//libraries
#include <LiquidCrystal_I2C.h>
#include <Keypad.h>


// Display
// set the LCD address to 0x27 for a 20 chars and 4 line display
LiquidCrystal_I2C lcd(0x27,20,4);  




// Keypad setup
const uint8_t ROWS = 5;
const uint8_t COLS = 5;
char keys[ROWS][COLS] = { 

  {'F', 'C', '√', '%', '÷'},
  {'A', '7', '8', '9', '*'},
  {'B', '4', '5', '6', '-'},
  {'X', '1', '2', '3', '+'},
  {'Y', '0', '.', 'P', '='}
};

uint8_t colPins[COLS] = { 5, 4, 3, 2 }; // Pins connected to C1, C2, C3, C4
uint8_t rowPins[ROWS] = { 9, 8, 7, 6 }; // Pins connected to R1, R2, R3, R4

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



void WellcomeScreen() {
  lcd.setCursor(2, 0);
  lcd.print("I am  M A Majeed");
  lcd.setCursor(5,1);
  lcd.print("This is my");
  lcd.setCursor(1, 2);
  String message = "Arduino Calculator";
  for (byte i = 0; i < message.length(); i++) {
    lcd.print(message[i]);
    delay(50);
  }
  delay(1000);
}

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

void setup() {
  Serial.begin(115200);
  lcd.begin(20, 4);

  WellcomeScreen();
  lcd.clear();
  lcd.cursor();

  lcd.setCursor(0, 0);
}

boolean presentValue = false; 
boolean next = false;
boolean next1 = false; 
boolean final = false; 
String num1, num2,num3; 
double answer; 
char Operator1=' ';
char Operator2=' ';
int numLength1 =0;
int numLength2 =0;
int DpState = LOW; 

void loop(){ 
// put your main code here, to run repeatedly:

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' ))
{

  Serial.print("op2: ");
     Serial.println(Operator2);
     Serial.print("op1: ");
     Serial.println(Operator1);

  if (presentValue !=true)
  { 

    num1 += key;
 
    lcd.setCursor(0,0);   
    lcd.print(num1);
    Serial.print("num1: ");
    Serial.println(num1); 
  numLength1 =num1.length();
  }


  else if (next ==true)
   {
    num2 += key;
    //int numLength = num2.length();
    lcd.setCursor(numLength1+1,0);   
    lcd.print(num2);
    Serial.print("num2: ");
    Serial.println(num2);
    numLength2 =num2.length();
    next1 = true;
   

   }
   else 
   {
    num3 += key;
     
    lcd.setCursor(numLength1+numLength2+2,0); 
    lcd.print(num3);
    Serial.print("num3: ");
    Serial.println(num3);
   

   }
}

 

else if ( key !=NO_KEY && (key== '/' ||key== '*' ||key== '-' ||key== '+' ))

{
  if (presentValue == false)
   {
    
    presentValue = true;
    Operator1=key;
   
    lcd.print(Operator1); 
    next= true;
    Serial.println(next);
   
   }

  else if (next1 == true && key!= '=')
   {
    
     next = false;
     Operator2=key;

     Serial.print("op2: ");
     Serial.println(Operator2);
     Serial.print("op1: ");
     Serial.println(Operator1);
    
     lcd.print(Operator2); 
     next1= false; 
   }

}

else if ( key != NO_KEY && key == '=')
{

     Serial.print("calop2: ");
     Serial.println(Operator2);
     Serial.print("calop1: ");
     Serial.println(Operator1);
 //calculation part for num1, num2
  if (Operator2 ==' ')
 {
   
  switch (Operator1) { 
      
        case '*':
          answer= num1.toDouble()* num2.toDouble();
          break;
     
        case '/':
          answer= num1.toDouble()/ num2.toDouble();
          break;
      
        case '+':
          answer= num1.toDouble()+ num2.toDouble();
          break;

        case '-':
          answer= num1.toDouble()- num2.toDouble();
          break;   

      }
 }	  
 
 else
//calculation part for num1,num2,num3
  switch (Operator1) {
      Serial.print("Operator2: ");
      Serial.println(Operator2); 
    
    case '*':
    {
      switch (Operator2) { 
      
        case '*':
          answer= num1.toDouble()* num2.toDouble()* num3.toDouble();
          break;
     
        case '/':
          answer= num1.toDouble()* num2.toDouble()/ num3.toDouble();
          break;
      
        case '+':
          answer= num1.toDouble()* num2.toDouble()+ num3.toDouble();
          break;

        case '-':
          answer= num1.toDouble()* num2.toDouble()- num3.toDouble();
          break;   

      }
    
    }
      break;

    case '/':
    { 
      switch (Operator2) { 
     
        case '*':
          answer= num1.toDouble()/ num2.toDouble()* num3.toDouble();
          break;
      
        case '/':
          answer= num1.toDouble()/ num2.toDouble()/ num3.toDouble();
          break;
        
        case '+':
          answer= num1.toDouble()/ num2.toDouble()+ num3.toDouble();
          break;

        case '-':
          answer= num1.toDouble()/ num2.toDouble()- num3.toDouble();
          break;   

      }
    }
    break;

    case '+': 
      switch (Operator2) { 
      
        case '*':
          answer= num1.toDouble()+ num2.toDouble()* num3.toDouble();
          break;
     
        case '/':
          answer= num1.toDouble()+ num2.toDouble()/ num3.toDouble();
          break;
      
        case '+':
          answer= num1.toDouble()+ num2.toDouble()+ num3.toDouble();
          break;

        case '-':
          answer= num1.toDouble()+ num2.toDouble()- num3.toDouble();
          break;   
      }
      break;

    case '-': 
     
     switch (Operator2) { 
      
        case '*':
          answer= num1.toDouble()- num2.toDouble()* num3.toDouble();
          break;
     
        case '/':
          answer= num1.toDouble()- num2.toDouble()/ num3.toDouble();
          break;
      
        case '+':
          answer= num1.toDouble()- num2.toDouble()+ num3.toDouble();
          break;

        case '-':
          answer= num1.toDouble()- num2.toDouble()- num3.toDouble();
          break;   

      }
      break;
  }  
  
  
 Serial.print("answer: ");
 Serial.println(answer);
 
  lcd.setCursor(0,3);
 //lcd.autoscroll();
  
  lcd.print(answer);
 //lcd.noAutoscroll();

 
}

else if (key != NO_KEY && key == 'c'){
  // toggle state of dp
    DpState = !DpState;
    if(DpState==HIGH)
    {
      lcd.noDisplay(); // turn off the display
      //lcd.print("hello, world!");
      lcd.noCursor(); // turn off the cursor
      //lcd.clear(); 
    }
      
    else if(DpState==LOW)
    {
      lcd.display();   // turn on the display
      lcd.cursor();
      lcd.clear();
      lcd.home();  // move the cursor to the upper-left corner of the LCD
   
      presentValue = false;
      final = false;
      next = false;
      next1 = false;

      num1 = "";
      num2 = ""; 
      num3 = "";
      answer=0;
  
      Operator1 = ' ';
      Operator2 = ' ';  

    } 
}
}