defmodule Mix.Tasks.Demacro do
  use Mix.Task

  def run([filename | _]) do
    File.read!(filename)
    |> Code.string_to_quoted!()
    |> Macro.postwalk(fn a -> try_expand(a) end)
    |> Macro.to_string()
    |> IO.puts()
  end
  def try_expand({:defmodule, _, _} = b), do: b
  def try_expand({:def, _, _} = b), do: b
  def try_expand({:defp, _, _} = b), do: b
  def try_expand({:defmacro, _, _} = b), do: b
  def try_expand({:defmacrop, _, _} = b), do: b
  def try_expand(block) do
    try do
      Macro.expand(block, __ENV__)
    rescue
      e in ArgumentError -> block
    end
  end

end