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

LiquidCrystal_I2C lcd(0x27, 16, 2); // Set the LCD address to 0x27 for a 16 chars and 2 line display
const int buttonPin = 2; // Pin for controlling the timer
const int ledPin = 4; // Pin for controlling the LED
volatile bool buttonPressed = false;
volatile unsigned long lastDebounceTime = 0;
volatile unsigned long debounceDelay = 50;
volatile int buttonState = HIGH;
volatile int lastButtonState = HIGH;
unsigned long startTime = 0;
unsigned long elapsedTime = 0;
unsigned long pausedTime = 0;
bool running = false;
int buttonPressCount = 0; // Keeps track of the number of button presses

void setup() {
  lcd.init();
  lcd.backlight();
  lcd.setCursor(0, 0);
  lcd.print("00:00:00");
  pinMode(buttonPin, INPUT_PULLUP);
  pinMode(ledPin, OUTPUT); // Initialize LED pin as output
  attachInterrupt(digitalPinToInterrupt(buttonPin), buttonISR, CHANGE);
}

void loop() {
  if (buttonPressed) {
    debounceButton();
    buttonPressed = false;
    if (buttonState == LOW) {
      buttonPressCount++;
      if (buttonPressCount == 1) {
        startTimer();
        digitalWrite(ledPin, HIGH); // Turn on LED when timer starts
      } else if (buttonPressCount == 2) {
        stopTimer();
        digitalWrite(ledPin, LOW); // Turn off LED when timer stops
      } else if (buttonPressCount >= 3) {
        resetTimer();
        digitalWrite(ledPin, LOW); // Turn off LED when timer resets
      }
    }
  }

  if (running) {
    updateTimer();
  }
}

void buttonISR() {
  buttonState = digitalRead(buttonPin);
  if (buttonState == LOW) {
    buttonPressed = true;
    delay(50); // Add a small delay to prevent immediate re-triggering
  }
}

void debounceButton() {
  int reading = digitalRead(buttonPin);
  if (reading != lastButtonState) {
    lastDebounceTime = millis();
  }
  if (millis() - lastDebounceTime > debounceDelay) {
    if (reading != buttonState) {
      buttonState = reading;
    }
  }
  lastButtonState = reading;
}

void startTimer() {
  if (!running) {
    if (elapsedTime == 0) {
      startTime = millis();
    } else {
      startTime = millis() - pausedTime;
    }
    running = true;
  }
}

void stopTimer() {
  if (running) {
    elapsedTime = millis() - startTime;
    pausedTime = elapsedTime;
    running = false;
  }
}

void resetTimer() {
  elapsedTime = 0;
  pausedTime = 0;
  lcd.setCursor(0, 0);
  lcd.print("00:00:00");
  buttonPressCount = 0; // Reset button press count
}

void updateTimer() {
  unsigned long currentTime = millis();
  elapsedTime = currentTime - startTime;

  unsigned long minutes = (elapsedTime / 60000) % 60;
  unsigned long seconds = (elapsedTime / 1000) % 60;
  unsigned long milliseconds = (elapsedTime % 1000) / 10; // Extracting two digits for milliseconds

  lcd.setCursor(0, 0);
  if (minutes < 10) {
    lcd.print("0");
  }
  lcd.print(String(minutes, DEC));
  lcd.print(":");
  if (seconds < 10) {
    lcd.print("0");
  }
  lcd.print(String(seconds, DEC));
  lcd.print(":");
  if (milliseconds < 10) {
    lcd.print("0");
  }
  lcd.print(String(milliseconds, DEC)); // Display two digits for milliseconds
}