Node Game

GameState 🏟

• GameState is a snapshot of the current game.
• Design should cover entire game flow.

Sample Game State 🏹

gameState = {
	players: {
		p1 : {
			...
		},
		p2 : {
			...
		}
	},
	state : {
		board : [],
		turn : []
	},
	winner : null,
	turn : null
}								
						

Code Time </> 💻

Let's look at some code for socket fundamentals.

Socket Backend 🎙

const app = require('express')();
const http = require('http').Server(app);
const io = require('socket.io')(http);
const port = process.env.PORT || 3000;

io.on('connection', (socket) => {
	socket.on('chat message', function(msg){
	io.emit('chat message', msg);
	socket.to({{socketId}}).emit('chat message', msg);
	});
});

http.listen(port, () => {
	console.log('listening on *:' + port);
});				
							

Socket Front End 📻

<script> src="https://cdn.socket.io/socket.io-1.2.0.js"></script>							
<script>
	$(function () {
		var socket = io();
		/*
		 * On some event trigger below code
		 */
		socket.emit('chat message', $('#m').val());

		socket.on('chat message', function(msg){
			console.log(msg)
		});
	});
</script>	
								

Code Time </> 🖥

Let's dive to some more code!

Joining Room 🏃‍♂️

/**
 * Front end code
 */
io.on('connection', (socket) => {

	/**
	 * During some action
	 */
	socket.join('room1');

	/**
	 * Inorder to leave a room
	 */
	socket.leave('room1');
});	

								

Emitting to a room 📡

/**
 * Backend code
 */
io.to('room1').emit('data', {data : 0}); 

/**
 * Front end, on a subscribed client
 */									
 io.on('connection', (socket) => {
	socket.on('data', (msg) => {
	   console.log(msg); //{data : 0}
	});
});
										

Move validation with library. 📚

Let's look at chess library.

											
											npm install --save chess.js
									

Initiating library 📕

const Chess = require('chess.js').Chess;
const chess = new Chess();
console.log('Printing the current board state');
console.log(chess.ascii());	

/** Output */
  +------------------------+
8 | r  n  b  q  k  b  n  r |
7 | p  p  p  p  p  p  p  p |
6 | .  .  .  .  .  .  .  . |
5 | .  .  .  .  .  .  .  . |
4 | .  .  .  .  .  .  .  . |
3 | .  .  .  .  .  .  .  . |
2 | P  P  P  P  P  P  P  P |
1 | R  N  B  Q  K  B  N  R |
  +------------------------+
    a  b  c  d  e  f  g  h
									

Making moves 🚴‍♀️

/**
 * moves can be triggered in different ways
 */
chess.move('e4'); // Standard algebraic notation
chess.move({from : 'e7', to : 'e5'}) // or with more readable way.
chess.move('Nh3'); // Moves the night to h3
chess.move({from : 'f8', to : 'a3' }) // Moving the bishop
									

Validity of moves. 🚧

/**
 * Checking the validity of the move
 */
console.log('Valid move output', chess.move('b3'));
{ 
color: 'w', 
from: 'b2', 
to: 'b3', 
flags: 'n', 
piece: 'p', 
san: 'b3' 
}

console.log('Invalid move output', chess.move('b2'));
null
									

Check! ? 🚔

/**
 * Check if the game is in check state
 */
console.log(chess.in_check()); 
// returns boolean

console.log(chess.in_checkmate());
// returns boolean
									

Further! ? 🚀

Chess have lots of situations like.
* Draw
* Settlement
* Castling, etc

/**
 * Check if the game is in check state
 */
console.log(chess..in_draw()); 
// returns boolean

console.log(chess.in_stalemate());
// returns boolean
									

Scaling 🔥

• Vertical scaling and Horizontal scaling.
• Socket scaling using broker.
• Game-state scaling using cache servers.
• Message queues.
• Reverse proxy using nginx.