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

U8G2_SSD1306_128X64_NONAME_F_SW_I2C u8g2(U8G2_R0, /* clock=*/ A4, /* data=*/ A5, /* reset=*/ U8X8_PIN_NONE);

// Keypad uchun konfiguratsiya
const byte ROWS = 4;
const byte COLS = 4;
char keys[ROWS][COLS] = {
  {'1','2','3','+'},
  {'4','5','6','-'},
  {'7','8','9','*'},
  {'C','0','=','/'}
};
byte rowPins[ROWS] = {9, 8, 7, 6}; // Row 1 to 4
byte colPins[COLS] = {5, 4, 3, 2}; // Column 1 to 4
Keypad keypad = Keypad(makeKeymap(keys), rowPins, colPins, ROWS, COLS);

String inputString = ""; // Kiritilgan raqamlarni saqlash uchun
float result = 0; // Natijani saqlash uchun

void setup() {
  u8g2.begin();
  u8g2.enableUTF8Print();
  u8g2.clearBuffer();
  u8g2.setFont(u8g2_font_ncenB14_tr);
  u8g2.drawStr(0, 20, "Calculator");
  u8g2.sendBuffer();

  delay(2000); // kichik intizor
}

void loop() {
  char key = keypad.getKey();

  if (key) {
    if (key == 'C') {
      inputString = "";
      result = 0;
    } else if (key == '=') {
      result = evaluateExpression(inputString);
      inputString = String(result);
    } else {
      inputString += key;
    }

    u8g2.clearBuffer();
    u8g2.setFont(u8g2_font_ncenB14_tr);
    u8g2.drawStr(0, 20, inputString.c_str());
    u8g2.sendBuffer();
  }
}

float evaluateExpression(String expression) {
  int length = expression.length() + 1;
  char charArray[length];
  expression.toCharArray(charArray, length);
  charArray[length - 1] = '\0';

  return atof(charArray);
}