export type TokenRetrieveType = "header" | "form";
/**
 * Client Credential OAuth Client
 *
 * Will automatically process the token refresh logic
 *
 * refresh policy: half expire-in
 *
 * @example
 * ```js
 * // please remember share client instance for a same OAuth server
 * const client = new ClientCredentialsOAuthClient(
 *  "http://example/oauth/token",
 *  "client_id",
 *  "client_secret"
 * )
 * const response = await client.fetch("http://protected.by.token/resource", {
 *  method: "GET",
 * })
 * ```
 *
 *
 */
declare class ClientCredentialsOAuthClient {
    private readonly tokenUrl;
    private readonly clientId;
    private readonly clientSecret;
    private readonly scope;
    private readonly mut;
    private token;
    private expiresAt;
    private tokenRetrieveType;
    /**
     * a very simple oauth client credential client
     *
     * @param tokenUrl oauth token url
     * @param clientId oauth client id
     * @param clientSecret oauth client secret
     * @param retrieveType the clientId and clientSecret is put into header or form body
     * @param scope oauth scope
     */
    constructor(tokenUrl: string, clientId: string, clientSecret: string, retrieveType?: TokenRetrieveType, scope?: string);
    /**
     * fetch token directly
     * @private
     * @returns {Promise<any>}
     */
    private fetchOAuthResponse;
    /**
     * get header pair
     */
    getHeader(): Promise<{
        Authorization: string;
    }>;
    /**
     * get current valid oauth token
     *
     * @returns {Promise<string>}
     */
    getToken(): Promise<string>;
    /**
     * send requests with oauth token
     *
     */
    fetch(...args: Parameters<typeof fetch>): Promise<Response>;
}
export { ClientCredentialsOAuthClient };