Fakturownia - dodanie kolumny z rabatem procentowym

/**
 * This adds the new weight unit to WooCommerce
 */

add_filter( 'fakturownia/invoice/data', 'wpdesk_fakturownia_set_discount', 10, 2 );
function wpdesk_fakturownia_set_discount( array $data, WPDesk\WooCommerceFakturownia\Data\DocumentData $document_data ) {
	$order_items = $document_data->getOrder()->get_items();
	foreach ( $data['positions'] as $data_item_id => $data_item ) {
		foreach ( $order_items as $item_id => $item ) {
			if ( $item instanceof WC_Order_Item_Product && $data_item['name'] === $item->get_name() ) {
				$discount_price = ( $item->get_subtotal() - $item->get_total() ) / $item->get_quantity();
				$discount_percent = 100 - ($item->get_total() / $item->get_subtotal() * 100);

				$data['positions'][ $data_item_id ]['discount_percent']  = $discount_percent;
				$data['positions'][ $data_item_id ]['total_price_gross'] = $item->get_subtotal();
			}
		}
	}

	$data['show_discount'] = 1;
	$data['discount_kind'] = 'percent_unit';

	return $data;
}