// BeatSaver exporter: map JSON and the zip of the exact version hash that was played.
import * as fs from 'node:fs';
import { get, limiters } from './http.ts';
import { archivePath, eachWithProgress, exists, readJson, save } from './store.ts';

const bs = (...p: string[]) => archivePath('beatsaver', ...p);
const MISSING_FILE = () => bs('missing.json');

type BSMap = { id: string; versions: { hash: string; downloadURL: string }[] };
type Missing = Record<string, { reason: string; checkedAt: string; recoveredFrom?: string }>;

function readMissing(): Missing {
	try {
		return readJson<Missing>(MISSING_FILE());
	} catch {
		return {};
	}
}

/** Entry names from a zip's central directory, or null if the zip is truncated or malformed. */
export function zipEntryNames(buf: Buffer): string[] | null {
	if (buf.length < 22 || buf.readUInt32LE(0) !== 0x04034b50) return null;
	const tailStart = Math.max(0, buf.length - 65_557);
	const eocd = buf.subarray(tailStart).lastIndexOf(Buffer.from([0x50, 0x4b, 0x05, 0x06]));
	if (eocd < 0) return null;
	const e = tailStart + eocd;
	const count = buf.readUInt16LE(e + 10);
	let p = buf.readUInt32LE(e + 16);
	const names: string[] = [];
	for (let i = 0; i < count; i++) {
		if (p + 46 > buf.length || buf.readUInt32LE(p) !== 0x02014b50) return null;
		const nameLen = buf.readUInt16LE(p + 28);
		const extraLen = buf.readUInt16LE(p + 30);
		const commentLen = buf.readUInt16LE(p + 32);
		names.push(buf.toString('utf-8', p + 46, p + 46 + nameLen));
		p += 46 + nameLen + extraLen + commentLen;
	}
	return names;
}

/** A zip is usable if its central directory is intact and lists an Info.dat (any case, any folder). */
export function looksLikeMapZip(buf: Buffer): boolean {
	return zipEntryNames(buf)?.some((n) => /(^|\/)info\.dat$/i.test(n)) ?? false;
}

export async function exportMaps(hashes: string[]): Promise<void> {
	const missing = readMissing();
	console.log(`BeatSaver maps: ${hashes.length} hashes`);
	const res = await eachWithProgress('maps', hashes, async (hash) => {
		const jsonFile = bs('maps', `${hash}.json`);
		const zipFile = bs('zips', `${hash}.zip`);
		if (exists(zipFile) && exists(jsonFile)) return 'skipped';

		let map: BSMap | null = null;
		if (exists(jsonFile)) {
			map = readJson<BSMap>(jsonFile);
		} else {
			const r = await get(`https://api.beatsaver.com/maps/hash/${hash}`, { limiter: limiters.beatsaver, accept: [404] });
			if (r.status === 200) {
				save(jsonFile, r.body);
				map = JSON.parse(r.body.toString('utf-8')) as BSMap;
			}
		}
		if (exists(zipFile)) return 'done';

		// Prefer the version entry for this exact hash; old versions often remain on the CDN.
		const version = map?.versions.find((v) => v.hash.toLowerCase() === hash);
		const candidates = [version?.downloadURL, `https://r2cdn.beatsaver.com/${hash}.zip`, `https://cdn.beatsaver.com/${hash}.zip`].filter(
			(u): u is string => Boolean(u)
		);
		for (const url of [...new Set(candidates)]) {
			const r = await get(url, { limiter: limiters.beatsaverCdn, accept: [403, 404] });
			if (r.status === 200 && looksLikeMapZip(r.body)) {
				save(zipFile, r.body);
				delete missing[hash];
				return 'done';
			}
		}
		missing[hash] = {
			reason: map ? `map ${map.id} found but version zip unavailable` : 'hash unknown to BeatSaver',
			checkedAt: new Date().toISOString()
		};
		return 'missing';
	});
	fs.mkdirSync(bs(), { recursive: true });
	save(MISSING_FILE(), JSON.stringify(missing, null, 2) + '\n');
	console.log(`  missing.json: ${Object.keys(missing).length} hashes`);
	if (res.failed.length) console.warn(`  ${res.failed.length} failed; rerun to retry`);
}