/**
 * SPDX-FileCopyrightText: 2019 Nextcloud GmbH and Nextcloud contributors
 * SPDX-License-Identifier: GPL-3.0-or-later
 */
export interface CsrfTokenObserver {
    (token: string): void;
}
/**
 * Get current request token
 *
 * @return Current request token or null if not set
 */
export declare function getRequestToken(): string | null;
/**
 * Set a new CSRF token (e.g. because of session refresh).
 * This also emits an event bus event for the updated token.
 *
 * @param token - The new token
 * @throws {Error} - If the passed token is not a potential valid token
 */
export declare function setRequestToken(token: string): void;
/**
 * Fetch the request token from the API.
 * This does also set it on the current context, see `setRequestToken`.
 *
 * @throws {Error} - If the request failed
 */
export declare function fetchRequestToken(): Promise<string>;
/**
 * Add an observer which is called when the CSRF token changes
 *
 * @param observer The observer
 * @return A function to unsubscribe the observer
 */
export declare function onRequestTokenUpdate(observer: CsrfTokenObserver): () => void;