class NodeForm

class NodeForm extends ContentEntityForm {
    
    /**
     * The tempstore factory.
     *
     * @var \Drupal\Core\TempStore\PrivateTempStoreFactory
     */
    protected $tempStoreFactory;
    
    /**
     * The Current User object.
     *
     * @var \Drupal\Core\Session\AccountInterface
     */
    protected $currentUser;
    
    /**
     * The date formatter service.
     *
     * @var \Drupal\Core\Datetime\DateFormatterInterface
     */
    protected $dateFormatter;
    
    /**
     * Constructs a NodeForm object.
     *
     * @param \Drupal\Core\Entity\EntityRepositoryInterface $entity_repository
     *   The entity repository.
     * @param \Drupal\Core\TempStore\PrivateTempStoreFactory $temp_store_factory
     *   The factory for the temp store object.
     * @param \Drupal\Core\Entity\EntityTypeBundleInfoInterface $entity_type_bundle_info
     *   The entity type bundle service.
     * @param \Drupal\Component\Datetime\TimeInterface $time
     *   The time service.
     * @param \Drupal\Core\Session\AccountInterface $current_user
     *   The current user.
     * @param \Drupal\Core\Datetime\DateFormatterInterface $date_formatter
     *   The date formatter service.
     */
    public function __construct(EntityRepositoryInterface $entity_repository, PrivateTempStoreFactory $temp_store_factory, EntityTypeBundleInfoInterface $entity_type_bundle_info = NULL, TimeInterface $time = NULL, AccountInterface $current_user, DateFormatterInterface $date_formatter) {
        parent::__construct($entity_repository, $entity_type_bundle_info, $time);
        $this->tempStoreFactory = $temp_store_factory;
        $this->currentUser = $current_user;
        $this->dateFormatter = $date_formatter;
    }
    
    /**
     * {@inheritdoc}
     */
    public static function create(ContainerInterface $container) {
        return new static($container->get('entity.repository'), $container->get('tempstore.private'), $container->get('entity_type.bundle.info'), $container->get('datetime.time'), $container->get('current_user'), $container->get('date.formatter'));
    }
    
    /**
     * {@inheritdoc}
     */
    public function form(array $form, FormStateInterface $form_state) {
        // Try to restore from temp store, this must be done before calling
        // parent::form().
        $store = $this->tempStoreFactory
            ->get('node_preview');
        // Attempt to load from preview when the uuid is present unless we are
        // rebuilding the form.
        $request_uuid = \Drupal::request()->query
            ->get('uuid');
        if (!$form_state->isRebuilding() && $request_uuid && ($preview = $store->get($request_uuid))) {
            
            /** @var \Drupal\Core\Form\FormStateInterface $preview */
            $form_state->setStorage($preview->getStorage());
            $form_state->setUserInput($preview->getUserInput());
            // Rebuild the form.
            $form_state->setRebuild();
            // The combination of having user input and rebuilding the form means
            // that it will attempt to cache the form state which will fail if it is
            // a GET request.
            $form_state->setRequestMethod('POST');
            $this->entity = $preview->getFormObject()
                ->getEntity();
            $this->entity->in_preview = NULL;
            $form_state->set('has_been_previewed', TRUE);
        }
        
        /** @var \Drupal\node\NodeInterface $node */
        $node = $this->entity;
        if ($this->operation == 'edit') {
            $form['#title'] = $this->t('<em>Edit @type</em> @title', [
                '@type' => node_get_type_label($node),
                '@title' => $node->label(),
            ]);
        }
        // Changed must be sent to the client, for later overwrite error checking.
        $form['changed'] = [
            '#type' => 'hidden',
            '#default_value' => $node->getChangedTime(),
        ];
        $form = parent::form($form, $form_state);
        $form['advanced']['#attributes']['class'][] = 'entity-meta';
        $form['meta'] = [
            '#type' => 'details',
            '#group' => 'advanced',
            '#weight' => -10,
            '#title' => $this->t('Status'),
            '#attributes' => [
                'class' => [
                    'entity-meta__header',
                ],
            ],
            '#tree' => TRUE,
            '#access' => $this->currentUser
                ->hasPermission('administer nodes'),
        ];
        $form['meta']['published'] = [
            '#type' => 'item',
            '#markup' => $node->isPublished() ? $this->t('Published') : $this->t('Not published'),
            '#access' => !$node->isNew(),
            '#wrapper_attributes' => [
                'class' => [
                    'entity-meta__title',
                ],
            ],
        ];
        $form['meta']['changed'] = [
            '#type' => 'item',
            '#title' => $this->t('Last saved'),
            '#markup' => !$node->isNew() ? $this->dateFormatter
                ->format($node->getChangedTime(), 'short') : $this->t('Not saved yet'),
            '#wrapper_attributes' => [
                'class' => [
                    'entity-meta__last-saved',
                ],
            ],
        ];
        $form['meta']['author'] = [
            '#type' => 'item',
            '#title' => $this->t('Author'),
            '#markup' => $node->getOwner()
                ->getAccountName(),
            '#wrapper_attributes' => [
                'class' => [
                    'entity-meta__author',
                ],
            ],
        ];
        $form['status']['#group'] = 'footer';
        // Node author information for administrators.
        $form['author'] = [
            '#type' => 'details',
            '#title' => $this->t('Authoring information'),
            '#group' => 'advanced',
            '#attributes' => [
                'class' => [
                    'node-form-author',
                ],
            ],
            '#attached' => [
                'library' => [
                    'node/drupal.node',
                ],
            ],
            '#weight' => 90,
            '#optional' => TRUE,
        ];
        if (isset($form['uid'])) {
            $form['uid']['#group'] = 'author';
        }
        if (isset($form['created'])) {
            $form['created']['#group'] = 'author';
        }
        // Node options for administrators.
        $form['options'] = [
            '#type' => 'details',
            '#title' => $this->t('Promotion options'),
            '#group' => 'advanced',
            '#attributes' => [
                'class' => [
                    'node-form-options',
                ],
            ],
            '#attached' => [
                'library' => [
                    'node/drupal.node',
                ],
            ],
            '#weight' => 95,
            '#optional' => TRUE,
        ];
        if (isset($form['promote'])) {
            $form['promote']['#group'] = 'options';
        }
        if (isset($form['sticky'])) {
            $form['sticky']['#group'] = 'options';
        }
        $form['#attached']['library'][] = 'node/form';
        return $form;
    }
    
    /**
     * {@inheritdoc}
     */
    protected function actions(array $form, FormStateInterface $form_state) {
        $element = parent::actions($form, $form_state);
        $node = $this->entity;
        $preview_mode = $node->type->entity
            ->getPreviewMode();
        $element['submit']['#access'] = $preview_mode != DRUPAL_REQUIRED || $form_state->get('has_been_previewed');
        $element['preview'] = [
            '#type' => 'submit',
            '#access' => $preview_mode != DRUPAL_DISABLED && ($node->access('create') || $node->access('update')),
            '#value' => $this->t('Preview'),
            '#weight' => 20,
            '#submit' => [
                '::submitForm',
                '::preview',
            ],
        ];
        if (array_key_exists('delete', $element)) {
            $element['delete']['#weight'] = 100;
        }
        return $element;
    }
    
    /**
     * Form submission handler for the 'preview' action.
     *
     * @param $form
     *   An associative array containing the structure of the form.
     * @param $form_state
     *   The current state of the form.
     */
    public function preview(array $form, FormStateInterface $form_state) {
        $store = $this->tempStoreFactory
            ->get('node_preview');
        $this->entity->in_preview = TRUE;
        $store->set($this->entity
            ->uuid(), $form_state);
        $route_parameters = [
            'node_preview' => $this->entity
                ->uuid(),
            'view_mode_id' => 'full',
        ];
        $options = [];
        $query = $this->getRequest()->query;
        if ($query->has('destination')) {
            $options['query']['destination'] = $query->get('destination');
            $query->remove('destination');
        }
        $form_state->setRedirect('entity.node.preview', $route_parameters, $options);
    }
    
    /**
     * {@inheritdoc}
     */
    public function save(array $form, FormStateInterface $form_state) {
        $node = $this->entity;
        $insert = $node->isNew();
        $node->save();
        $node_link = $node->toLink($this->t('View'))
            ->toString();
        $context = [
            '@type' => $node->getType(),
            '%title' => $node->label(),
            'link' => $node_link,
        ];
        $t_args = [
            '@type' => node_get_type_label($node),
            '%title' => $node->toLink()
                ->toString(),
        ];
        if ($insert) {
            $this->logger('content')
                ->notice('@type: added %title.', $context);
            $this->messenger()
                ->addStatus($this->t('@type %title has been created.', $t_args));
        }
        else {
            $this->logger('content')
                ->notice('@type: updated %title.', $context);
            $this->messenger()
                ->addStatus($this->t('@type %title has been updated.', $t_args));
        }
        if ($node->id()) {
            $form_state->setValue('nid', $node->id());
            $form_state->set('nid', $node->id());
            if ($node->access('view')) {
                $form_state->setRedirect('entity.node.canonical', [
                    'node' => $node->id(),
                ]);
            }
            else {
                $form_state->setRedirect('<front>');
            }
            // Remove the preview entry from the temp store, if any.
            $store = $this->tempStoreFactory
                ->get('node_preview');
            $store->delete($node->uuid());
        }
        else {
            // In the unlikely case something went wrong on save, the node will be
            // rebuilt and node form redisplayed the same way as in preview.
            $this->messenger()
                ->addError($this->t('The post could not be saved.'));
            $form_state->setRebuild();
        }
    }

}