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

const io = socket(server);

const chess = new Chess();

let player = {}
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) { //assigning the role white or black
    console.log("connected");

    if(!player.white){
      player.white = uniquesocket.id;
      uniquesocket.emit("playerRole", "w");
    }
    else if(!player.black){
      player.black = uniquesocket.id;
      uniquesocket.emit("playerRole", "b");
    }
    else{
      uniquesocket.emit("soectatorRole");
    }

    uniquesocket.on("disconnected", function(){ //if player is disconnected
      if(uniquesocket.id === player.white){
        delete player.white;
      }
      else if(uniquesocket.id === player.black){
        delete player.black;
      }
    });

    uniquesocket.on("move", (move) =>{
      try{ //making sure that hte move is valid by white and black
        if(chess.turn() === "w" && uniquesocket.id !== player.white) return;
        if(chess.turn() === "b" && uniquesocket.id!== player.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");
        }
      }
      catch(err){
        console.log(err);
        uniquesocket.emit("invalidMove", move);
      }
    })
});


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