// default pass is 12ABC
// enter pass and then use "#" to unlock.
// when unlocked, use # after 5 sec to lock (no pass required)
// to change pass click "*" and enter old pass. 
// then click #.
// now type the new pass and click # and wait 5 sec.
// you have successfully set your new pass

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

// OLED display settings
#define SCREEN_WIDTH 128 // OLED display width, in pixels
#define SCREEN_HEIGHT 64 // OLED display height, in pixels
#define SCREEN_ADDRESS 0x3D // Address of the SSD1306 OLED display
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, -1);

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] = { 2, 3, 4, 5 }; // Connect keypad rows to Arduino pins
byte colPins[COLS] = { 6, 7, 8, 9 }; // Connect keypad columns to Arduino pins

Keypad keypad = Keypad(makeKeymap(keys), rowPins, colPins, ROWS, COLS); // Initialize the keypad
Servo myServo; // Servo for locking/unlocking the door

const int lockPosition = 90;   // Servo locked position
const int unlockPosition = 180; // Servo unlocked position
String password = "12ABC";     // Default password
String input = "";             // To store user input from keypad
bool settingNewPassword = false; // Flag for setting a new password
bool verifyOldPassword = false;  // Flag for verifying the old password
bool doorLocked = true;          // Door state: true means locked

void setup() {
  Serial.begin(9600); // Start serial communication
  myServo.attach(10); // Attach servo to pin 10
  myServo.write(lockPosition); // Lock the door initially

  // Initialize the OLED display
  if (!display.begin(SSD1306_SWITCHCAPVCC, SCREEN_ADDRESS)) { // Set I2C address to 0x3C
    Serial.println(F("SSD1306 allocation failed")); // Print error to Serial Monitor
    for (;;); // Stop execution if initialization fails
  }

  // Clear the display and show the welcome message
  display.clearDisplay();
  display.setTextSize(1); // Set text size for OLED
  display.setTextColor(SSD1306_WHITE); // Set text color to white
  display.setCursor(0, 0); // Set cursor to top-left
  display.println("Enter Password:"); // Display initial prompt
  display.display(); // Update OLED
}

void loop() {
  char key = keypad.getKey(); // Get keypress from keypad
  if (key) {
    Serial.print(key); // Print keypress to Serial Monitor
    input += key; // Append keypress to input string

    // Update the OLED with the current input
    display.clearDisplay();
    display.setTextSize(1); // Set text size for OLED
    display.setCursor(0, 0); // Set cursor to top-left
    if (verifyOldPassword) {
      display.println("Enter Old Pass:"); // Show "Enter Old Pass" prompt
    } else if (settingNewPassword) {
      display.println("Set New Password:"); // Show "Set New Password" prompt
    } else if (doorLocked) {
      display.println("Enter Password:"); // Show "Enter Password" prompt
    } else {
      display.println("Door Locked"); // Show "Door Locked" message
    }
    display.setCursor(0, 10); // Move cursor down for input display
    display.println(input); // Show the current input
    display.display(); // Update OLED

    if (key == '#') { // Handle # keypress (confirm/enter)
      if (verifyOldPassword) { // Verify old password
        if (input.substring(0, input.length() - 1) == password) { // Compare input with current password
          Serial.println("\nOld Password Correct!");
          displayMessage("Old Password OK"); // Show success message
          delay(2000);
          settingNewPassword = true; // Enable new password setup
          verifyOldPassword = false;
          input = ""; // Reset input
          displayMessage("Set New Password:"); // Prompt for new password
          Serial.println("Set New Password:");
        } else {
          Serial.println("\nOld Password Incorrect!");
          displayMessage("Old Password NO"); // Show error message
          delay(2000);
          input = ""; // Reset input
          verifyOldPassword = false; // Disable verification mode
          displayMessage("Enter Password:"); // Reset to default prompt
          Serial.println("Enter Password:");
        }
      } else if (doorLocked) { // Handle door unlocking/locking
        if (settingNewPassword) { // Set new password
          password = input.substring(0, input.length() - 1); // Update password
          Serial.println("\nNew Password Set!");
          displayMessage("New Password Set!"); // Show success message
          delay(5000);
          settingNewPassword = false; // Disable new password setup
          input = ""; // Reset input
          displayMessage("Enter Password:"); // Reset to default prompt
          Serial.println("Enter Password:");
        } else { // Verify and unlock door
          if (input.substring(0, input.length() - 1) == password) { // Compare input with password
            Serial.println("\nPassword Correct!");
            displayMessage("Password Correct!"); // Show success message
            unlockDoor(); // Unlock the door
            delay(5000);
          } else {
            Serial.println("\nPassword Incorrect!");
            displayMessage("Password Incorrect!"); // Show error message
            delay(5000);
          }
          input = ""; // Reset input
          displayMessage("Enter Password:"); // Reset to default prompt
          Serial.println("Enter Password:");
        }
      } else { // Lock the door
        lockDoor(); // Lock the door
        displayMessage("Door Locked"); // Show door locked message
        delay(5000);
        displayMessage("Enter Password:"); // Reset to default prompt
        input = ""; // Reset input
        Serial.println("Enter Password:");
      }
    }

    if (key == '*') { // Handle * keypress (start password change)
      input = ""; // Reset input
      verifyOldPassword = true; // Enable verification mode
      displayMessage("Enter Old Pass:"); // Prompt for old password
      Serial.println("\nEnter Old Pass:");
    }
  }
}

void unlockDoor() {
  myServo.write(unlockPosition); // Move servo to unlocked position
  doorLocked = false; // Update door state
}

void lockDoor() {
  myServo.write(lockPosition); // Move servo to locked position
  doorLocked = true; // Update door state
}

void displayMessage(String message) {
  display.clearDisplay(); // Clear OLED
  display.setTextSize(1); // Set text size for OLED
  display.setCursor(0, 0); // Set cursor to top-left
  display.println(message); // Display custom message
  display.display(); // Update OLED
}