function showAuthModal() {
    document.getElementById('auth-modal').classList.remove('hidden');
}

function hideAuthModal() {
    document.getElementById('auth-modal').classList.add('hidden');
}

async function verifyToken(token) {
    try {
        const res = await fetch('/api/v1/tasks', {
            headers: { 'Authorization': `Bearer ${token}` }
        });
        return res.status === 200;
    } catch (err) {
        return false;
    }
}

async function handleLogin(e) {
    e.preventDefault();
    const tokenInput = document.getElementById('auth-token-input');
    const errorEl = document.getElementById('auth-error');
    const token = tokenInput.value.trim();

    if (!token) return;

    errorEl.classList.add('hidden');
    const isValid = await verifyToken(token);

    if (isValid) {
        API_TOKEN = token;
        IS_GUEST = false;
        localStorage.setItem(AUTH_TOKEN_KEY, token);
        localStorage.removeItem('scud_is_guest');
        hideAuthModal();
        updateUIState();
        loadTasks();
    } else {
        errorEl.classList.remove('hidden');
    }
}

function enableGuestMode() {
    IS_GUEST = true;
    API_TOKEN = "";
    localStorage.setItem('scud_is_guest', 'true');
    hideAuthModal();
    updateUIState();
}

function logout() {
    localStorage.removeItem(AUTH_TOKEN_KEY);
    localStorage.removeItem('scud_is_guest');
    API_TOKEN = "";
    IS_GUEST = false;
    document.getElementById('auth-token-input').value = "";
    showAuthModal();
}

function updateUIState() {
    const tasksBtn = document.getElementById('tasks-drawer-btn');
    const guestBadge = document.getElementById('guest-badge');
    
    if (IS_GUEST) {
        if (tasksBtn) tasksBtn.classList.add('hidden');
        if (guestBadge) guestBadge.classList.remove('hidden');
    } else {
        if (tasksBtn) tasksBtn.classList.remove('hidden');
        if (guestBadge) guestBadge.classList.add('hidden');
    }
}