/**
 * OAuth2 Authentication Provider
 *
 * Handles OAuth2 authentication with support for:
 * - Client credentials grant
 * - Password grant (resource owner)
 * - Authorization code grant (requires pre-issued code)
 *
 * P0: Refresh token support for automatic token renewal
 */
import { AuthProvider, AuthResult, OAuth2AuthConfig } from './index.js';
export declare class OAuth2Provider implements AuthProvider<OAuth2AuthConfig> {
    readonly type: "oauth2";
    authenticate(config: OAuth2AuthConfig): Promise<AuthResult>;
    /**
     * P0: Refresh OAuth2 access token using refresh token
     */
    refresh(config: OAuth2AuthConfig): Promise<AuthResult>;
    /**
     * P0: Perform refresh token flow
     */
    private performRefresh;
    clear(config: OAuth2AuthConfig): Promise<void>;
    validate(config: OAuth2AuthConfig): Promise<boolean>;
    private getCacheKey;
}