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

int BUZZER_PIN = 11;
int CLICK_FREQ = 600;
int CLICK_FREQ_MS = 25;
int EQUAL_FREQ = 800;
int EQUAL_FREQ_MS = 25;

int rs = 9;  // Pin 9 on Arduino to pin(RS)
int en = 8;  // Pin 8 on Arduino to pin(E)
int d4 = 7;  // Pin 7 on Arduino to pin(D4)
int d5 = 6;  // Pin 6 on Arduino to pin(D5)
int d6 = 5;   // Pin 5  on Arduino to pin(D6)
int d7 = 4;   // Pin 4  on Arduino to pin(D7)

LiquidCrystal lcd(rs, en, d4, d5, d6, d7);

/* Keypad setup */
const byte KEYPAD_ROWS = 4;
const byte KEYPAD_COLS = 4;
byte rowPins[KEYPAD_ROWS] = {3, 2, 1, 0};
byte colPins[KEYPAD_COLS] = {A3, A2, A1, A0};
char keys[KEYPAD_ROWS][KEYPAD_COLS] = {
  {'1', '2', '3', '+'},
  {'4', '5', '6', '-'},
  {'7', '8', '9', '*'},
  {'.', '0', '=', '/'}
};

Keypad keypad = Keypad(makeKeymap(keys), rowPins, colPins, KEYPAD_ROWS, KEYPAD_COLS);

float firstNumber = 0.0;
float secondNumber = 0.0;
float claculationResult = 0.0;
char mathOperation;

void sayWelcome() {
  lcd.setCursor(1, 0);
  String welcome_message = "Welcome Again!";
  for (int i = 0 ; i < welcome_message.length() ; i++)
  {
    lcd.print(welcome_message[i]);
    delay(100);
  }
  delay(1000);
}


int getNumber()
{
  String number = "";
  char digit;
  do
  {
    digit = keypad.waitForKey();
    if (digit != '=')
    {
      lcd.print(digit);
      tone(BUZZER_PIN, CLICK_FREQ, CLICK_FREQ_MS);
      if ((digit != '+') && (digit != '-') && (digit != '*') && (digit != '/') && (digit != '='))
      {
        number += digit;
      }
      else
      {
        mathOperation = digit;
      }
    }
    else
    {
      tone(BUZZER_PIN, EQUAL_FREQ, EQUAL_FREQ_MS);
    }

  } while ((digit != '+') && (digit != '-') && (digit != '*') && (digit != '/') && (digit != '='));
  return number.toInt();
}

void printResult(float result)
{
  lcd.setCursor(0, 1);
  lcd.print(result);
}

float calculate(char op, float left, float right) {
  float result = 0.0;
  if (op == '+')
  {
    result = left + right;
  }
  else if (op == '-')
  {
    result = left - right;
  }
  else if (op == '*')
  {
    result = left * right;
  }
  else if (op == '/')
  {
    result = left / right;
  }
  return result;
}


void setup() {

  lcd.begin(16, 2);
  sayWelcome();
  lcd.clear();
  lcd.blink();
}


void loop() {
  firstNumber = getNumber();
  secondNumber = getNumber();
  claculationResult = calculate(mathOperation, firstNumber, secondNumber);
  printResult(claculationResult);
  delay(1000);
  lcd.clear();
}