#include <Wire.h>
#include <LiquidCrystal_I2C.h>

// Define the LCD address and dimensions
LiquidCrystal_I2C lcd(0x27, 16, 2);

// Define the GPIO pins for the buttons
const int buttonStartStopPin = 14;
const int buttonResetPin = 27;

// Variables for debounce logic
unsigned long lastDebounceTimeStartStop = 0;
unsigned long lastDebounceTimeReset = 0;
const unsigned long debounceDelay = 5; // Debounce time in milliseconds

// Variables to keep track of the button states
bool lastButtonStateStartStop = HIGH;
bool lastButtonStateReset = HIGH;
bool currentButtonStateStartStop = HIGH;
bool currentButtonStateReset = HIGH;
bool timerRunning = false;

// Variables for timekeeping
unsigned long startTime = 0;
unsigned long elapsedTime = 0;

void setup() {
  // Initialize the LCD
  lcd.init();
  lcd.setBacklight(HIGH);
  lcd.clear();
  
  // Set up the buttons
  pinMode(buttonStartStopPin, INPUT_PULLUP);
  pinMode(buttonResetPin, INPUT_PULLUP);
  
  // Initial display
  lcd.setCursor(0, 0);
  lcd.print("Stopwatch");
  lcd.setCursor(0, 1);
  lcd.print("000:00:00.000");
}

void loop() {
  // Read the state of the buttons
  bool readingStartStop = digitalRead(buttonStartStopPin);
  bool readingReset = digitalRead(buttonResetPin);

  // Debounce the start/stop button
  if (readingStartStop != lastButtonStateStartStop) {
    lastDebounceTimeStartStop = millis();
  }
  if ((millis() - lastDebounceTimeStartStop) > debounceDelay) {
    if (readingStartStop != currentButtonStateStartStop) {
      currentButtonStateStartStop = readingStartStop;
      if (currentButtonStateStartStop == LOW) {
        timerRunning = !timerRunning;
        if (timerRunning) {
          startTime = millis() - elapsedTime;
        } else {
          elapsedTime = millis() - startTime;
        }
      }
    }
  }
  lastButtonStateStartStop = readingStartStop;

  // Debounce the reset button
  if (readingReset != lastButtonStateReset) {
    lastDebounceTimeReset = millis();
  }
  if ((millis() - lastDebounceTimeReset) > debounceDelay) {
    if (readingReset != currentButtonStateReset) {
      currentButtonStateReset = readingReset;
      if (currentButtonStateReset == LOW) {
        elapsedTime = 0;
        if (timerRunning) {
          startTime = millis();
        }
        updateDisplay(0);
      }
    }
  }
  lastButtonStateReset = readingReset;

  // Update the display if the timer is running
  if (timerRunning) {
    elapsedTime = millis() - startTime;
    updateDisplay(elapsedTime);
  }
}

// Function to update the LCD display with the current elapsed time
void updateDisplay(unsigned long time) {
  unsigned long milliseconds = time % 1000;
  unsigned long seconds = (time / 1000) % 60;
  unsigned long minutes = (time / (1000 * 60)) % 60;
  unsigned long hours = (time / (1000 * 60 * 60));

  char buffer[17];
  sprintf(buffer, "%03lu:%02lu:%02lu.%03lu", hours, minutes, seconds, milliseconds);
  lcd.setCursor(0, 1);
  lcd.print(buffer);
}