#include <Adafruit_GFX.h>
#include <Adafruit_ILI9341.h>
#include <Adafruit_FT6206.h>

// TFT pins
#define TFT_CS   10
#define TFT_DC    9
#define TFT_RST   8

Adafruit_ILI9341 tft = Adafruit_ILI9341(TFT_CS, TFT_DC, TFT_RST);

// Capacitive Touch
Adafruit_FT6206 cts = Adafruit_FT6206();

String expression = "";

const int btnW = 80;
const int btnH = 60;
const int btnLeft = 0;
const int btnTop = 120;

char buttons[4][4] = {
  {'1','2','3','+'},
  {'4','5','6','-'},
  {'7','8','9','*'},
  {'C','0','=','/'}
};

void drawButtons() {
  tft.setTextColor(ILI9341_WHITE);
  tft.setTextSize(3);

  for(int r=0; r<4; r++){
    for(int c=0; c<4; c++){
      int x = btnLeft + c * btnW;
      int y = btnTop + r * btnH;
      tft.drawRect(x, y, btnW, btnH, ILI9341_WHITE);
      tft.setCursor(x + btnW/2 - 10, y + btnH/2 - 14);
      tft.print(buttons[r][c]);
    }
  }
}

void showExpression() {
  tft.fillRect(0, 0, 240, 100, ILI9341_BLACK);
  tft.setTextColor(ILI9341_GREEN);
  tft.setTextSize(3);
  tft.setCursor(10, 40);
  tft.print(expression);
}

float calculate(String expr){
  int opIndex = -1;
  char op = 0;

  for(int i=1; i<expr.length(); i++){
    char c = expr.charAt(i);
    if(c=='+'||c=='-'||c=='*'||c=='/'){ op = c; opIndex = i; break; }
  }

  if(opIndex == -1) return expr.toFloat();

  float a = expr.substring(0, opIndex).toFloat();
  float b = expr.substring(opIndex+1).toFloat();

  switch(op){
    case '+': return a+b;
    case '-': return a-b;
    case '*': return a*b;
    case '/': return (b != 0 ? a/b : 0);
  }
  return 0;
}

void setup() {
  tft.begin();
  cts.begin();
  tft.setRotation(0);   // <<< ASL ORIENTATSIYA (VERTIKAL)
  tft.fillScreen(ILI9341_BLACK);

  drawButtons();
  showExpression();
}

void loop() {
  if (!cts.touched()) return;

  TS_Point p = cts.getPoint();

  // FT6206 sensor koordinatalari (VERTIKAL uchun to‘g‘ri)
  int tx = p.x;
  int ty = p.y;

  int col = tx / btnW;
  int row = (ty - btnTop) / btnH;

  if (row >= 0 && row < 4 && col >= 0 && col < 4) {
    char v = buttons[row][col];

    if (v == 'C') expression = "";
    else if (v == '=') expression = String(calculate(expression));
    else expression += v;

    showExpression();
    delay(200);
  }
}