedRoom);
            
            // Notify other users in the room
            socket.to(sanitizedRoom).emit("user:joined", { 
                email: sanitizedEmail, 
                id: socket.id,
                timestamp: new Date().toISOString()
            });

            // Confirm room join to the user
            socket.emit("room:join", { 
                email: sanitizedEmail, 
                room: sanitizedRoom,
                participants: Array.from(roomData.participants),
                timestamp: new Date().toISOString()
            });

        } catch (error) {
            console.error("Error in room:join:", error);
            socket.emit("error", { message: "Internal server error" });
        }
    });

    socket.on("user:call", (data) => {
        try {
            const { error, value } = callSchema.validate(data);
            if (error) {
                socket.emit("error", { message: "Invalid call data" });
                return;
            }

            const { to, offer } = value;
            
            // Verify that the target socket exists
            const targetSocket = io.sockets.sockets.get(to);
            if (!targetSocket) {
                socket.emit("error", { message: "Target user not found" });
                return;
            }

            io.to(to).emit("incoming:call", { 
                from: socket.id, 
                offer,
                timestamp: new Date().toISOString()
            });
        } catch (error) {
            console.error("Error in user:call:", error);
            socket.emit("error", { message: "Internal server error" });
        }
    });

    socket.on("call:accepted", (data) => {
        try {
            const { error, value } = callAcceptedSchema.validate(data);
            if (error) {
                socket.emit("error", { message: "Invalid call acceptance data" });
                return;
            }

            const { to, ans } = value;
            
            const targetSocket = io.sockets.sockets.get(to);
            if (!targetSocket) {
                socket.emit("error", { message: "Target user not found" });
                return;
            }

            io.to(to).emit("call:accepted", { 
                from: socket.id, 
                ans,
                timestamp: new Date().toISOString()
            });
        } catch (error) {
            console.error("Error in call:accepted:", error);
            socket.emit("error", { message: "Internal server error" });
        }
    });

    socket.on("peer:nego:needed", (data) => {
        try {
            const { to, offer } = data;
            if (!to || !offer) {
                socket.emit("error", { message: "Invalid negotiation data" });
                return;
            }

            const targetSocket = io.sockets.sockets.get(to);
            if (!targetSocket) {
                socket.emit("error", { message: "Target user not found" });
                return;
            }

            io.to(to).emit("peer:nego:needed", { 
                from: socket.id, 
                offer,
                timestamp: new Date().toISOString()
            });
        } catch (error) {
            console.error("Error in peer:nego:needed:", error);
            socket.emit("error", { message: "Internal server error" });
        }
    });

    socket.on("peer:nego:done", (data) => {
        try {
            const { to, ans } = data;
            if (!to || !ans) {
                socket.emit("error", { message: "Invalid negotiation data" });
                return;
            }

            const targetSocket = io.sockets.sockets.get(to);
            if (!targetSocket) {
                socket.emit("error", { message: "Target user not found" });
                return;
            }

            io.to(to).emit("peer:nego:final", { 
                from: socket.id, 
                ans,
                timestamp: new Date().toISOString()
            });
        } catch (error) {
            console.error("Error in peer:nego:done:", error);
            socket.emit("error", { message: "Internal server error" });
        }
    });

    socket.on("call:end", (data) => {
        try {
            const { to } = data;
            if (!to) {
                socket.emit("error", { message: "Invalid call end data" });
                return;
            }

            const targetSocket = io.sockets.sockets.get(to);
            if (targetSocket) {
                io.to(to).emit("call:end", { 
                    from: socket.id,
                    timestamp: new Date().toISOString()
                });
            }
        } catch (error) {
            console.error("Error in call:end:", error);
            socket.emit("error", { message: "Internal server error" });
        }
    });

    socket.on("call:initiated", (data) => {
        try {
            const { to } = data;
            if (!to) {
                socket.emit("error", { message: "Invalid call initiation data" });
                return;
            }

            const targetSocket = io.sockets.sockets.get(to);
            if (targetSocket) {
                io.to(to).emit("call:initiated", { 
                    from: socket.id,
                    timestamp: new Date().toISOString()
                });
            }
        } catch (error) {
            console.error("Error in call:initiated:", error);
            socket.emit("error", { message: "Internal server error" });
        }
    });

    socket.on("disconnect", (reason) => {
        try {
            console.log(`Socket Disconnected: ${socket.id}, Reason: ${reason}`);
            
            const email = socketToEmail.get(socket.id);
            if (email) {
                emailToSocket.delete(email);
                socketToEmail.delete(socket.id);
                
                // Remove from all rooms
                rooms.forEach((roomData, roomName) => {
                    if (roomData.participants.has(email)) {
                        roomData.participants.delete(email);
                        
                        // If room is empty, delete it
                        if (roomData.participants.size === 0) {
                            rooms.delete(roomName);
                        } else {
                            // Notify other participants
                            socket.to(roomName).emit("user:left", { 
                                email,
                                timestamp: new Date().toISOString()
                            });
                        }
                    }
                });
            }
            
            clearTimeout(connectionTimeout);
        } catch (error) {
            console.error("Error in disconnect:", error);
        }
    });
});

// Error handling middleware
app.use((err, req, res, next) => {
    console.error('Error:', err);
    res.status(500).json({ 
        message: 'Internal server error',
        timestamp: new Date().toISOString()
    });
});

const PORT = process.env.PORT || 8000;
server.listen(PORT, () => {
    console.log(`🚀 Server running on port ${PORT}`);
    console.log(`🕒 Started at ${new Date().toISOString()}`);
});