#include <LiquidCrystal.h>
#include <avr/io.h>
#include <avr/interrupt.h>

// Initialize the LCD (update pins as needed)
LiquidCrystal lcd(12, 11, 10, 8, 7, 6);

// Pin definitions
const int buttonCountUpPin = 5;   // PD5
const int buttonCountDownPin = 4; // PD4
const int buttonStopResetPin = 3; // PD3

// State definitions
enum State {
    STOP,
    COUNT_UP,
    COUNT_DOWN
};

// Global variables
volatile State currentState = STOP;
volatile float countValue = 0.0;

// Timer setup function
void setupTimer() {
    TCCR1A = 0;               // Clear control register A
    TCCR1B = 0;               // Clear control register B
    TCCR1B |= (1 << WGM12);  // Set CTC mode
    TCCR1B |= (1 << CS12);   // Set prescaler to 256
    OCR1A = 625;             // Set compare value for 1 second (16MHz/256)
    TIMSK1 |= (1 << OCIE1A); // Enable compare interrupt
}

ISR(TIMER1_COMPA_vect) {
    if (currentState == COUNT_UP) {
        countValue += 1.0; // Increment count
        if (countValue >= 20.0) {
            currentState = STOP; // Stop at 20 seconds
        }
    } else if (currentState == COUNT_DOWN) {
        countValue -= 1.0; // Decrement count
        if (countValue <= 0.0) {
            currentState = STOP; // Stop at 0 seconds
            countValue = 0.0; // Ensure countValue does not go negative
        }
    }
}

void setup() {
    // Set up LCD
    lcd.begin(16, 2);
    lcd.print("Status: STOP");
    lcd.setCursor(0, 1);
    lcd.print("Count: 0.0 s");

    // Set up button pins as inputs (using direct port manipulation)
    DDRD &= ~((1 << buttonCountUpPin) | (1 << buttonCountDownPin) | (1 << buttonStopResetPin)); // Set pins as input
    PORTD |= (1 << buttonCountUpPin) | (1 << buttonCountDownPin) | (1 << buttonStopResetPin); // Enable pull-up resistors

    // Set up timer
    setupTimer();
    sei(); // Enable global interrupts
}

void loop() {
    // Read button states
    bool buttonCountUp = !(PIND & (1 << buttonCountUpPin));
    bool buttonCountDown = !(PIND & (1 << buttonCountDownPin));
    bool buttonStopReset = !(PIND & (1 << buttonStopResetPin));

    // Button handling
    if (buttonCountUp && currentState == STOP) {
        currentState = COUNT_UP;
        delay(200); // Debounce delay
    } 
    else if (buttonCountDown && currentState == STOP) {
        currentState = COUNT_DOWN;
        countValue = 20.0; // Start from 20 seconds
        delay(200); // Debounce delay
    } 
    else if (buttonStopReset) {
        if (currentState == COUNT_UP || currentState == COUNT_DOWN) {
            currentState = STOP;
        } 
        else if (currentState == STOP) {
            countValue = 0.0; // Reset count
        }
        delay(200); // Debounce delay
    }

    // Update the LCD
    updateLCD();
}

void updateLCD() {
    lcd.clear();
    // Display current state
    switch (currentState) {
        case STOP:
            lcd.print("Status: STOP");
            break;
        case COUNT_UP:
            lcd.print("Status: COUNT_UP");
            break;
        case COUNT_DOWN:
            lcd.print("Status: COUNT_DOWN");
            break;
    }
    // Display count value
    lcd.setCursor(0, 1);
    lcd.print("Count: ");
    lcd.print(countValue, 1); // One decimal place
    lcd.print(" s");
}