#include <Button_SL.hpp>  // https://github.com/DoImant/Button_SL

using namespace Btn;

//////////////////////////////////////////////////
// Global constants and variables
//////////////////////////////////////////////////
constexpr uint8_t buttonPin {4};
constexpr uint8_t relaisPins[] {5, 6, 7, 8};      // Relais pins
constexpr uint8_t relaisPinsRev[] {8, 7, 6, 5};   // The same pins in reverse order
constexpr unsigned long switchInterval_ms {500};

enum class State : uint8_t { off, on };

ButtonSL button {buttonPin};

//////////////////////////////////////////////////
// Functions
//////////////////////////////////////////////////
template <size_t N> void switchRelais(const uint8_t (&pins)[N], State state, unsigned long period) {
  for (auto& pin : pins) {
    digitalWrite(pin, static_cast<int>(state));
    delay(period);
  }
}

//////////////////////////////////////////////////
// Main Program
//////////////////////////////////////////////////
void setup() {
  for (auto& relaisPin : relaisPins) {
    pinMode(relaisPin, OUTPUT);
  }
  button.begin();
  button.releaseOn();   // Releases button as soon as the time for a long button press has been reached.
}

void loop() {
  static State lightState {State::off};

  if (button.tick() != Btn::ButtonState::notPressed) {
    lightState = (lightState == State::off) ? State::on : State::off;
    (lightState == State::off) ? switchRelais(relaisPinsRev, lightState, switchInterval_ms)
                               : switchRelais(relaisPins, lightState, switchInterval_ms);
  }
}