#include <EEPROM.h>        // Include the EEPROM library
#include <LiquidCrystal.h> // Include LCD library
#include <Keypad.h>        // Include Keypad library

// LCD Initialization
LiquidCrystal lcd(A0, A1, A2, A3, A4, A5);

// Keypad Configuration
const byte numRows = 4;
const byte numCols = 4;
char keymap[numRows][numCols] = {
  {'1', '2', '3', 'A'},
  {'4', '5', '6', 'B'},
  {'7', '8', '9', 'C'},
  {'*', '0', '#', 'D'}
};
byte rowPins[numRows] = {5, 4, 3, 2};
byte colPins[numCols] = {6, 7, 8, 9};
Keypad mykeypad = Keypad(makeKeymap(keymap), rowPins, colPins, numRows, numCols);

// Variables for Password Storage and Input
String password = "";
String input_password = "";
bool isEnteringPassword = false;  // Track if the user is inputting a password

// Function Declarations
void mainMenu();
void addPassword();
void editPassword();
void deletePassword();
void enterPassword(String message, bool isNewPassword = false);
void displayMessage(String line1, String line2, int delayTime);
void savePasswordToEEPROM(String password);
String readPasswordFromEEPROM();
void clearEEPROM();

// Setup Function
void setup() {
  Serial.begin(9600);
  lcd.begin(16, 2);
  delay(100); // Add delay for LCD initialization
  pinMode(10, OUTPUT); // Access Granted LED
  pinMode(11, OUTPUT); // Access Denied LED

  // Load the stored password from EEPROM
  password = readPasswordFromEEPROM();
  Serial.print("Loaded Password: ");
  Serial.println(password); // Debugging line
  mainMenu();
}

// Main Menu Loop
void loop() {
  char key = mykeypad.getKey();
  if (key) {
    delay(100); // Debounce delay for keypad
    Serial.print("Key Pressed: ");
    Serial.println(key); // Debugging line
    
    if (isEnteringPassword) {
      if (key == '*') {  
        // Backspace functionality only if input exists
        if (input_password.length() > 0) {
          input_password.remove(input_password.length() - 1);
          lcd.setCursor(input_password.length(), 1);
          lcd.print(" ");
          lcd.setCursor(input_password.length(), 1);
        } else {
          // If no input, return to main menu
          mainMenu();
        }
      }
    } else if (key == '*') {
      // Always return to main menu if not in password input mode
      mainMenu();
    } else {
      // Handle menu options
      switch (key) {
        case 'A': // Access Check
          enterPassword("Enter PIN:");
          if (input_password == password) {
            displayMessage("Access", "Granted", 2000);
            digitalWrite(10, HIGH); // Access Granted LED On
            delay(1000);
            digitalWrite(10, LOW);  // Access Granted LED Off
          } else {
            displayMessage("Access Denied", "Invalid Password", 2000);
            digitalWrite(11, HIGH); // Access Denied LED On
            delay(1000);
            digitalWrite(11, LOW);  // Access Denied LED Off
          }
          input_password = "";
          mainMenu();
          break;

        case 'B': // Add Password
          if (password != "") {
            enterPassword("New Password:", true);
          } else {
            displayMessage("Password", "Exists", 2000);
          }
          break;

        case 'C': // Edit Password
          if (password == "") {
            displayMessage("No Password", "Stored", 2000);
          } else {
            enterPassword("PIN to edit:");
            if (input_password == password) {
              enterPassword("New Password:", true);
              displayMessage("Password", "Updated", 2000);
            } else {
              displayMessage("Invalid", "Password", 2000);
            }
          }
          input_password = "";
          mainMenu();
          break;

        case 'D': // Delete Password
          if (password == "") {
            displayMessage("No Password", "Stored", 2000);
          } else {
            enterPassword("PIN to delete:");
            if (input_password == password) {
              clearEEPROM();
              displayMessage("Password", "Deleted", 2000);
            } else {
              displayMessage("Delete", "Invalid", 2000);
            }
          }
          input_password = "";
          mainMenu();
          break;

        default: // Invalid Option for other keys
          displayMessage("Invalid", "Option", 2000);
          mainMenu();
          break;
      }
    }
  }
}

// Display the Main Menu
void mainMenu() {
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("Choose: A B C D");
  isEnteringPassword = false;  // Not in password input mode
}

// Add/Edit Password with Validation
void enterPassword(String message, bool isNewPassword) {
  input_password = "";
  lcd.clear();
  lcd.print(message);
  lcd.setCursor(0, 1);
  isEnteringPassword = true;  // In password input mode

  while (true) {
    char key = mykeypad.getKey();
    if (key) {
      delay(100); // Debounce delay
      if (key == '#' && input_password.length() == 4) {
        // Only submit if the input is exactly 4 digits
        if (isNewPassword) {
          password = input_password;
          savePasswordToEEPROM(password); // Save to EEPROM
          displayMessage("Password", "Set Successfully", 2000);
        }
        break;
      }
      if (key == '#' && input_password.length() < 4) {
        // Warn if the input is less than 4 digits
        displayMessage("PIN must be", "4 digits", 2000);
        input_password = "";
        lcd.clear();
        lcd.print(message);
        lcd.setCursor(0, 1);
      } else if (key == '*' && input_password.length() > 0) {
        // Backspace functionality
        input_password.remove(input_password.length() - 1);
        lcd.setCursor(input_password.length(), 1);
        lcd.print(" ");
        lcd.setCursor(input_password.length(), 1);
      } else if (isDigit(key) && input_password.length() < 4) {
        input_password += key;
        lcd.print(key);  // Directly show input (no masking)
      }
    }
  }
  isEnteringPassword = false;  // Exit password input mode after submission
}

// Display Message on LCD
void displayMessage(String line1, String line2, int delayTime) {
  lcd.clear();
  lcd.print(line1);
  lcd.setCursor(0, 1);
  lcd.print(line2);
  delay(delayTime);
  lcd.clear();
}

// Save Password to EEPROM
void savePasswordToEEPROM(String password) {
  for (int i = 0; i < password.length(); i++) {
    EEPROM.write(i, password[i]); // Store each character
    delay(5); // Small delay for EEPROM write
  }
  EEPROM.write(password.length(), '\0'); // Null terminator
  delay(5); // Small delay after writing null terminator
  Serial.println("Password saved to EEPROM"); // Debugging line
}

// Read Password from EEPROM
String readPasswordFromEEPROM() {
  String password = "";
  char ch;
  for (int i = 0; (ch = EEPROM.read(i)) != '\0'; i++) {
    password += ch;
    delay(5); // Small delay for EEPROM read
  }
  Serial.println("Password read from EEPROM: " + password); // Debugging line
  return password;
}

// Clear EEPROM
void clearEEPROM() {
  for (int i = 0; i < 10; i++) { // Clear the first 10 bytes (enough for a 4-character password)
    EEPROM.write(i, '\0');
    delay(5); // Small delay for EEPROM clear
  }
  password = ""; // Clear the stored password variable as well
  Serial.println("EEPROM cleared"); // Debugging line
}