let mimetype_ext_assoc =
  [
    (("text", "plain"), ".txt"); (("text", "markdown"), ".md")
  ; (("text", "html"), ".html"); (("text", "html"), ".htm")
  ; (("application", "pdf"), ".pdf"); (("image", "jpeg"), ".jpg")
  ; (("image", "jpeg"), ".jpeg"); (("image", "png"), ".png")
  ; (("image", "gif"), ".gif")
  ]

(* <> than the actual set of "supported" extension (which depends on config files) *)
let all_known_mimetypes, all_known_extensions = List.split mimetype_ext_assoc
let is_valid_filename path = Fpath.mem_ext all_known_extensions path

let media_to_known_mimetype = function
  | Cohttp.Accept.MediaType (m, m_sub) ->
      List.find_opt (( = ) (m, m_sub)) all_known_mimetypes
  | AnyMediaSubtype m ->
      List.find_opt (fun (m', _) -> String.equal m m') all_known_mimetypes
  | AnyMedia -> Some Config.default_mimetype

let mimetype_to_extension (m, m_sub) =
  assert (m <> "*");
  assert (m_sub <> "*");
  List.assoc_opt (m, m_sub) mimetype_ext_assoc

let extension_to_mimetype ext =
  List.find_map
    (fun (mime, ext') ->
      match String.equal ext ext' with false -> None | true -> Some mime)
    mimetype_ext_assoc

(* -- pretty printers -- *)
let pp_mime fmt mime = Fmt.pf fmt "%s/%s" (fst mime) (snd mime)
let pp_array pp_item item = Fmt.array ~sep:(Fmt.any ", ") pp_item item