(*****************************************************************************)
(*                                                                           *)
(* Open Source License                                                       *)
(* Copyright (c) 2022 Nomadic Labs, <contact@nomadic-labs.com>               *)
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(* copy of this software and associated documentation files (the "Software"),*)
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(* DEALINGS IN THE SOFTWARE.                                                 *)
(*                                                                           *)
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let make_transform_callback forwarding_endpoint callback conn req body =
  let open Lwt_syntax in
  let* answer = callback conn req body in
  let open Cohttp in
  let uri = Request.uri req in
  let answer_has_not_found_status = function
    | `Expert (response, _) | `Response (response, _) ->
        Cohttp.Response.status response = `Not_found
  in
  if answer_has_not_found_status answer then
    let overriding = Uri.to_string forwarding_endpoint ^ Uri.path uri in
    let headers = Cohttp.Header.of_list [("Location", overriding)] in
    let response =
      Cohttp.Response.make ~status:`Moved_permanently ~headers ()
    in
    Lwt.return (`Response (response, Cohttp_lwt.Body.empty))
  else Lwt.return answer

let query_forwarder forwarding_endpoint =
  Resto_cohttp_server.Server.
    {transform_callback = make_transform_callback forwarding_endpoint}