/**
 * Encapsulates credential detection logic.
 *
 * @public
 */
export default class Credentials {
    /**
     * @param {Function=} usernameExtractor
     * @param {Function=} passwordExtractor
     */
    constructor(usernameExtractor?: Function | undefined, passwordExtractor?: Function | undefined);
    /**
     * The password extractor.
     *
     * @public
     * @returns {Function}
     */
    public get usernameExtractor(): Function;
    /**
     * The password extractor.
     *
     * @public
     * @returns {Function}
     */
    public get passwordExtractor(): Function;
    /**
     * Throws an {@link Error} if the instance is invalid.
     *
     * @public
     */
    public validate(): void;
    /**
     * Returns a string representation.
     *
     * @public
     * @returns {string}
     */
    public toString(): string;
    #private;
}