/*
Project: Calculator

Name: Kevin Hessel

Date: 23.10.2023

Libraries:
- LiquidCrystal.h
- Keypad.h

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

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

LiquidCrystal lcd(5, 4, 3, 2, 1, 0);  //LCD pins

String num1, num2;
boolean gotNum1 = false;
boolean gotOp = false;
boolean showResult = false;
boolean keepCalculating = false;
char op;
float answer;
unsigned long pressStart;
int treshholdHold = 2000;

const byte ROWS = 4;  //number of rows
const byte COLS = 4;  //number of coloumns

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

byte rowPins[ROWS] = { 13, 12, 11, 10 };  //row pins
byte colPins[COLS] = { 9, 8, 7, 6 };      //coloumn pins

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


void setup() {
  lcd.begin(16, 2);
  lcd.print("   Calculator");
  delay(2000);
  lcd.clear();
}

//prints the answer on the lcd and sets it in the top right corner - 1
//answer first needs to be converted into a string, then count the length of the string, then convert the new value back into an integer and subtract it
void printAnswer(float answerToPrint) {
  String StringAnswer;
  int answerLength;
  lcd.clear();
  StringAnswer = String(answerToPrint, 7);
  answerLength = StringAnswer.length();
  lcd.setCursor(15 - answerLength, 0);
  lcd.print(answerToPrint, 7);
  lcd.setCursor(0, 0);
  lcd.print("=");
  keepCalculating = true;
  gotOp = false;
  gotNum1 = true;
  num2 = "";
  op = "";
}

void printNum1(String NUM) {
  int numLength = NUM.length();
  lcd.setCursor(15 - numLength, 0);
  lcd.print(NUM);
}

void printNum2(String NUM) {
  int numLength = NUM.length();
  lcd.setCursor(15 - numLength, 1);
  lcd.print(NUM);
}


void loop() {

  char key = keypad.getKey();


  //input for the first number of the calculation and sets it into the right top corner - 1 of the lcd
  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 (gotOp == false && keepCalculating == false) {
      num1 = num1 + key;
      printNum1(num1);
      gotNum1 = true;
    }
  }
  //input for the operator of the calculation and sets it into the very right top corner of the lcd
  if (key != NO_KEY && (key == '+' || key == '-' || key == '*' || key == '/')) {
    if (gotNum1 == true) {  //if number 1 has a value
      op = "";
      op = key;
      lcd.setCursor(15, 0);
      lcd.print(op);
      gotOp = true;
    }
  }
  //input for the second number of the calculation and sets it into the right bottom corner - 1 of the lcd
  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 (gotOp == true || keepCalculating == true) {  //if an operator has been assigned //or answer has already been printed
      num2 = num2 + key;
      printNum2(num2);
      showResult = true;
    }
    if (gotNum1 == true && keepCalculating == true && gotOp == false) {  //if number 1 has a value //if answer has already been printed
      op = '+';
      lcd.setCursor(15, 0);
      lcd.print(op);
      gotOp = true;
    }
  }
  //calculates and shows the result depending on the chosen operator
  if (key != NO_KEY && key == '#' && showResult == true) {

    if (keepCalculating == false) {

      switch (op) {
        case '+':
          answer = num1.toInt() + num2.toInt();
          printAnswer(answer);
          break;
        case '-':
          answer = num1.toInt() - num2.toInt();
          printAnswer(answer);
          break;
        case '*':
          answer = num1.toInt() * num2.toInt();
          printAnswer(answer);
          break;
        case '/':
          answer = num1.toFloat() / num2.toFloat();
          printAnswer(answer);
          break;
      }
    }
    //after the first calculation you can keep on calculating with the "answer"
    if (keepCalculating == true) {  //if an answer has been printed

      switch (op) {
        case '+':
          answer = answer + num2.toInt();
          printAnswer(answer);
          break;
        case '-':
          answer = answer - num2.toInt();
          printAnswer(answer);
          break;
        case '*':
          answer = answer * num2.toInt();
          printAnswer(answer);
          break;
        case '/':
          answer = answer / num2.toInt();
          printAnswer(answer);
          break;
      }
    }
  }
  //deletes all the data and resets the lcd monitor
  if (key != NO_KEY && key == 'C') {
    num1 = "";
    num2 = "";
    op = "";
    gotNum1 = false;
    gotOp = false;
    showResult = false;
    keepCalculating = false;
    lcd.clear();
  }
}