import { CommandContext } from "./command.js";
import { HttpRequest, HttpResponse } from "./request-response.js";
export interface MiddlewareInput<In> {
    request: HttpRequest;
    context: In;
    next: <O extends CommandContext>(context: O) => Promise<MiddlewareOutput<O>>;
}
export interface MiddlewareOutput<Context> extends HttpResponse {
    context?: Context;
}
export type Middleware<In, Out> = (input: MiddlewareInput<In>) => Promise<MiddlewareOutput<Out>> | MiddlewareOutput<Out>;
/**
 * Utility for creating a Middleware function that combines its output context
 * with the input context.
 *
 * ```ts
 * const auth = middleware(({request, next}) => {
 *   return next({
 *     isAuthenticated: request.headers.Authorization !== undefined
 *   })
 * });
 *
 * api.use(auth).command("myAuthorizedCommand", async (request, { isAuthenticated }) => {
 *   if (isAuthenticated) {
 *     // do work
 *   }
 * })
 * ```
 *
 * @param fn
 * @returns
 */
export declare function middleware<PrevContext extends CommandContext = CommandContext, OutContext extends CommandContext = CommandContext>(fn: Middleware<PrevContext, OutContext>): <In extends PrevContext>(input: MiddlewareInput<In>) => Promise<MiddlewareOutput<OutContext>>;
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