#include <LiquidCrystal.h>

// Define pins
const int forceSensorPin = A1;
const int ultrasonicPin = A0;  // Single pin for trigger and echo
const int piezoPin = 3;

// LCD setup
LiquidCrystal lcd(4, 5, 6, 7, 8, 9);

// Constants
const int forceThreshold = 100; // Adjust this based on the force sensor's values
const long distanceThreshold = 50; // Distance in cm for ultrasonic detection

void setup() {
  // Initialize the LCD
  lcd.begin(16, 2);
  lcd.clear();
  
  // Display default message
  lcd.setCursor(0, 0);
  lcd.print("No one at the");
  lcd.setCursor(0, 1);
  lcd.print("door");

  // Initialize pins
  pinMode(piezoPin, OUTPUT);

  Serial.begin(9600); // For debugging
}

void loop() {
  bool someoneDetected = false;  // Reset detection flag each loop

  // Read force sensor value
  int forceValue = analogRead(forceSensorPin);
  // Measure distance from ultrasonic sensor
  long distance = readUltrasonicDistance(ultrasonicPin);

  // Check if force sensor is triggered
  if (forceValue > forceThreshold) {
    lcd.clear();
    lcd.setCursor(0, 0);
    lcd.print("Someone at the");
    lcd.setCursor(0, 1);
    lcd.print("door");
    tone(piezoPin, 1000); // Activate piezo
    delay(500);
    noTone(piezoPin); // Turn off piezo after brief sound
    someoneDetected = true; // Mark detection
  }
  // Check if movement detected by ultrasonic sensor
  else if (distance < distanceThreshold) {
    lcd.clear();
    lcd.setCursor(0, 0);
    lcd.print("Someone at the");
    lcd.setCursor(0, 1);
    lcd.print("door moving");
    tone(piezoPin, 1000); // Activate piezo
    delay(500);
    noTone(piezoPin); // Turn off piezo
    someoneDetected = true; // Mark detection
  }

  // Default display if no detection
  if (!someoneDetected) {
    lcd.clear();
    lcd.setCursor(0, 0);
    lcd.print("No one at the");
    lcd.setCursor(0, 1);
    lcd.print("door");
    noTone(piezoPin); // Ensure piezo is off
  }

  delay(200); // Brief delay between readings
}

long readUltrasonicDistance(int pin) {
  pinMode(pin, OUTPUT);  // Set pin as output for trigger
  digitalWrite(pin, LOW);
  delayMicroseconds(2);
  digitalWrite(pin, HIGH);
  delayMicroseconds(10);
  digitalWrite(pin, LOW);
  
  pinMode(pin, INPUT);  // Set pin as input for echo
  long duration = pulseIn(pin, HIGH);
  return duration * 0.034 / 2; // Convert to distance in cm
}