#include <Keypad.h>
#include <Wire.h>
#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x27, 16, 2);

int upButton = 10;
int downButton = 11;
int selectButton = 12;
int backButton = 13;
int menu = 1;

////////////////////////////////////////////////////////////////////

const byte rows=4;
const byte cols=4;
char hexaButtons[rows][cols]={
  {'1', '2', '3', '+'},
  {'4', '5', '6', '-'},
  {'7', '8', '9', '*'},
  {'C', '0', '=', '/'},  
};
byte rowPins[rows]={6, 7, 8, 9};
byte colPins[cols]={5, 4, 3, 2};
Keypad myKeypad = Keypad( makeKeymap(hexaButtons), rowPins, colPins, rows, cols );

boolean firstNumState = true;
String firstNum="";
String secondNum="";
char op=' ';
char num = myKeypad.getKey();
float result=0.0;

///////////////////////////////////////////////////////////

void setup() 
{
  Serial.begin(9600);
  lcd.begin(16, 2);
  lcd.backlight();
  pinMode(upButton, INPUT_PULLUP);
  pinMode(downButton, INPUT_PULLUP);
  pinMode(selectButton, INPUT_PULLUP);
  pinMode(backButton, INPUT_PULLUP);
  updateMenu();
}

void loop() 
{
  if ( !digitalRead(downButton) ){
    menu++;
    updateMenu();
    delay(200);
    while(!digitalRead(downButton));
  }
  if (!digitalRead(upButton))
  {
    menu--;
    updateMenu();
    delay(200);
    while(!digitalRead(upButton));
  }
  if (!digitalRead(selectButton))
  {
    executeAction();
    updateMenu();
    delay(200);
    while (!digitalRead(selectButton));
  }
  if (!digitalRead(backButton))
  {
    lcd.clear();
    menu = 1;
    delay(200);
    while(!digitalRead(backButton));
  }
  //////////////////////////////CALCULATOR///////////////////////////////

  
  if(num != NO_KEY && (num == '1' || num == '2' || num == '3' || num == '4' || num == '5' || num == '6' || num == '7' || num == '8' || num == '9' || num == '0')){
    if(firstNumState = true){
      firstNum = firstNum + num;
     }
     else{
      secondNum = secondNum + num;
      
     }
  }
  if(num != NO_KEY && (num == '+' || num == '-' || num == '*' || num == '/')){
    if(firstNumState = true){
      op = num;
      firstNumState = false;
    }
  }
  if(num != NO_KEY && num == '='){
    if (op == '+') {
      result = firstNum.toFloat()+ secondNum.toFloat();
    }

    if(op == '-'){
      result = firstNum.toFloat()- secondNum.toFloat();
    }

    if(op == '*'){
      result = firstNum.toFloat()* secondNum.toFloat();
    }

    if(op == '/'){
      result = firstNum.toFloat()/ secondNum.toFloat();
    }
       
 }
}

void updateMenu() 
{
  switch (menu) 
  {
    case 0:
      menu = 1;
      break;
    case 1:
      lcd.clear();
      lcd.print(">Jam");
      lcd.setCursor(0, 1);
      lcd.print(" Alarm");
      break;
    case 2:
      lcd.clear();
      lcd.print(" Jam");
      lcd.setCursor(0, 1);
      lcd.print(">Alarm");
      break;
    case 3:
      lcd.clear();
      lcd.print(">Temperatur");
      lcd.setCursor(0, 1);
      lcd.print(" Kalkulator");
      break;
    case 4:
      lcd.clear();
      lcd.print(" Temperatur");
      lcd.setCursor(0, 1);
      lcd.print(">Kalkulator");
      break;
    case 5:
      menu = 4;
      break;
  }
}

void executeAction() 
{
  switch (menu) 
  {
    case 1:
      action1();
      break;
    case 2:
      action2();
      break;
    case 3:
      action3();
      break;
    case 4:
      action4();
      break;
  }
}

void action1() 
{
  lcd.clear();
  lcd.print(">Executing #1");
  delay(1500);
}
void action2() 
{
  lcd.clear();
  lcd.print(">Executing #2");
  delay(1500);
}
void action3() 
{
  lcd.clear();
  lcd.print(">Executing #3");
  delay(1500);
}
void action4() 
{
  
    lcd.clear();
    lcd.print(num);
    lcd.print(op);
    lcd.clear();
    lcd.setCursor(0,0);
    lcd.print(firstNum);
    lcd.print(op);
    lcd.print(secondNum);
    lcd.setCursor(0,1);
    lcd.print("=");
    lcd.print(result);
    firstNumState = true;

  if (num != NO_KEY && num == 'C') {
    delay(100);
    lcd.clear();
    lcd.setCursor(0,0);
    firstNum = "";
    num = "";
    op = ' ';
  }
  delay(1000*1000);

  
 
}