#include <Servo.h>

#define TRIG_PIN 2   // Ultrasonic Trigger pin
#define ECHO_PIN 3   // Ultrasonic Echo pin

Servo steeringServo;

// Steering angles
#define LEFT_ANGLE   30
#define CENTER_ANGLE 90
#define RIGHT_ANGLE  150

long duration;
int distance;

// Function to measure distance in cm
int getDistance() {
  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(2);

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

  duration = pulseIn(ECHO_PIN, HIGH, 30000); // timeout added for safety
  distance = duration * 0.034 / 2;           // convert to cm

  return distance;
}

void setup() {
  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);

  steeringServo.attach(9);   // Servo signal connected to D9
  steeringServo.write(CENTER_ANGLE);

  Serial.begin(9600);
}

void loop() {
  distance = getDistance();

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

  // -------- OBSTACLE AVOIDANCE CONTROL --------
  if (distance > 0 && distance <= 91) {   // ≤ 3 ft
    steeringServo.write(LEFT_ANGLE);
    Serial.println("Obstacle within 3ft → Steering LEFT");
  }
  else if (distance > 91 && distance <= 152) { // ≤ 5 ft
    steeringServo.write(RIGHT_ANGLE);
    Serial.println("Obstacle within 5ft → Steering RIGHT");
  }
  else if (distance > 152) { // > 5 ft
    steeringServo.write(CENTER_ANGLE);
    Serial.println("Path clear → STOP (CENTER)");
  }

  delay(200);
}