/**
 * StorageBackend — Unified storage abstraction layer
 *
 * Provides a common interface for AI sub-systems (session, context, memory,
 * user profile, follow-up) to switch between in-memory and database backends
 * without changing business logic.
 *
 * Usage:
 *   const backend = new MemoryStorageBackend<MyRecord>();
 *   // ... later, when DB is ready:
 *   const dbBackend = new DatabaseStorageBackend<MyRecord>(model, { keyField: 'session_id' });
 *   service.upgradeBackend(dbBackend);
 */
export interface StorageBackend<T extends Record<string, any>> {
    get(key: string): Promise<T | null>;
    set(key: string, value: T): Promise<void>;
    delete(key: string): Promise<boolean>;
    list(filter?: Partial<T>): Promise<T[]>;
    clear(): Promise<void>;
    readonly type: 'memory' | 'database';
}
/**
 * In-memory storage backend.
 */
export declare class MemoryStorageBackend<T extends Record<string, any>> implements StorageBackend<T> {
    readonly type: "memory";
    private data;
    get(key: string): Promise<T | null>;
    set(key: string, value: T): Promise<void>;
    delete(key: string): Promise<boolean>;
    list(filter?: Partial<T>): Promise<T[]>;
    clear(): Promise<void>;
}
/**
 * Database model interface aligned with @zhin.js/database's RelatedModel API.
 */
export interface DbModel {
    select(...fields: string[]): any;
    create(data: Record<string, any>): Promise<any>;
    update(data: Partial<any>): any;
    delete(condition: Record<string, any>): any;
}
/**
 * Database-backed storage backend.
 */
export declare class DatabaseStorageBackend<T extends Record<string, any>> implements StorageBackend<T> {
    private model;
    private options;
    readonly type: "database";
    constructor(model: DbModel, options: {
        /** The field name used as lookup key (e.g. 'session_id', 'user_id') */
        keyField: string;
    });
    get(key: string): Promise<T | null>;
    set(key: string, value: T): Promise<void>;
    delete(key: string): Promise<boolean>;
    list(filter?: Partial<T>): Promise<T[]>;
    clear(): Promise<void>;
}
/**
 * Helper to create a swappable backend ref.
 * Call `swap(newBackend)` to atomically upgrade from memory to database.
 */
export declare function createSwappableBackend<T extends Record<string, any>>(initial: StorageBackend<T>): {
    backend: StorageBackend<T>;
    swap: (next: StorageBackend<T>) => void;
};
//# sourceMappingURL=storage.d.ts.map