/// <reference lib="deno.ns" />

export function startServer(
	hostname: string = "localhost",
	port: number = 8042,
): () => Promise<void> {
	let nextId = 1;
	const clientsMap = new Map<number, WebSocket>();

	const broadcast = (message: string): void => {
		for (const socket of clientsMap.values()) {
			if (socket.readyState === WebSocket.OPEN) {
				socket.send(message);
			}
		}
	};

	const handleConnection = (socket: WebSocket): void => {
		const id = nextId++;

		socket.onopen = () => {
			clientsMap.set(id, socket);
			broadcast(`${id} has joined!`);
		};

		socket.onclose = () => {
			clientsMap.delete(id);
			broadcast(`${id} has left!`);
		};

		socket.onmessage = console.log;
		socket.onerror = console.error;
	};

	const ac = new AbortController();
	const server = Deno.serve(
		{ hostname, port, signal: ac.signal },
		(request) => {
			if (request.headers.get("upgrade") !== "websocket") {
				return new Response("Upgrade Required", { status: 426 });
			}

			const { socket, response } = Deno.upgradeWebSocket(request);
			handleConnection(socket);

			return response;
		},
	);

	return () => {
		ac.abort();
		return server.finished;
	};
}