import { MessageTransport, IOfflineStorage, OfflineStorageOptions } from "./types";
export declare class OfflineStorage implements IOfflineStorage {
    cachePath: string;
    cacheLimit: number;
    transport: MessageTransport;
    constructor(transport: MessageTransport);
    private _sendAndDelete;
    init(offlineStorageOptions: OfflineStorageOptions | undefined): this;
    save(transportItem: string, callback: (err: Error | null) => void): void;
    retrieve(callback: (error: NodeJS.ErrnoException | null, items: string[]) => void): void;
    send(callback: (error: Error | null, items?: string[]) => void): void;
}