class ThemeHandler

class ThemeHandler implements ThemeHandlerInterface {
  
  /**
   * A list of all currently available themes.
   *
   * @var array
   */
  protected $list;
  
  /**
   * The config factory to get the installed themes.
   *
   * @var \Drupal\Core\Config\ConfigFactoryInterface
   */
  protected $configFactory;
  
  /**
   * An extension discovery instance.
   *
   * @var \Drupal\Core\Extension\ThemeExtensionList
   */
  protected $themeList;
  
  /**
   * The app root.
   *
   * @var string
   */
  protected $root;
  
  /**
   * Constructs a new ThemeHandler.
   *
   * @param string $root
   *   The app root.
   * @param \Drupal\Core\Config\ConfigFactoryInterface $config_factory
   *   The config factory to get the installed themes.
   * @param \Drupal\Core\Extension\ThemeExtensionList $theme_list
   *   An extension discovery instance.
   */
  public function __construct($root, ConfigFactoryInterface $config_factory, ThemeExtensionList $theme_list) {
    $this->root = $root;
    $this->configFactory = $config_factory;
    $this->themeList = $theme_list;
  }
  
  /**
   * {@inheritdoc}
   */
  public function getDefault() {
    return $this->configFactory
      ->get('system.theme')
      ->get('default');
  }
  
  /**
   * {@inheritdoc}
   */
  public function listInfo() {
    if (!isset($this->list)) {
      $this->list = [];
      $installed_themes = array_keys($this->configFactory
        ->get('core.extension')
        ->get('theme'));
      if (!empty($installed_themes)) {
        $list = $this->themeList
          ->getList();
        foreach ($installed_themes as $theme) {
          // Do not add installed themes that cannot be found by the
          // extension.list.theme service. If a theme does go missing from the
          // file system any call to ::getTheme() will result in an exception
          // and an error being logged. Ignoring the problem here allows the
          // theme system to fix itself while updating.
          if (isset($list[$theme])) {
            $this->addTheme($list[$theme]);
          }
        }
      }
    }
    return $this->list;
  }
  
  /**
   * {@inheritdoc}
   */
  public function addTheme(Extension $theme) {
    // Register the namespaces of installed themes.
    // @todo Implement proper theme registration
    // https://www.drupal.org/project/drupal/issues/2941757
    \Drupal::service('class_loader')->addPsr4('Drupal\\' . $theme->getName() . '\\', $this->root . '/' . $theme->getPath() . '/src');
    if (!empty($theme->info['libraries'])) {
      foreach ($theme->info['libraries'] as $library => $name) {
        $theme->libraries[$library] = $name;
      }
    }
    if (isset($theme->info['engine'])) {
      $theme->engine = $theme->info['engine'];
    }
    if (isset($theme->info['base theme'])) {
      $theme->base_theme = $theme->info['base theme'];
    }
    $this->list[$theme->getName()] = $theme;
  }
  
  /**
   * {@inheritdoc}
   */
  public function refreshInfo() {
    $installed = $this->configFactory
      ->get('core.extension')
      ->get('theme');
    // Only refresh the info if a theme has been installed. Modules are
    // installed before themes by the installer and this method is called during
    // module installation.
    if (empty($installed) && empty($this->list)) {
      return;
    }
    $this->reset();
  }
  
  /**
   * {@inheritdoc}
   */
  public function reset() {
    $this->themeList
      ->reset();
    $this->list = NULL;
  }
  
  /**
   * {@inheritdoc}
   */
  public function rebuildThemeData() {
    @trigger_error("\\Drupal\\Core\\Extension\\ThemeHandlerInterface::rebuildThemeData() is deprecated in drupal:10.3.0 and is removed from drupal:12.0.0. Use \\Drupal::service('extension.list.theme')->reset()->getList() instead. See https://www.drupal.org/node/3413196", E_USER_DEPRECATED);
    return $this->themeList
      ->reset()
      ->getList();
  }
  
  /**
   * {@inheritdoc}
   */
  public function getBaseThemes(array $themes, $theme) {
    @trigger_error("\\Drupal\\Core\\Extension\\ThemeHandlerInterface::getBaseThemes() is deprecated in drupal:10.3.0 and is removed from drupal:12.0.0. There is no direct replacement. See https://www.drupal.org/node/3413187", E_USER_DEPRECATED);
    return $this->themeList
      ->getBaseThemes($themes, $theme);
  }
  
  /**
   * {@inheritdoc}
   */
  public function getName($theme) {
    return $this->themeList
      ->getName($theme);
  }
  
  /**
   * {@inheritdoc}
   */
  public function getThemeDirectories() {
    $dirs = [];
    foreach ($this->listInfo() as $name => $theme) {
      $dirs[$name] = $this->root . '/' . $theme->getPath();
    }
    return $dirs;
  }
  
  /**
   * {@inheritdoc}
   */
  public function themeExists($theme) {
    $themes = $this->listInfo();
    return isset($themes[$theme]);
  }
  
  /**
   * {@inheritdoc}
   */
  public function getTheme($name) {
    $themes = $this->listInfo();
    if (isset($themes[$name])) {
      return $themes[$name];
    }
    throw new UnknownExtensionException(sprintf('The theme %s does not exist.', $name));
  }
  
  /**
   * {@inheritdoc}
   */
  public function hasUi($name) {
    $themes = $this->listInfo();
    if (isset($themes[$name])) {
      if (!empty($themes[$name]->info['hidden'])) {
        $theme_config = $this->configFactory
          ->get('system.theme');
        return $name == $theme_config->get('default') || $name == $theme_config->get('admin');
      }
      return TRUE;
    }
    return FALSE;
  }

}