(** Common attribute utilities used across checkers. *)

type attrs = (string * string) list

let has_attr name attrs =
  List.exists (fun (n, _) -> Astring.String.Ascii.lowercase n = name) attrs

let get_attr name attrs =
  List.find_map (fun (n, v) ->
    if Astring.String.Ascii.lowercase n = name then Some v else None
  ) attrs

let get_attr_or name ~default attrs =
  Option.value ~default (get_attr name attrs)

let is_non_empty_attr name attrs =
  match get_attr name attrs with
  | Some v -> String.trim v <> ""
  | None -> false

(** Create a unit hashtable from a list of keys for O(1) membership testing. *)
let hashtbl_of_list items =
  let tbl = Hashtbl.create (List.length items) in
  List.iter (fun x -> Hashtbl.add tbl x ()) items;
  tbl

(** Check a list of attributes and report errors for any that are present. *)
let check_disallowed_attrs ~element ~collector ~attrs disallowed =
  List.iter (fun attr ->
    if has_attr attr attrs then
      Message_collector.add_typed collector
        (`Attr (`Not_allowed (`Attr attr, `Elem element)))
  ) disallowed