class LanguageNegotiationSession

class LanguageNegotiationSession extends LanguageNegotiationMethodBase implements OutboundPathProcessorInterface, LanguageSwitcherInterface, ContainerFactoryPluginInterface {
  
  /**
   * Flag used to determine whether query rewriting is active.
   *
   * @var bool
   */
  protected $queryRewrite;
  
  /**
   * The query parameter name to rewrite.
   *
   * @var string
   */
  protected $queryParam;
  
  /**
   * The query parameter value to be set.
   *
   * @var string
   */
  protected $queryValue;
  
  /**
   * The request stack.
   *
   * @var \Symfony\Component\HttpFoundation\RequestStack
   */
  protected $requestStack;
  
  /**
   * The language negotiation method id.
   */
  const METHOD_ID = 'language-session';
  
  /**
   * Constructs a LanguageNegotiationSession object.
   *
   * @param \Symfony\Component\HttpFoundation\RequestStack $request_stack
   *   The request stack.
   */
  public function __construct(RequestStack $request_stack) {
    $this->requestStack = $request_stack;
  }
  
  /**
   * {@inheritdoc}
   */
  public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition) {
    return new static($container->get('request_stack'));
  }
  
  /**
   * {@inheritdoc}
   */
  public function getLangcode(?Request $request = NULL) {
    $config = $this->config
      ->get('language.negotiation')
      ->get('session');
    if (($param = $config['parameter']) && $request) {
      if ($request->query
        ->has($param)) {
        return $request->query
          ->get($param);
      }
      if ($request->getSession()
        ->has($param)) {
        return $request->getSession()
          ->get($param);
      }
    }
    return NULL;
  }
  
  /**
   * {@inheritdoc}
   */
  public function persist(LanguageInterface $language) {
    // We need to update the session parameter with the request value only if we
    // have an authenticated user.
    $langcode = $language->getId();
    if ($langcode && $this->languageManager) {
      $languages = $this->languageManager
        ->getLanguages();
      if ($this->currentUser
        ->isAuthenticated() && isset($languages[$langcode])) {
        $config = $this->config
          ->get('language.negotiation')
          ->get('session');
        $this->requestStack
          ->getCurrentRequest()
          ->getSession()
          ->set($config['parameter'], $langcode);
      }
    }
  }
  
  /**
   * {@inheritdoc}
   */
  public function processOutbound($path, &$options = [], ?Request $request = NULL, ?BubbleableMetadata $bubbleable_metadata = NULL) {
    if ($request) {
      // The following values are not supposed to change during a single page
      // request processing.
      if (!isset($this->queryRewrite)) {
        if ($this->currentUser
          ->isAnonymous()) {
          $languages = $this->languageManager
            ->getLanguages();
          $config = $this->config
            ->get('language.negotiation')
            ->get('session');
          $this->queryParam = $config['parameter'];
          $this->queryValue = $request->query
            ->has($this->queryParam) ? $request->query
            ->get($this->queryParam) : NULL;
          $this->queryRewrite = isset($languages[$this->queryValue]);
        }
        else {
          $this->queryRewrite = FALSE;
        }
      }
      // If the user is anonymous, the user language negotiation method is
      // enabled, and the corresponding option has been set, we must preserve
      // any explicit user language preference even with cookies disabled.
      if ($this->queryRewrite) {
        if (!isset($options['query'][$this->queryParam])) {
          $options['query'][$this->queryParam] = $this->queryValue;
        }
        if ($bubbleable_metadata) {
          // Cached URLs that have been processed by this outbound path
          // processor must be:
          $bubbleable_metadata->addCacheTags($this->config
            ->get('language.negotiation')
            ->getCacheTags())
            ->addCacheContexts([
            'url.query_args:' . $this->queryParam,
          ]);
        }
      }
    }
    return $path;
  }
  
  /**
   * {@inheritdoc}
   */
  public function getLanguageSwitchLinks(Request $request, $type, Url $url) {
    $links = [];
    $query = [];
    parse_str($request->getQueryString() ?? '', $query);
    $config = $this->config
      ->get('language.negotiation')
      ->get('session');
    $param = $config['parameter'];
    $language_query = $request->getSession()
      ->has($param) ? $request->getSession()
      ->get($param) : $this->languageManager
      ->getCurrentLanguage($type)
      ->getId();
    foreach ($this->languageManager
      ->getNativeLanguages() as $language) {
      $langcode = $language->getId();
      $links[$langcode] = [
        // We need to clone the $url object to avoid using the same one for all
        // links. When the links are rendered, options are set on the $url
        // object, so if we use the same one, they would be set for all links.
'url' => clone $url,
        'title' => $language->getName(),
        'attributes' => [
          'class' => [
            'language-link',
          ],
        ],
        'query' => $query,
      ];
      if ($language_query != $langcode) {
        $links[$langcode]['query'][$param] = $langcode;
      }
      else {
        $links[$langcode]['attributes']['class'][] = 'session-active';
      }
    }
    return $links;
  }

}