// Pin definitions
const int trigPinLeft = 8;
const int echoPinLeft = 9;
const int trigPinRight = 10;
const int echoPinRight = 11;

const int motorLeftForward = 4;
const int motorLeftBackward = 5;
const int motorRightForward = 6;
const int motorRightBackward = 7;

// Threshold distance (in cm)
const int thresholdDistance = 20;

void setup() {
  // Set motor pins as output
  pinMode(motorLeftForward, OUTPUT);
  pinMode(motorLeftBackward, OUTPUT);
  pinMode(motorRightForward, OUTPUT);
  pinMode(motorRightBackward, OUTPUT);

  // Set ultrasonic sensor pins
  pinMode(trigPinLeft, OUTPUT);
  pinMode(echoPinLeft, INPUT);
  pinMode(trigPinRight, OUTPUT);
  pinMode(echoPinRight, INPUT);

  // Start the serial communication
  Serial.begin(9600);
}

void loop() {
  // Measure distance from left sensor
  long distanceLeft = measureDistance(trigPinLeft, echoPinLeft);

  // Measure distance from right sensor
  long distanceRight = measureDistance(trigPinRight, echoPinRight);

  // Decision-making logic
  if (distanceLeft < thresholdDistance && distanceRight < thresholdDistance) {
    // If obstacles are detected on both sides, choose the best direction
    if (distanceLeft > distanceRight) {
      turnLeft();
    } else {
      turnRight();
    }
  } else if (distanceLeft < thresholdDistance) {
    // If obstacle on the left, turn right
    turnRight();
  } else if (distanceRight < thresholdDistance) {
    // If obstacle on the right, turn left
    turnLeft();
  } else {
    // Move forward if no obstacle is detected
    moveForward();
  }

  delay(100);
}

long measureDistance(int trigPin, int echoPin) {
  long duration, distance;
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
  duration = pulseIn(echoPin, HIGH);
  distance = duration * 0.034 / 2;
  return distance;
}

void moveForward() {
  digitalWrite(motorLeftForward, HIGH);
  digitalWrite(motorLeftBackward, LOW);
  digitalWrite(motorRightForward, HIGH);
  digitalWrite(motorRightBackward, LOW);
}

void moveBackward() {
  digitalWrite(motorLeftForward, LOW);
  digitalWrite(motorLeftBackward, HIGH);
  digitalWrite(motorRightForward, LOW);
  digitalWrite(motorRightBackward, HIGH);
}

void stopCar() {
  digitalWrite(motorLeftForward, LOW);
  digitalWrite(motorLeftBackward, LOW);
  digitalWrite(motorRightForward, LOW);
  digitalWrite(motorRightBackward, LOW);
}

void turnRight() {
  digitalWrite(motorLeftForward, HIGH);
  digitalWrite(motorLeftBackward, LOW);
  digitalWrite(motorRightForward, LOW);
  digitalWrite(motorRightBackward, HIGH);
}

void turnLeft() {
  digitalWrite(motorLeftForward, LOW);
  digitalWrite(motorLeftBackward, HIGH);
  digitalWrite(motorRightForward, HIGH);
  digitalWrite(motorRightBackward, LOW);
}