defmodule Macra do
  @arg_names ~w[a b c d e f g h i j k l m n o p q r s t u v w x y z]a

  def take_arguments(many) do
    for arg_name <- Enum.take(@arg_names, many), do: {arg_name, [], Elixir}
  end

  defmacro defreverse({:/, _, [{name, meta, _ }, arity]} , to: {function, call_meta, _ }) do
    args = take_arguments(arity)
    function_definition = { name, meta, args}
    call = {function, call_meta, Enum.reverse(args) }

    quote do
      def unquote(function_definition), do: unquote(call)
    end
  end

  defmacro defswap({:/, _, [{name, meta, _ }, arity]} , to: {function, call_meta, _ }) do
    args = take_arguments(arity)
    function_definition = { name, meta, args}
    {first, [second]} = Enum.split(args,arity-1)
    call = {function, call_meta, [second | first] }

    quote do
      def unquote(function_definition), do: unquote(call)
    end
  end


end

defmodule Test do

  require Macra
  import Macra

  def test(uno, due, tres,quatro) do
    IO.inspect uno
    IO.inspect due
    IO.inspect tres
    IO.inspect quatro
  end

  defreverse test_rev/4, to: test

  defswap swapped/4, to: test

end
IO.inspect "Original"
Test.test(1,2,3,4)
IO.inspect "Reversed"
Test.test_rev(1,2,3,4)
IO.inspect "Swapped"
Test.swapped(1,2,3,4)