     end
   end
 
+  @spec zero_pad(non_neg_integer, non_neg_integer) :: String.t
   def zero_pad(n, len) when is_integer(n) do
     n |> to_string |> String.rjust(len, ?0)
   end

  Helper utilities used throughout LexibombServer.
  """

  def draw_grid_line(size, :top),    do: do_draw_grid_line(size, "┌", "┬", "┐")
  def draw_grid_line(size, :middle), do: do_draw_grid_line(size, "├", "┼", "┤")
  def draw_grid_line(size, :bottom), do: do_draw_grid_line(size, "└", "┴", "┘")

  defp do_draw_grid_line(1, first, _, last) do
    Enum.join([first, "───", last])

    Enum.join(separators, "───")
  end

  @spec draw_segments([String.t], String.t) :: String.t
  def draw_segments(strings, sep \\ "│") do
    sep <> Enum.join(strings, sep) <> sep
  end
