import { OnModuleInit } from '@nestjs/common';
import { Cache } from 'cache-manager';
import { CacheModuleOptions } from './cache-module-options.interface';
/**
 * Service responsible for centralized cache management.
 *
 * This service abstracts caching operations such as retrieving,
 * storing, and deleting values. It supports Redis caching using
 * Azure Workload Identity for authentication and handles automatic
 * token refresh to maintain cache connectivity.
 */
export declare class CacheService implements OnModuleInit {
    private readonly namespace;
    private readonly options;
    private readonly cache;
    private readonly logger;
    /**
     * Constructs CacheService with injected dependencies.
     *
     * @param namespace Optional namespace to scope cache keys and avoid collisions.
     * @param options Configuration options for cache connection (e.g., Redis credentials).
     * @param cache Injected NestJS cache manager instance for cache operations.
     */
    constructor(namespace: string | undefined, options: CacheModuleOptions, cache: Cache);
    /**
     * Lifecycle hook called after module initialization.
     * Ensures cache stores are configured and ready.
     */
    onModuleInit(): void;
    /**
     * Sets up the cache store, connecting to Redis with Azure Workload Identity.
     * Automatically refreshes the Redis access token before expiration.
     *
     * If Redis config is incomplete or connection fails, falls back to empty store.
     */
    private initializeCacheStore;
    /**
     * Retrieves the cached value by key.
     *
     * @param key Cache key.
     * @returns The cached value or null if not found.
     */
    fetch<T>(key: string): Promise<T | null>;
    /**
     * Stores a value in the cache under the given key with optional TTL.
     *
     * @param key Cache key.
     * @param value Value to store.
     * @param expiration Optional time to live in seconds.
     */
    store<T>(key: string, value: T, expiration?: number): Promise<void>;
    /**
     * Removes a cached value by key.
     *
     * @param key Cache key to delete.
     */
    remove(key: string): Promise<void>;
    /**
     * Clears all cached entries.
     */
    clearAll(): Promise<void>;
    /**
     * Retrieves a value from the cache or fetches it using the provided function
     * if not found, then stores it with an optional expiration.
     *
     * @param key Cache key.
     * @param fetcher Function that fetches the data if cache miss occurs.
     * @param expiration Optional TTL in seconds.
     * @returns Cached or freshly fetched value.
     */
    fetchOrStore<T>(key: string, fetcher: () => Promise<T>, expiration?: number): Promise<T>;
}