// +1,00 € / kos, če je izbrano "GRAVURA / TISK" (samo v določenih kategorijah)
add_action('woocommerce_cart_calculate_fees', function ($cart) {
    if (is_admin() && !defined('DOING_AJAX')) return;

    // Slugi tvojih kategorij (po potrebi prilagodi):
    $target_cat_slugs = ['elektronika','pisarna','moleskine'];

    $attr_tax_slug   = 'pa_moznost-personalizacije';
    // Slug termina bo v WooCommerce skoraj zagotovo 'gravura-tisk'
    // (ker se iz imena "GRAVURA / TISK" naredi slug brez znakov).
    $charge_term_slugs = ['gravura-tisk'];
    $surcharge_each    = 1.00;
    $taxable           = true;

    $total_fee = 0;

    foreach ($cart->get_cart() as $item) {
        $product = $item['data'];
        $pid     = $product->get_id();

        if (!has_term($target_cat_slugs, 'product_cat', $pid)) {
            continue;
        }

        // pri variabilnem izdelku WOO v $item['variation'][taxonomy] shrani SLUG termina
        $chosen_slug = '';
        if (!empty($item['variation'][$attr_tax_slug])) {
            $chosen_slug = strtolower(sanitize_title($item['variation'][$attr_tax_slug]));
        } else {
            continue;
        }

        if (in_array($chosen_slug, $charge_term_slugs, true)) {
            $total_fee += $surcharge_each * (int) $item['quantity'];
        }
    }

    if ($total_fee > 0) {
        $cart->add_fee(__('GRAVURA / TISK', 'dk'), $total_fee, $taxable);
    }
});