int LED_PIN = 5;
int BUTTON_PIN = 8;
volatile int userClickCount = 0;
volatile unsigned long lastClickTimestamp = 0;
int debounceThresholdInMilliseconds = 250;

void setup() {
  Serial.begin(9600);
  enableOutputOn(LED_PIN);
  enableInputOn(BUTTON_PIN);
  digitalWrite(BUTTON_PIN, LOW);  // enable internal pull-up resistor

  attachInterrupt(digitalPinToInterrupt(BUTTON_PIN), changeState, FALLING);

  blinkWelcome();

}

void changeState(){
  if(validClick()){
    userClickCount++;
    Serial.print("valid click: ");
    Serial.println(userClickCount);
  }else{
    Serial.println("skipping fake signal");
  }
}

boolean validClick(){
  boolean isValid = false;
  unsigned long now = millis();
  long timeElapsedSinceLastClick = now - lastClickTimestamp;

  if(timeElapsedSinceLastClick > debounceThresholdInMilliseconds){
    isValid = true;
  }else{
  }
  lastClickTimestamp = millis();
  return isValid;
}

void loop() {
  delay(2000);
  blinkFast(userClickCount);
}

void enableOutputOn(int pin){
  pinMode(pin, OUTPUT);
}

void enableInputOn(int pin){
  pinMode(pin, INPUT);
}

void blinkWelcome(){
  blinkFast(5);
  delay(1000);
}

void blinkFast(int count){
  blink(count, 150);
}

void blink(int count, int delayMillis){
  for(int i = 0; i < count; i++) {
    blinkOnce(delayMillis);
  }
}

void blinkOnce(int delayMillis){
  digitalWrite(LED_PIN, HIGH);
  delay(delayMillis);
  digitalWrite(LED_PIN, LOW);
  delay(delayMillis);
}