#include <Wire.h>
#include <LiquidCrystal_I2C.h>
LiquidCrystal_I2C lcd(0x27, 20, 4);

// Button pins
const int selectButton = 2;
const int backButton = 3;
const int upButton = 4;
const int downButton = 5;

// LED pins
const int ledPin = 13;

// State variables
volatile bool enterLoop = false;
int level = 0;
int index0 = 0;
int index1 = 0;

void main_screen() {
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("Home");
}

void menu1_screen() {
  lcd.clear();
  lcd.setCursor(1, 0);
  lcd.print("Setting");
  lcd.setCursor(1, 1);
  lcd.print("About Device");
  lcd.setCursor(1, 2);
  lcd.print("About Developer");
  lcd.setCursor(0, index0);  // Show selection
  lcd.print(">");
}

void menu2_screen() {
  lcd.clear();
  lcd.setCursor(1, 0);
  lcd.print("T1");
  lcd.setCursor(1, 1);
  lcd.print("T2");
  lcd.setCursor(1, 2);
  lcd.print("T3");
  lcd.setCursor(0, index1);  // Show selection
  lcd.print(">");
}

void executeAction() {
  switch (level) {
    case 0:  // Move to main menu
      level = 1;
      index0 = 0;
      break;
    case 1:  // Navigate submenus
      if (index0 == 0) level = 2;  // Example action for first menu item
      break;
  }
}

void updateMenu() {
  switch (level) {
    case 0:
      main_screen();
      break;
    case 1:
      checkBounds(index0, 0, 2);
      menu1_screen();
      break;
    case 2:
      checkBounds(index1, 0, 2);
      menu2_screen();
      break;
  }
}

void checkBounds(int &value, int min, int max) {
  if (value < min) value = max;
  if (value > max) value = min;
}

void setup() {
  pinMode(selectButton, INPUT_PULLUP);
  pinMode(backButton, INPUT_PULLUP);
  pinMode(upButton, INPUT_PULLUP);
  pinMode(downButton, INPUT_PULLUP);
  pinMode(ledPin, OUTPUT);
 
  lcd.init();
  lcd.backlight();
  main_screen();

  attachInterrupt(digitalPinToInterrupt(selectButton), startInterrupt, FALLING);
  attachInterrupt(digitalPinToInterrupt(backButton), stopInterrupt, FALLING);

  Serial.begin(9600);
  Serial.println("Setup complete. Waiting for interrupts.");
}

void loop() {
  if (enterLoop) {
    updateMenu();  // Initial update when entering loop

    while (enterLoop) {  // Menu navigation loop
      if (!digitalRead(upButton)) {
        switch (level) {
          case 1: index0++; break;
          case 2: index1++; break;
        }
        updateMenu();
        delay(200);  // Debounce
        while (!digitalRead(upButton));  // Wait for release
      }

      if (!digitalRead(downButton)) {
        switch (level) {
          case 1: index0--; break;
          case 2: index1--; break;
        }
        updateMenu();
        delay(200);  // Debounce
        while (!digitalRead(downButton));  // Wait for release
      }

      if (!digitalRead(selectButton)) {
        executeAction();
        updateMenu();
        delay(200);  // Debounce
        while (!digitalRead(selectButton));  // Wait for release
      }

      if (!digitalRead(backButton)) {
        switch (level) {
          case 1: level = 0; enterLoop = false; Serial.println("Exited menu loop"); break;
          case 2: level = 1; break;
        }
        updateMenu();
        delay(200);  // Debounce
        while (!digitalRead(backButton));  // Wait for release
      }
    }
  } else {
    digitalWrite(ledPin, HIGH);  // Blink LED in normal mode
    delay(500);
    digitalWrite(ledPin, LOW);
    delay(500);
  }
}

void startInterrupt() {
  if (!enterLoop) {
    enterLoop = true;
    level = 1;
    Serial.println("Entered menu loop");
  }
}

void stopInterrupt() {
  
}