const int trigPin = D3;
const int echoPin = D2;

const int greenLed = D4;
const int yellowLed = D5;
const int redLed = D6;

const int buzzer = D7;

void setup() {
  Serial.begin(115200);

  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);

  pinMode(greenLed, OUTPUT);
  pinMode(yellowLed, OUTPUT);
  pinMode(redLed, OUTPUT);

  pinMode(buzzer, OUTPUT);
}

void loop() {
  // Send ultrasonic pulse
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);

  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);

  digitalWrite(trigPin, LOW);

  // Measure echo time
  long duration = pulseIn(echoPin, HIGH);

  // Calculate distance in cm
  float distance = duration * 0.0340 / 2.0;

  Serial.print("Distance: ");
  Serial.print(distance);
  Serial.println(" cm");

  // Turn everything OFF first
  digitalWrite(greenLed, LOW);
  digitalWrite(yellowLed, LOW);
  digitalWrite(redLed, LOW);
  noTone(buzzer);

  // Parking logic
  if (distance > 100) {
    digitalWrite(greenLed, HIGH);
  }

  else if (distance >= 50) {
    digitalWrite(yellowLed, HIGH);
  }

  else {
    digitalWrite(redLed, HIGH);
    tone(buzzer, 1000);
  }

  delay(300);
}