#define btn1 2
#define btn2 3
#define btn3 4
#define ledPin 5

#define debounceDelay 300
#define blinkDelay 1000

enum lightMode {
  off,
  on,
  blinking,
  emergencyStop
};

lightMode state = off;

void setup() {
  // put your setup code here, to run once:
  pinMode(btn1, INPUT_PULLUP);
  pinMode(btn2, INPUT_PULLUP);
  pinMode(btn3, INPUT_PULLUP);
  pinMode(ledPin, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  static unsigned long lastbtnPress = millis();

  // put your main code here, to run repeatedly:
  if (lastbtnPress + debounceDelay < millis()) { 
    if (!digitalRead(btn1) && state != emergencyStop) {
      lastbtnPress = millis();
      state = state +1;
      if (state > 2) {
        state = 0;
      }
    }
    if (!digitalRead(btn2) && state != emergencyStop) {
      lastbtnPress = millis();
      state = state - 1;
      if (state < 0) {
        state = 2;
      }
    }
    if (!digitalRead(btn3)) {
      lastbtnPress = millis();
      state = emergencyStop;
    }
  }

  switch (state) {
    case off:
      digitalWrite(ledPin, LOW);
      break;
    case on:
      digitalWrite(ledPin, HIGH);
      break;
    case blinking:
      static unsigned long lastBlink = millis();
      if (lastBlink + blinkDelay < millis()) {
        digitalWrite(ledPin, !digitalRead(ledPin));
        lastBlink = millis();
      }
      break;
    case emergencyStop:
      digitalWrite(ledPin, LOW);
      break;
  }
}