/// <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 clientRoomMap = new Map<number, string>();
	const roomsMap = new Map<string, number[]>();

	const broadcast = (room: string, message: string): void => {
		const members = roomsMap.get(room)!;

		for (const member of members) {
			const socket = clientsMap.get(member);
			if (socket && socket.readyState === WebSocket.OPEN) {
				socket.send(message);
			}
		}
	};

	const commands = {
		join: (id: number, args: string[]) => {
			const room = args[0];
			if (roomsMap.has(room)) {
				roomsMap.get(room)!.push(id);
			} else {
				roomsMap.set(room, [id]);
			}

			clientRoomMap.getOrInsert(id, room); // not sure about that
			broadcast(room, `${id} has joined!`);
		},
	} as const;

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

		socket.onopen = () => {
			clientsMap.set(id, socket);
			socket.send(`Welcome ${id}, type /join <room>.`);
		};

		socket.onclose = () => {
			const room = clientRoomMap.get(id);
			if (room) {
				clientRoomMap.delete(id);
				const members = roomsMap.get(room)!;
				members.splice(members.indexOf(id), 1);
				broadcast(room, `${id} has left!`);
			}
			clientsMap.delete(id);
		};

		socket.onmessage = (message: MessageEvent) => {
			const text = String(message.data);
			if (text.startsWith("/")) {
				const [command, ...args] = text.substring(1).split(" ");
				try {
					// @ts-ignore
					commands[command](id, args);
				} catch (error) {
					socket.send(JSON.stringify(error));
				}
			}
		};

		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;
	};
}