// --- START: Additions/Modifications in app.js ---

const express = require('express');
const http = require('http');
const socketIo = require('socket.io');
const path = require('path');
const fs = require('fs').promises; // Use promise-based fs
// const bcrypt = require('bcrypt'); // Still commented out, needed for secure apps

// Create express app and server
const app = express();
const server = http.createServer(app);
const io = socketIo(server);

// --- Configuration ---
const PUBLIC_DIR = path.join(__dirname, 'public');
const DATA_DIR = path.join(__dirname, 'data'); // Directory for data files
const USERS_FILE_PATH = path.join(DATA_DIR, 'users.json'); // Path to users file

// Serve static files from the 'public' directory
app.use(express.static(PUBLIC_DIR));

// --- State ---
let registeredUsers = {}; // Will be loaded from file
// onlineUsers structure: { socketId: { username, isTyping, inCallWith: null | string (socketId) } }
const onlineUsers = {};
const usernameToSocketId = {}; // Helper map: { username: socketId }

// --- File Helper Functions (loadUsers, saveUsers - remain the same) ---
// ... (Keep existing loadUsers and saveUsers functions) ...

async function loadUsers() {
    try {
        await fs.mkdir(DATA_DIR, { recursive: true });
        const data = await fs.readFile(USERS_FILE_PATH, 'utf8');
        return JSON.parse(data);
    } catch (error) {
        if (error.code === 'ENOENT') {
            console.log('users.json not found, starting with empty user list.');
            return {};
        } else if (error instanceof SyntaxError) {
            console.error('Error parsing users.json:', error);
            return {};
        } else {
            console.error('Error loading users.json:', error);
            return {};
        }
    }
}

async function saveUsers(usersData) {
    try {
        await fs.mkdir(DATA_DIR, { recursive: true });
        const data = JSON.stringify(usersData, null, 2);
        await fs.writeFile(USERS_FILE_PATH, data, 'utf8');
        console.log('User data saved to users.json');
    } catch (error) {
        console.error('Error saving users.json:', error);
    }
}


// --- Socket.IO Logic ---
io.on('connection', (socket) => {
    console.log('A user connected:', socket.id);
    // Note: currentUsername is only valid *after* successful login within this closure.
    // Use onlineUsers[socket.id]?.username safely elsewhere.

    // --- Handle Login/Registration Attempt (Modified to track usernameToSocketId) ---
    socket.on('attempt_login', async (credentials) => {
        if (!credentials || !credentials.username || !credentials.password) {
            socket.emit('login_fail', 'Username and password are required.');
            return;
        }

        const { username, password } = credentials;

        const isAlreadyOnline = usernameToSocketId[username]; // Check map directly
        if (isAlreadyOnline) {
            socket.emit('login_fail', `User "${username}" is already logged in.`);
            return;
        }

        if (registeredUsers.hasOwnProperty(username)) {
            if (registeredUsers[username] === password) { // INSECURE
                console.log(`Login success: ${username} (${socket.id})`);
                loginUser(socket, username);
            } else {
                console.log(`Login fail: Invalid password for ${username} (${socket.id})`);
                socket.emit('login_fail', 'Invalid username or password.');
            }
        } else {
            console.log(`Registering new user: ${username} (${socket.id})`);
            registeredUsers[username] = password; // INSECURE
            await saveUsers(registeredUsers);
            loginUser(socket, username);
        }
    });

    // Modified loginUser to update maps and state
    function loginUser(socketInstance, username) {
        // Store user info
        onlineUsers[socketInstance.id] = {
            username: username,
            isTyping: false,
            inCallWith: null // Initially not in a call
        };
        usernameToSocketId[username] = socketInstance.id; // Add to lookup map

        socketInstance.emit('login_success', username);
        io.emit('user_join', username);
        io.emit('user_list', getUsersPublicInfo());
    }

    // --- Message Handling (remains the same) ---
    socket.on('message', (data) => {
        const senderInfo = onlineUsers[socket.id];
        if (!senderInfo || !data || !data.text) return;

        if (senderInfo.isTyping) {
            senderInfo.isTyping = false;
            // Don't need to exclude sender ID here as getUsersTyping doesn't include self by default logic
            socket.broadcast.emit('user_typing_status', getUsersTyping());
        }

        io.emit('message', {
            username: senderInfo.username,
            text: data.text,
            timestamp: new Date().toISOString() // Use ISO string for consistency
        });
    });

    // --- Typing Indicator Handling (remains the same) ---
    socket.on('typing', () => {
        const userInfo = onlineUsers[socket.id];
        if (userInfo && !userInfo.isTyping) {
            userInfo.isTyping = true;
            socket.broadcast.emit('user_typing_status', getUsersTyping(socket.id)); // Exclude self
        }
    });

    socket.on('stop_typing', () => {
        const userInfo = onlineUsers[socket.id];
        if (userInfo && userInfo.isTyping) {
            userInfo.isTyping = false;
            socket.broadcast.emit('user_typing_status', getUsersTyping(socket.id)); // Exclude self
        }
    });

    // --- Disconnect Handling (Modified to handle calls and maps) ---
    socket.on('disconnect', () => {
        const userInfo = onlineUsers[socket.id];
        if (userInfo) {
            const username = userInfo.username;
            const userInCallWithSocketId = userInfo.inCallWith;

            console.log(`${username} (${socket.id}) disconnected`);

            // --- Hang up any active call ---
            if (userInCallWithSocketId && onlineUsers[userInCallWithSocketId]) {
                console.log(`Disconnect: Hanging up call between ${username} and ${onlineUsers[userInCallWithSocketId].username}`);
                io.to(userInCallWithSocketId).emit('call-ended'); // Notify the other user
                onlineUsers[userInCallWithSocketId].inCallWith = null; // Clear call state for the other user
            }
            // --- End hang up ---

            delete onlineUsers[socket.id];          // Remove from online list
            delete usernameToSocketId[username];    // Remove from lookup map

            socket.broadcast.emit('user_leave', username);
            io.emit('user_list', getUsersPublicInfo()); // Send updated list
            // Update typing status if the disconnected user was typing
            if (userInfo.isTyping) {
                socket.broadcast.emit('user_typing_status', getUsersTyping());
            }
        } else {
            console.log('User disconnected before login:', socket.id);
        }
    });


    // --- START: WebRTC Signaling Handlers ---

    /**
     * Initiates a call request from caller to target.
     * data: { targetUsername: string }
     */
    socket.on('request-call', (data) => {
        const callerInfo = onlineUsers[socket.id];
        if (!callerInfo) return; // Should not happen if logged in

        const targetUsername = data.targetUsername;
        const targetSocketId = usernameToSocketId[targetUsername];
        const targetInfo = targetSocketId ? onlineUsers[targetSocketId] : null;

        console.log(`Call request from ${callerInfo.username} (${socket.id}) to ${targetUsername}`);

        if (!targetInfo) {
            console.log(`Call target ${targetUsername} not found or offline.`);
            socket.emit('call-denied', { reason: 'User is offline.' });
            return;
        }

        if (targetInfo.inCallWith) {
            console.log(`Call target ${targetUsername} is already in a call.`);
            socket.emit('call-denied', { reason: `${targetUsername} is busy.` });
            return;
        }

        if (callerInfo.inCallWith) {
             console.log(`Caller ${callerInfo.username} is already in a call.`);
             socket.emit('call-denied', { reason: `You are already in a call.` });
             return;
        }

        // Send call offer prompt to the target user
        console.log(`Sending incoming call notification to ${targetUsername} (${targetSocketId})`);
        io.to(targetSocketId).emit('incoming-call', {
            callerUsername: callerInfo.username
        });
    });

     /**
     * Target user accepts the call.
     * data: { callerUsername: string }
     */
    socket.on('accept-call', (data) => {
        const acceptorInfo = onlineUsers[socket.id]; // The user accepting the call
        if (!acceptorInfo) return;

        const callerUsername = data.callerUsername;
        const callerSocketId = usernameToSocketId[callerUsername];
        const callerInfo = callerSocketId ? onlineUsers[callerSocketId] : null;

        console.log(`${acceptorInfo.username} accepted call from ${callerUsername}`);

        if (!callerInfo) {
            console.log(`Original caller ${callerUsername} not found.`);
            socket.emit('call-denied', { reason: 'Caller went offline.' });
            return;
        }

        if (callerInfo.inCallWith || acceptorInfo.inCallWith) {
             console.log(`Call conflict: ${callerUsername} or ${acceptorInfo.username} already in call.`);
             // Notify both potential parties that call cannot proceed
             socket.emit('call-denied', { reason: 'Call conflict or one party is busy.' });
             io.to(callerSocketId).emit('call-denied', { reason: 'Call conflict or the other party became busy.'});
             return;
        }

        // Mark both users as in call with each other
        acceptorInfo.inCallWith = callerSocketId;
        callerInfo.inCallWith = socket.id; // socket.id is the acceptor's socket id

        // Notify the original caller to start the WebRTC offer process
        io.to(callerSocketId).emit('call-accepted', {
            acceptorUsername: acceptorInfo.username
        });

        // Notify the acceptor to wait for the offer
        socket.emit('prepare-for-offer', {
             callerUsername: callerInfo.username
        });

        console.log(`Call established between ${callerUsername} (${callerSocketId}) and ${acceptorInfo.username} (${socket.id})`);
    });


     /**
     * Target user rejects the call.
     * data: { callerUsername: string }
     */
    socket.on('reject-call', (data) => {
        const rejectorInfo = onlineUsers[socket.id];
        if (!rejectorInfo) return;

        const callerUsername = data.callerUsername;
        const callerSocketId = usernameToSocketId[callerUsername];

        console.log(`${rejectorInfo.username} rejected call from ${callerUsername}`);

        if (callerSocketId) {
            io.to(callerSocketId).emit('call-rejected', {
                rejectorUsername: rejectorInfo.username
            });
        }
    });

    /**
     * Relays the WebRTC Offer from caller to acceptor.
     * data: { targetUsername: string, offer: RTCSessionDescriptionInit }
     */
    socket.on('webrtc-offer', (data) => {
        const callerInfo = onlineUsers[socket.id];
        if (!callerInfo) return;

        const targetUsername = data.targetUsername;
        const targetSocketId = usernameToSocketId[targetUsername];

        if (targetSocketId && onlineUsers[targetSocketId]?.inCallWith === socket.id) {
             console.log(`Relaying WebRTC offer from ${callerInfo.username} to ${targetUsername}`);
             io.to(targetSocketId).emit('webrtc-offer', {
                 offer: data.offer,
                 callerUsername: callerInfo.username // Send caller username with the offer
             });
        } else {
            console.warn(`WebRTC Offer: Target ${targetUsername} not found or not in call with ${callerInfo.username}`);
        }
    });

    /**
     * Relays the WebRTC Answer from acceptor to caller.
     * data: { targetUsername: string (original caller), answer: RTCSessionDescriptionInit }
     */
    socket.on('webrtc-answer', (data) => {
        const acceptorInfo = onlineUsers[socket.id];
        if (!acceptorInfo) return;

        const targetUsername = data.targetUsername; // This is the original caller
        const targetSocketId = usernameToSocketId[targetUsername];

        if (targetSocketId && onlineUsers[targetSocketId]?.inCallWith === socket.id) {
             console.log(`Relaying WebRTC answer from ${acceptorInfo.username} to ${targetUsername}`);
             io.to(targetSocketId).emit('webrtc-answer', {
                 answer: data.answer,
                 acceptorUsername: acceptorInfo.username // Send acceptor username with the answer
             });
        } else {
             console.warn(`WebRTC Answer: Target ${targetUsername} not found or not in call with ${acceptorInfo.username}`);
        }
    });

    /**
     * Relays ICE Candidates between peers.
     * data: { targetUsername: string, candidate: RTCIceCandidateInit }
     */
    socket.on('webrtc-ice-candidate', (data) => {
        const senderInfo = onlineUsers[socket.id];
        if (!senderInfo) return;

        const targetUsername = data.targetUsername;
        const targetSocketId = usernameToSocketId[targetUsername];

        // Check if the target is actually the one sender is in call with
        if (targetSocketId && senderInfo.inCallWith === targetSocketId) {
            // console.log(`Relaying ICE candidate from ${senderInfo.username} to ${targetUsername}`); // Too noisy
            io.to(targetSocketId).emit('webrtc-ice-candidate', {
                candidate: data.candidate
            });
        } else {
             // console.warn(`ICE Candidate: Target ${targetUsername} not found or sender ${senderInfo.username} not in call with them.`);
        }
    });

    /**
     * Handles user explicitly hanging up the call.
     * data: {} (might include target if needed, but server knows from inCallWith)
     */
    socket.on('hangup-call', () => {
        const userInfo = onlineUsers[socket.id];
        if (!userInfo || !userInfo.inCallWith) {
            // Not in a call, nothing to hang up
            return;
        }

        const targetSocketId = userInfo.inCallWith;
        const targetInfo = onlineUsers[targetSocketId];

        console.log(`${userInfo.username} is hanging up call with ${targetInfo?.username || 'unknown'}`);

        // Notify the other user
        if (targetInfo) {
            io.to(targetSocketId).emit('call-ended');
            targetInfo.inCallWith = null; // Clear target's call state
        }

        // Clear caller's call state
        userInfo.inCallWith = null;

        // Optional: send confirmation back to the hanger-upper
        socket.emit('call-ended');
    });

    // --- END: WebRTC Signaling Handlers ---

});

// --- Helper Functions (Modified getUsersTyping) ---
function getUsersPublicInfo() {
    // Return username and potentially busy status? For now just usernames.
    return Object.values(onlineUsers).map(u => u.username);
}

// Modified to exclude the caller from the list sent back to them
function getUsersTyping(excludeSocketId = null) {
    return Object.entries(onlineUsers)
                 .filter(([id, user]) => id !== excludeSocketId && user.isTyping)
                 .map(([id, user]) => user.username);
}

// --- Find Local IP (remains the same) ---
function getLocalIp() {
    // ... (Keep existing getLocalIp function) ...
     const { networkInterfaces } = require('os');
     const nets = networkInterfaces();
     for (const name of Object.keys(nets)) {
         for (const net of nets[name]) {
             if (net.family === 'IPv4' && !net.internal) {
                 return net.address;
             }
         }
     }
     return '127.0.0.1';
}
const localIp = getLocalIp();

// --- Start Server (IIFE remains the same) ---
(async () => {
    registeredUsers = await loadUsers();
    console.log(`Loaded ${Object.keys(registeredUsers).length} registered users.`);

    // const PORT = process.env.PORT || 3000; // Find this line or similar
const PORT = process.env.PORT || 7860; // Change 3000 to 7860
    server.listen(PORT, () => {
        console.log(`Server running on port ${PORT}`);
        console.log(`Access it locally at: http://localhost:${PORT}`);
        if (localIp !== '127.0.0.1') {
            console.log(`Access on local network (e.g., mobile): http://${localIp}:${PORT}`);
        }
        console.log(`Serving files from: ${PUBLIC_DIR}`);
        console.log(`User data file: ${USERS_FILE_PATH}`);
        console.warn('--- SECURITY WARNING: Storing plain text passwords in users.json! ---');
        console.warn('--- WebRTC Note: Using public STUN servers. TURN server might be needed for reliability. ---');
    });

    server.on('error', (error) => {
        console.error('Server failed to start:', error);
        process.exit(1);
    });
})();

// --- END: Additions/Modifications in app.js ---