#include <U8g2lib.h>
#include <Wire.h>

// Display
U8G2_SSD1306_128X64_NONAME_F_HW_I2C u8g2(U8G2_R0);

// Menu items
const char* menuItems[] = {"Add", "Subtract", "Multiply", "Divide"};
const int menuLength = sizeof(menuItems) / sizeof(menuItems[0]);
int currentSelection = 0;
int formula = 0;
// Button pins
const int btnNext = 2;     // Scroll through menu
const int btnSelect = 3;   // Select current item
const int btn = 4;
bool lastBtnNextState = HIGH;
bool lastBtnSelectState = HIGH;
bool lastBtnState = HIGH;
void setup() {
  u8g2.begin();
  pinMode(btnNext, INPUT_PULLUP);
  pinMode(btnSelect, INPUT_PULLUP);
  pinMode(btn,INPUT);
}

void loop() {
  // Read buttons (active LOW)
  bool btnNextState = digitalRead(btnNext);
  bool btnSelectState = digitalRead(btnSelect);

  // Handle menu scroll
  if (btnNextState == LOW && lastBtnNextState == HIGH) {
    currentSelection = (currentSelection + 1) % menuLength;
    delay(200);  // Simple debounce
  }


  if (btnSelectState == LOW && lastBtnSelectState == HIGH) {
    performOperation(currentSelection);
    delay(500); 
  }

  lastBtnNextState = btnNextState;
  lastBtnSelectState = btnSelectState;

  drawMenu();
}

void drawMenu() {
  u8g2.clearBuffer();
  u8g2.setFont(u8g2_font_6x13_tr);

  for (int i = 0; i < menuLength; i++) {
    if (i == currentSelection) {
     
      u8g2.drawStr(10, 15 + i * 12, ">");
    }
    u8g2.drawStr(20, 15 + i * 12, menuItems[i]);
  }

  u8g2.sendBuffer();
}
void performOperation(int index) {
  u8g2.clearBuffer();
  u8g2.setFont(u8g2_font_ncenB08_tr);

  switch (index) {
    case 0:
      
      Add();
      break;
    case 1:
      u8g2.drawStr(20, 30, "Subtraction Selected");
      break;
    case 2:
      u8g2.drawStr(20, 30, "Multiplication Selected");
      break;
    case 3:
      u8g2.drawStr(20, 30, "Division Selected");
      break;
  }

  u8g2.sendBuffer();
  delay(1000); // Pause to display message
}
void Add(){
  const int btnVal = digitalRead(btn);

  u8g2.setFont(u8g2_font_ncenB08_tr);
    u8g2.drawStr(20, 30, "Addition Selected");
    bool btnState = digitalRead(btn);
    if (btnState == LOW && lastBtnState == HIGH) {
      formula++;
      delay(200);  // debounce
    }
    lastBtnState = btnState;

  char buf[10];
  sprintf(buf, "Total: %d", formula);
  u8g2.drawStr(10, 40, buf);
   u8g2.sendBuffer();

}