class Timer {
public:
  void start() { timeStamp = millis(); }
  bool operator()(const uint32_t duration) const { return (millis() - timeStamp >= duration) ? true : false; }

private:
  uint32_t timeStamp {0};
};

enum class ProgramMode : byte { stop, modeA, modeB };
enum class LightStatus : byte { start, on, off };

// constexpr uint32_t TIME_MODE_A {1000 * 3600UL * 2};   // 2 Hours
// constexpr uint32_t TIME_MODE_B {1000 * 3600UL * 8};   // 8 Hours

// constexpr uint32_t LIGHT_ON_MS {1000 * 5UL};          // 5 Seconds
// constexpr uint32_t LIGHT_OFF_MS {1000 * 60UL * 15};   // 15 Minutes

constexpr uint32_t TIME_MODE_A {1000 * 120UL};   // 2 Minutes
constexpr uint32_t TIME_MODE_B {1000 * 60UL};    // 1 Minute

constexpr uint32_t LIGHT_ON_MS {1000 * 2UL};
constexpr uint32_t LIGHT_OFF_MS {1000 * 1UL};

constexpr uint32_t mainIntervalls[3] {0, TIME_MODE_A, TIME_MODE_B};
constexpr uint32_t ledIntervalls[3] {0, LIGHT_ON_MS, LIGHT_OFF_MS};

constexpr uint8_t LED_PIN {4};
constexpr uint8_t BUTTON_MODE_A {5};
constexpr uint8_t BUTTON_MODE_B {6};
constexpr uint8_t BUTTON_STOP {7};

Timer mainTimer;
Timer ledTimer;

ProgramMode checkButtons(ProgramMode md, Timer &mt) {
  if (md == ProgramMode::stop) {   // Check Mode buttons only when mode "Stop" is active
    if (digitalRead(BUTTON_MODE_A) == LOW) {
      Serial.println("Start Mode A (2 Minutes)");
      md = ProgramMode::modeA;
      mt.start();
    } else if (digitalRead(BUTTON_MODE_B) == LOW) {
      Serial.println("Start Mode B (1 Minute)");
      md = ProgramMode::modeB;
      mt.start();
    }
  } else {   // Check Stop button only if modeA or modeB is active.
    if (digitalRead(BUTTON_STOP) == LOW) {
      md = ProgramMode::stop;
      Serial.println("Stop");
    }
  }
  return md;
}

LightStatus switchLight(LightStatus ls) {
  if (ledTimer(ledIntervalls[static_cast<byte>(ls)])) {
    ledTimer.start();
    digitalWrite(LED_PIN, !digitalRead(LED_PIN));
    ls = (ls != LightStatus::on) ? LightStatus::on : LightStatus::off;
  }
  return ls;
}

void setup() {
  Serial.begin(115200);
  pinMode(LED_PIN, OUTPUT);

  pinMode(BUTTON_MODE_A, INPUT_PULLUP);
  pinMode(BUTTON_MODE_B, INPUT_PULLUP);
  pinMode(BUTTON_STOP, INPUT_PULLUP);
}

void loop() {
  static LightStatus ledStatus {LightStatus::start};
  static ProgramMode mode {ProgramMode::stop};

  mode = checkButtons(mode, mainTimer);
  if (mainTimer(mainIntervalls[static_cast<byte>(mode)])) {
    if (digitalRead(LED_PIN)) { digitalWrite(LED_PIN, LOW); }
    mode = ProgramMode::stop;
  } else {
    ledStatus = switchLight(ledStatus);
  }
}