class TextWithSummaryItem

class TextWithSummaryItem extends TextItemBase {
    
    /**
     * {@inheritdoc}
     */
    public static function defaultFieldSettings() {
        return [
            'display_summary' => 0,
            'required_summary' => FALSE,
        ] + parent::defaultFieldSettings();
    }
    
    /**
     * {@inheritdoc}
     */
    public static function propertyDefinitions(FieldStorageDefinitionInterface $field_definition) {
        $properties = parent::propertyDefinitions($field_definition);
        $properties['summary'] = DataDefinition::create('string')->setLabel(new TranslatableMarkup('Summary'));
        $properties['summary_processed'] = DataDefinition::create('string')->setLabel(new TranslatableMarkup('Processed summary'))
            ->setDescription(new TranslatableMarkup('The summary text with the text format applied.'))
            ->setComputed(TRUE)
            ->setClass('\\Drupal\\text\\TextProcessed')
            ->setSetting('text source', 'summary');
        return $properties;
    }
    
    /**
     * {@inheritdoc}
     */
    public static function schema(FieldStorageDefinitionInterface $field_definition) {
        return [
            'columns' => [
                'value' => [
                    'type' => 'text',
                    'size' => 'big',
                ],
                'summary' => [
                    'type' => 'text',
                    'size' => 'big',
                ],
                'format' => [
                    'type' => 'varchar_ascii',
                    'length' => 255,
                ],
            ],
            'indexes' => [
                'format' => [
                    'format',
                ],
            ],
        ];
    }
    
    /**
     * {@inheritdoc}
     */
    public function isEmpty() {
        $value = $this->get('summary')
            ->getValue();
        return parent::isEmpty() && ($value === NULL || $value === '');
    }
    
    /**
     * {@inheritdoc}
     */
    public function fieldSettingsForm(array $form, FormStateInterface $form_state) {
        $element = [];
        $settings = $this->getSettings();
        $element['display_summary'] = [
            '#type' => 'checkbox',
            '#title' => $this->t('Summary input'),
            '#default_value' => $settings['display_summary'],
            '#description' => $this->t('This allows authors to input an explicit summary, to be displayed instead of the automatically trimmed text when using the "Summary or trimmed" display type.'),
        ];
        $element['required_summary'] = [
            '#type' => 'checkbox',
            '#title' => $this->t('Require summary'),
            '#description' => $this->t('The summary will also be visible when marked as required.'),
            '#default_value' => $settings['required_summary'],
        ];
        return $element;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getConstraints() {
        $constraints = parent::getConstraints();
        if ($this->getSetting('required_summary')) {
            $manager = $this->getTypedDataManager()
                ->getValidationConstraintManager();
            $constraints[] = $manager->create('ComplexData', [
                'summary' => [
                    'NotNull' => [
                        'message' => $this->t('The summary field is required for @name', [
                            '@name' => $this->getFieldDefinition()
                                ->getLabel(),
                        ]),
                    ],
                ],
            ]);
        }
        return $constraints;
    }

}