index.js

const express = require('express');
const app = express();
const http = require('http');
const server = http.createServer(app);
const { Server } = require("socket.io");
const io = new Server(server, { cors: { origin: '*' } });

// Mapped as:  9-digit code => socket.id
const activeUsers = {};

io.on('connection', (socket) => {
  console.log('⚡ A user connected:', socket.id);

  socket.on('register', (data) => {
    activeUsers[data.code] = socket.id;
    console.log(`✅ User registered with code: ${data.code}`);
  });

  socket.on('message', (data) => {
    /* 
     data structure:
     {
        target: '123456789',  // person receiving the message
        sender: '987654321',  // person sending the message
        payload: { type: 'offer', sdp: '...' }
     }
    */
    const targetSocketId = activeUsers[data.target];
    if (targetSocketId) {
      console.log(`Passing ${data.payload.type} from ${data.sender} to ${data.target}`);
      io.to(targetSocketId).emit('message', {
        ...data.payload,
        sender: data.sender
      });
    } else {
      console.log(`❌ Target ${data.target} not found.`);
      socket.emit('error_msg', 'Partner is offline or code is invalid.');
    }
  });

  socket.on('disconnect', () => {
    console.log('🔴 User disconnected:', socket.id);
    const code = Object.keys(activeUsers).find((key) => activeUsers[key] === socket.id);
    if (code) {
      delete activeUsers[code];
      console.log(`Unregistered code: ${code}`);
    }
  });
});

const PORT = process.env.PORT || 3000;
server.listen(PORT, () => {
  console.log(`🚀 Signaling server running on port ${PORT}`);
});