import { STATUS_CODE, STATUS_TEXT, type StatusCode } from "jsr:@std/http";

const ALLOWED_ORIGIN = "http://0.0.0.0:8042";

type Session = {
	id: string;
	connId: number;
	createdAt: number;
	lastSeenAt: number;
};

function createResponse(
	status: StatusCode,
	body: BodyInit | null = null,
): Response {
	return new Response(body, { status, statusText: STATUS_TEXT[status] });
}

const sessions = new Map<string, Session>();
const connections = new Map<number, WebSocket>();

export function createSession(): string {
	const id = crypto.randomUUID();
	const now = Date.now();
	sessions.set(id, {
		id,
		connId: 0,
		createdAt: now,
		lastSeenAt: 0,
	});

	return id;
}

let currentId = 1;
const nextId = (): number => {
	return currentId++;
};

const connectSession = (session: Session, request: Request): Response => {
	const { response, socket } = Deno.upgradeWebSocket(request);
	const connId = nextId();

	socket.onopen = () => {
		session.lastSeenAt = Date.now();
		session.connId = connId;
		connections.set(connId, socket);
	};
	socket.onclose = () => {
		session.lastSeenAt = Date.now();
		connections.delete(connId);
	};
	socket.onmessage = () => {
		session.lastSeenAt = Date.now();
	};
	socket.onerror = (e) => {
		session.lastSeenAt = Date.now();
		console.error(e);
	};

	return response;
};

export default function (request: Request): Response {
	if (request.headers.get("upgrade")?.toLowerCase() !== "websocket") {
		return createResponse(STATUS_CODE.UpgradeRequired);
	}

	const url = new URL(request.url);
	const sessionId = url.searchParams.get("sessionId");
	if (url.origin !== ALLOWED_ORIGIN || sessionId === null) {
		return createResponse(STATUS_CODE.BadRequest);
	}

	const session = sessions.get(sessionId);
	if (session === undefined) {
		return createResponse(STATUS_CODE.Unauthorized);
	}

	return connectSession(session, request);
}