server.js

require("dotenv").config();
const express = require("express");
const http = require("http");
const app = express();
const server = http.createServer(app);
const socket = require("socket.io");
const io = socket(server);

const port = process.env.PORT || 5000;

const users = {};
const socketToRoom = {};

io.on("connection", (socket) => {
	socket.on("join room", (roomID) => {
		if (users[roomID]) {
			const length = users[roomID].length;
			if (length === 2) {
				socket.emit("room full");
				return;
			}
			users[roomID].push(socket.id);
		} else {
			users[roomID] = [socket.id];
		}
		socketToRoom[socket.id] = roomID;
		const usersInThisRoom = users[roomID].filter((id) => id !== socket.id);

		socket.emit("all users", usersInThisRoom);
	});

	socket.on("sending signal", (payload) => {
		io.to(payload.userToSignal).emit("user joined", { signal: payload.signal, callerID: payload.callerID });
	});

	socket.on("returning signal", (payload) => {
		io.to(payload.callerID).emit("receiving returned signal", { signal: payload.signal, id: socket.id });
	});

	socket.on("disconnect", () => {
		const roomID = socketToRoom[socket.id];
		let room = users[roomID];
		if (room) {
			room = room.filter((id) => id !== socket.id);
			users[roomID] = room;
		}
	});
});

server.listen(port, () => console.log(`Listening on port ${port}`));