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interface DownloadParams {
  appId?: string;
  appVersion?: string;
}

interface Env {
  R2_BUCKET: R2Bucket;
  ORIGIN_URL: string;
  ENVIRONMENT: "dev" | "prod";
}


type AddCtxAndEnvType<T> = Omit<T, "ctx" | "env"> & {
  ctx?: ExecutionContext;
  env?: Env;
};

type Awaitable<T> = T | PromiseLike<T>;
type TypedMiddleware<T extends (...args) => any> = Handler<
  Awaited<ReturnType<T>> & RouteContext
>;
const typedParams =
  () =>
  async <X extends BasicsContext>(
    ax: Awaitable<X>
  ): Promise<X & { downloadParams?: DownloadParams }> => {
    const x = await ax;
    return Object.assign(x, { downloadParams: x.params as DownloadParams });
  };

const middleware = combine(basics(), typedParams());

const handler: TypedMiddlware<typeof middleware> = async (
  req,
  {
    downloadParams,
    userAgent,
    env,
    ctx,
    waitUntil,
    url,
  }: AddCtxAndEnvType<Parameters<TypedMiddleware<typeof middleware>>[1]>
): Promise<Response> => {
  // ...
}