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

const uint8_t ROWS =4;
const uint8_t COLS = 4;
char keys[ROWS][COLS] = {
  {'1', '2', '3', '+'},
  {'4', '5', '6', '-'},
  {'7', '8', '9', '*'},
  {'.', '0', '=', '/'}
};

uint8_t colPins[COLS] = {5,4,3,2};
uint8_t rowPins[ROWS] = {9,8,7,6};

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


LiquidCrystal lcd(A0, A1, A2, A3, A4, A5);


void showStartScreen(){
   lcd.setCursor(4,0);
 lcd.print("VA_LUHA");
  lcd.setCursor(3,1);
  String message = "Calculator";
  for (byte i=0; i<message.length();i++) {
    lcd.print(message[i]);
    delay(50);
  }
  delay(500);
}

void updateCursor() {
  if (millis()/250%2==0){
    lcd.cursor();
  } else {
    lcd.noCursor();
  }
}

void setup() {
  // put your setup code here, to run once:
 //Serial.begin(9600);
 lcd.begin(16,2);
 showStartScreen();
 lcd.clear();
 lcd.cursor();

 lcd.setCursor(1,0);
 //lcd.print("Hello SerafimGamer");

}

char operation = 0;
String memory = "";
String current ="";
uint64_t currentDecimal;
bool decimalPoint = false;

double calculate(char operation, double left, double right) {
  switch (operation) {
      case '+': return left + right;
      case '-': return left - right;
      case '*': return left * right;
      case '/': return left / right;
  }
}

void processInput(char key) {
  if ('-'==key && current == "") {
    current ="-";
    lcd.print("-");
    return;
  }

  switch (key) {
    case '+':
    case '-':
    case '*':
    case '/':
      if (!operation) {
        memory = current;
        current = "";
      }
      operation = key;
      lcd.setCursor(0,1);
      lcd.print(key);
      lcd.setCursor(current.length()+1,1);
      return;
      
      case '=':
      float leftNum = memory.toDouble();
      float rightNum = current.toDouble();
      memory = String(calculate(operation, leftNum, rightNum));
      current = "";
      lcd.clear();
      lcd.setCursor(1,0);
      lcd.print(memory);
      lcd.setCursor(0,1);
      lcd.print(operation);
      return;
}

if ('.' == key && current.indexOf('.') >= 0) {
  return;
}

if ('.' != key && current == "0") {
  current = String(key);
  } else if (key) {
    current+= String(key);
  }

lcd.print(key);
}
void loop() {
  // put your main code here, to run repeatedly:
  updateCursor();

  char key = KLAWA.getKey();
  if (key) {
    processInput(key);
  }
}