#include "lcd_1.h"
#include <Arduino.h> 
// Global Declaration:
char get_key(uint8_t row, uint8_t col) {
    const char keys[4][4] = {
        {'1', '2', '3', '+'},
        {'4', '5', '6', '-'},
        {'7', '8', '9', '*'},
        {'d', '0', '=', '/'}
    };
    return keys[row][col];
}

long output_1, num1, num2;
char action, key;
boolean result = false;
boolean error = false;

void write_data(char);
void write_string(char *ptr);

void setup() {
    init_program();  // Initialize program
    lcd_init();      // Initialize LCD
    Serial.begin(9600);
}

void write_data(char wr_data)
{
  out_data(wr_data);
  out_con(0x01);    // RS = 1, E = 0
  delay1(1);
  out_con(0x03);   // RS = 1, E = 1
  delay1(1);
  out_con(0x01);  // RS = 1, E = 0
  delay1(1);
}

void loop() {
    // Intentionally left empty
      for (int row = 0; row < 4; row++) {
        switch_in(1 << row);  // Activate one row at a time
        uint8_t colValue = switch_out();  // Read column values
        
        for (int col = 0; col < 4; col++) {
            if (colValue & (1 << col)) { // Check if column is active
                key = get_key(row, col);
                write_data(key);
                Serial.print(key);
                delay1(5); // Debounce delay
                capture_key();
                if(result)
                {
                  calculate(); 
                  if (!error) { // Only print if no error
                        write_long(output_1);
                        Serial.print(output_1);
                        Serial.println();
                  }
                  delay1(5);
                  result=false;
                  out_data(0x02);  // Reset Display
                  lcd_control();
                  out_data(0x01);  // Clear Display
                  lcd_control();
                }
            }
        }
    }
}

void write_long(long data) {
    char str[20]; // Buffer to hold the string representation of the number
    sprintf(str, "%ld", data); // Convert long to string using sprintf

    for (char *ptr = str; *ptr != '\0'; ++ptr) { // Loop through each character
        write_data(*ptr); // Output the character one by one
    }
}


void capture_key() {
    if (key == 'd') {
        lcd_step_back(); // Step back and clear the last character
        output_1 /= 10;  // Remove the last digit from the number
        return;
    }
    
    if (key >= '0' && key <= '9') {
        int digit = key - '0';
        output_1 = (output_1 * 10) + digit;
        return;
    }

    if (key == '+' || key == '-' || key == '*' || key == '/') {
        num1 = output_1;
        action = key;
        output_1 = 0;
        return;
    }

    if (key == '=') {
        num2 = output_1;
        result = true;
    }
}

void calculate() {
    output_1 = 0; // Reset output

    if (action == '+') {
        output_1 = num1 + num2;
    } 
    else if (action == '-') {
        output_1 = num1 - num2;
    } 
    else if (action == '*') {
        output_1 = num1 * num2;
    } 
    else if (action == '/') {
        if (num2 == 0) {
            // Handle division by zero
            Serial.println("Illegal Operation: Division by Zero\n");
            write_string("Illegal");
            error = true; // Set error flag
            return; // Exit function to avoid incorrect computation
        } else {
            output_1 = num1 / num2;
        }
    } 
    else {
      out_data(0x02);  // Reset Display
      lcd_control();
      out_data(0x01);  // Clear Display
      lcd_control();
      write_string("Illegal");
      error = true; // Set error flag
    }

    // Reset input numbers
    num1 = 0;
    num2 = 0;
}

void write_string(char *ptr) {
    while (*ptr) {
        write_data(*ptr++);
    }
}