#include <Wire.h>
#include <Adafruit_SSD1306.h>
#include <Keypad.h>

#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64

Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, -1);

#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};

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

int values[3] = {0, 0, 0};
int current_value = 0;
bool inputting = false;
bool calculate_sum = false;

void setup() {
  Serial.begin(9600);

  display.begin(SSD1306_SWITCHCAPVCC, 0x3C);
  display.setTextSize(1);
  display.setTextColor(WHITE);
  display.clearDisplay();
  display.setCursor(0, 0);
  display.println("Press * to start");
  display.display();
}

void loop() {
  char key = keypad.getKey();

  if (key == '*') {
    inputting = true;
    display.clearDisplay();
    display.setCursor(0, 0);
    display.println("Enter 3 values:");
    display.display();
  }

  if (inputting && !calculate_sum) {
    if (key) {
      if (key >= '0' && key <= '9') {
        values[current_value] = values[current_value] * 10 + (key - '0');
        display.clearDisplay();
        display.setCursor(0, 0);
        display.print("Value ");
        display.print(current_value + 1);
        display.print(": ");
        display.println(values[current_value]);
        display.display();

        if (values[current_value] >= 10) {
          current_value++;
          if (current_value == 3) {
            calculate_sum = true;
          }
        }
      }
    }
  } else {
    if (calculate_sum) {
      int sum = values[0] + values[1] + values[2];

      display.clearDisplay();
      display.setCursor(0, 0);
      display.print("Sum: ");
      display.println(sum);
      display.display();

      delay(5000); // Display sum for 5 seconds

      current_value = 0;
      for (int i = 0; i < 3; i++) {
        values[i] = 0;
      }
      calculate_sum = false;
      inputting = false;
    }
  }
}