#define SOUND_SPEED 0.034

// Sensor 1
const int trig1 = 19;
const int echo1 = 18;

// Sensor 2
const int trig2 = 5;
const int echo2 = 17;

// Sensor 3
const int trig3 = 16;
const int echo3 = 4;

// Sensor 4
const int trig4 = 21;
const int echo4 = 22;

// Buzzer
const int buzzer = 23;

// Threshold
const int threshold = 20;

bool objectDetected = false;

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

  pinMode(trig1, OUTPUT); pinMode(echo1, INPUT);
  pinMode(trig2, OUTPUT); pinMode(echo2, INPUT);
  pinMode(trig3, OUTPUT); pinMode(echo3, INPUT);
  pinMode(trig4, OUTPUT); pinMode(echo4, INPUT);

  pinMode(buzzer, OUTPUT);

  Serial.println("Simulation Started");
}

long getDistance(int trig, int echo) {
  digitalWrite(trig, LOW);
  delayMicroseconds(2);

  digitalWrite(trig, HIGH);
  delayMicroseconds(10);
  digitalWrite(trig, LOW);

  long duration = pulseIn(echo, HIGH, 30000);

  if (duration == 0) return 999;

  return duration * SOUND_SPEED / 2;
}

void loop() {

  long d1 = getDistance(trig1, echo1);
  long d2 = getDistance(trig2, echo2);
  long d3 = getDistance(trig3, echo3);
  long d4 = getDistance(trig4, echo4);

  bool s1 = d1 < threshold;
  bool s2 = d2 < threshold;
  bool s3 = d3 < threshold;
  bool s4 = d4 < threshold;

  bool currentState = s1 || s2 || s3 || s4;

  if (currentState && !objectDetected) {
    Serial.print("Object detected by: ");

    if (s1) Serial.print("Sensor1 ");
    if (s2) Serial.print("Sensor2 ");
    if (s3) Serial.print("Sensor3 ");
    if (s4) Serial.print("Sensor4 ");

    Serial.println();

    digitalWrite(buzzer, HIGH);
    objectDetected = true;
  }

  else if (!currentState && objectDetected) {
    Serial.println("No object");
    digitalWrite(buzzer, LOW);
    objectDetected = false;
  }

  delay(200);
}