//ENEL301-Lab1, 26-Jan-2023
//Xinyun Zhou (UCID: 30141745), Aarti Chandiramani (UCID: 30145899), Aileen Mulaw (30161059), Juhi Mehra (UCID: 30140435)


#include <LiquidCrystal.h>
#include <Keypad.h>
using namespace std;


//Connecting LCD to the Arduino with the corresponding pins
const int rs = 12, en = 11, d4 = 5, d5 = 4, d6 = 3, d7 = 2;
//Defining the pins as we connected then in the simulation
LiquidCrystal lcd(rs, en, d4, d5, d6, d7);


//Setting rows and columns of keypad
const byte ROWS = 4;
const byte COLS = 4;


//Defining the operation from each key in keypad
char keys[ROWS][COLS] = {
  {'1', '2', '3', '+'},
  {'4', '5', '6', '-'},
  {'7', '8', '9', '*'},
  {'C', '0', '=', '/'}  
};


//Connecting keypad to the Arduino with the corresponding pins
byte rowPins[ROWS] = {22, 23, 25, 27};
byte colPins[COLS] = {29, 31, 33, 35};


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


void setup() {
  //The following sets up the assembly to run once
  //Setting the size of the LCD (cols,rows)
  lcd.begin(16,2);
  //Printing to the screen
  String intro = "Welcome to ENEL 301 Arduino Calculator";
  lcd.print(intro);
  //
  Serial.begin(9600);
  delay(1000);
  for (int i=0; i<=(intro.length()-16); i++){
    lcd.scrollDisplayLeft();
    delay(250);
  }
  lcd.clear();
  delay(700);

  lcd.print( "A = +, B = -");
  lcd.setCursor(0,1);
  lcd.print( "C = *, D = /");
  delay(2500);
  lcd.clear();
  lcd.print("* = Clear");
  lcd.setCursor(0,1);
  lcd.print( "# = Equal");
  delay(2500);
  lcd.clear();

  delay(700);

  lcd.print("Please press any");
  lcd.setCursor(0,1);
  lcd.print("keys to start");
}




//User-defined variables and functions
String to_print = "";
String temp = "";
long firstval = 0.0;
long secondval = 0.0;
long finalval = 0.0;
int n = 0;

char op;
bool operation = false;
void check_op(char input){
  if ((input == '+') || (input == '-') || (input == '/') || (input == '*')){
    operation = true;
  }
  else{
    operation = false;
  }
}


long calculate(char input){
  if(input == '+')
    return (firstval + secondval);
  if(input == '*')
    return (firstval * secondval);
  if(input == '/'){
    if(secondval == 0){
        to_print = "Error";
        return;
    }
    else
      return (firstval / secondval);
  }
  if(input == '-')
    return (firstval - secondval);
  if(input == '=')
    return firstval;
  //Add other operations
}


void loop() {
  //The following allows for repeatable use of program
  //Sets the location of cursor
  lcd.setCursor(16,2);


  char button = keypad.getKey();
  if (button != NO_KEY){
    lcd.clear();
    Serial.println(button);
    check_op(button);
    to_print += button;
    temp += button;
    if (button == '='){
      if (firstval == 0 && n == 0){
        firstval = temp.toInt();
        op = button;
      }
      secondval = temp.toInt();
      finalval = calculate(op);
    }
    lcd.print(to_print);
    lcd.setCursor(0,1);
    lcd.print(finalval);

    if (operation == true){
      op = button;
      firstval = temp.toInt();
      n = 1;
      temp = "";
    }
    if (button == 'C' || button == '='){
      firstval = 0.0;
      secondval = 0.0;
      finalval = 0.0;
      temp = "";
      to_print = "";
      if (button == 'C') lcd.clear();
    }
  }
}