const int trig = 4;
const int echo = 2;
long duration;
int distance;
const int relayPin = 12;

void setup() {
  Serial.begin(115200);
  pinMode(trig, OUTPUT);
  pinMode(echo, INPUT);
  pinMode(relayPin, OUTPUT);
  pinMode(5, OUTPUT);
  pinMode(18, OUTPUT);
  pinMode(19, OUTPUT);
  pinMode(21, OUTPUT);
}

void loop() {
  // Trigger the ultrasonic sensor
  digitalWrite(trig, LOW);
  delayMicroseconds(2);
  digitalWrite(trig, HIGH);
  delayMicroseconds(10);
  digitalWrite(trig, LOW);

  // Read the echo pin
  duration = pulseIn(echo, HIGH);
  distance = (duration * 0.034 / 2) + 1;

  // Control the LEDs and relay based on distance
  if (distance == 30) {
    digitalWrite(5, HIGH);
    digitalWrite(18, LOW);
    digitalWrite(19, LOW);
    digitalWrite(21, LOW);
    digitalWrite(relayPin, LOW); // Relay OFF
  } else if (distance <= 20 && distance >= 10) {
    digitalWrite(5, HIGH);
    digitalWrite(18, HIGH);
    digitalWrite(19, LOW);
    digitalWrite(21, LOW);
    digitalWrite(relayPin, LOW); // Relay OFF
  } else if (distance <= 10 && distance >= 6) {
    digitalWrite(5, HIGH);
    digitalWrite(18, HIGH);
    digitalWrite(19, HIGH);
    digitalWrite(21, LOW);
    digitalWrite(relayPin, LOW); // Relay OFF
  } else if (distance < 5 && distance >= 4) {
    digitalWrite(5, HIGH);
    digitalWrite(18, HIGH);
    digitalWrite(19, HIGH);
    digitalWrite(21, HIGH);
    digitalWrite(relayPin, HIGH); // Relay ON
  } else if (distance == 41) {
    digitalWrite(relayPin, HIGH); // Relay ON
    digitalWrite(5, LOW);
    digitalWrite(18, LOW);
    digitalWrite(19, LOW);
    digitalWrite(21, LOW);
  } else {
    digitalWrite(5, LOW);
    digitalWrite(18, LOW);
    digitalWrite(19, LOW);
    digitalWrite(21, LOW);
    digitalWrite(relayPin, LOW); // Relay OFF
  }

  // Print distance to the Serial Monitor
  Serial.println("Distance: " + String(distance) + " cm");
}