defmodule Understated do
  defmacro __using__(_options) do
    quote do
      import Understated.Machine
      import Understated.State
      import Understated.Transition
      import Understated.Entry

      Module.register_attribute(__MODULE__, :transitions, accumulate: true)
      Module.register_attribute(__MODULE__, :states, accumulate: true)
      Module.register_attribute(__MODULE__, :current_state, accumulate: false)

      @current_state ""

      @before_compile unquote(__MODULE__)
    end
  end

  defmacro __before_compile__(_env) do
    quote do
      def valid_states() do
        @states
        |> Enum.reverse()
      end

      def before_event(machine, _from, _to), do: machine
      def after_event(machine, _from, _to), do: machine

      def enter_state(machine, _from_state), do: machine

      def trigger(machine, _to_state), do: machine

      defp apply_state(machine, _state), do: machine
    end
  end
end