(*  MTE - the MirageOS Taler Exchange
    Copyright (C) 2025 Olivier Pierre <swrup@protonmail.com>

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU Affero General Public License as published by
    the Free Software Foundation, version 3.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU Affero General Public License for more details.

    You should have received a copy of the GNU Affero General Public License
    along with this program.  If not, see <https://www.gnu.org/licenses/>. *)

module Static = struct
  let select_file headers kind =
    let open Syntax in
    let* ext =
      Option.to_result ~none:"no acceptable mimetype"
        (Headers.select_extension headers)
    in
    let* lang =
      Option.to_result ~none:"no acceptable language"
        (Headers.select_language headers)
    in
    let content = Assets.get_content ~lang ~ext kind in
    content

  (* /terms + /privacy

     - try to find a response with an acceptable mime-type,
     - then pick the version in the most preferred language of the user,
     - and finally apply compression if that is allowed by the client
     - set ETAG header
     - If it did not change, a "304 Not Modified" response will be returned

     TODO:
       - The ETAG is encoded in Crockford base-32
       - A "Taler-Terms-Version" header is generated to indicate the legal version of the terms
       - When returning a full response (not a "304 Not Modified"), the server
         should also include a "Avail-Languages" header which includes a
         comma-separated list of the languages in which the terms of service are available in
  *)
  let static kind req _server _env =
    let get_ok = function
      | Error e -> Fmt.failwith "TODO handle me, %s" e
      | Ok v -> v
    in
    let etag =
      (* TODO keep our static asset etag as Etag.t in Config? *)
      Assets.etag kind |> Headers.Etag.of_crockford32 |> Result.get_ok
    in
    let headers = Vif.Request.headers req in
    let has_matching_etag =
      get_ok
      @@
      match Vif.Headers.get headers "if-none-match" with
      | None -> Ok false
      | Some s ->
          Headers.Etag.parse s |> Result.map (Headers.Etag.evaluate etag)
    in
    let open Vif.Response.Syntax in
    match has_matching_etag with
    | true ->
        let* () = Vif.Response.empty in
        Vif.Response.respond `Not_modified
    | false ->
        let data = select_file headers kind |> get_ok in
        let compression = Headers.select_encoding headers in
        let* () = Vif.Response.with_string ?compression req data in
        let etag_field_value = Headers.Etag.to_field_value etag in
        let* () = Vif.Response.add ~field:"etag" etag_field_value in
        (* TODO content-type *)
        let* () =
          Vif.Response.add ~field:"content-type" "html; charset=utf-8"
        in
        Vif.Response.respond `OK

  let terms = static Assets.Terms
  let privacy = static Assets.Privacy
end

let routes =
  let open Vif.Uri in
  let open Vif.Route in
  (*let open Vif.Type in*)
  [
    get (rel / "terms" /?? nil) --> Static.terms
  ; get (rel / "privacy" /?? nil) --> Static.privacy
  ]

let () =
  Miou_unix.run @@ fun () ->
  let env = () in
  let middlewares = Vif.Middlewares.[] in
  Vif.run ~middlewares routes env