external set_value : Dom.element -> string -> unit = "value"
  [@@bs.set]

external value : Dom.element -> string = "value"
  [@@bs.get]

external set_attribute : Dom.element -> string -> string -> unit = "setAttribute"
  [@@bs.send]

external set_class_name : Dom.element -> string -> unit = "className"
  [@@bs.set]

external add_event_listener : Dom.element -> string -> (Dom.event -> unit) -> unit
  = "addEventListener"
  [@@bs.send]

external remove_event_listener : Dom.element -> string -> (Dom.event -> unit) -> unit
  = "removeEventListener"
  [@@bs.send]

external append_child : Dom.element -> Dom.element -> unit = "appendChild"
  [@@bs.send]

external first_child : Dom.element -> Dom.element Js.Nullable.t = "firstChild"
  [@@bs.get]

external remove_child : Dom.element -> Dom.element -> unit = "removeChild"
  [@@bs.send]

external click : Dom.element -> unit = "click"
  [@@bs.send]

let remove_first_child element =
  match Js.toOption (first_child element) with
  | Some child ->
      let () = remove_child element child in
      true
  | _ -> false

let rec remove_children element =
  if remove_first_child element then remove_children element else ()

let mount_on base element =
  let () = remove_children base in
  append_child base element

external files : Dom.element -> string Js.Array.t = "files"
  [@@bs.get]

external focus : Dom.element -> unit = "focus"
  [@@bs.send]