class LanguageServiceProvider

class LanguageServiceProvider extends ServiceProviderBase {
    const CONFIG_PREFIX = 'language.entity.';
    
    /**
     * {@inheritdoc}
     */
    public function register(ContainerBuilder $container) {
        // The following services are needed only on multilingual sites.
        if ($this->isMultilingual()) {
            $container->register('language_request_subscriber', 'Drupal\\language\\EventSubscriber\\LanguageRequestSubscriber')
                ->addTag('event_subscriber')
                ->addArgument(new Reference('language_manager'))
                ->addArgument(new Reference('language_negotiator'))
                ->addArgument(new Reference('string_translation'))
                ->addArgument(new Reference('current_user'));
            $container->register('path_processor_language', 'Drupal\\language\\HttpKernel\\PathProcessorLanguage')
                ->addTag('path_processor_inbound', [
                'priority' => 300,
            ])
                ->addTag('path_processor_outbound', [
                'priority' => 100,
            ])
                ->addArgument(new Reference('config.factory'))
                ->addArgument(new Reference('language_manager'))
                ->addArgument(new Reference('language_negotiator'))
                ->addArgument(new Reference('current_user'))
                ->addArgument(new Reference('language.config_subscriber'))
                ->addMethodCall('initConfigSubscriber');
        }
    }
    
    /**
     * {@inheritdoc}
     */
    public function alter(ContainerBuilder $container) {
        $definition = $container->getDefinition('language_manager');
        $definition->setClass('Drupal\\language\\ConfigurableLanguageManager')
            ->addArgument(new Reference('config.factory'))
            ->addArgument(new Reference('module_handler'))
            ->addArgument(new Reference('language.config_factory_override'))
            ->addArgument(new Reference('request_stack'));
        if ($default_language_values = $this->getDefaultLanguageValues()) {
            $container->setParameter('language.default_values', $default_language_values);
        }
    }
    
    /**
     * Checks whether the site is multilingual.
     *
     * @return bool
     *   TRUE if the site is multilingual, FALSE otherwise.
     */
    protected function isMultilingual() {
        // Assign the prefix to a local variable so it can be used in an anonymous
        // function.
        $prefix = static::CONFIG_PREFIX;
        // @todo Try to swap out for config.storage to take advantage of database
        //   and caching. This might prove difficult as this is called before the
        //   container has finished building.
        $config_storage = BootstrapConfigStorageFactory::get();
        $config_ids = array_filter($config_storage->listAll($prefix), function ($config_id) use ($prefix) {
            return $config_id != $prefix . LanguageInterface::LANGCODE_NOT_SPECIFIED && $config_id != $prefix . LanguageInterface::LANGCODE_NOT_APPLICABLE;
        });
        return count($config_ids) > 1;
    }
    
    /**
     * Gets the default language values.
     *
     * @return array|bool
     *   Returns the default language values for the language configured in
     *   system.site:default_langcode if the corresponding configuration entity
     *   exists, otherwise FALSE.
     */
    protected function getDefaultLanguageValues() {
        $config_storage = BootstrapConfigStorageFactory::get();
        $system = $config_storage->read('system.site');
        // In Kernel tests it's possible this code is called before system.site
        // exists. In such cases behave as though the corresponding language
        // configuration entity does not exist.
        if ($system === FALSE) {
            return FALSE;
        }
        $default_language = $config_storage->read(static::CONFIG_PREFIX . $system['default_langcode']);
        if (is_array($default_language)) {
            return $default_language;
        }
        return FALSE;
    }

}