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

#define BUZZER_PIN 4
#define LED_PIN 5

LiquidCrystal_I2C lcd(0x3F, 16, 2);

// Keypad Configuration
const byte ROWS = 4;  
const byte COLS = 4;  
char keys[ROWS][COLS] = {
  {'1', '2', '3', 'A'},
  {'4', '5', '6', 'B'},
  {'7', '8', '9', 'C'},
  {'*', '0', '#', 'D'}
};

byte rowPins[ROWS] = {13, 12, 14, 27};
byte colPins[COLS] = {26, 25, 33, 32};

Keypad keypad = Keypad(makeKeymap(keys), rowPins, colPins, ROWS, COLS);

// Simulated RFID Codes (Predefined)
String registered_IDs[] = {"123A", "456B", "789C"};
String entered_ID = "";

void setup() {
    Serial.begin(115200);
    
    lcd.init();
    lcd.backlight();
    
    pinMode(BUZZER_PIN, OUTPUT);
    pinMode(LED_PIN, OUTPUT);

    lcd.setCursor(0, 0);
    lcd.print("Smart Attendance");
    delay(2000);
    lcd.clear();
}

void loop() {
    char key = keypad.getKey();
    
    if (key) {
        Serial.print("Key Pressed: ");
        Serial.println(key);
        
        if (key == '#') { // Enter button
            checkAttendance();
            entered_ID = "";
        } 
        else if (key == '*') { // Reset input
            entered_ID = "";
            lcd.clear();
            lcd.setCursor(0, 0);
            lcd.print("Enter ID:");
        } 
        else {
            entered_ID += key;
            lcd.setCursor(0, 1);
            lcd.print(entered_ID);
        }
    }
}

void checkAttendance() {
    bool isRegistered = false;
    
    for (int i = 0; i < 3; i++) {
        if (entered_ID == registered_IDs[i]) {
            isRegistered = true;
            break;
        }
    }

    lcd.clear();
    
    if (isRegistered) {
        lcd.setCursor(0, 0);
        lcd.print("Attendance Marked!");
        Serial.println("Attendance Marked!");
        
        digitalWrite(LED_PIN, HIGH);
        digitalWrite(BUZZER_PIN, HIGH);
        delay(1000);
        digitalWrite(BUZZER_PIN, LOW);
        digitalWrite(LED_PIN, LOW);
    } 
    else {
        lcd.setCursor(0, 0);
        lcd.print("Invalid ID!");
        Serial.println("Invalid ID!");

        for (int i = 0; i < 3; i++) {
            digitalWrite(BUZZER_PIN, HIGH);
            delay(200);
            digitalWrite(BUZZER_PIN, LOW);
            delay(200);
        }
    }
    
    delay(2000);
    lcd.clear();
    lcd.setCursor(0, 0);
    lcd.print("Enter ID:");
}