#include <LiquidCrystal.h>

const int rs = 26;
const int en = 25;
const int D4 = 13;
const int D5 = 12;
const int D6 = 14;
const int D7 = 27;

int lcdDelay = 3000;

LiquidCrystal lcd(rs, en, D4, D5, D6, D7);

float firstNum;
float secNum;
float answer;
String op;

void setup() {
  lcd.begin(16, 2);
  lcd.clear();
  Serial.begin(115200);
}

void loop() {
  firstNum = getNumber("Input 1st Number");
  clearSerialBuffer(); // Clear any remaining newline or unwanted characters
  secNum = getNumber("Input 2nd Number");
  clearSerialBuffer(); // Clear buffer again after second input
  op = getOperator("Input (+,-,*,/)");
  
  bool validOperation = true;

  if (op == "+") {
    answer = firstNum + secNum;
  } else if (op == "-") {
    answer = firstNum - secNum;
  } else if (op == "*") {
    answer = firstNum * secNum;
  } else if (op == "/") {
    if (secNum != 0) {
      answer = firstNum / secNum;
    } else {
      displayError("Error: Div by 0");
      validOperation = false;
    }
  } else {
    displayError("Invalid Operator");
    validOperation = false;
  }

  if (validOperation) {
    displayResult(firstNum, secNum, op, answer);
  }
  delay(lcdDelay);
  lcd.clear();
}

float getNumber(const char* prompt) {
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print(prompt);
  Serial.println(prompt);

  while (Serial.available() == 0) {}
  float number = Serial.parseFloat();
  Serial.println(number);
  return number;
}

String getOperator(const char* prompt) {
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print(prompt);
  Serial.println(prompt);

  while (Serial.available() == 0) {}
  String operatorSymbol = Serial.readString();
  operatorSymbol.trim(); // Trim whitespace or newline
  Serial.println(operatorSymbol);
  return operatorSymbol;
}

void displayError(const char* message) {
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print(message);
  Serial.println(message);
}

void displayResult(float firstNum, float secNum, String op, float answer) {
  
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print(firstNum);
  lcd.print(" ");
  lcd.print(op);
  lcd.print(" ");
  lcd.print(secNum);
  lcd.print("=");
  lcd.setCursor(0, 1);
  lcd.print(answer);

  Serial.print(firstNum);
  Serial.print(" ");
  Serial.print(op);
  Serial.print(" ");
  Serial.print(secNum);
  Serial.print(" = ");
  Serial.println(answer);

  lcd.setCursor(0, 1);
  lcd.print("Thank You");
  Serial.println("Thank You");
}

void clearSerialBuffer() {
  while (Serial.available() > 0) {
    Serial.read(); // Read and discard any remaining characters
  }
}