import type { Database } from "bun:sqlite";
import { type Bucket, BucketWriteError, KEPR_PREFIX } from "../bucket/reader.ts";
import { filesAt, objectBytes, stripCount } from "../mirror/queries.ts";
import { buildTarball } from "./tar.ts";

const tarballsOf = (repo: string) => `${KEPR_PREFIX}tarballs/${repo}/`;

/**
 * A save's tarball, kept in the bucket under Kepr's own folder (June, 2026-09-30) as
 * `.kepr/tarballs/<repo>/<generation>/<id>.tar.gz` once first requested. 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. Without a write key nothing is kept, and each
 * request builds it again.
 */
export async function cachedTarball(
	bucket: Bucket,
	db: Database,
	repo: string,
	saveId: string,
): Promise<Uint8Array> {
	const stored = await bucket.get(`${tarballsOf(repo)}${stripCount(db)}/${saveId}.tar.gz`);
	if (stored) return stored;
	// Read again after the await: the generation and the build below run in one synchronous go, so
	// a strip landing meanwhile can't file new contents under the old generation or the reverse.
	const key = `${tarballsOf(repo)}${stripCount(db)}/${saveId}.tar.gz`;
	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);
	try {
		await bucket.put(key, tarball, "application/gzip");
	} catch (error) {
		if (!(error instanceof BucketWriteError)) throw error;
	}
	return tarball;
}

/** Deletes a repo's kept tarballs: after a strip, or from the console. They rebuild on request. */
export async function dropTarballs(bucket: Bucket, repo: string): Promise<void> {
	for (const key of await bucket.list(tarballsOf(repo))) await bucket.remove(key);
}