#include <Wire.h>
#include <LiquidCrystal_I2C.h>

#define MOTION_SENSOR_PIN 2    // Pin connected to the PIR sensor output
#define LED_PIN 13             // Red LED pin

int motion_state = LOW;        // Current state of the sensor
int prev_motion_state = LOW;   // Previous state of the sensor

// Initialize the LCD
LiquidCrystal_I2C lcd(0x27, 20, 4);  // Adjust I2C address if needed

void setup() {
  Serial.begin(9600);          // Initialize serial communication for debugging
  pinMode(MOTION_SENSOR_PIN, INPUT);  // Set PIR sensor pin as input
  pinMode(LED_PIN, OUTPUT);           // Set LED pin as output
  
  // Initialize LCD
  lcd.begin(20, 4);
  lcd.backlight();
  
  // Initial message on the LCD
  lcd.setCursor(0, 0);
  lcd.print("System Armed");
}

void loop() {
  prev_motion_state = motion_state;               // Store previous state
  motion_state = digitalRead(MOTION_SENSOR_PIN);  // Read current state of PIR sensor

  // Check if motion is detected (LOW -> HIGH)
  if (prev_motion_state == LOW && motion_state == HIGH) {
    Serial.println("Motion detected!");
    lcd.clear();
    lcd.setCursor(0, 0);
    lcd.print("Intruder Detected!");

    // Blink the red LED
    for (int i = 0; i < 6; i++) {  // Blink 3 times
      digitalWrite(LED_PIN, HIGH);
      delay(500);
      digitalWrite(LED_PIN, LOW);
      delay(500);
    }
  }

  // Check if motion stopped (HIGH -> LOW)
  else if (prev_motion_state == HIGH && motion_state == LOW) {
    Serial.println("Motion stopped!");
    lcd.clear();
    lcd.setCursor(0, 0);
    lcd.print("System Armed");
    digitalWrite(LED_PIN, LOW);  // Ensure LED is off
  }
}