#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>

#define Ancho 128
#define Alto 64
#define OLED_RESET    -1
Adafruit_SSD1306 display(Ancho, Alto, &Wire, OLED_RESET);

const byte Filas = 4;
const byte Column = 4;
char keys[Filas][Column] = {
  {'1','2','3','A'},
  {'4','5','6','B'},
  {'7','8','9','C'},
  {'*','0','#','D'}
};
byte filPin[Filas] = {13, 12, 14, 27};
byte colPins[Column] = {26, 25, 33, 32};

void setup() {
  Wire.begin();
  display.begin(SSD1306_SWITCHCAPVCC, 0x3C);
  display.display();
  delay(2000);
  display.clearDisplay();
  display.setTextSize(1);
  display.setTextColor(SSD1306_WHITE);
}

void loop() {
  char customKey = getKey();
  if (customKey != '\0') {
    if (customKey == 'C') {
      checkPassword();
    }
  }
}

char getKey() {
  for (byte i = 0; i < Column; i++) {
    pinMode(colPins[i], OUTPUT);
    digitalWrite(colPins[i], LOW);
    for (byte j = 0; j < Filas; j++) {
      pinMode(filPin[j], INPUT_PULLUP);
      if (digitalRead(filPin[j]) == LOW) {
        delay(50);
        while (digitalRead(filPin[j]) == LOW);
        return keys[j][i];
      }
    }
    digitalWrite(colPins[i], HIGH);
  }
  return '\0';
}

void checkPassword() {

  String password = "";
  while (password.length() < 4) {
    char key = getKey();
    if (key != '\0') {
      password += key;
      display.clearDisplay();
      display.setCursor(0, 0);
      display.println("Enter Password:");
      display.println(password);
      display.display();
    }
  }

  if (password == "1234") {
    display.clearDisplay();
    display.setCursor(0, 0);
    display.println("Access Granted");
    display.display();
    delay(2000);
  } else {
    display.clearDisplay();
    display.setCursor(0, 0);
    display.println("Access Denied");
    display.display();
    delay(2000);
  }

  // Clear password
  password = "";
}