/**
 * A generic LRU cache service with TTL support.
 */
export declare class CacheService<K, V> {
    private cache;
    private accessOrder;
    private maxCacheSize;
    private defaultTTL;
    /**
     * Creates a new instance of the CacheService class.
     *
     * @param maxCacheSize - Maximum number of items to keep in the cache (default: 1000).
     * @param defaultTTL - Default time-to-live in milliseconds, or null for no expiry (default: null).
     */
    constructor(maxCacheSize?: number, defaultTTL?: number | null);
    /**
     * Retrieves an item from the cache.
     *
     * @param key - The key of the item to retrieve.
     * @returns The cached item, or undefined if not found or expired.
     */
    get(key: K): V | undefined;
    /**
     * Adds or updates an item in the cache.
     *
     * @param key - The key of the item to add or update.
     * @param value - The item to cache.
     * @param ttl - Time-to-live in milliseconds, or null for no expiry. Uses defaultTTL if not specified.
     */
    set(key: K, value: V, ttl?: number | null): void;
    /**
     * Checks if an item exists in the cache and is not expired.
     *
     * @param key - The key of the item to check.
     * @returns True if the item exists and is not expired, false otherwise.
     */
    has(key: K): boolean;
    /**
     * Deletes an item from the cache.
     *
     * @param key - The key of the item to delete.
     */
    delete(key: K): void;
    /**
     * Returns an array of keys in the cache.
     * This does not check for expired items.
     *
     * @returns An array of keys.
     */
    keys(): K[];
    /**
     * Returns an array of values in the cache.
     * This does not check for expired items.
     *
     * @returns An array of values.
     */
    values(): V[];
    /**
     * Clears all items from the cache.
     */
    clear(): void;
    /**
     * Removes all expired items from the cache.
     *
     * @returns The number of items removed.
     */
    cleanExpired(): number;
    /**
     * Updates the access order for the LRU cache.
     * @param key - The key that was accessed.
     */
    private updateAccessOrder;
    /**
     * Enforces the cache size limit by removing least recently used items.
     */
    private enforceCacheLimit;
}