import type { Database } from "bun:sqlite";
import { mkdirSync, readFileSync, renameSync, rmSync, writeFileSync } from "node:fs";
import { join } from "node:path";
import { filesAt, objectBytes, stripCount } from "../mirror/queries.ts";
import { buildTarball } from "./tar.ts";

/**
 * A save's tarball, built on first request into `<tarballDir>/<repo>/<generation>/<id>.tar.gz`. The
 * generation is how many strip events the mirror holds, so once a strip lands no older file is ever
 * looked up again, even if Kepr stops before the sync's cleanup runs. Built and written in one
 * synchronous run, so a strip can't land mid-build either.
 */
export function cachedTarball(
	tarballDir: string,
	db: Database,
	repo: string,
	saveId: string,
): Uint8Array<ArrayBuffer> {
	const dir = join(tarballDir, repo, String(stripCount(db)));
	const path = join(dir, `${saveId}.tar.gz`);
	try {
		return readFileSync(path);
	} catch (error) {
		if ((error as NodeJS.ErrnoException).code !== "ENOENT") throw error;
	}
	const files = filesAt(db, saveId).map((file) => {
		const bytes = objectBytes(db, file.hash);
		if (!bytes) throw new Error(`${repo}: object ${file.hash} is missing from the mirror`);
		return { path: file.path, bytes, executable: file.executable };
	});
	const tarball = buildTarball(`${repo}-${saveId.slice(0, 8)}`, files);
	mkdirSync(dir, { recursive: true });
	writeFileSync(`${path}.tmp`, tarball);
	renameSync(`${path}.tmp`, path);
	return tarball;
}

/** Clears a repo's cached tarballs after a strip; cleanup only, since the new generation never reads them. */
export function dropTarballs(tarballDir: string, repo: string): void {
	rmSync(join(tarballDir, repo), { recursive: true, force: true });
}