import type { ImapFlow } from '../imap-flow.js';
/**
 * Credentials for the AUTHENTICATE command
 */
export interface AuthenticateCredentials {
    /** OAuth2 access token for OAUTHBEARER/XOAUTH2 authentication */
    accessToken?: string | undefined;
    /** Password for PLAIN or LOGIN authentication */
    password?: string | undefined;
    /** Force a specific login method (e.g., 'AUTH=PLAIN', 'AUTH=LOGIN') */
    loginMethod?: string | undefined;
    /** Authorization identity for PLAIN authentication */
    authzid?: string | undefined;
}
/**
 * Authenticates user using the best available method.
 *
 * @param connection - IMAP connection instance
 * @param username - The username to authenticate with
 * @param credentials - Authentication credentials
 * @returns The authenticated username, or undefined if already authenticated
 * @throws {Error} If no supported authentication mechanism is available or if authentication fails
 */
export default function authenticate(connection: ImapFlow, username: string, { accessToken, password, loginMethod, authzid }: AuthenticateCredentials): Promise<string | undefined>;