import { browser } from "$app/environment";
import anime from "$stores/anime";
import lastPruneTimes from "$stores/lastPruneTimes";
import manga from "$stores/manga";
import localforage from "localforage";

type MediaCacheKind = "anime" | "manga";
const cacheStorageKey = (kind: MediaCacheKind) => `${kind}:v3`;

interface StoredLastPruneTimes {
	anime: number;
	chapters: number;
	manga: number;
}

const hydration = new Map<MediaCacheKind, Promise<void>>();

const isStoredLastPruneTimes = (
	value: unknown,
): value is StoredLastPruneTimes =>
	typeof value === "object" &&
	value !== null &&
	typeof (value as StoredLastPruneTimes).anime === "number" &&
	typeof (value as StoredLastPruneTimes).chapters === "number" &&
	typeof (value as StoredLastPruneTimes).manga === "number";

export const hydrateMediaListCache = (kind: MediaCacheKind) => {
	if (!browser) return Promise.resolve();

	const existing = hydration.get(kind);

	if (existing) return existing;

	const promise = (async () => {
		const [cache, pruneTimes] = await Promise.all([
			localforage.getItem<string>(cacheStorageKey(kind)),
			localforage.getItem<StoredLastPruneTimes>("lastPruneTimes"),
		]);

		if (typeof cache === "string" && cache.length)
			(kind === "anime" ? anime : manga).set(cache);

		if (isStoredLastPruneTimes(pruneTimes)) lastPruneTimes.set(pruneTimes);
	})();

	hydration.set(kind, promise);

	return promise;
};