#include <SPI.h>
#include <MFRC522.h>
#include <Wire.h>
#include <LiquidCrystal_I2C.h>
#include <RTClib.h>

#define SS_PIN 10
#define RST_PIN 9
#define BUZZER 8

MFRC522 mfrc522(SS_PIN, RST_PIN);
LiquidCrystal_I2C lcd(0x27, 16, 2);
RTC_DS1307 rtc;

String validUID = "AA BB CC DD";

void setup() {
  Serial.begin(9600);
  SPI.begin();
  mfrc522.PCD_Init();
  Wire.begin();

  lcd.init();
  lcd.backlight();
  pinMode(BUZZER, OUTPUT);

  rtc.begin();

  lcd.print("Scan Your Card");
}

void loop() {

  if (!mfrc522.PICC_IsNewCardPresent()) return;
  if (!mfrc522.PICC_ReadCardSerial()) return;

  String readUID = "";

  for (byte i = 0; i < mfrc522.uid.size; i++) {
    if (mfrc522.uid.uidByte[i] < 0x10) readUID += "0";
    readUID += String(mfrc522.uid.uidByte[i], HEX);
    if (i != mfrc522.uid.size - 1) readUID += " ";
  }

  readUID.toUpperCase();
  lcd.clear();

  if (readUID == validUID) {

    // ✅ SUCCESS
    lcd.print("Attendance OK");

    DateTime now = rtc.now();
    lcd.setCursor(0,1);
    lcd.print(now.hour());
    lcd.print(":");
    lcd.print(now.minute());

    // 🔊 ONE LONG BEEP
    tone(BUZZER, 1000);
    delay(800);
    noTone(BUZZER);

  } else {

    // ❌ FAILED
    lcd.print("Access Denied");

    // 🔊 TWO LONG BEEPS
    for(int i=0; i<2; i++){
      tone(BUZZER, 800);
      delay(500);
      noTone(BUZZER);
      delay(300);
    }
  }

  delay(2000);
  lcd.clear();
  lcd.print("Scan Your Card");
}