import Session from "../model/Session";
import StorageEngine from './StorageEngine';
declare class SessionStorage {
    private static readonly LOCAL_SESSION_STORAGE_KEY;
    private static readonly LOCAL_CHECKPOINT_STORAGE_KEY;
    private static readonly LOCAL_NTP_CHECKPOINT_STORAGE_KEY;
    private _session?;
    private _checkpoint?;
    private _ntpCheckpoint?;
    private storage;
    constructor(storageEngine: StorageEngine, externalSessionId?: string);
    set session(session: Session);
    get session(): Session | undefined;
    set checkpoint(date: Date);
    get checkpoint(): Date | undefined;
    set ntpCheckpoint(date: Date);
    get ntpCheckpoint(): Date | undefined;
    private storeSession;
    private retrieveSession;
    private retrieveCheckpoint;
}
export default SessionStorage;