#include <LiquidCrystal_I2C.h>

#define RED_BUTTON 2
#define GREEN_BUTTON 4

#define DEBOUNCE_PERIOD 10UL

LiquidCrystal_I2C lcd(0x27,16,2);

unsigned long startTime = 0;
unsigned long elapsedTime = 0;
bool isRunning = false;

bool isGreenButtonPressed()
{
    static int debounced_button_state = HIGH;
    static int previous_reading = HIGH;
    static unsigned long last_change_time = 0UL;
    bool isPressed = false;

    int current_reading = digitalRead(GREEN_BUTTON);

    if (previous_reading != current_reading)
    {
        last_change_time = millis();
    }

    if (millis() - last_change_time > DEBOUNCE_PERIOD)
    {
        if (current_reading != debounced_button_state)
        {
            if (debounced_button_state == HIGH && current_reading == LOW)
            {
                isPressed = true;
            }
            debounced_button_state = current_reading;
        }
    }

    previous_reading = current_reading;

    return isPressed;
}

bool isRedButtonPressed()
{
    static int debounced_button_state = HIGH;
    static int previous_reading = HIGH;
    static unsigned long last_change_time = 0UL;
    bool isPressed = false;

    int current_reading = digitalRead(RED_BUTTON);

    if (previous_reading != current_reading)
    {
        last_change_time = millis();
    }

    if (millis() - last_change_time > DEBOUNCE_PERIOD)
    {
        if (current_reading != debounced_button_state)
        {
            if (debounced_button_state == HIGH && current_reading == LOW)
            {
                isPressed = true;
            }
            debounced_button_state = current_reading;
        }
    }

    previous_reading = current_reading;

    return isPressed;
}

void updateLCD(unsigned long seconds);

void setup(){
    pinMode(RED_BUTTON, INPUT_PULLUP);
    pinMode(GREEN_BUTTON, INPUT_PULLUP);

    lcd.init();
    lcd.clear();
    lcd.backlight();
}

void loop(){
    if(isGreenButtonPressed()) {
        if(isRunning) {
            elapsedTime += (millis() - startTime) / 1000;
            isRunning = false;
        } else {
            startTime = millis();
            isRunning = true;
        }
    }

    if(isRedButtonPressed()) {
        if(isRunning) {
            elapsedTime += (millis() - startTime) / 1000;
            isRunning = false;
        }
        elapsedTime = 0;
    }

    if(isRunning) {
        updateLCD(elapsedTime + (millis() - startTime) / 1000);
    } else {
        updateLCD(elapsedTime);
    }
    delay(1000);
}

void updateLCD(unsigned long seconds) {
    lcd.clear();
    lcd.setCursor(0, 0);
    lcd.print("Elapsed Time:");
    lcd.setCursor(0, 1);
    lcd.print(seconds);
}