class LanguageArgument

class LanguageArgument extends ArgumentPluginBase {
    
    /**
     * Overrides \Drupal\views\Plugin\views\argument\ArgumentPluginBase::summaryName().
     *
     * Gets the user-friendly version of the language name.
     */
    public function summaryName($data) {
        return $this->language($data->{$this->name_alias});
    }
    
    /**
     * Overrides \Drupal\views\Plugin\views\argument\ArgumentPluginBase::title().
     *
     * Gets the user friendly version of the language name for display as a
     * title placeholder.
     */
    public function title() {
        return $this->language($this->argument);
    }
    
    /**
     * Returns the language name for a given langcode.
     *
     * @param string $langcode
     *   The language code.
     *
     * @return string
     *   The translated name for the language, or "Unknown language" if the
     *   language was not found.
     */
    public function language($langcode) {
        $languages = $this->listLanguages();
        return isset($languages[$langcode]) ? $languages[$langcode] : $this->t('Unknown language');
    }

}