/**
 * Filesystem Storage Adapter
 *
 * File-based storage implementation for Node.js environments.
 * Each key is stored as a separate JSON file in a directory.
 *
 * **Node.js only** - throws an error if used in browser environments.
 *
 * @example
 * ```typescript
 * const adapter = new FileSystemStorageAdapter({
 *   baseDir: '.frontmcp/storage',
 * });
 *
 * await adapter.connect();
 * await adapter.set('user:123', JSON.stringify({ name: 'John' }));
 * const value = await adapter.get('user:123');
 * await adapter.disconnect();
 * ```
 */
import { BaseStorageAdapter } from './base';
import type { SetOptions } from '../types';
/**
 * Options for FileSystemStorageAdapter.
 */
export interface FileSystemAdapterOptions {
    /**
     * Base directory for storage (absolute or relative to cwd).
     * Each key is stored as a file in this directory.
     */
    baseDir: string;
    /**
     * File extension for stored files.
     * @default '.json'
     */
    extension?: string;
    /**
     * Directory permissions (Unix mode).
     * @default 0o700
     */
    dirMode?: number;
    /**
     * File permissions (Unix mode).
     * @default 0o600
     */
    fileMode?: number;
}
/**
 * Filesystem-based storage adapter.
 *
 * Features:
 * - Persists data to individual JSON files
 * - Atomic writes using temp file + rename
 * - Restricted file permissions (0o600)
 * - TTL support with lazy expiration
 *
 * Limitations:
 * - No pub/sub support
 * - TTL not enforced with background sweeper
 * - Not suitable for high-throughput scenarios
 *
 * @example
 * ```typescript
 * import { FileSystemStorageAdapter } from '@frontmcp/utils';
 *
 * const adapter = new FileSystemStorageAdapter({
 *   baseDir: '.frontmcp/keys',
 *   extension: '.json',
 * });
 *
 * await adapter.connect();
 *
 * // Store data
 * await adapter.set('my-key', 'my-value');
 *
 * // Retrieve data
 * const value = await adapter.get('my-key');
 *
 * // List all keys
 * const keys = await adapter.keys();
 *
 * await adapter.disconnect();
 * ```
 */
export declare class FileSystemStorageAdapter extends BaseStorageAdapter {
    protected readonly backendName = "filesystem";
    private readonly baseDir;
    private readonly extension;
    private readonly dirMode;
    private readonly fileMode;
    constructor(options: FileSystemAdapterOptions);
    connect(): Promise<void>;
    disconnect(): Promise<void>;
    ping(): Promise<boolean>;
    get(key: string): Promise<string | null>;
    protected doSet(key: string, value: string, options?: SetOptions): Promise<void>;
    delete(key: string): Promise<boolean>;
    exists(key: string): Promise<boolean>;
    expire(key: string, ttlSeconds: number): Promise<boolean>;
    ttl(key: string): Promise<number | null>;
    keys(pattern?: string): Promise<string[]>;
    incr(key: string): Promise<number>;
    decr(key: string): Promise<number>;
    incrBy(key: string, amount: number): Promise<number>;
    /**
     * Convert a storage key to a file path.
     * Sanitizes the key to be filesystem-safe.
     */
    private keyToPath;
    /**
     * Convert a filename back to a storage key.
     */
    private pathToKey;
    /**
     * Encode a key to be filesystem-safe.
     * Uses URL encoding to handle special characters.
     */
    private encodeKey;
    /**
     * Decode a filesystem-safe key back to original.
     */
    private decodeKey;
    /**
     * Read an entry from a file.
     */
    private readEntry;
    /**
     * Check if an entry is expired.
     */
    private isExpired;
    /**
     * Delete a file, returning true if it existed.
     */
    private deleteFile;
    /**
     * Atomic write: write to temp file then rename.
     * This ensures we don't corrupt the file if write is interrupted.
     */
    private atomicWrite;
    /**
     * Get suggestion message for pub/sub not supported error.
     */
    protected getPubSubSuggestion(): string;
}