// Next.js API route support: https://nextjs.org/docs/api-routes/introduction
import type {NextApiRequest, NextApiResponse} from "next";
import {app} from "@/firebase";
import {getFirestore, collection, getDocs} from "firebase/firestore";
import {withIronSessionApiRoute} from "iron-session/next";
import {sessionOptions} from "@/lib/session";
import {getGroupsForUser} from "@/utils/groups.be";
import {uniq} from "lodash";

const db = getFirestore(app);

export default withIronSessionApiRoute(handler, sessionOptions);

async function handler(req: NextApiRequest, res: NextApiResponse) {
	if (!req.session.user && !req.headers["page"] && req.headers["page"] !== "register") {
		res.status(401).json({ok: false});
		return;
	}

	const snapshot = await getDocs(collection(db, "users"));
	const users = snapshot.docs.map((doc) => ({
		id: doc.id,
		...doc.data(),
	}));

	if (!req.session.user) return res.status(200).json(users);
	if (req.session.user.type === "admin" || req.session.user.type === "developer") return res.status(200).json(users);
	if (req.session.user.type === "teacher") {
		const adminGroups = await getGroupsForUser(req.session.user.id);
		const belongingGroups = await getGroupsForUser(undefined, req.session.user.id);

		const participants = uniq([...adminGroups.flatMap((x) => x.participants), ...belongingGroups.flat().flatMap((x) => x.participants)]);
		return res.status(200).json(users.filter((x) => participants.includes(x.id)));
	}

	const adminGroups = await getGroupsForUser(req.session.user.id);
	const groups = await Promise.all(adminGroups.flatMap((x) => x.participants).map(async (x) => await getGroupsForUser(x)));
	const participants = uniq([...adminGroups.flatMap((x) => x.participants), ...groups.flat().flatMap((x) => x.participants)]);

	res.status(200).json(users.filter((x) => participants.includes(x.id)));
}