less_naive.ex

defmodule LessNaive do
  def trim_string(string) do
    string
    |> String.graphemes()
    |> Enum.reduce_while("", fn grapheme, acc ->
      if counter(acc <> grapheme) <= 80,
        do: {:cont, acc <> grapheme},
        else: {:halt, acc}
    end)
  end
  
  defp counter(string), do: string |> String.codepoints |> Enum.count
end