/**
 * Logs in a user with the given credentials.
 *
 * @param natsUrl - The url to connect to the NATS server.
 * @param username - The username for authentication.
 * @param password - The password for authentication.
 *
 * @returns A promise that resolves once the user is logged in.
 * The resolved value is the logged-in user object.
 *
 * @throws Error If the provided credentials are incorrect.
 */
export declare function login(natsUrl: string, username: string, password: string): Promise<import("./model.ts").User | null>;
/**
 * Logs out the user if currently logged in.
 *
 * @returns A promise that resolves once the user is logged out.
 */
export declare function logout(): Promise<void>;
/**
 * Checks if a user is logged in.
 *
 * @returns `true` if the user is logged in, `false` otherwise.
 */
export declare function isLoggedIn(): boolean;