/** @link [Proof Key for Code Exchange by OAuth Public Clients](https://datatracker.ietf.org/doc/html/rfc7636) */
/**
 * Generates random string for state and encodes them in url safe base64
 */
export declare const generateState: () => string;
/**
 * Generates code verifier
 *
 * @link [Client Creates a Code Verifier](https://datatracker.ietf.org/doc/html/rfc7636#section-4.1)
 */
export declare const generateCodeVerifier: () => string;
/**
 * Calculates the S256 PKCE code challenge for an arbitrary code verifier and encodes it in url safe base64
 *
 * @param {String} codeVerifier Code verifier to calculate the S256 code challenge for
 * @link [Client Creates the Code Challenge](https://datatracker.ietf.org/doc/html/rfc7636#section-4.2)
 */
export declare const generateCodeChallenge: (codeVerifier: string) => Promise<string>;