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

// Initialize the LCD with I2C address 0x27
LiquidCrystal_I2C lcd(0x27, 20, 4);

// Button Pin Definitions
#define BUTTON_UP 26
#define BUTTON_DOWN 27
#define BUTTON_LEFT 28
#define BUTTON_RIGHT 29
#define BUTTON_ENTER 30

// Variables
int currentIndex = 0;         // Current variable index
int currentDigit = 0;         // Active digit (0 = first, 1 = second)
int values[4] = {0, 0, 0, 0}; // Array for Length, Width, Rotational Range, Distance
int inputDigits[2] = {0, 0};  // Temporary input digits for active variable

void setup() {
  // Initialize LCD
  lcd.init();
  lcd.backlight();

  // Initialize Buttons
  pinMode(BUTTON_UP, INPUT_PULLUP);
  pinMode(BUTTON_DOWN, INPUT_PULLUP);
  pinMode(BUTTON_LEFT, INPUT_PULLUP);
  pinMode(BUTTON_RIGHT, INPUT_PULLUP);
  pinMode(BUTTON_ENTER, INPUT_PULLUP);

  // Load Initial Value
  loadCurrentValue();
  updateLCD();
}

void loop() {
  // Increment Current Digit
  if (digitalRead(BUTTON_UP) == LOW) {
    inputDigits[currentDigit] = (inputDigits[currentDigit] + 1) % 10;
    delay(200); // Debounce
    updateLCD();
  }

  // Decrement Current Digit
  if (digitalRead(BUTTON_DOWN) == LOW) {
    inputDigits[currentDigit] = (inputDigits[currentDigit] - 1 + 10) % 10;
    delay(200); // Debounce
    updateLCD();
  }

  // Move to Previous Variable
  if (digitalRead(BUTTON_LEFT) == LOW) {
    saveCurrentValue();
    currentIndex = (currentIndex - 1 + 4) % 4; // Wrap around
    loadCurrentValue();
    delay(200); // Debounce
    updateLCD();
  }

  // Move to Next Variable
  if (digitalRead(BUTTON_RIGHT) == LOW) {
    saveCurrentValue();
    currentIndex = (currentIndex + 1) % 4; // Wrap around
    loadCurrentValue();
    delay(200); // Debounce
    updateLCD();
  }

  // Switch Digits or Save Input
  if (digitalRead(BUTTON_ENTER) == LOW) {
    if (currentDigit == 0) {
      currentDigit = 1; // Move to the second digit
    } else {
      saveCurrentValue(); // Save the input value
      currentDigit = 0;   // Reset to the first digit
      currentIndex = (currentIndex + 1) % 4; // Move to next variable
      loadCurrentValue(); // Load new variable's value
    }
    delay(200); // Debounce
    updateLCD();
  }
}

// Save the input value to the values array
void saveCurrentValue() {
  values[currentIndex] = inputDigits[0] * 10 + inputDigits[1];
}

// Load the value of the current variable into the input digits
void loadCurrentValue() {
  inputDigits[0] = values[currentIndex] / 10; // Extract first digit
  inputDigits[1] = values[currentIndex] % 10; // Extract second digit
}

// Update the LCD Display
void updateLCD() {
  lcd.clear();

  // Display Variables
  lcd.setCursor(0, 0);
  lcd.print("Length: ");
  lcd.print(values[0]);

  lcd.setCursor(0, 1);
  lcd.print("Width: ");
  lcd.print(values[1]);

  lcd.setCursor(0, 2);
  lcd.print("Rotation: ");
  lcd.print(values[2]);

  lcd.setCursor(0, 3);
  lcd.print("Distance: ");
  lcd.print(values[3]);

  // Highlight Current Variable and Show Input
  lcd.setCursor(12, currentIndex); // Position for the input
  lcd.print("<");
  lcd.print(inputDigits[0]);
  lcd.print(inputDigits[1]);
  lcd.print(">");

  // Highlight Active Digit
  if (currentDigit == 0) {
    lcd.setCursor(13, currentIndex); // Highlight first digit
  } else {
    lcd.setCursor(14, currentIndex); // Highlight second digit
  }
  lcd.blink();
}