/**
 * @template T
 * @description Implements an LRU (Least Recently Used) Cache with TTL (Time-to-Live) support.
 * Allows for efficient storage and retrieval of key-value pairs.
 */
export declare class LRUCacheOption<T> {
    private static instance;
    private readonly capacity;
    private readonly hash;
    private head?;
    private tail?;
    private hitCount;
    private missCount;
    private evictionCount;
    private constructor();
    /**
     * Creates or retrieves the singleton instance of the LRU cache.
     * @template T
     * @param {number} [capacity=10] - Maximum capacity of the cache.
     * @returns {LRUCacheOption<T>} The singleton instance of the cache.
     */
    static getInstance<T>(capacity?: number): LRUCacheOption<T>;
    /**
     * Inserts or updates an item in the cache.
     * If the key already exists, it updates its value and moves it to the head.
     * If the cache exceeds capacity, the least recently used item is evicted.
     * @param {string} key - The key associated with the value.
     * @param {T} value - The value to store in the cache.
     * @param {number} [ttl=60000] - Time-to-Live in milliseconds for the item.
     * @returns {LRUCacheOption<T>} The current cache instance for chaining.
     */
    put(key: string, value: T, ttl?: number): LRUCacheOption<T>;
    /**
     * Retrieves an item from the cache by key.
     * If the item has expired, it returns undefined and counts as a miss.
     * @param {string} key - The key to search for.
     * @returns {T | undefined} The value associated with the key, or undefined if not found or expired.
     */
    get(key: string): T | undefined;
    /**
     * Clears all items from the cache.
     */
    clear(): void;
    private prepend;
    private pop;
    private evict;
    private getHitRate;
    private getMissRate;
    private getEvictionRate;
    /**
     * Resets cache performance metrics.
     */
    clearMetrics(): void;
    /**
     * Logs cache performance metrics to the console.
     * Includes hit rate, miss rate, and eviction rate.
     */
    logMetrics(): void;
    /**
     * Logs debugging information about the cache to the console.
     * Includes the current state of the linked list and the hash map.
     */
    debugLRU(): void;
}