config.ml

open Rresult
open Sexplib0.Sexp

let parse root_path =
  let read_config path =
    let root_path = path |> Fpath.to_dir_path |> Fpath.normalize in
    let odot_file = Fpath.append root_path Model.config_file in
    Bos.OS.File.read odot_file
  in

  let read_link l =
    let sep_l =
      let sep_l' (models, invalids) l' =
        match l' with
        | List [ Atom s; Atom t ] ->
            ( Model.{ source = Fpath.v s; target = Fpath.v t } :: models,
              invalids )
        | _ -> (models, l' :: invalids)
      in

      List.fold_left sep_l' ([], []) l
    in

    if List.length (snd sep_l) > 0 then Error (`Invalid_Symlink (snd sep_l))
    else Ok (fst sep_l)
  in

  let read_rules = function
    | List ss -> Ok (read_link ss)
    | Atom s -> Error (`Invalid_Config s)
  in

  let to_result path contents =
    contents |> Parsexp.Single.parse_string >>| read_rules
    |> R.error_to_msg
         ~pp_error:(Parsexp.Parse_error.report ~filename:(Fpath.to_string path))
  in
  let path = Fpath.v root_path in
  path |> read_config >>= to_result path