defmodule Irc.Parser.Mode do
  @moduledoc """
  Mode change parser
  """

  def changes(string, previous) do
    list = to_charlist(string)
    acc_changes(list, nil, previous)
  end

  defp acc_changes([?+ | rest], _, acc) do
    acc_changes(rest, true, acc)
  end

  defp acc_changes([?- | rest], _, acc) do
    acc_changes(rest, false, acc)
  end

  defp acc_changes([0x20 | _], _, acc), do: acc

  defp acc_changes([char | rest], action, acc) do
    acc = if action do
      [char | acc]
    else
      List.delete(acc, char)
    end
    acc_changes(rest, action, acc)
  end

  defp acc_changes([], _, acc), do: acc

end