/*
Project: Calculator

Name: Kevin Hessel

Date: 20.10.2023

Libraries:
- LiquidCrystal.h
- Keypad.h

-----------------------------
*/

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

LiquidCrystal lcd(5, 4, 3, 2, 1, 0);
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] = { 13, 12, 11, 10 };
byte colPins[COLS] = { 9, 8, 7, 6 };

Keypad myKeypad = Keypad(makeKeymap(keys), rowPins, colPins, ROWS, COLS);

boolean keepCalculating = false;
boolean presentValue = false;
boolean next = false;
boolean final = false;
String num1, num2;
int answer;
char op;

void setup() {
  lcd.begin(16, 2);
  lcd.setCursor(0, 0);
  lcd.print("   Calculator");
  delay(3000);
  lcd.clear();
}

void loop() {

  char key = myKeypad.getKey();

  if (key != NO_KEY && (key == '1' || key == '2' || key == '3' || key == '4' || key == '5' || key == '6' || key == '7' || key == '8' || key == '9' || key == '0')) {
    if (presentValue != true && keepCalculating != true) {
      num1 = num1 + key;
      int numLength = num1.length();
      lcd.setCursor(15 - numLength, 0);
      lcd.print(num1);
    } else if (presentValue != true && keepCalculating == true) {
      lcd.setCursor(0, 1);
      presentValue = true;
      op = '+';
      lcd.print(op);
      num2 = num2 + key;
      lcd.print(num2);
    }


    else if (presentValue == true && keepCalculating != true) {
      num2 = num2 + key;
      int numLength = num2.length();
      lcd.setCursor(15 - numLength, 1);
      lcd.print(num2);
      final = true;
    } else {
      num2 = num2 + key;
      lcd.setCursor(1, 1);
      lcd.print(num2);
      final = true;
    }
  }


  else if (presentValue == false && key != NO_KEY && (key == '/' || key == '*' || key == '-' || key == '+')) {
    if (presentValue == false && keepCalculating != true) {
      presentValue = true;
      op = key;
      lcd.setCursor(15, 0);
      lcd.print(op);
    } else if (presentValue == false && keepCalculating == true) {
      num2 = "";
      presentValue = true;
      op = key;
      lcd.setCursor(0, 1);
      lcd.print(op);
    }
  }

  else if (final == true && keepCalculating != true && key != NO_KEY && key == '=') {
    if (op == '+') {
      answer = num1.toInt() + num2.toInt();
    } else if (op == '-') {
      answer = num1.toInt() - num2.toInt();
    } else if (op == '*') {
      answer = num1.toInt() * num2.toInt();
    } else if (op == '/') {
      answer = num1.toInt() / num2.toInt();
    }
    lcd.clear();
    lcd.setCursor(0, 0);
    lcd.print(answer);
    keepCalculating = true;
    presentValue = false;
    num1 = "";
    num2 = "";
  } else if (final == true && keepCalculating == true && key != NO_KEY && key == '=') {
    if (op == '+') {
      answer = answer + num2.toInt();
    } else if (op == '-') {
      answer = answer - num2.toInt();
    } else if (op == '*') {
      answer = answer * num2.toInt();
    } else if (op == '/') {
      answer = answer / num2.toInt();
    }
    lcd.clear();
    lcd.setCursor(0, 0);
    lcd.print(answer);
    keepCalculating = true;
    presentValue = false;
    num1 = "";
    num2 = "";
  } else if (key != NO_KEY && key == 'C') {
    lcd.clear();
    keepCalculating = false;
    presentValue = false;
    final = false;
    num1 = "";
    num2 = "";
    answer = 0;
    op = ' ';
  }
}