#include <LiquidCrystal.h>  // Include the LiquidCrystal library for LCD control
#include <Servo.h>          // Include the Servo library for servo motor control
#include <EEPROM.h>         // Include the EEPROM library for reading and writing to EEPROM memory

Servo doorServo;            // Create a servo motor object
LiquidCrystal lcd(8, 9, 4, 5, 6, 7);  // Create an LCD object with specified pins

const int trigPin = 2;      // Define the trigger pin for the ultrasonic sensor
const int echoPin = 3;      // Define the echo pin for the ultrasonic sensor
const int thresholdAdjustPin = A0;  // Define the analog pin for threshold adjustment
const int servoPin = 10;    // Define the pin for the servo motor

int thresholdDistance = 30;  // Initialize threshold distance variable
int doorState = 0;           // Initialize door state variable

int getDistance() {         // Function to measure distance using ultrasonic sensor
  digitalWrite(trigPin, LOW);   // Set trigger pin to low
  delayMicroseconds(2);          // Wait for stabilization
  digitalWrite(trigPin, HIGH);  // Generate 10us pulse on trigger pin
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

  int duration = pulseIn(echoPin, HIGH);  // Measure duration of echo pulse
  int distance = duration * 0.034 / 2;     // Convert duration to distance in cm

  return distance;   // Return the calculated distance
}

void openDoor() {   // Function to open the door
  doorServo.write(180);  // Rotate servo motor to open position (180°)
  doorState = 1;          // Update door state to open
}

void closeDoor() {    // Function to close the door
  doorServo.write(0);   // Rotate servo motor to close position (0°)
  doorState = 0;         // Update door state to closed
}

void adjustThreshold() {   // Function to adjust threshold distance
  int thresholdValue = analogRead(thresholdAdjustPin);  // Read potentiometer value
  thresholdDistance = map(thresholdValue, 0, 1023, 10, 100);  // Map potentiometer value to threshold distance range
  EEPROM.update(0, thresholdDistance);  // Update threshold distance in EEPROM memory
}

void setup() {
  doorServo.attach(servoPin);  // Attach servo motor to specified pin
  lcd.begin(16, 2);            // Initialize LCD with 16x2 characters
  pinMode(trigPin, OUTPUT);     // Set trigger pin as output
  pinMode(echoPin, INPUT);      // Set echo pin as input
  pinMode(servoPin, OUTPUT);    // Set servo pin as output
  Serial.begin(9600);           // Initialize serial communication
  // Read threshold distance from EEPROM
  int storedThreshold = EEPROM.read(0);
  if (storedThreshold >= 10 && storedThreshold <= 100) {
    thresholdDistance = storedThreshold;
  }
}

void loop() {
  int distance = getDistance();  // Get current distance from ultrasonic sensor

  lcd.clear();            // Clear the LCD display
  lcd.setCursor(0, 0);   // Set cursor to first row, first column
  lcd.print("Door: ");    // Display "Door: " on LCD
  lcd.print(doorState == 1 ? "Open " : "Closed");  // Display door state (Open/Closed) on LCD
  lcd.setCursor(0, 1);    // Set cursor to second row, first column
  lcd.print("Distance: ");  // Display "Distance: " on LCD
  lcd.print(distance);      // Display current distance on LCD
  lcd.print(" cm");         // Display unit (cm) on LCD

  if (distance < thresholdDistance && doorState == 0) {  // If object is within threshold distance and door is closed
    openDoor();   // Open the door
  } else if (distance >= thresholdDistance && doorState == 1) {  // If object is beyond threshold distance and door is open
    closeDoor();  // Close the door
  }

  adjustThreshold();  // Adjust threshold distance based on potentiometer

  delay(100);  // Delay for stability
}