type purpose = {
  number: int32;
  name: string;
  comment: string;
}

let download ~output ~url =
  let open Bos in
  let res =
    OS.Cmd.run
      Cmd.(
        v "curl"
        % "--silent"
        % "--show-error"
        % "-o"
        % output
        % "-X"
        % "GET"
        % url)
  in
  match res with
  | Error (`Msg s) -> Fmt.failwith "download failure: %s" s
  | Ok () -> ()

let parse_purposes records =
  records
  |> List.filter_map (fun l ->
      match l with
      | a :: b :: c :: _ -> (
          let open Recfile_parser in
          match a.k = "Number" && b.k = "Name" && c.k = "Comment" with
          | false -> None
          | true ->
              Some
                {
                  number= Int32.of_int (int_of_string a.v);
                  name= String.lowercase_ascii b.v;
                  comment= c.v;
                })
      | _ -> None)
  |> List.filter (fun v -> v.number >= 1000_l)

let print_module purposes =
  let header =
    {|(* This file was generated from the GANA database:
   https://git-www.gnunet.org/gana.git/tree/gnunet-signatures/registry.rec *)|}
  in
  let pp ppf { number; name; comment } =
    Fmt.pf ppf "(** %s *)\nlet %s : int32 = %ld_l\n\n" comment name number
  in
  Fmt.pr "%s\n\n%a@." header (Fmt.list ~sep:Fmt.nop pp) purposes;
  ()

(* --- *)

let url =
  "https://git-www.gnunet.org/gana.git/plain/gnunet-signatures/registry.rec"

let main () =
  let tmp_file = Bos.OS.File.tmp "registry.rec.%s" |> Result.get_ok in
  download ~output:(Fpath.to_string tmp_file) ~url;
  let content = Bos.OS.File.read tmp_file |> Result.get_ok in
  match Recfile_parser.parse content with
  | Error msg -> Fmt.failwith "Recfile_parser parse error: %s" msg
  | Ok records -> print_module (parse_purposes records)

let () = main ()