class ConfigTranslationFormBase

abstract class ConfigTranslationFormBase extends FormBase implements BaseFormIdInterface {
    
    /**
     * The typed configuration manager.
     *
     * @var \Drupal\Core\Config\TypedConfigManagerInterface
     */
    protected $typedConfigManager;
    
    /**
     * The configuration mapper manager.
     *
     * @var \Drupal\config_translation\ConfigMapperManagerInterface
     */
    protected $configMapperManager;
    
    /**
     * The mapper for configuration translation.
     *
     * @var \Drupal\config_translation\ConfigMapperInterface
     */
    protected $mapper;
    
    /**
     * The language manager.
     *
     * @var \Drupal\language\ConfigurableLanguageManagerInterface
     */
    protected $languageManager;
    
    /**
     * The language of the configuration translation.
     *
     * @var \Drupal\Core\Language\LanguageInterface
     */
    protected $language;
    
    /**
     * The language of the configuration translation source.
     *
     * @var \Drupal\Core\Language\LanguageInterface
     */
    protected $sourceLanguage;
    
    /**
     * An array of base language configuration data keyed by configuration names.
     *
     * @var array
     */
    protected $baseConfigData = [];
    
    /**
     * Constructs a ConfigTranslationFormBase.
     *
     * @param \Drupal\Core\Config\TypedConfigManagerInterface $typed_config_manager
     *   The typed configuration manager.
     * @param \Drupal\config_translation\ConfigMapperManagerInterface $config_mapper_manager
     *   The configuration mapper manager.
     * @param \Drupal\language\ConfigurableLanguageManagerInterface $language_manager
     *   The configurable language manager.
     */
    public function __construct(TypedConfigManagerInterface $typed_config_manager, ConfigMapperManagerInterface $config_mapper_manager, ConfigurableLanguageManagerInterface $language_manager) {
        $this->typedConfigManager = $typed_config_manager;
        $this->configMapperManager = $config_mapper_manager;
        $this->languageManager = $language_manager;
    }
    
    /**
     * {@inheritdoc}
     */
    public static function create(ContainerInterface $container) {
        return new static($container->get('config.typed'), $container->get('plugin.manager.config_translation.mapper'), $container->get('language_manager'));
    }
    
    /**
     * {@inheritdoc}
     */
    public function getBaseFormId() {
        return 'config_translation_form';
    }
    
    /**
     * Implements \Drupal\Core\Form\FormInterface::buildForm().
     *
     * Builds configuration form with metadata and values from the source
     * language.
     *
     * @param array $form
     *   An associative array containing the structure of the form.
     * @param \Drupal\Core\Form\FormStateInterface $form_state
     *   The current state of the form.
     * @param \Drupal\Core\Routing\RouteMatchInterface $route_match
     *   (optional) The route match.
     * @param string $plugin_id
     *   (optional) The plugin ID of the mapper.
     * @param string $langcode
     *   (optional) The language code of the language the form is adding or
     *   editing.
     *
     * @return array
     *   The form structure.
     *
     * @throws \Symfony\Component\HttpKernel\Exception\NotFoundHttpException
     *   Throws an exception if the language code provided as a query parameter in
     *   the request does not match an active language.
     */
    public function buildForm(array $form, FormStateInterface $form_state, RouteMatchInterface $route_match = NULL, $plugin_id = NULL, $langcode = NULL) {
        
        /** @var \Drupal\config_translation\ConfigMapperInterface $mapper */
        $mapper = $this->configMapperManager
            ->createInstance($plugin_id);
        $mapper->populateFromRouteMatch($route_match);
        $language = $this->languageManager
            ->getLanguage($langcode);
        if (!$language) {
            throw new NotFoundHttpException();
        }
        $this->mapper = $mapper;
        $this->language = $language;
        // ConfigTranslationFormAccess will not grant access if this raises an
        // exception, so we can call this without a try-catch block here.
        $langcode = $this->mapper
            ->getLangcode();
        $this->sourceLanguage = $this->languageManager
            ->getLanguage($langcode);
        // Get base language configuration to display in the form before setting the
        // language to use for the form. This avoids repetitively settings and
        // resetting the language to get original values later.
        $this->baseConfigData = $this->mapper
            ->getConfigData();
        // Set the translation target language on the configuration factory.
        $original_language = $this->languageManager
            ->getConfigOverrideLanguage();
        $this->languageManager
            ->setConfigOverrideLanguage($this->language);
        // Add some information to the form state for easier form altering.
        $form_state->set('config_translation_mapper', $this->mapper);
        $form_state->set('config_translation_language', $this->language);
        $form_state->set('config_translation_source_language', $this->sourceLanguage);
        $form['#attached']['library'][] = 'config_translation/drupal.config_translation.admin';
        // Even though this is a nested form, we do not set #tree to TRUE because
        // the form value structure is generated by using #parents for each element.
        // @see \Drupal\config_translation\FormElement\FormElementBase::getElements()
        $form['config_names'] = [
            '#type' => 'container',
        ];
        foreach ($this->mapper
            ->getConfigNames() as $name) {
            $form['config_names'][$name] = [
                '#type' => 'container',
            ];
            $schema = $this->typedConfigManager
                ->get($name);
            $source_config = $this->baseConfigData[$name];
            $translation_config = $this->configFactory()
                ->get($name)
                ->get();
            if ($form_element = $this->createFormElement($schema)) {
                $parents = [
                    'config_names',
                    $name,
                ];
                $form['config_names'][$name] += $form_element->getTranslationBuild($this->sourceLanguage, $this->language, $source_config, $translation_config, $parents);
            }
        }
        $form['actions']['#type'] = 'actions';
        $form['actions']['submit'] = [
            '#type' => 'submit',
            '#value' => $this->t('Save translation'),
            '#button_type' => 'primary',
        ];
        // Set the configuration language back.
        $this->languageManager
            ->setConfigOverrideLanguage($original_language);
        return $form;
    }
    
    /**
     * {@inheritdoc}
     */
    public function submitForm(array &$form, FormStateInterface $form_state) {
        $form_values = $form_state->getValue([
            'translation',
            'config_names',
        ]);
        foreach ($form_values as $name => $value) {
            $schema = $this->typedConfigManager
                ->get($name);
            // Set configuration values based on form submission and source values.
            $base_config = $this->configFactory()
                ->getEditable($name);
            $config_translation = $this->languageManager
                ->getLanguageConfigOverride($this->language
                ->getId(), $name);
            $element = $this->createFormElement($schema);
            $element->setConfig($base_config, $config_translation, $value);
            // If no overrides, delete language specific configuration file.
            $saved_config = $config_translation->get();
            if (empty($saved_config)) {
                $config_translation->delete();
                $this->messenger()
                    ->addStatus($this->t('@language translation was not added. To add a translation, you must modify the configuration.', [
                    '@language' => $this->language
                        ->getName(),
                ]));
            }
            else {
                $config_translation->save();
                $this->messenger()
                    ->addStatus($this->t('Successfully saved @language translation.', [
                    '@language' => $this->language
                        ->getName(),
                ]));
            }
        }
        $form_state->setRedirect($this->mapper
            ->getOverviewRoute(), $this->mapper
            ->getOverviewRouteParameters());
    }
    
    /**
     * Creates a form element builder.
     *
     * @param \Drupal\Core\TypedData\TypedDataInterface $schema
     *   Schema definition of configuration.
     *
     * @return \Drupal\config_translation\FormElement\ElementInterface|null
     *   The element builder object if possible.
     */
    public static function createFormElement(TypedDataInterface $schema) {
        $definition = $schema->getDataDefinition();
        // Form element classes can be specified even for non-translatable elements
        // such as the ListElement form element which is used for Mapping and
        // Sequence schema elements.
        if (isset($definition['form_element_class'])) {
            if (!$definition->getLabel()) {
                $definition->setLabel(new TranslatableMarkup('n/a'));
            }
            $class = $definition['form_element_class'];
            return $class::create($schema);
        }
    }

}