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

LiquidCrystal_I2C lcd(0x27, 20, 4);

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

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

Servo myServo;
#define SERVO_PIN 10

String password = "";
String inputPassword = "";
bool isPasswordSet = false;

void setup() {
  lcd.begin(20, 4);
  myServo.attach(SERVO_PIN);
  myServo.write(0);
  lcd.backlight();
  lcd.setCursor(0, 0);
  lcd.print("System Ready");
  delay(2000);
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("Enter Password:");
}

void loop() {
  char key = keypad.getKey();
  if (key) {
    if (key == 'A') {
      setPassword();
    } else if (key == 'B') {
      resetPassword();
    } else if (key == 'C') {
      backspace();
    } else if (key == 'D') {
      verifyPassword();
    } else {
      inputPassword += key;
      lcd.setCursor(inputPassword.length() - 1, 1);
      lcd.print("*");
    }
  }
}

void setPassword() {
  lcd.clear();
  if (isPasswordSet) {
    lcd.print("Password Exists");
    delay(2000);
  } else {
    lcd.print("Set Password:");
    inputPassword = "";
    while (inputPassword.length() < 4) {
      char key = keypad.getKey();
      if (key) {
        inputPassword += key;
        lcd.setCursor(inputPassword.length() - 1, 1);
        lcd.print("*");
      }
    }
    password = inputPassword;
    inputPassword = "";
    isPasswordSet = true;
    lcd.clear();
    lcd.print("Password Saved");
    delay(2000);
  }
  lcd.clear();
  lcd.print("Enter Password:");
}

void resetPassword() {
  lcd.clear();
  if (!isPasswordSet) {
    lcd.print("Set Password 1st");
    delay(2000);
  } else {
    lcd.print("Enter Old Pass:");
    inputPassword = "";
    while (inputPassword.length() < 4) {
      char key = keypad.getKey();
      if (key) {
        inputPassword += key;
        lcd.setCursor(inputPassword.length() - 1, 1);
        lcd.print("*");
      }
    }
    if (inputPassword == password) {
      lcd.clear();
      lcd.print("Set New Pass:");
      inputPassword = "";
      while (inputPassword.length() < 4) {
        char key = keypad.getKey();
        if (key) {
          inputPassword += key;
          lcd.setCursor(inputPassword.length() - 1, 1);
          lcd.print("*");
        }
      }
      password = inputPassword;
      inputPassword = "";
      lcd.clear();
      lcd.print("Password Reset");
      delay(2000);
    } else {
      lcd.clear();
      lcd.print("Incorrect Pass");
      delay(2000);
    }
  }
  lcd.clear();
  lcd.print("Enter Password:");
}


void backspace() {
  if (inputPassword.length() > 0) {
    inputPassword.remove(inputPassword.length() - 1);
    lcd.setCursor(inputPassword.length(), 1);
    lcd.print(" ");
    lcd.setCursor(inputPassword.length(), 1);
  }
}

void verifyPassword() {
  lcd.clear();
  if (inputPassword == password) {
    lcd.print("Unlocked");
    myServo.write(90);
    delay(5000);
    myServo.write(0);
  } else {
    lcd.print("Wrong Password");
    delay(2000);
  }
  inputPassword = "";
  lcd.clear();
  lcd.print("Enter Password:");
}