mc-server-watcher/watch-server.js

const { exec } = require("child_process");
const https = require("https");

const SERVER = process.argv[2];
const WEBHOOK_URL = process.env.WEBHOOK_URL;

let oldServerStatus = {
	online: false,
	players: -1,
	samplePlayers: [],
};

getServerStatus(SERVER);
setInterval(() => getServerStatus(SERVER), 10000);

function getServerStatus(server) {
	console.log(`Getting server status of ${server}`);

	return new Promise((resolve, reject) => {
		exec("mcstatus -j " + server, async (error, stdout, stderr) => {
			if  (error) {
				console.log(stderr);
				if (oldServerStatus.online) {
					sendMessage(":red_circle: The server is now offline");
					oldServerStatus = {
						online: false,
						players: -1,
						samplePlayers: [],
					};
				}
				return resolve();
			}

			console.log(stdout);

			const json = JSON.parse(stdout);

			if (json.version.name.match(/Offline/)) {
				if (oldServerStatus.online) {
					sendMessage(":red_circle: The server is now offline");
					oldServerStatus = {
						online: false,
						players: -1,
						samplePlayers: [],
					};
				}
				return resolve();
			}

			const match = json.description.text.match(new RegExp(`Connect to §a(${SERVER}:\\d+)§7§8`));
			if (match) {
				resolve(await getServerStatus(match[1]));
				return resolve();
			}

			if (!oldServerStatus.online) {
				await sendMessage(":green_circle: The server is now online");
			}

			const samplePlayers = json.players.sample || [];
			samplePlayers.forEach(player => {
				if (!oldServerStatus.samplePlayers.map(p => p.id).includes(player.id)) {
					sendMessage(`**${player.name}** joined the server`);
				}
			});

			oldServerStatus.samplePlayers.forEach(player => {
				if (!samplePlayers.map(p => p.id).includes(player.id)) {
					sendMessage(`**${player.name}** left the server`);
				}
			});

			/*if (oldServerStatus.players != json.players.online) {
				sendMessage(`There are now **${json.players.online}** players online`);
			}*/

			oldServerStatus = {
				online: true,
				players: json.players.online,
				samplePlayers,
			};
		});
	});
}

function sendMessage(text) {
	console.log(text);

	return new Promise((resolve, reject) => {
		const data = JSON.stringify({
			content: text,
		});

		const options = {
			method: "POST",
			headers: {
				"Accept": "application/json",
				"Content-Type": "application/json",
				"Content-Length": data.length,
			}
		};
		const req = https.request(WEBHOOK_URL, options, (res) => {

			let data = "";
			res.on("data", chunk => data += chunk);
			res.on("end", () => {
				console.log(res.statusCode);
				resolve();
			});

		});
		req.write(data);
		req.end();
	});
}