import type { BasicCredentials, BearerCredentials, Credentials } from "../types";
/**
 * Type predicate narrowing {@link Credentials} to {@link BasicCredentials}
 * (username/password). Prefer this over inline `"username" in credentials`
 * checks so the discrimination lives in one place.
 */
export declare const isBasicCredentials: (credentials?: Credentials) => credentials is BasicCredentials;
/**
 * Type predicate narrowing {@link Credentials} to {@link BearerCredentials}.
 */
export declare const isBearerCredentials: (credentials?: Credentials) => credentials is BearerCredentials;
/**
 * Render a {@link Credentials} value as the verbatim value of an
 * `Authorization` HTTP header (`"Basic ..."` or `"Bearer ..."`).
 *
 * Shared between the gRPC metadata generator and the HTTP fallback so the two
 * paths stay in lockstep.
 */
export declare const toAuthorizationHeader: (credentials: Credentials) => string;