/**
 * @module
 *
 * Implements the `client_secret_basic` client authentication method, where the
 * client authenticates by sending its `client_id` and `client_secret` as a
 * Base64-encoded `Authorization: Basic` header.
 *
 * @see https://datatracker.ietf.org/doc/html/rfc6749#section-2.3.1
 */
import { ClientAuthMethod, ClientAuthMethodResponse } from "./types.js";
/**
 * {@link ClientAuthMethod} implementation for the `client_secret_basic` authentication method.
 *
 * Extracts client credentials from the `Authorization: Basic <base64(client_id:client_secret)>`
 * request header, as defined in RFC 6749 §2.3.1.
 *
 * @see https://datatracker.ietf.org/doc/html/rfc6749#section-2.3.1
 */
export declare class ClientSecretBasic implements ClientAuthMethod {
    /**
     * The identifier for this authentication method.
     * Always `"client_secret_basic"`.
     */
    get method(): "client_secret_basic";
    /**
     * Whether the client secret is optional for this method.
     * Always `false` - a client secret is required for `client_secret_basic`.
     */
    get secretIsOptional(): boolean;
    /**
     * Extracts the `client_id` and `client_secret` from the `Authorization: Basic` header.
     *
     * Sets `hasAuthMethod` to `true` only when a `Basic` scheme is detected, allowing
     * the caller to distinguish between "this method was attempted" and "no credentials provided".
     *
     * @param request - The incoming HTTP request.
     * @returns The extracted client credentials, or `{ hasAuthMethod: false }` if the
     *   `Authorization` header is absent or does not use the `Basic` scheme.
     */
    extractClientCredentials(request: Request): ClientAuthMethodResponse;
}
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