import { OptimizelyGraphConfig } from "../types.js";
import { AuthMode, type IOptiGraphClient, type FrontendUser } from "./types.js";
/**
 * Test if the provided value is a valid FrontendUser object
 *
 * @param       toTest      The value to test
 * @returns     `true` If toTest is a FrontendUser, `false` otherwise
 */
export declare function isValidFrontendUser(toTest?: any): toTest is FrontendUser;
export declare function validateToken(newToken?: string): boolean;
export declare function getAuthMode(token?: string): AuthMode;
export declare function base64encode(binaryString: string): string;
export declare function isError(toTest: any): toTest is Error;
/**
 *
 * @deprecated
 * @see         `isOptiGraphClient()`
 * @param       client      The value to test
 * @returns     `true` when the value can be used as IOptiGraphClient, `false` if not
 */
export declare function isContentGraphClient(client: any): client is IOptiGraphClient;
/**
 * Test if the provided GraphQL Client is an IOptiGraphClient instance and thus allows
 * the extended API of this interface to be used.
 *
 * @param       client      The GraphQL Client to test
 * @returns     `true` when the value can be used as IOptiGraphClient, `false` if not
 */
export declare function isOptiGraphClient(client: any): client is IOptiGraphClient;
/**
 * Test if the provided Object can be understood to be an instance of the
 * Optimizely Graph configuration
 *
 * @param       client      The value to test
 * @returns     `true` when the value can be understood as a config object, `false` otherwise
 */
export declare function isOptiGraphConfig(client: any): client is OptimizelyGraphConfig;