#include <Keypad.h>
#include <LiquidCrystal.h>

const byte ROWS = 4; // Four rows
const byte COLS = 4; // Three columns

// Define the Keymap
char keys[ROWS][COLS] = {

    { '1', '2', '3', 'D' },

    { '4', '5', '6', 'C' },

    { '7', '8', '9', 'B' },

    { '*', '0', '#', 'A' }

};

byte rowPins[ROWS] = { 0, 1, 2, 3 }; // Connect keypad ROW0, ROW1, ROW2 and ROW3 to these Arduino pins.
byte colPins[COLS] = { 4, 5, 6, 7 }; // Connect keypad COL0, COL1 and COL2 to these Arduino pins.

Keypad kpd = Keypad(makeKeymap(keys), rowPins, colPins, ROWS, COLS); // Create the Keypad

const int rs = 8,
    en = 9,
    d4 = 10,
    d5 = 11,
    d6 = 12,
    d7 = 13; //Pins to which LCD is connected
LiquidCrystal lcd(rs, en, d4, d5, d6, d7);

long Num1, Num2, Number;
char key, action;
boolean result = false;

void setup() {
    lcd.begin(16, 2); //We are using a 16*2 LCD display
    lcd.print("DIY Calculator"); //Display a intro message
    lcd.setCursor(0, 1); // set the cursor to column 0, line 1
    lcd.print("-CircuitDigest"); //Display a intro message 

    delay(2000); //Wait for display to show info
    lcd.clear(); //Then clean it
}

void loop() {

    key = kpd.getKey(); //storing pressed key value in a char

    if (key != NO_KEY)
        DetectButtons();

    if (result == true)
        CalculateResult();

    DisplayResult();
}

void DetectButtons() {
    lcd.clear(); //Then clean it
    if (key == '*') //If cancel Button is pressed
    { Serial.println("Button Cancel");
        Number = Num1 = Num2 = 0;
        action=' ';
        result = false; }

    if (key == '1') //If Button 1 is pressed
    {
        Serial.println("Button 1");
        if (Number == 0)
            Number = 1;
        else
            Number = (Number * 10) + 1; //Pressed twice
    }

    if (key == '4') //If Button 4 is pressed
    {
        Serial.println("Button 4");
        if (Number == 0)
            Number = 4;
        else
            Number = (Number * 10) + 4; //Pressed twice
    }

    if (key == '7') //If Button 7 is pressed
    {
        Serial.println("Button 7");
        if (Number == 0)
            Number = 7;
        else
            Number = (Number * 10) + 7; //Pressed twice
    }


    if (key == '0') {
        Serial.println("Button 0"); //Button 0 is Pressed
        if (Number == 0)
            Number = 0;
        else
            Number = (Number * 10) + 0; //Pressed twice
    }

    if (key == '2') //Button 2 is Pressed
    {
        Serial.println("Button 2");
        if (Number == 0)
            Number = 2;
        else
            Number = (Number * 10) + 2; //Pressed twice
    }

    if (key == '5') {
        Serial.println("Button 5");
        if (Number == 0)
            Number = 5;
        else
            Number = (Number * 10) + 5; //Pressed twice
    }

    if (key == '8') {
        Serial.println("Button 8");
        if (Number == 0)
            Number = 8;
        else
            Number = (Number * 10) + 8; //Pressed twice
    }


    if (key == '#') {
        Serial.println("Button Equal");
        Num2 = Number;
        result = true;
    }

    if (key == '3') {
        Serial.println("Button 3");
        if (Number == 0)
            Number = 3;
        else
            Number = (Number * 10) + 3; //Pressed twice
    }

    if (key == '6') {
        Serial.println("Button 6");
        if (Number == 0)
            Number = 6;
        else
            Number = (Number * 10) + 6; //Pressed twice
    }

    if (key == '9') {
        Serial.println("Button 9");
        if (Number == 0)
            Number = 9;
        else
            Number = (Number * 10) + 9; //Pressed twice
    }

    if (key == 'A' || key == 'B' || key == 'C' || key == 'D') //Detecting Buttons on Column 4
    {
        Num1 = Number;
        Number = 0;
        if (key == 'A') { Serial.println("Addition");
            action = '+'; }
        if (key == 'B') { Serial.println("Subtraction");
            action = '-'; }
        if (key == 'C') { Serial.println("Multiplication");
            action = '*'; }
        if (key == 'D') { Serial.println("Devesion");
            action = '/'; }

        delay(100);
    }

}

void CalculateResult() {
    if (action == '+')
        Number = Num1 + Num2;

    if (action == '-')
        Number = Num1 - Num2;

    if (action == '*')
        Number = Num1 * Num2;

    if (action == '/')
        Number = Num1 / Num2;
}

void DisplayResult() {
    lcd.setCursor(0, 0); // set the cursor to column 0, line 1
    lcd.print(Num1);
    lcd.print(action);
    lcd.print(Num2);

    if (result == true) { lcd.print(" =");
    if (Number > 100000000){
      int remainder = Number % 100000000;
      
      lcd.print(remainder);
      lcd.print("e1");
    } else {
      lcd.print(Number);
    }
     } //Display the result

    lcd.setCursor(0, 1); // set the cursor to column 0, line 1
    //lcd.print(Number); //Display the result

    if (Number > 100000000){
      int remainder = Number % 100000000;
      lcd.print(remainder);
      lcd.print("e1");
    } else {
      lcd.print(Number);
    }
}