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();
        $elements[0]['#description'] = \Drupal::service('renderer')->renderPlain($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.
    $element['#upload_validators']['file_validate_is_image'] = [];
    // Add upload resolution validation.
    if ($field_settings['max_resolution'] || $field_settings['min_resolution']) {
      $element['#upload_validators']['file_validate_image_resolution'] = [
        $field_settings['max_resolution'],
        $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']['file_validate_extensions'][0] = 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;
  }

}