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

int cnt = 0;
int numbers[3] = {0};
int sum = 0;
float average = 0.0;
bool inputStarted = false;
bool resultDisplayed = false;

#define ROW_NUM 4
#define COLUMN_NUM 4

char keys[ROW_NUM][COLUMN_NUM] = {
  {'1','2','3', 'A'},
  {'4','5','6', 'B'},
  {'7','8','9', 'C'},
  {'*','0','#', 'D'}
};

byte pin_rows[ROW_NUM]      = {12, 14, 27, 26};
byte pin_column[COLUMN_NUM] = {25, 33, 32, 35};   

const int startButtonPin = 18;
const int lcdColumns = 16;

Keypad keypad = Keypad(makeKeymap(keys), pin_rows, pin_column, ROW_NUM, COLUMN_NUM );

LiquidCrystal_I2C lcd(0x27, 16, 2);

void getInput() {
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("Enter 3 numbers:");
  inputStarted = true;
  resultDisplayed = false;
  cnt = 0;
  for (int i = 0; i < 3; i++) {
    numbers[i] = 0; 
  }
}

void calculateAndDisplay() {
  sum = numbers[0] + numbers[1] + numbers[2];
  average = sum / 3.0;

  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("Sum:");
  lcd.setCursor(5, 0);
  lcd.print(sum);

  lcd.setCursor(0, 1);
  lcd.print("Average:");
  lcd.setCursor(9, 1);
  lcd.print(average);
}

void setup() {
  Serial.begin(9600);
  pinMode(startButtonPin, INPUT_PULLUP);
  lcd.init();
  lcd.backlight();
  lcd.setCursor(0, 0);
  lcd.print("Press START");
}

void loop() {
  if (!inputStarted && digitalRead(startButtonPin) == LOW) {
    getInput();
  }

  if (inputStarted) {
    char keypressed = keypad.getKey();
    if (keypressed && keypressed >= '0' && keypressed <= '9' && cnt < 3) {
      numbers[cnt] = numbers[cnt] * 10 + (keypressed - '0');
      lcd.setCursor(cnt, 1);
      lcd.print(keypressed);
      cnt++;
    }
    
    // Check for delete/backspace key ('*')
    if (keypressed == '*') {
      if (cnt > 0) {
        // Clear the last entered digit
        cnt--;
        numbers[cnt] = 0;
        lcd.setCursor(cnt, 1);
        lcd.print(" "); // Clear the digit on the LCD
      }
    }

    // Check for enter/submit key ('#')
    if (keypressed == '#') {
      if (cnt == 3) {
        calculateAndDisplay();
        resultDisplayed = true;
        inputStarted = false;
      }
    }
  }

  // Check if it's time to return to input process
  if (resultDisplayed && digitalRead(startButtonPin) == LOW) {
    getInput(); // Reset input process
  }
}