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

// --- I2C LCD address might be 0x27 or 0x3F ---
LiquidCrystal_I2C lcd(0x27, 16, 2); // (I2C address, cols, rows)

// --- Pin setup ---
const int pirPin = PA6;       // PIR sensor
const int buzzerPin = PA0;    // Buzzer
const int ldrPin = PA2;       // LDR analog input
const int ledPin = PA5;       // LED when dark

// Motion logic
bool motionActive = false;
unsigned long motionStartTime = 0;
String lastMessage = "";

void setup() {
  delay(500);  // Allow power to stabilize
  Serial.begin(9600);

  pinMode(pirPin, INPUT);
  pinMode(buzzerPin, OUTPUT);
  pinMode(ledPin, OUTPUT);

  // Start I2C LCD
  lcd.init();         // Initialize the LCD
  lcd.backlight();    // Turn on backlight

  lcd.setCursor(0, 0);
  lcd.print("System Starting...");
  delay(1000);
  lcd.clear();
}

void loop() {
  // --- LDR logic ---
  int lightLevel = analogRead(ldrPin);
  digitalWrite(ledPin, lightLevel > 500 ? LOW : HIGH); // LED on when dark

  // --- PIR logic ---
  int pirState = digitalRead(pirPin);

  // Detect new motion
  if (pirState == HIGH && !motionActive) {
    motionActive = true;
    motionStartTime = millis();
    digitalWrite(buzzerPin, HIGH);
    updateLCD("Object Detected");
  }

  // Keep buzzer ON for 20s
  if (motionActive) {
    if (millis() - motionStartTime >= 20000) {
      digitalWrite(buzzerPin, LOW);
      motionActive = false;
      updateLCD("Safe");
    }
  }

  // Idle state (no motion)
  if (!motionActive && pirState == LOW) {
    updateLCD("Safe");
  }

  delay(200);
}

// Only update LCD when message changes
void updateLCD(String message) {
  if (message != lastMessage) {
    lcd.clear();
    lcd.setCursor(0, 0);
    lcd.print(message);
    lastMessage = message;
  }
}