class ImageWidget

class ImageWidget extends FileWidget {
    
    /**
     * The image factory service.
     *
     * @var \Drupal\Core\Image\ImageFactory
     */
    protected $imageFactory;
    
    /**
     * Constructs an ImageWidget object.
     *
     * @param string $plugin_id
     *   The plugin_id for the widget.
     * @param mixed $plugin_definition
     *   The plugin implementation definition.
     * @param \Drupal\Core\Field\FieldDefinitionInterface $field_definition
     *   The definition of the field to which the widget is associated.
     * @param array $settings
     *   The widget settings.
     * @param array $third_party_settings
     *   Any third party settings.
     * @param \Drupal\Core\Render\ElementInfoManagerInterface $element_info
     *   The element info manager service.
     * @param \Drupal\Core\Image\ImageFactory $image_factory
     *   The image factory service.
     */
    public function __construct($plugin_id, $plugin_definition, FieldDefinitionInterface $field_definition, array $settings, array $third_party_settings, ElementInfoManagerInterface $element_info, ImageFactory $image_factory = NULL) {
        parent::__construct($plugin_id, $plugin_definition, $field_definition, $settings, $third_party_settings, $element_info);
        $this->imageFactory = $image_factory ?: \Drupal::service('image.factory');
    }
    
    /**
     * {@inheritdoc}
     */
    public static function defaultSettings() {
        return [
            'progress_indicator' => 'throbber',
            'preview_image_style' => 'thumbnail',
        ] + parent::defaultSettings();
    }
    
    /**
     * {@inheritdoc}
     */
    public function settingsForm(array $form, FormStateInterface $form_state) {
        $element = parent::settingsForm($form, $form_state);
        $element['preview_image_style'] = [
            '#title' => $this->t('Preview image style'),
            '#type' => 'select',
            '#options' => image_style_options(FALSE),
            '#empty_option' => '<' . $this->t('no preview') . '>',
            '#default_value' => $this->getSetting('preview_image_style'),
            '#description' => $this->t('The preview image will be shown while editing the content.'),
            '#weight' => 15,
        ];
        return $element;
    }
    
    /**
     * {@inheritdoc}
     */
    public function settingsSummary() {
        $summary = parent::settingsSummary();
        $image_styles = image_style_options(FALSE);
        // Unset possible 'No defined styles' option.
        unset($image_styles['']);
        // Styles could be lost because of enabled/disabled modules that defines
        // their styles in code.
        $image_style_setting = $this->getSetting('preview_image_style');
        if (isset($image_styles[$image_style_setting])) {
            $preview_image_style = $this->t('Preview image style: @style', [
                '@style' => $image_styles[$image_style_setting],
            ]);
        }
        else {
            $preview_image_style = $this->t('No preview');
        }
        array_unshift($summary, $preview_image_style);
        return $summary;
    }
    
    /**
     * Overrides \Drupal\file\Plugin\Field\FieldWidget\FileWidget::formMultipleElements().
     *
     * Special handling for draggable multiple widgets and 'add more' button.
     */
    protected function formMultipleElements(FieldItemListInterface $items, array &$form, FormStateInterface $form_state) {
        $elements = parent::formMultipleElements($items, $form, $form_state);
        $cardinality = $this->fieldDefinition
            ->getFieldStorageDefinition()
            ->getCardinality();
        $file_upload_help = [
            '#theme' => 'file_upload_help',
            '#description' => '',
            '#upload_validators' => $elements[0]['#upload_validators'],
            '#cardinality' => $cardinality,
        ];
        if ($cardinality == 1) {
            // If there's only one field, return it as delta 0.
            if (empty($elements[0]['#default_value']['fids'])) {
                $file_upload_help['#description'] = $this->getFilteredDescription();
                $elements[0]['#description'] = \Drupal::service('renderer')->renderInIsolation($file_upload_help);
            }
        }
        else {
            $elements['#file_upload_description'] = $file_upload_help;
        }
        return $elements;
    }
    
    /**
     * {@inheritdoc}
     */
    public function formElement(FieldItemListInterface $items, $delta, array $element, array &$form, FormStateInterface $form_state) {
        $element = parent::formElement($items, $delta, $element, $form, $form_state);
        $field_settings = $this->getFieldSettings();
        // Add image validation.
        $element['#upload_validators']['FileIsImage'] = [];
        // Add upload dimensions validation.
        if ($field_settings['max_resolution'] || $field_settings['min_resolution']) {
            $element['#upload_validators']['FileImageDimensions'] = [
                'maxDimensions' => $field_settings['max_resolution'],
                'minDimensions' => $field_settings['min_resolution'],
            ];
        }
        $extensions = $field_settings['file_extensions'];
        $supported_extensions = $this->imageFactory
            ->getSupportedExtensions();
        // If using custom extension validation, ensure that the extensions are
        // supported by the current image toolkit. Otherwise, validate against all
        // toolkit supported extensions.
        $extensions = !empty($extensions) ? array_intersect(explode(' ', $extensions), $supported_extensions) : $supported_extensions;
        $element['#upload_validators']['FileExtension']['extensions'] = implode(' ', $extensions);
        // Add mobile device image capture acceptance.
        $element['#accept'] = 'image/*';
        // Add properties needed by process() method.
        $element['#preview_image_style'] = $this->getSetting('preview_image_style');
        $element['#title_field'] = $field_settings['title_field'];
        $element['#title_field_required'] = $field_settings['title_field_required'];
        $element['#alt_field'] = $field_settings['alt_field'];
        $element['#alt_field_required'] = $field_settings['alt_field_required'];
        // Default image.
        $default_image = $field_settings['default_image'];
        if (empty($default_image['uuid'])) {
            $default_image = $this->fieldDefinition
                ->getFieldStorageDefinition()
                ->getSetting('default_image');
        }
        // Convert the stored UUID into a file ID.
        if (!empty($default_image['uuid']) && ($entity = \Drupal::service('entity.repository')->loadEntityByUuid('file', $default_image['uuid']))) {
            $default_image['fid'] = $entity->id();
        }
        $element['#default_image'] = !empty($default_image['fid']) ? $default_image : [];
        return $element;
    }
    
    /**
     * Form API callback: Processes an image_image field element.
     *
     * Expands the image_image type to include the alt and title fields.
     *
     * This method is assigned as a #process callback in formElement() method.
     */
    public static function process($element, FormStateInterface $form_state, $form) {
        $item = $element['#value'];
        $item['fids'] = $element['fids']['#value'];
        $element['#theme'] = 'image_widget';
        // Add the image preview.
        if (!empty($element['#files']) && $element['#preview_image_style']) {
            $file = reset($element['#files']);
            $variables = [
                'style_name' => $element['#preview_image_style'],
                'uri' => $file->getFileUri(),
            ];
            $dimension_key = $variables['uri'] . '.image_preview_dimensions';
            // Determine image dimensions.
            if (isset($element['#value']['width']) && isset($element['#value']['height'])) {
                $variables['width'] = $element['#value']['width'];
                $variables['height'] = $element['#value']['height'];
            }
            elseif ($form_state->has($dimension_key)) {
                $variables += $form_state->get($dimension_key);
            }
            else {
                $image = \Drupal::service('image.factory')->get($file->getFileUri());
                if ($image->isValid()) {
                    $variables['width'] = $image->getWidth();
                    $variables['height'] = $image->getHeight();
                }
                else {
                    $variables['width'] = $variables['height'] = NULL;
                }
            }
            $element['preview'] = [
                '#weight' => -10,
                '#theme' => 'image_style',
                '#width' => $variables['width'],
                '#height' => $variables['height'],
                '#style_name' => $variables['style_name'],
                '#uri' => $variables['uri'],
            ];
            // Store the dimensions in the form so the file doesn't have to be
            // accessed again. This is important for remote files.
            $form_state->set($dimension_key, [
                'width' => $variables['width'],
                'height' => $variables['height'],
            ]);
        }
        elseif (!empty($element['#default_image'])) {
            $default_image = $element['#default_image'];
            $file = File::load($default_image['fid']);
            if (!empty($file)) {
                $element['preview'] = [
                    '#weight' => -10,
                    '#theme' => 'image_style',
                    '#width' => $default_image['width'],
                    '#height' => $default_image['height'],
                    '#style_name' => $element['#preview_image_style'],
                    '#uri' => $file->getFileUri(),
                ];
            }
        }
        // Add the additional alt and title fields.
        $element['alt'] = [
            '#title' => new TranslatableMarkup('Alternative text'),
            '#type' => 'textfield',
            '#default_value' => $item['alt'] ?? '',
            '#description' => new TranslatableMarkup('Short description of the image used by screen readers and displayed when the image is not loaded. This is important for accessibility.'),
            // @see https://www.drupal.org/node/465106#alt-text
'#maxlength' => 512,
            '#weight' => -12,
            '#access' => (bool) $item['fids'] && $element['#alt_field'],
            '#required' => $element['#alt_field_required'],
            '#element_validate' => $element['#alt_field_required'] == 1 ? [
                [
                    static::class,
                    'validateRequiredFields',
                ],
            ] : [],
        ];
        $element['title'] = [
            '#type' => 'textfield',
            '#title' => new TranslatableMarkup('Title'),
            '#default_value' => $item['title'] ?? '',
            '#description' => new TranslatableMarkup('The title is used as a tool tip when the user hovers the mouse over the image.'),
            '#maxlength' => 1024,
            '#weight' => -11,
            '#access' => (bool) $item['fids'] && $element['#title_field'],
            '#required' => $element['#title_field_required'],
            '#element_validate' => $element['#title_field_required'] == 1 ? [
                [
                    static::class,
                    'validateRequiredFields',
                ],
            ] : [],
        ];
        return parent::process($element, $form_state, $form);
    }
    
    /**
     * Validate callback for alt and title field, if the user wants them required.
     *
     * This is separated in a validate function instead of a #required flag to
     * avoid being validated on the process callback.
     */
    public static function validateRequiredFields($element, FormStateInterface $form_state) {
        // Only do validation if the function is triggered from other places than
        // the image process form.
        $triggering_element = $form_state->getTriggeringElement();
        if (!empty($triggering_element['#submit']) && in_array('file_managed_file_submit', $triggering_element['#submit'], TRUE)) {
            $form_state->setLimitValidationErrors([]);
        }
    }
    
    /**
     * {@inheritdoc}
     */
    public function calculateDependencies() {
        $dependencies = parent::calculateDependencies();
        $style_id = $this->getSetting('preview_image_style');
        
        /** @var \Drupal\image\ImageStyleInterface $style */
        if ($style_id && ($style = ImageStyle::load($style_id))) {
            // If this widget uses a valid image style to display the preview of the
            // uploaded image, add that image style configuration entity as dependency
            // of this widget.
            $dependencies[$style->getConfigDependencyKey()][] = $style->getConfigDependencyName();
        }
        return $dependencies;
    }
    
    /**
     * {@inheritdoc}
     */
    public function onDependencyRemoval(array $dependencies) {
        $changed = parent::onDependencyRemoval($dependencies);
        $style_id = $this->getSetting('preview_image_style');
        
        /** @var \Drupal\image\ImageStyleInterface $style */
        if ($style_id && ($style = ImageStyle::load($style_id))) {
            if (!empty($dependencies[$style->getConfigDependencyKey()][$style->getConfigDependencyName()])) {
                
                /** @var \Drupal\image\ImageStyleStorageInterface $storage */
                $storage = \Drupal::entityTypeManager()->getStorage($style->getEntityTypeId());
                $replacement_id = $storage->getReplacementId($style_id);
                // If a valid replacement has been provided in the storage, replace the
                // preview image style with the replacement.
                if ($replacement_id && ImageStyle::load($replacement_id)) {
                    $this->setSetting('preview_image_style', $replacement_id);
                }
                else {
                    $this->setSetting('preview_image_style', '');
                }
                // Signal that the formatter plugin settings were updated.
                $changed = TRUE;
            }
        }
        return $changed;
    }

}