/**
 * Pluggable Backend API for Named Blackboards
 *
 * Defines the `BlackboardBackend` interface that abstracts the storage layer
 * used by `SharedBlackboard`. Two built-in implementations are provided:
 *
 *  - `FileBackend`   — persisted to disk via LockedBlackboard (default)
 *  - `MemoryBackend` — pure in-memory, no disk writes (testing / ephemeral boards)
 *
 * Custom backends (Redis, CRDT, cloud storage, etc.) can be implemented by
 * satisfying the `BlackboardBackend` interface and passing the instance to
 * `orchestrator.getBlackboard(name, { backend: myBackend })`.
 *
 * @module BlackboardBackend
 * @version 1.0.0
 * @license MIT
 */
import type { BlackboardEntry } from './locked-blackboard';
export type { BlackboardEntry };
/**
 * Storage abstraction for a `SharedBlackboard` instance.
 *
 * Implement this interface to plug in any storage backend:
 * file system, Redis, an in-memory Map, a cloud KV store, etc.
 *
 * @example
 * ```typescript
 * class RedisBackend implements BlackboardBackend {
 *   constructor(private client: RedisClient) {}
 *   read(key: string) { ... }
 *   write(key, value, sourceAgent, ttl) { ... }
 *   delete(key) { ... }
 *   listKeys() { ... }
 *   getSnapshot() { ... }
 * }
 * const board = orchestrator.getBlackboard('prod', { backend: new RedisBackend(client) });
 * ```
 */
export interface BlackboardBackend {
    /**
     * Read a single entry. Returns `null` if not found or expired.
     */
    read(key: string): BlackboardEntry | null;
    /**
     * Write a value. Returns the stored entry including generated metadata.
     * @param key         The entry key
     * @param value       Any JSON-serializable value
     * @param sourceAgent The agent performing the write
     * @param ttl         Optional time-to-live in seconds
     */
    write(key: string, value: unknown, sourceAgent: string, ttl?: number): BlackboardEntry;
    /**
     * Delete an entry by key. Returns `true` if it existed.
     */
    delete(key: string): boolean;
    /**
     * Return all non-expired keys.
     */
    listKeys(): string[];
    /**
     * Return a full snapshot of all non-expired entries, keyed by entry key.
     */
    getSnapshot(): Record<string, BlackboardEntry>;
}
/**
 * File-backed persistent storage using `LockedBlackboard`.
 *
 * All writes are atomic and file-locked. Data survives process restarts.
 * This is the default backend used when no `backend` option is provided to
 * `orchestrator.getBlackboard()`.
 *
 * @example
 * ```typescript
 * const board = orchestrator.getBlackboard('reports', {
 *   backend: new FileBackend('./data/reports'),
 * });
 * ```
 */
export declare class FileBackend implements BlackboardBackend {
    private lb;
    constructor(basePath: string);
    read(key: string): BlackboardEntry | null;
    write(key: string, value: unknown, sourceAgent: string, ttl?: number): BlackboardEntry;
    delete(key: string): boolean;
    listKeys(): string[];
    getSnapshot(): Record<string, BlackboardEntry>;
}
/**
 * Pure in-memory backend — data lives only for the lifetime of the process.
 *
 * Ideal for:
 * - Unit testing (no temp directories, instant, isolated)
 * - Short-lived ephemeral boards
 * - Read-heavy caches that don't need persistence
 *
 * Thread-safety note: Node.js is single-threaded; no locking is needed for
 * in-process use. For multi-process scenarios use `FileBackend` or a
 * distributed backend (Redis, etc.).
 *
 * @example
 * ```typescript
 * const board = orchestrator.getBlackboard('ephemeral', {
 *   backend: new MemoryBackend(),
 * });
 * ```
 */
export declare class MemoryBackend implements BlackboardBackend {
    private store;
    private isExpired;
    read(key: string): BlackboardEntry | null;
    write(key: string, value: unknown, sourceAgent: string, ttl?: number): BlackboardEntry;
    delete(key: string): boolean;
    listKeys(): string[];
    getSnapshot(): Record<string, BlackboardEntry>;
    /**
     * Clear all entries. Useful for test teardown.
     */
    clear(): void;
    /**
     * Returns the current entry count (including expired entries not yet evicted).
     */
    size(): number;
}
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