class EditorImageDialog

class EditorImageDialog extends FormBase {
    
    /**
     * The file storage service.
     *
     * @var \Drupal\Core\Entity\EntityStorageInterface
     */
    protected $fileStorage;
    
    /**
     * Constructs a form object for image dialog.
     *
     * @param \Drupal\Core\Entity\EntityStorageInterface $file_storage
     *   The file storage service.
     */
    public function __construct(EntityStorageInterface $file_storage) {
        $this->fileStorage = $file_storage;
    }
    
    /**
     * {@inheritdoc}
     */
    public static function create(ContainerInterface $container) {
        return new static($container->get('entity_type.manager')
            ->getStorage('file'));
    }
    
    /**
     * {@inheritdoc}
     */
    public function getFormId() {
        return 'editor_image_dialog';
    }
    
    /**
     * {@inheritdoc}
     *
     * @param \Drupal\editor\Entity\Editor $editor
     *   The text editor to which this dialog corresponds.
     */
    public function buildForm(array $form, FormStateInterface $form_state, Editor $editor = NULL) {
        // This form is special, in that the default values do not come from the
        // server side, but from the client side, from a text editor. We must cache
        // this data in form state, because when the form is rebuilt, we will be
        // receiving values from the form, instead of the values from the text
        // editor. If we don't cache it, this data will be lost.
        if (isset($form_state->getUserInput()['editor_object'])) {
            // By convention, the data that the text editor sends to any dialog is in
            // the 'editor_object' key. And the image dialog for text editors expects
            // that data to be the attributes for an <img> element.
            $image_element = $form_state->getUserInput()['editor_object'];
            $form_state->set('image_element', $image_element);
            $form_state->setCached(TRUE);
        }
        else {
            // Retrieve the image element's attributes from form state.
            $image_element = $form_state->get('image_element') ?: [];
        }
        $form['#tree'] = TRUE;
        $form['#attached']['library'][] = 'editor/drupal.editor.dialog';
        $form['#prefix'] = '<div id="editor-image-dialog-form">';
        $form['#suffix'] = '</div>';
        // Construct strings to use in the upload validators.
        $image_upload = $editor->getImageUploadSettings();
        if (!empty($image_upload['max_dimensions']['width']) || !empty($image_upload['max_dimensions']['height'])) {
            $max_dimensions = $image_upload['max_dimensions']['width'] . 'x' . $image_upload['max_dimensions']['height'];
        }
        else {
            $max_dimensions = 0;
        }
        $max_filesize = min(Bytes::toInt($image_upload['max_size']), Environment::getUploadMaxSize());
        $existing_file = isset($image_element['data-entity-uuid']) ? \Drupal::service('entity.repository')->loadEntityByUuid('file', $image_element['data-entity-uuid']) : NULL;
        $fid = $existing_file ? $existing_file->id() : NULL;
        $form['fid'] = [
            '#title' => $this->t('Image'),
            '#type' => 'managed_file',
            '#upload_location' => $image_upload['scheme'] . '://' . $image_upload['directory'],
            '#default_value' => $fid ? [
                $fid,
            ] : NULL,
            '#upload_validators' => [
                'file_validate_extensions' => [
                    'gif png jpg jpeg',
                ],
                'file_validate_size' => [
                    $max_filesize,
                ],
                'file_validate_image_resolution' => [
                    $max_dimensions,
                ],
            ],
            '#required' => TRUE,
        ];
        $form['attributes']['src'] = [
            '#title' => $this->t('URL'),
            '#type' => 'textfield',
            '#default_value' => isset($image_element['src']) ? $image_element['src'] : '',
            '#maxlength' => 2048,
            '#required' => TRUE,
        ];
        // If the editor has image uploads enabled, show a managed_file form item,
        // otherwise show a (file URL) text form item.
        if ($image_upload['status']) {
            $form['attributes']['src']['#access'] = FALSE;
            $form['attributes']['src']['#required'] = FALSE;
        }
        else {
            $form['fid']['#access'] = FALSE;
            $form['fid']['#required'] = FALSE;
        }
        // The alt attribute is *required*, but we allow users to opt-in to empty
        // alt attributes for the very rare edge cases where that is valid by
        // specifying two double quotes as the alternative text in the dialog.
        // However, that *is* stored as an empty alt attribute, so if we're editing
        // an existing image (which means the src attribute is set) and its alt
        // attribute is empty, then we show that as two double quotes in the dialog.
        // @see https://www.drupal.org/node/2307647
        $alt = isset($image_element['alt']) ? $image_element['alt'] : '';
        if ($alt === '' && !empty($image_element['src'])) {
            $alt = '""';
        }
        $form['attributes']['alt'] = [
            '#title' => $this->t('Alternative text'),
            '#description' => $this->t('Short description of the image used by screen readers and displayed when the image is not loaded. This is important for accessibility.'),
            '#type' => 'textfield',
            '#required' => TRUE,
            '#required_error' => $this->t('Alternative text is required.<br />(Only in rare cases should this be left empty. To create empty alternative text, enter <code>""</code> — two double quotes without any content).'),
            '#default_value' => $alt,
            '#maxlength' => 2048,
        ];
        // When Drupal core's filter_align is being used, the text editor may
        // offer the ability to change the alignment.
        if (isset($image_element['data-align']) && $editor->getFilterFormat()
            ->filters('filter_align')->status) {
            $form['align'] = [
                '#title' => $this->t('Align'),
                '#type' => 'radios',
                '#options' => [
                    'none' => $this->t('None'),
                    'left' => $this->t('Left'),
                    'center' => $this->t('Center'),
                    'right' => $this->t('Right'),
                ],
                '#default_value' => $image_element['data-align'] === '' ? 'none' : $image_element['data-align'],
                '#wrapper_attributes' => [
                    'class' => [
                        'container-inline',
                    ],
                ],
                '#attributes' => [
                    'class' => [
                        'container-inline',
                    ],
                ],
                '#parents' => [
                    'attributes',
                    'data-align',
                ],
            ];
        }
        // When Drupal core's filter_caption is being used, the text editor may
        // offer the ability to in-place edit the image's caption: show a toggle.
        if (isset($image_element['hasCaption']) && $editor->getFilterFormat()
            ->filters('filter_caption')->status) {
            $form['caption'] = [
                '#title' => $this->t('Caption'),
                '#type' => 'checkbox',
                '#default_value' => $image_element['hasCaption'] === 'true',
                '#parents' => [
                    'attributes',
                    'hasCaption',
                ],
            ];
        }
        $form['actions'] = [
            '#type' => 'actions',
        ];
        $form['actions']['save_modal'] = [
            '#type' => 'submit',
            '#value' => $this->t('Save'),
            // No regular submit-handler. This form only works via JavaScript.
'#submit' => [],
            '#ajax' => [
                'callback' => '::submitForm',
                'event' => 'click',
            ],
        ];
        return $form;
    }
    
    /**
     * {@inheritdoc}
     */
    public function submitForm(array &$form, FormStateInterface $form_state) {
        $response = new AjaxResponse();
        // Convert any uploaded files from the FID values to data-entity-uuid
        // attributes and set data-entity-type to 'file'.
        $fid = $form_state->getValue([
            'fid',
            0,
        ]);
        if (!empty($fid)) {
            
            /** @var \Drupal\file\FileInterface $file */
            $file = $this->fileStorage
                ->load($fid);
            $file_url = $file->createFileUrl();
            $form_state->setValue([
                'attributes',
                'src',
            ], $file_url);
            $form_state->setValue([
                'attributes',
                'data-entity-uuid',
            ], $file->uuid());
            $form_state->setValue([
                'attributes',
                'data-entity-type',
            ], 'file');
        }
        // When the alt attribute is set to two double quotes, transform it to the
        // empty string: two double quotes signify "empty alt attribute". See above.
        if (trim($form_state->getValue([
            'attributes',
            'alt',
        ])) === '""') {
            $form_state->setValue([
                'attributes',
                'alt',
            ], '');
        }
        if ($form_state->getErrors()) {
            unset($form['#prefix'], $form['#suffix']);
            $form['status_messages'] = [
                '#type' => 'status_messages',
                '#weight' => -10,
            ];
            $response->addCommand(new HtmlCommand('#editor-image-dialog-form', $form));
        }
        else {
            $response->addCommand(new EditorDialogSave($form_state->getValues()));
            $response->addCommand(new CloseModalDialogCommand());
        }
        return $response;
    }

}