// Electric Safe Lock System
// Components: 16x2 LCD, Servo Motor, 4x4 Keypad, Green LED, Red LED
// Functionality:
// 1. Enter 4-digit code; if correct -> "Success" + green LED + unlock (servo to 90° for 5s)
//    if incorrect -> "Incorrect" + red LED
// 2. Press 'C' to change code: enter old code, then new code

#include <LiquidCrystal.h>
#include <Keypad.h>
#include <Servo.h>

// ----- PIN DEFINITIONS -----
// LCD pins: RS, E, D4, D5, D6, D7
LiquidCrystal lcd(8, 7, 5, 4, 3, 2);

// Keypad setup
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, 10, 11, 12 };      // Connect to the row pinouts of the keypad
byte colPins[COLS] = { 13, A0, A1, A2 };  // Connect to the column pinouts of the keypad
Keypad keypad = Keypad(makeKeymap(keys), rowPins, colPins, ROWS, COLS);

// Servo setup
Servo lockServo;
const int servoPin = 6;

// LED pins
const int greenLedPin = A3;
const int redLedPin = A4;

// Code variables
String code = "1234";  // Default 4-digit code
String inputCode = "";
const int codeLength = 4;

void setup() {
  // Initialize LCD
  lcd.begin(16, 2);
  lcd.print("Enter Code:");

  // Initialize LEDs
  pinMode(greenLedPin, OUTPUT);
  pinMode(redLedPin, OUTPUT);

  digitalWrite(greenLedPin, LOW);
  digitalWrite(redLedPin, LOW);

  // Initialize Servo
  lockServo.attach(servoPin);
  lockServo.write(0);  // Locked position set the angle as 0
}

void loop() {
  char key = keypad.getKey();
  if (key) {
    // If user wants to change code press 'C'
    if (key == 'C') {
      changeCode();
      return;
    }

    if (isDigit(key)) {  // If numeric key, add to input
      inputCode += key;
      lcd.setCursor(inputCode.length() - 1, 1);
      lcd.print('*');  // Mask input
    }

    if (inputCode.length() >= codeLength) {  // If input length reached, check code
      checkCode();
    }
  }
}

// Function to check entered code
void checkCode() {
  lcd.clear();
  if (inputCode == code) {
    // Correct code
    lcd.print("Success");
    digitalWrite(greenLedPin, HIGH);
    // Unlock
    lockServo.write(90);
    delay(5000);         // Keep unlocked for 5 seconds
    lockServo.write(0);  // Lock back
    digitalWrite(greenLedPin, LOW);
  } else {
    // Incorrect code
    lcd.print("Incorrect");
    digitalWrite(redLedPin, HIGH);
    delay(3000);
    digitalWrite(redLedPin, LOW);
  }
  // Reset for next attempt
  inputCode = "";
  delay(500);
  lcd.clear();
  lcd.print("Enter Code:");
}

// Function to change the current code
void changeCode() {
  String oldCode = "";
  String newCode = "";
  lcd.clear();
  lcd.print("Enter Old Code:");
  oldCode = readCodeEntry();

  if (oldCode == code) {
    lcd.clear();
    lcd.print("Enter New Code:");
    newCode = readCodeEntry();
    code = newCode;  // Update code
    lcd.clear();
    lcd.print("Code Changed");
    delay(2000);
  } else {
    lcd.clear();
    lcd.print("Wrong Old Code");
    delay(2000);
  }
  // Reset display
  inputCode = "";
  lcd.clear();
  lcd.print("Enter Code:");
}

// Helper to read a fixed-length code from keypad
String readCodeEntry() {
  String entry = "";
  while (entry.length() < codeLength) {
    char k = keypad.getKey();
    if (k && isDigit(k)) {
      entry += k;
      lcd.setCursor(entry.length() - 1, 1);
      lcd.print('*');
    }
  }
  delay(500);
  return entry;
}