import "server-only";

type CacheEntry<T> = {
  value: T;
  expiresAt: number;
};

export class LruCache<T> {
  private readonly entries = new Map<string, CacheEntry<T>>();

  constructor(
    private readonly maxEntries: number,
    private readonly defaultTtlMs: number,
  ) {}

  get(key: string): T | null {
    const entry = this.entries.get(key);
    if (!entry) return null;

    if (entry.expiresAt <= Date.now()) {
      this.entries.delete(key);
      return null;
    }

    this.entries.delete(key);
    this.entries.set(key, entry);
    return entry.value;
  }

  set(key: string, value: T, ttlMs = this.defaultTtlMs): void {
    if (this.entries.has(key)) {
      this.entries.delete(key);
    }

    this.entries.set(key, {
      value,
      expiresAt: Date.now() + ttlMs,
    });

    if (this.entries.size > this.maxEntries) {
      const oldestKey = this.entries.keys().next().value;
      if (oldestKey) {
        this.entries.delete(oldestKey);
      }
    }
  }

  delete(key: string): void {
    this.entries.delete(key);
  }

  clear(): void {
    this.entries.clear();
  }
}