import { FetchClientOptions, FetchRequestOptions, HttpResponse } from './types';
export declare class FetchClient {
    private readonly options;
    constructor(options?: FetchClientOptions);
    fetch(url: string, options?: FetchRequestOptions): Promise<Response>;
    request<T = unknown>(url: string, options?: FetchRequestOptions): Promise<HttpResponse<T>>;
    /**
     * Merges the three header layers, later ones replacing earlier ones.
     *
     * Deliberately not an object spread into `new Headers()`: header names are
     * case-insensitive, but object keys are not, so `Authorization` and `authorization` would
     * both survive the spread — and a record init is applied with `append`, which joins the
     * two into `Bearer stale, Bearer fresh` instead of overriding. `set()` per entry is
     * case-insensitive and replaces, which is what a layered merge means.
     */
    private buildHeaders;
    private buildBody;
    private buildError;
    private readBodySafely;
    private readBody;
    private appendParams;
    private resolveUrl;
}