#include 

// ---- Servo motor setup ----
Servo servo;
const int servoPin = 9;       // Servo control pin
const int openAngle = 0;      // Angle when the lid is open
const int closeAngle = 90;    // Angle when the lid is closed

// ---- Ultrasonic sensor setup ----
const int trigPin = 5;        // Trigger pin of ultrasonic sensor
const int echoPin = 6;        // Echo pin of ultrasonic sensor
float distance, averageDistance;

// ---- Buzzer and LEDs ----
const int buzzerPin = 2;      // Buzzer pin
const int redLedPin = 3;      // Red LED pin
const int greenLedPin = 4;    // Green LED pin

// ---- Distance threshold ----
const int distanceThreshold = 20;  // Distance (cm) to open the lid

// ---- Lid open time ----
unsigned long lidOpenTime = 0;
const unsigned long holdOpenMs = 2000;  // Lid stays open for 2 seconds
bool isLidOpen = false;

// ---- Beep/flash timing ----
const unsigned long beepInterval = 200; // Interval for buzzer and red LED (200 ms = fast beep/blink)
unsigned long lastBeepTime = 0;
bool beepState = false;

void setup() {
  Serial.begin(9600);

  // Set up ultrasonic sensor pins
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);

  // Set up buzzer and LEDs
  pinMode(buzzerPin, OUTPUT);
  pinMode(redLedPin, OUTPUT);
  pinMode(greenLedPin, OUTPUT);

  // Initialize servo to closed position
  servo.attach(servoPin);
  servo.write(closeAngle);
  delay(100);
  servo.detach();

  // Initial LED state: green ON means closed
  digitalWrite(buzzerPin, LOW);
  digitalWrite(redLedPin, LOW);
  digitalWrite(greenLedPin, HIGH);
}

void loop() {
  // Measure distance from ultrasonic sensor
  averageDistance = readDistance();

  // If lid is closed and someone is close, open it
  if (!isLidOpen && averageDistance > 0 && averageDistance <= distanceThreshold) {
    servo.attach(servoPin);
    delay(1);
    servo.write(openAngle);   // Move servo to open position
    isLidOpen = true;
    lidOpenTime = millis();

    digitalWrite(greenLedPin, LOW);  // Turn off green LED when open
  }

  // If lid is open, keep it open for a while
  if (isLidOpen) {
    unsigned long now = millis();

    // Make buzzer and red LED blink/beep quickly
    if (now - lastBeepTime >= beepInterval) {
      lastBeepTime = now;
      beepState = !beepState;
      digitalWrite(buzzerPin, beepState ? HIGH : LOW);
      digitalWrite(redLedPin, beepState ? HIGH : LOW);
    }

    // After holdOpenMs, close the lid
    if (millis() - lidOpenTime >= holdOpenMs) {
      servo.write(closeAngle);   // Move servo to closed position
      delay(200);
      servo.detach();
      isLidOpen = false;

      // Reset buzzer and LEDs
      digitalWrite(buzzerPin, LOW);
      digitalWrite(redLedPin, LOW);
      digitalWrite(greenLedPin, HIGH); // Green LED ON means closed
    }
  }

  delay(50); // Small delay to avoid too many sensor reads
}

// ---- Function to measure distance with ultrasonic sensor ----
float readDistance() {
  // Send a short pulse to trigger pin
  digitalWrite(trigPin, LOW);  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH); delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

  // Measure how long echo pin stays HIGH
  unsigned long duration = pulseIn(echoPin, HIGH, 25000UL); // Timeout after ~4 meters
  if (duration == 0) return -1.0; // If no signal, return invalid
  return duration / 58.0;         // Convert to centimeters
}