class ThemeController

class ThemeController implements ControllerInterface {

  /**
   * The system.theme config object.
   *
   * @var \Drupal\Core\Config\Config
   */
  protected $config;

  /**
   * Constructs a ThemeController object.
   *
   * @param \Drupal\Core\Config\Config $config
   *   The config.
   */
  public function __construct(Config $config) {
    $this->config = $config;
  }

  /**
   * {@inheritdoc}
   */
  public static function create(ContainerInterface $container) {
    return new static($container
      ->get('config.factory')
      ->get('system.theme'));
  }

  /**
   * Disables a theme.
   *
   * @param \Symfony\Component\HttpFoundation\Request $request
   *   A request object containing a theme name and a valid token.
   *
   * @return \Symfony\Component\HttpFoundation\RedirectResponse
   *   Redirects back to the appearance admin page.
   *
   * @throws \Symfony\Component\HttpKernel\Exception\AccessDeniedHttpException
   *   Throws access denied when no theme or token is set in the request or when
   *   the token is invalid.
   */
  public function disable(Request $request) {
    $theme = $request
      ->get('theme');
    $token = $request
      ->get('token');
    if (isset($theme) && isset($token) && drupal_valid_token($token, 'system-theme-operation-link')) {

      // Get current list of themes.
      $themes = list_themes();

      // Check if the specified theme is one recognized by the system.
      if (!empty($themes[$theme])) {

        // Do not disable the default or admin theme.
        if ($theme === $this->config
          ->get('default') || $theme === $this->config
          ->get('admin')) {
          drupal_set_message(t('%theme is the default theme and cannot be disabled.', array(
            '%theme' => $themes[$theme]->info['name'],
          )), 'error');
        }
        else {
          theme_disable(array(
            $theme,
          ));
          drupal_set_message(t('The %theme theme has been disabled.', array(
            '%theme' => $themes[$theme]->info['name'],
          )));
        }
      }
      else {
        drupal_set_message(t('The %theme theme was not found.', array(
          '%theme' => $theme,
        )), 'error');
      }
      return new RedirectResponse(url('admin/appearance', array(
        'absolute' => TRUE,
      )));
    }
    throw new AccessDeniedHttpException();
  }

  /**
   * Enables a theme.
   *
   * @param \Symfony\Component\HttpFoundation\Request $request
   *   A request object containing a theme name and a valid token.
   *
   * @return \Symfony\Component\HttpFoundation\RedirectResponse
   *   Redirects back to the appearance admin page.
   *
   * @throws \Symfony\Component\HttpKernel\Exception\AccessDeniedHttpException
   *   Throws access denied when no theme or token is set in the request or when
   *   the token is invalid.
   */
  public function enable(Request $request) {
    $theme = $request
      ->get('theme');
    $token = $request
      ->get('token');
    if (isset($theme) && isset($token) && drupal_valid_token($token, 'system-theme-operation-link')) {

      // Get current list of themes.
      $themes = list_themes();

      // Check if the specified theme is one recognized by the system.
      if (!empty($themes[$theme])) {
        theme_enable(array(
          $theme,
        ));
        drupal_set_message(t('The %theme theme has been enabled.', array(
          '%theme' => $themes[$theme]->info['name'],
        )));
      }
      else {
        drupal_set_message(t('The %theme theme was not found.', array(
          '%theme' => $theme,
        )), 'error');
      }
      return new RedirectResponse(url('admin/appearance', array(
        'absolute' => TRUE,
      )));
    }
    throw new AccessDeniedHttpException();
  }

}