app.js

const express = require("express");
const socket = require("socket.io");
const http = require("http");
const { Chess } = require("chess.js");
const path = require("path");
const { log } = require("console");
const app = express();
const server = http.createServer(app);
const io = socket(server);
const chess = new Chess();

let players = {};
let currentPlayer = "w";

app.set("view engine","ejs");
app.use(express.static(path.join(__dirname, "public")));

app.get("/", (req,res) => {
    res.render("index" , {title: "Chess Game"});
});

io.on("connection", function(uniqueSocket){
    if(!players.white){
        players.white = uniqueSocket.id;
        uniqueSocket.emit("playerRole", "w");
    }else if(!players.black){
        players.black = uniqueSocket.id;
        uniqueSocket.emit("playerRole", "b");
    }else{
        uniqueSocket.emit("spectatorRole");
    }

    uniqueSocket.on("disconnect", function(){
        if(uniqueSocket.id === players.white){
            delete players.white;
        }else if(uniqueSocket.id === players.black){
            delete players.black;
        }
    });

    uniqueSocket.on("move", (move) =>{
        try{
            if(chess.turn() === 'w' && uniqueSocket.id !== players.white) return;
            if(chess.turn() === 'b' && uniqueSocket.id !== players.black) return;
            const result = chess.move(move);
            if(result){
                currentPlayer = chess.turn();
                io.emit("move", move);
                io.emit("boardState", chess.fen());
            }else{
                console.log("Invalid move : ", move);
                uniqueSocket.emit("invalidMove", move);
            }
        }catch(err){
            console.log(err);
            uniqueSocket.emit("error", "An error occurred");
        }
    })
});

server.listen(3000, function() {
    console.log("Server is listening on port 3000");
});