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

LiquidCrystal_I2C lcd(0x27, 16, 2);

const byte ROWS = 4;
const byte COLS = 4;

char hexaKeys[ROWS][COLS] = {
  {'1', '2', '3', 'A'},
  {'4', '5', '6', 'B'},
  {'7', '8', '9', 'C'},
  {'*', '0', '#', 'D'}
};

byte rowPins[ROWS] = {9, 8, 7, 6};
byte colPins[COLS] = {5, 4, 3, 2};

Keypad customKeypad = Keypad(makeKeymap(hexaKeys), rowPins, colPins, ROWS, COLS);

const int passwordLength = 4;
char password[passwordLength];
char enteredPassword[passwordLength];

void setup() {
  lcd.backlight();
  lcd.init();
  pinMode(13, OUTPUT); // Lock output

  setNewPassword();
}

void loop() {
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("Enter code:");

  checkCode();
}

void setNewPassword() {
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("Set password:");

  for (int i = 0; i < passwordLength; ++i) {
    char key = getKey();
    password[i] = key;
    lcd.setCursor(i, 1);
    lcd.print('*');
    delay(500);
  }

  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("Type code:");
}

void checkCode() {
  for (int i = 0; i < passwordLength; ++i) {
    char key = getKey();
    enteredPassword[i] = key;
    lcd.setCursor(i, 1);
    lcd.print('*');
    delay(500);
  }

  if (checkPassword()) {
    lcd.clear();
    lcd.setCursor(0, 0);
    lcd.print("You won!");
    digitalWrite(13, HIGH); // Lock
    delay(2000);
    digitalWrite(13, LOW); // Unlock
    setNewPassword();
  } else {
    lcd.clear();
    lcd.setCursor(0, 0);
    lcd.print("You lost!");
    delay(2000);
    setNewPassword();
  }
}

bool checkPassword() {
  for (int i = 0; i < passwordLength; ++i) {
    if (enteredPassword[i] != password[i]) {
      return false;
    }
  }
  return true;
}

char getKey() {
  char key = customKeypad.getKey();
  while (!key) {
    key = customKeypad.getKey();
  }
  return key;
}