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

LiquidCrystal_I2C lcd(0x27, 16, 2); // I2C address 0x27, 16 column and 2 rows

const byte KEYPAD_ROWS = 4;
const byte KEYPAD_COLS = 4;
byte RowPins[KEYPAD_ROWS] = {5,4,3,2};
byte ColPins[KEYPAD_COLS] = {A3, A2, A1, A0};

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

Keypad keypad = Keypad(makeKeymap(keys), RowPins, ColPins, KEYPAD_ROWS, KEYPAD_COLS);

char enteredKeys[17]; // Buffer to store entered keys (plus one for null-terminator)
byte index = 0;

void setup() {
  // put your setup code here, to run once:
  lcd.init(); 
  lcd.backlight();
}

void loop() {
  char key = keypad.getKey();
  if (key) {
    if (index < 16){
            enteredKeys[index] = key; // Store the key in the buffer
      index++;
      lcd.setCursor(index - 1, 0); // Set the cursor to the next position
      lcd.print(key); // Print the pressed key
    }

    if (index == 16) { // If 4 keys have been entered
      enteredKeys[index] = '\0'; // Null-terminate the buffer
      lcd.setCursor(0, 1); // Set the cursor to the beginning of the second line
      lcd.print(enteredKeys); // Display the entered sequence
      delay(2000); // Delay to show the sequence
      lcd.clear(); // Clear the LCD screen
      index = 0; // Reset the buffer index for the next sequence
    }

    if (key == 'D'){
      lcd.setCursor(0,1);
      lcd.print(enteredKeys);
      delay(2000);
      lcd.clear();
      index = 0;
    }
    delay(100); // Small delay to avoid bouncing issues
  }
    }