// Thin wrapper around Roblox's public Users API for resolving usernames <-> user ids. These
// endpoints require no authentication, so we just use the runtime's built-in fetch() - same
// pattern as lib/webhooks.js and the group-role lookup in routes/api/v1/ingame.js - rather than
// pulling in the heavier noblox.js package (which is mainly aimed at cookie-authenticated game
// automation, not simple id/username lookups).
//
// All lookups are cached in-memory (including negative/not-found results) for CACHE_TTL_MS, both
// to keep the dashboard snappy when the same ids show up repeatedly (ACL entries, access group
// members, scan logs) and to avoid tripping Roblox's rate limits.

const USERNAME_TO_ID_URL = 'https://users.roblox.com/v1/usernames/users';
const IDS_TO_USERS_URL = 'https://users.roblox.com/v1/users';
const singleUserUrl = (id) => `https://users.roblox.com/v1/users/${id}`;

const CACHE_TTL_MS = 10 * 60 * 1000; // 10 minutes
const byId = new Map(); // id (string) -> { value: {id,name,displayName} | null, expires }
const byUsername = new Map(); // lowercased username -> same shape

function getCached(map, key) {
	const entry = map.get(key);
	if (!entry) return undefined;
	if (Date.now() > entry.expires) {
		map.delete(key);
		return undefined;
	}
	return entry.value;
}

function setCached(map, key, value) {
	map.set(key, { value, expires: Date.now() + CACHE_TTL_MS });
}

// Caches a resolved user under both its id and username, so a lookup by either later hits cache.
function cacheUser(user) {
	setCached(byId, String(user.id), user);
	setCached(byUsername, user.name.toLowerCase(), user);
}

// Splits an array into chunks of at most `size` items (Roblox's bulk endpoints are happy with
// large batches, but we chunk defensively so one call can't grow unbounded).
function chunk(arr, size) {
	const out = [];
	for (let i = 0; i < arr.length; i += size) out.push(arr.slice(i, i + size));
	return out;
}

// Looks up a single Roblox user by username. Returns { id, name, displayName } or null if no such
// user exists (or the lookup failed). Both hits and misses are cached.
async function getUserByUsername(username) {
	const key = String(username || '').trim().toLowerCase();
	if (!key) return null;

	const cached = getCached(byUsername, key);
	if (cached !== undefined) return cached;

	try {
		const res = await fetch(USERNAME_TO_ID_URL, {
			method: 'POST',
			headers: { 'Content-Type': 'application/json' },
			body: JSON.stringify({ usernames: [username], excludeBannedUsers: false })
		});
		if (!res.ok) throw new Error(`Roblox responded with ${res.status}`);
		const body = await res.json();
		const match = (body.data || [])[0];
		const value = match ? { id: match.id, name: match.name, displayName: match.displayName } : null;

		setCached(byUsername, key, value);
		if (value) setCached(byId, String(value.id), value);
		return value;
	} catch (err) {
		console.error('Roblox username lookup failed:', err.message);
		return null;
	}
}

// Looks up a single Roblox user by id. Returns { id, name, displayName } or null.
async function getUserById(userId) {
	const key = String(userId || '').trim();
	if (!key || Number.isNaN(Number(key))) return null;

	const cached = getCached(byId, key);
	if (cached !== undefined) return cached;

	try {
		const res = await fetch(singleUserUrl(key));
		if (res.status === 404) {
			setCached(byId, key, null);
			return null;
		}
		if (!res.ok) throw new Error(`Roblox responded with ${res.status}`);
		const body = await res.json();
		const value = { id: body.id, name: body.name, displayName: body.displayName };
		cacheUser(value);
		return value;
	} catch (err) {
		console.error('Roblox user id lookup failed:', err.message);
		return null;
	}
}

// Batch-resolves multiple Roblox user ids to usernames at once (e.g. for a whole page of ACL
// entries or scan logs), to avoid one request per row. Returns a plain object mapping id (string)
// -> { id, name, displayName }; ids that don't resolve are simply omitted from the result.
async function getUsersByIds(userIds) {
	const ids = [...new Set((userIds || []).map(id => String(id).trim()).filter(id => id && !Number.isNaN(Number(id))))];
	const result = {};
	const uncached = [];

	for (const id of ids) {
		const cached = getCached(byId, id);
		if (cached !== undefined) {
			if (cached) result[id] = cached;
		} else {
			uncached.push(id);
		}
	}

	for (const batch of chunk(uncached, 100)) {
		try {
			const res = await fetch(IDS_TO_USERS_URL, {
				method: 'POST',
				headers: { 'Content-Type': 'application/json' },
				body: JSON.stringify({ userIds: batch.map(Number), excludeBannedUsers: false })
			});
			if (!res.ok) throw new Error(`Roblox responded with ${res.status}`);
			const body = await res.json();

			const found = new Set();
			for (const user of body.data || []) {
				const value = { id: user.id, name: user.name, displayName: user.displayName };
				cacheUser(value);
				result[String(user.id)] = value;
				found.add(String(user.id));
			}
			// Cache misses too, so we don't keep re-requesting ids that don't exist.
			for (const id of batch) {
				if (!found.has(id)) setCached(byId, id, null);
			}
		} catch (err) {
			console.error('Roblox batch user lookup failed:', err.message);
		}
	}

	return result;
}

module.exports = { getUserByUsername, getUserById, getUsersByIds };