'use strict';

const { spawn } = require('child_process');
const dgram = require('dgram');

// SSH credentials for the public server you want to proxy to
const HOST = 'hostname';
const USER = 'username';
const PASS = 'password';

// Public port of the server
const PORT = 25565;


const run = () => {

	console.log('Starting UDP server...');
	const server = dgram.createSocket('udp4');

	server.bind(4445, () => {
		server.addMembership('224.0.2.60');
		console.log('Waiting for Minecraft LAN server...');
	});

	let ssh = null;
	let offlineTimeout = 0;

	server.on('message', (msg, info) => {
		const [ motd, port ] = String(msg)
			.match(/\[MOTD\]([^\[]*)\[\/MOTD\]\[AD\]([^\[]*)\[\/AD\]/)
			.slice(1, 3);

		if (!ssh) {
			console.log(`Found server: ${motd} (${info.address}:${port})`);
			console.log('Starting reverse SSH proxy...');
			ssh = spawn('plink', [
				[ USER, HOST ].join('@'),
				'-pw',
				PASS,
				'-N',
				'-C',
				'-R',
				[ '*', PORT, info.address, port ].join(':')
			]);
			ssh.stderr.pipe(process.stderr);
			ssh.stdout.pipe(process.stdout);
		} else {
			console.log(new Date().toLocaleString() + ` Got ping from: ${motd} (${info.address}:${port})`);
		}
		clearTimeout(offlineTimeout);
		offlineTimeout = setTimeout(() => {
			console.log('Closing reverse SSH proxy due to timeout from Minecraft LAN server...');
			if (ssh) {
				ssh.kill();
				ssh = null;
			}
			server.close(() =>
				run());
		}, 10000);
	});
};

run();