export interface QueryCacheOptions {
  ttlMs: number;
  maxEntries: number;
  now?: () => number;
}

export function createQueryCache(options: QueryCacheOptions) {
  const now = options.now ?? Date.now;
  const entries = new Map<string, { data: unknown; ts: number }>();

  async function cached<T>(key: string, fn: () => Promise<T>): Promise<T> {
    const hit = entries.get(key);
    if (hit && now() - hit.ts < options.ttlMs) {
      return hit.data as T;
    }

    const data = await fn();
    entries.set(key, { data, ts: now() });

    while (entries.size > options.maxEntries) {
      const oldestKey = entries.keys().next().value;
      if (oldestKey === undefined) break;
      entries.delete(oldestKey);
    }

    return data;
  }

  function clear() {
    entries.clear();
  }

  return { cached, clear };
}

export const queryCache = createQueryCache({
  ttlMs: 120_000,
  maxEntries: 500,
});