/**
 * @license
 * Copyright 2026 Google LLC
 * SPDX-License-Identifier: Apache-2.0
 */
import type { HttpHeaders } from '@a2a-js/sdk/client';
import type { A2AAuthProvider, A2AAuthProviderType } from './types.js';
/**
 * Abstract base class for A2A authentication providers.
 * Provides default implementations for optional methods.
 */
export declare abstract class BaseA2AAuthProvider implements A2AAuthProvider {
    /**
     * The type of authentication provider.
     */
    abstract readonly type: A2AAuthProviderType;
    /**
     * Get the HTTP headers to include in requests.
     * Subclasses must implement this method.
     */
    abstract headers(): Promise<HttpHeaders>;
    protected static readonly MAX_AUTH_RETRIES = 2;
    protected authRetryCount: number;
    /**
     * Check if a request should be retried with new headers.
     *
     * The default implementation checks for 401/403 status codes and
     * returns fresh headers for retry. Subclasses can override for
     * custom retry logic.
     *
     * @param _req The original request init
     * @param res The response from the server
     * @returns New headers for retry, or undefined if no retry should be made
     */
    shouldRetryWithHeaders(_req: RequestInit, res: Response): Promise<HttpHeaders | undefined>;
    /**
     * Initialize the provider. Override in subclasses that need async setup.
     */
    initialize(): Promise<void>;
}