#include <math.h>
#include <stdlib.h>
void init_port(void);
void outdata(char);
void outcontrol(char);
void init_lcd(void);
void lcd_control_write(void);
void write_data(char);
void write_string(char);
void set_cursor_second_row(void);
char str[50] = "CALCULATOR";
void setup() {
  init_port();
  init_lcd();
  volatile char *dirF, *dirK;
  dirF = 0x30, dirK = 0x10;
  *dirF = 0xFF, *dirK = 0x00;
   Serial.begin(9600);
  write_string(str);
}
void write_string(char *ptr) {
  volatile long count = 0;
  while (*ptr != 0) {
    if (count == 16) {
      set_cursor_second_row();
      lcd_control_write();
    }
    write_data(*ptr);                // Write character to the LCD
    ptr++;
    count++;

  }
}
void init_port(void) {
  volatile char *portA_dir = (volatile char *)0x21;
  volatile char *portC_dir = (volatile char *)0x27;
  *portA_dir = 0xFF;
  *portC_dir = 0x03;
}
void outdata(char out_data) {
  volatile char *portA_data;
  portA_data = 0x22;
  *portA_data = out_data;
}
void outcontrol(char out_data) {
  volatile char *portC_data;
  portC_data = 0x28;
  *portC_data = out_data;
}
void init_lcd(void) {
  outdata(0x38);  //function set: 8bit ,2line , 5*8
  lcd_control_write();  //giving pulse to enable
  outdata(0x0F);   //display on ,cursor blinking
  lcd_control_write();
  outdata(0x01);  //clear display
  lcd_control_write();
  outdata(0x06);   //auto increment after writing 1 char; entry mode
  lcd_control_write();


}
void lcd_control_write(void) {
  outcontrol(0x01);
  delay(1);
  outcontrol(0x00);
  delay(1);
}
void write_data(char wr_data) {
  outdata(wr_data);
  outcontrol(0x02);    //giving pulse to enable and sending data
  delay(1);
  outcontrol(0x03);
  delay(1);
  outcontrol(0x02);
  delay(1);
}
void set_cursor_second_row(void) {
  outdata(0xC0);  // Address of the second row in 16x2 LCD(DDRAM)
  lcd_control_write();
}
void set_cursor_first_row(void) {
  outdata(0x80);  // Address of the first row in 16x2 LCD(DDRAM)
  lcd_control_write();
}
void loop() {
  // put your main code here, to run repeatedly:
  volatile int col, row;
  char keys[4][4] = {
    {'1', '2', '3', '+'},
    {'4', '5', '6', '-'},
    {'7', '8', '9', '*'},
    {'.', '0', '=', '/'}
  };


  volatile char *outF, *inK;
  outF = 0x31, inK = 0x106 ;
  volatile long i, j;
  int num1 = -1, num2 = -1;
  int num3 = -1, num4 = -1;
  uint8_t sum;
  bool firstNumberComplete = false;
  bool inputComplete = false;
  char *Operator;
  int firstNumber;
  int secondNumber;
  int result;

  while (1) {
    for (i = 0; i < 4 ; i++) {
      *outF = 1 << i;

      if (*inK != 0) {
        col = *inK;
        row = 1 << i;
        char key = keys[int(log(row) / log(2))][int(log(col) / log(2))];

        if (key >= '0' && key <= '9') {
          int digit = key - '0';

          if (!firstNumberComplete) {
            if (num1 == -1) {
              num1 = digit;
              sprintf(str, "%d", num1);
              init_lcd();
              write_string(" ");
              write_string(str);
            }
            else {
              num2 = digit;
              sprintf(str, "%d", num2);
              write_string(str);
              firstNumber = num1 * 10 + num2;
              firstNumberComplete = true;
              num1 = -1;
              num2 = -1;

            }
          } else {
            // Getting the second two-digit number
            if (num3 == -1) {
              num3 = digit;  // Store first digit of second number
              sprintf(str, "%d", num3);
              write_string(str);
            }
            else {
              num4 = digit;  // Store second digit of second number
              sprintf(str, "%d", num4);
              write_string(str);

              secondNumber = num3 * 10 + num4;
              num3 = -1;
              num4 = -1;
              firstNumberComplete = false;
              inputComplete = true;
            }
          }



        }
        else if (key == '+' ) {
          Operator = "add";
          set_cursor_second_row();
          lcd_control_write();
          write_string("+");
        }
        else if (key == '-') {
          Operator = "subtract";
          set_cursor_second_row();
          lcd_control_write();
          write_string("-");
        }
        else if (key == '*') {
          Operator = "multiply";
          set_cursor_second_row();
          lcd_control_write();
          write_string("*");
        }
        else if (key == '/') {
          Operator = "divide";
          set_cursor_second_row();
          lcd_control_write();
          write_string("/");
        }
        else if (key == '=') {
          if (Operator == "add") {
            result = firstNumber + secondNumber;
          }
          else if (Operator == "subtract") {
            result = firstNumber - secondNumber;
          }
          else if (Operator == "multiply") {
            result = firstNumber * secondNumber;
          }
          else if (Operator == "divide") {
           float result = (float)firstNumber / secondNumber;
          dtostrf(result, 6, 2, str);  // Convert float to string
           init_lcd();
          write_string("ANSWER: ");
          write_string(str);
          }
          if(Operator != "divide"){
           sprintf(str, "%d", result);  // Convert float to string
           init_lcd();
          write_string("ANSWER: ");
          write_string(str);
          }
        // Debounce delay

        }
        delay(50);
        // Wait for key release
        while (*inK != 0);
        delay(10);  // Short delay between each iteration
      }


    }

  }


}