#include <Arduino.h>
#include <avr/io.h>
#include <avr/interrupt.h>
#include <util/atomic.h>

#define LED_MASK 0x07

volatile uint8_t buttonEvent = 0;
uint8_t patternStep = 0;
unsigned long lastPressTime = 0;

// This is purely AI generated Code

// External interrupt INT0: Arduino D2
ISR(INT0_vect)
{
    buttonEvent = 1;
}

void setup()
{
    // D8, D9, D10 = PB0, PB1, PB2
    DDRB |= LED_MASK;
    PORTB &= ~LED_MASK;

    // D2 / PD2 input with internal pull-up
    DDRD &= ~(1 << DDD2);
    PORTD |= (1 << PORTD2);

    // Configure INT0 for falling-edge trigger
    EICRA &= ~((1 << ISC00) | (1 << ISC01));
    EICRA |= (1 << ISC01);

    // Clear pending interrupt and enable INT0
    EIFR = (1 << INTF0);
    EIMSK |= (1 << INT0);

    lastPressTime = millis() - 200;

    // Enable global interrupts
    sei();
}

void loop()
{
    uint8_t event;

    // Read and clear the event safely
    ATOMIC_BLOCK(ATOMIC_RESTORESTATE)
    {
        event = buttonEvent;
        buttonEvent = 0;
    }

    // Debounce outside the ISR
    if (event && (millis() - lastPressTime >= 200))
    {
        lastPressTime = millis();

        patternStep++;

        if (patternStep > 4)
            patternStep = 1;
    }

    uint8_t leds = 0;

    switch (patternStep)
    {
        case 1: leds = 0b001; break;
        case 2: leds = 0b010; break;
        case 3: leds = 0b100; break;
        case 4: leds = 0b111; break;
        default: leds = 0; break;
    }

    // Update LED outputs using PORTB
    PORTB = (PORTB & ~LED_MASK) | (leds & LED_MASK);
}