/**
 * Persistent Cache: Disk-based cache storage
 * Features:
 * - Save/load cache entries to/from disk
 * - Atomic writes to prevent corruption
 * - Auto-create cache directory
 * - Operation serialization to prevent race conditions
 * - Batched writes to reduce disk I/O
 */
import type { LRUCacheEntry } from './cache-types.js';
export declare class PersistentCache<T = unknown> {
    private filePath;
    private writeQueue;
    private isProcessing;
    private pendingWrites;
    private batchTimer;
    private readonly BATCH_DELAY_MS;
    constructor(filePath: string);
    /**
     * Ensure cache directory exists
     */
    private ensureDirectory;
    /**
     * Load all cache entries from disk
     */
    loadAll(): LRUCacheEntry<T>[];
    /**
     * Save all cache entries to disk synchronously (atomic write)
     * Internal use only
     */
    private saveAllSync;
    /**
     * Save all cache entries to disk (queued)
     */
    saveAll(entries: LRUCacheEntry<T>[]): Promise<void>;
    /**
     * Flush all pending writes immediately
     * Call this before process exit to ensure all writes are persisted
     */
    flush(): Promise<void>;
    /**
     * Queue a write operation
     */
    private queueWrite;
    /**
     * Process the write queue serially
     */
    private processQueue;
    /**
     * Execute a single write operation
     */
    private executeOperation;
    /**
     * Schedule a batched write operation
     */
    private scheduleBatchWrite;
    /**
     * Flush all pending writes to disk
     */
    private flushPendingWrites;
    /**
     * Save a single entry (batched and queued)
     */
    save(key: string, entry: LRUCacheEntry<T>): Promise<void>;
    /**
     * Delete a single entry (queued)
     */
    delete(key: string): Promise<void>;
    /**
     * Clear all cache entries (queued)
     */
    clear(): Promise<void>;
    /**
     * Get cache file size in bytes
     */
    getFileSize(): number;
    /**
     * Check if cache file exists
     */
    exists(): boolean;
}
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