import { NextRequest } from "next/server.js";
import { ProxyOptions } from "../types/index.js";
/**
 * Securely builds a Headers object for forwarding a NextRequest via fetch.
 *
 * This function:
 * 1. Uses a strict **allow-list** (DEFAULT_HEADER_ALLOW_LIST).
 * 2. Strips all hop-by-hop headers as defined by https://datatracker.ietf.org/doc/html/rfc2616#section-13.5.1.
 *
 * @param request The incoming NextRequest object.
 * @returns A WHATWG Headers object suitable for `fetch`.
 */
export declare function buildForwardedRequestHeaders(request: NextRequest): Headers;
/**
 * Securely builds a Headers object for forwarding a fetch response.
 *
 * This function:
 * 1. Strips all hop-by-hop headers as defined by https://datatracker.ietf.org/doc/html/rfc2616#section-13.5.1.
 *
 * @param request The incoming Response object.
 * @returns A WHATWG Headers object suitable for `fetch`.
 */
export declare function buildForwardedResponseHeaders(response: Response): Headers;
/**
 * Builds a URL representing the upstream target for a proxied request.
 *
 * This function correctly handles the path transformation by:
 * 1. Extracting the path segment that comes AFTER the proxyPath
 * 2. Intelligently combining it with targetBaseUrl to avoid path segment duplication
 *
 * Example:
 *   - proxyPath: "/me"
 *   - targetBaseUrl: "https://issuer/me/v1"
 *   - incoming: "/me/v1/some-endpoint"
 *   - remaining path: "/v1/some-endpoint" (after removing "/me")
 *   - result: "https://issuer/me/v1/some-endpoint" (no /v1 duplication)
 *
 * @param req - The incoming request to mirror when constructing the target URL.
 * @param options - Proxy configuration containing the base URL and proxy path.
 * @returns A URL object pointing to the resolved target endpoint with forwarded query parameters.
 */
export declare function transformTargetUrl(req: NextRequest, options: ProxyOptions): URL;