#include <avr/sleep.h>
#include <Arduino.h> // Include Arduino tone library

#define trigPin 9
#define echoPin 8
#define buzzerPin 5
#define proximityLED 7

unsigned long previousMillis = 0;
const long interval = 2000;

void setup() {
  Serial.begin(9600);
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  pinMode(buzzerPin, OUTPUT);
  pinMode(proximityLED, OUTPUT);
}

void loop() {
  long duration, distance;
  
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
  
  duration = pulseIn(echoPin, HIGH);
  // Adjust the constant below to calibrate for 20 cm
  distance = duration * 0.035 / 2;

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

  if (distance < 40 && distance >= 20) {
    digitalWrite(proximityLED, LOW);
  }

  if (distance < 20 && distance >= 10) {
    digitalWrite(proximityLED, HIGH);
    tone(buzzerPin, 1000, 200);
  } else {
    digitalWrite(proximityLED, LOW);
    noTone(buzzerPin);
  }

  if (distance < 10) {
    digitalWrite(proximityLED, HIGH);
    tone(buzzerPin, 1000, 800);
  } else {
    noTone(buzzerPin);
  }

  delay(100);

  if (millis() - previousMillis >= interval) {
    previousMillis = millis();
    sleep();
  }
}

void sleep() {
  digitalWrite(proximityLED, LOW);
  digitalWrite(buzzerPin, LOW);
  delay(1);
  
  set_sleep_mode(SLEEP_MODE_PWR_DOWN);
  sleep_enable();
  sleep_mode();
  
  delay(100); // Delay after waking up
  digitalWrite(buzzerPin, HIGH);
  sleep_disable();
}