import { ExtensionKey, type HttpRequest } from "../http/index.js";
import type { HttpLayer } from "../layer/index.js";
import type { HttpService } from "../service/index.js";
export declare const REQUEST_ID: ExtensionKey<string>;
export type MakeRequestId = (req: HttpRequest) => string | null;
/**
 * A layer that manages request IDs for incoming requests.
 *
 * This function ensures that each request is associated with a unique
 * identifier, which can be either provided in the request headers or
 * dynamically generated.
 *
 * @example
 * ```ts
 * import { SetRequestIdLayer } from "@taxum/core/middleware/request-id";
 * import { m, Router } from "@taxum/core/routing";
 *
 * const router = new Router()
 *     .route("/", m.get(() => "Hello World))
 *     .layer(SetRequestIdLayer.default());
 * ```
 */
export declare class SetRequestIdLayer implements HttpLayer {
    private readonly headerName;
    private readonly makeRequestId;
    /**
     * Creates a new {@link SetRequestIdLayer}.
     *
     * @param headerName - the name of the header to be used.
     * @param makeRequestId - a function to generate a request ID.
     */
    constructor(headerName?: string, makeRequestId?: MakeRequestId);
    /**
     * Creates a new middleware with the header name defaulting to `X-Request-Id`
     * with UUID request IDs.
     */
    static default(): SetRequestIdLayer;
    layer(inner: HttpService): HttpService;
}
/**
 * A layer that propagates a request ID header from the incoming request to the
 * outgoing response.
 *
 * The purpose of this layer is to ensure consistency of the request ID header
 * across the request-response cycle. If the response does not already include
 * the request ID header, it will include the one from the incoming request.
 * Additionally, the request ID is stored in the response extensions for further
 * processing.
 *
 * @example
 * ```ts
 * import { PropagateRequestId } from "@taxum/core/middleware/request-id";
 * import { m, Router } from "@taxum/core/routing";
 *
 * const router = new Router()
 *     .route("/", m.get(() => "Hello World))
 *     .layer(PropagateRequestIdLayer.default());
 * ```
 */
export declare class PropagateRequestIdLayer implements HttpLayer {
    private readonly headerName;
    /**
     * Creates a new {@link PropagateRequestIdLayer}.
     *
     * @param headerName - the name of the header to be used.
     */
    constructor(headerName?: string);
    /**
     * Creates a new middleware with the header name defaulting to `X-Request-Id`.
     */
    static default(): PropagateRequestIdLayer;
    layer(inner: HttpService): HttpService;
}