export type MiddlewareExchange<T, R> = (req: T) => Promise<R>;
export type RequestMiddleware<T> = (req: T) => Promise<T>;
export type ResultMiddleware<T> = (res: T) => Promise<T>;
export declare class MiddlewareChain<T, R> {
    middlewareChain: MiddlewareExchange<T, R>;
    constructor(requestChain: MiddlewareExchange<T, R>);
    prepend(middleware: RequestMiddleware<T>): void;
    append(middleware: ResultMiddleware<R>): void;
    request(req: T): Promise<R>;
}