#define T0_BUTTON_GPIO 2  // Button
#define T1_BUTTON_GPIO 3 // Button
#define P0_LED_GPIO 4     // LED
#define P1_LED_GPIO 5     // LED

class Grafcet
{
public:

  Grafcet()
  {
    initGPIO();
    resetStates();
  }

  void resetStates()
  {
      // Activation des etapes initiales.
      // Desactivation des autres etapes.
      etapes[0] = true;  // Etape P0
      etapes[1] = false; // Etape P1
  }

  void update()
  {
      // Do actions (set outputs)
      outputs[0] = false;
      outputs[1] = false;
      if (etapes[0])
      {
        outputs[0] = true;
      }
      if (etapes[1])
      {
        outputs[1] = true;
      }

      digitalWrite(P0_LED_GPIO, outputs[0]);
      digitalWrite(P1_LED_GPIO, outputs[1]);

      // Get sensor values (read inputs)
      inputs[0] = !digitalRead(T0_BUTTON_GPIO);
      inputs[1] = !digitalRead(T1_BUTTON_GPIO);

      // Update transitions
      transitions[0] = etapes[0] && T0();
      transitions[1] = etapes[1] && T1();

      // Update states
      if (transitions[0])
      {
          etapes[0] = false;
          etapes[1] = true;
      }
      if (transitions[1])
      {
          etapes[1] = false;
          etapes[0] = true;
      }
  }

private:

    void initGPIO()
    {
      // Initialisation des entrees
      pinMode(T0_BUTTON_GPIO, INPUT_PULLUP);
      pinMode(T1_BUTTON_GPIO, INPUT_PULLUP);

      // Initialisation des sorties
      pinMode(P0_LED_GPIO, OUTPUT);
      pinMode(P1_LED_GPIO, OUTPUT);
    }

    inline bool T0() { return inputs[0]; } const;
    inline bool T1() { return inputs[1] && (!inputs[0]); } const;

private:

    bool etapes[2];
    bool transitions[2];
    bool inputs[2];
    bool outputs[2];
};

static Grafcet g;

void setup()
{
}

void loop()
{
  g.update();
}