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

// LCD and Keypad Initialization
LiquidCrystal_I2C lcd(0x27, 16, 2);
const byte rows = 4;
const byte columns = 4;
char hexaKeys[rows][columns] = {
  {'1', '2', '3', 'A'},
  {'4', '5', '6', 'B'},
  {'7', '8', '9', 'C'},
  {'*', '0', '#', 'D'}
};
byte row_pins[rows] = {2, 3, 4, 5};
byte column_pins[columns] = {6, 7, 8, 9};
Keypad keypad_key = Keypad(makeKeymap(hexaKeys), row_pins, column_pins, rows, columns);

char inputPIN[5];         // To store the entered PIN
char storedPIN[5] = "1234"; // Default PIN
int relayPin = 11;        // Relay connected to pin 11
int attemptIndex = 0;     // Keeps track of the PIN entry progress

void setup() {
  lcd.begin(16, 2);         // Initialize LCD with 16 columns and 2 rows
  lcd.backlight();
  pinMode(relayPin, OUTPUT);
  digitalWrite(relayPin, HIGH); // Ensure relay starts off (locked)

  lcd.print("Electronic Lock");
  delay(2000);
  lcd.clear();
  lcd.print("Enter PIN:");
}

void loop() {
  char key = keypad_key.getKey();

  if (key) {
    // If a key is pressed, display it and store the input
    lcd.setCursor(attemptIndex, 1);
    lcd.print("*"); // Hide the actual input for security
    inputPIN[attemptIndex++] = key;

    // When 4 digits are entered, process the input
    if (attemptIndex == 4) {
      inputPIN[4] = '\0'; // Null-terminate the input

      if (strcmp(inputPIN, storedPIN) == 0) {
        // PIN is correct
        lcd.clear();
        lcd.print("Access Granted");
        digitalWrite(relayPin, LOW); // Unlock the door
        delay(5000);                 // Keep the relay open for 5 seconds
        digitalWrite(relayPin, HIGH); // Lock the door
        lcd.clear();
        lcd.print("Enter PIN:");
      } else {
        // PIN is incorrect
        lcd.clear();
        lcd.print("Access Denied");
        delay(2000);
        lcd.clear();
        lcd.print("Enter PIN:");
      }

      attemptIndex = 0; // Reset input index
    }
  }

  // Change PIN function if '#' is pressed
  if (key == '#') {
    changePIN();
  }
}

// Function to change the stored PIN
void changePIN() {
  char currentPIN[5], newPIN[5];
  int index = 0;

  lcd.clear();
  lcd.print("Current PIN:");
  while (index < 4) {
    char key = keypad_key.getKey();
    if (key) {
      lcd.setCursor(index, 1);
      lcd.print("*"); // Hide input
      currentPIN[index++] = key;
    }
  }
  currentPIN[4] = '\0'; // Null-terminate

  if (strcmp(currentPIN, storedPIN) != 0) {
    // Incorrect current PIN
    lcd.clear();
    lcd.print("Wrong PIN");
    delay(2000);
    lcd.clear();
    lcd.print("Enter PIN:");
    return;
  }

  // Ask for new PIN
  lcd.clear();
  lcd.print("New PIN:");
  index = 0;
  while (index < 4) {
    char key = keypad_key.getKey();
    if (key) {
      lcd.setCursor(index, 1);
      lcd.print("*"); // Hide input
      newPIN[index++] = key;
    }
  }
  newPIN[4] = '\0'; // Null-terminate

  // Save new PIN to memory
  strcpy(storedPIN, newPIN);
  lcd.clear();
  lcd.print("PIN Changed");
  delay(2000);
  lcd.clear();
  lcd.print("Enter PIN:");
}