CssAssetController.php

<?php

namespace Drupal\system\Controller;

use Symfony\Component\DependencyInjection\ContainerInterface;
use Symfony\Component\HttpFoundation\Request;
use Drupal\Core\Asset\AttachedAssetsInterface;
use Drupal\Core\Asset\AssetGroupSetHashTrait;

/**
 * Defines a controller to serve CSS aggregates.
 */
class CssAssetController extends AssetControllerBase {
    use AssetGroupSetHashTrait;
    
    /**
     * {@inheritdoc}
     */
    protected string $contentType = 'text/css';
    
    /**
     * {@inheritdoc}
     */
    protected string $assetType = 'css';
    
    /**
     * {@inheritdoc}
     */
    public static function create(ContainerInterface $container) {
        return new static($container->get('stream_wrapper_manager'), $container->get('library.dependency_resolver'), $container->get('asset.resolver'), $container->get('theme.initialization'), $container->get('theme.manager'), $container->get('asset.css.collection_grouper'), $container->get('asset.css.collection_optimizer'), $container->get('asset.css.dumper'));
    }
    
    /**
     * {@inheritdoc}
     */
    protected function getGroups(AttachedAssetsInterface $attached_assets, Request $request) : array {
        $language = $this->languageManager()
            ->getLanguage($request->get('language'));
        $assets = $this->assetResolver
            ->getCssAssets($attached_assets, FALSE, $language);
        return $this->grouper
            ->group($assets);
    }

}