/**
 * @license
 * Copyright Google LLC All Rights Reserved.
 *
 * Use of this source code is governed by an MIT-style license that can be
 * found in the LICENSE file at https://angular.io/license
 */
import { Provider } from '@angular/core';
import { Observable } from 'rxjs';
import { HttpHandlerFn } from './interceptor';
import { HttpRequest } from './request';
import { HttpEvent } from './response';
/**
 * Options to configure how TransferCache should be used to cache requests made via HttpClient.
 *
 * @param includeHeaders Specifies which headers should be included into cached responses. No
 *     headers are included by default.
 * @param filter A function that receives a request as an argument and returns a boolean to indicate
 *     whether a request should be included into the cache.
 * @param includePostRequests Enables caching for POST requests. By default, only GET and HEAD
 *     requests are cached. This option can be enabled if POST requests are used to retrieve data
 *     (for example using GraphQL).
 *
 * @publicApi
 */
export type HttpTransferCacheOptions = {
    includeHeaders?: string[];
    filter?: (req: HttpRequest<unknown>) => boolean;
    includePostRequests?: boolean;
};
/**
 * Keys within cached response data structure.
 */
export declare const BODY = "b";
export declare const HEADERS = "h";
export declare const STATUS = "s";
export declare const STATUS_TEXT = "st";
export declare const URL = "u";
export declare const RESPONSE_TYPE = "rt";
export declare function transferCacheInterceptorFn(req: HttpRequest<unknown>, next: HttpHandlerFn): Observable<HttpEvent<unknown>>;
/**
 * Returns the DI providers needed to enable HTTP transfer cache.
 *
 * By default, when using server rendering, requests are performed twice: once on the server and
 * other one on the browser.
 *
 * When these providers are added, requests performed on the server are cached and reused during the
 * bootstrapping of the application in the browser thus avoiding duplicate requests and reducing
 * load time.
 *
 */
export declare function withHttpTransferCache(cacheOptions: HttpTransferCacheOptions): Provider[];