import { HttpMessage } from "@http4t/core/contract";
import { MessageLens, RoutingResult } from "../lenses";
export declare class HeaderLens<TMessage extends HttpMessage = HttpMessage> implements MessageLens<TMessage, string> {
    readonly name: string;
    constructor(name: string);
    get(output: TMessage): Promise<RoutingResult<string>>;
    set<SetInto extends TMessage>(into: SetInto, value: string): Promise<SetInto>;
}
export declare function header<TMessage extends HttpMessage>(name: string): MessageLens<TMessage, string>;
export declare function headers<T extends {
    [k: string]: string;
}, TMessage extends HttpMessage>(them: T): MessageLens<TMessage, T>;
//# sourceMappingURL=HeaderLens.d.ts.map