import { ICache } from "../cache";

interface CacheEntry<V> {
  value: V;
  expiry: number | null;
}

/**
 * A simple LRU cache implementation.
 */
export class LRUCache<K, V> implements ICache<K, V> {
  private cache = new Map<K, CacheEntry<V>>();

  constructor(private maxSize: number = 100) {}

  get(key: K): V | undefined {
    const entry = this.cache.get(key);
    if (!entry) return undefined;

    if (entry.expiry !== null && Date.now() > entry.expiry) {
      this.cache.delete(key);
      return undefined;
    }

    // Update the key to mark it as recently used
    this.cache.delete(key);
    this.cache.set(key, entry);
    return entry.value;
  }

  set(key: K, value: V, ttl?: number): void {
    if (this.cache.has(key)) {
      this.cache.delete(key);
    } else if (this.cache.size >= this.maxSize) {
      // Remove the least recently used item (first inserted)
      const firstKey = this.cache.keys().next().value;
      if (firstKey !== undefined) {
        this.cache.delete(firstKey);
      }
    }
    const expiry = ttl ? Date.now() + ttl : null;
    this.cache.set(key, { value, expiry });
  }

  delete(key: K): void {
    this.cache.delete(key);
  }

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