def_maybe.exs

  defmodule DefMaybe do
    defmacro defmaybe(fun) do
      quote bind_quoted: [fun: Macro.escape(fun, unquote: true)], location: :keep do
        {fun_name, fun_args} = Macro.decompose_call(fun)
        resource = List.first(fun_args)
        action = Keyword.get(opts, :action)

        def unquote(:"maybe_#{fun_name}")({:ok, unquote_splicing(fun_args)}) do
          {:ok, unquote(fun_name)(unquote_splicing(fun_args))}
        end

        def unquote(:"maybe_#{fun_name}")(otherwise) do
          otherwise
        end
      end
    end
  end

defmodule Test do
  import DefMaybe

  defmaybe foo(bar) 

  def foo(bar), do: bar
  
  def test do
    maybe_foo({:ok, "bar"})
  end
end