class Core

class Core extends PluginBase implements CKEditor4To5UpgradePluginInterface {
  
  /**
   * {@inheritdoc}
   */
  public function mapCKEditor4ToolbarButtonToCKEditor5ToolbarItem(string $cke4_button, HTMLRestrictions $text_format_html_restrictions) : ?array {
    static $alignment_mapped;
    switch ($cke4_button) {
      // @see \Drupal\ckeditor\Plugin\CKEditorPlugin\DrupalImage
      case 'DrupalImage':
        return [
          'drupalInsertImage',
        ];
      // @see \Drupal\ckeditor\Plugin\CKEditorPlugin\DrupalLink
      case 'DrupalLink':
        return [
          'link',
        ];
      case 'DrupalUnlink':
        return NULL;
      // @see \Drupal\ckeditor\Plugin\CKEditorPlugin\Internal
      case 'Bold':
      case 'Italic':
      case 'Underline':
      case 'Superscript':
      case 'Subscript':
      case 'BulletedList':
      case 'NumberedList':
      case 'Outdent':
      case 'Indent':
      case 'Undo':
      case 'Redo':
        return [
          lcfirst($cke4_button),
        ];
      case 'Blockquote':
        return [
          'blockQuote',
        ];
      case 'JustifyLeft':
      case 'JustifyCenter':
      case 'JustifyRight':
      case 'JustifyBlock':
        if (!isset($alignment_mapped)) {
          $alignment_mapped = TRUE;
          return [
            'alignment',
          ];
        }
        return NULL;
      case 'HorizontalRule':
        return [
          'horizontalLine',
        ];
      case 'Format':
        if ($text_format_html_restrictions->isUnrestricted()) {
          // When no restrictions exist, all tags possibly supported by "Format"
          // in CKEditor 4 must be supported.
          return [
            'heading',
            'codeBlock',
          ];
        }
        $allowed_elements = $text_format_html_restrictions->getAllowedElements();
        // Check if <h*> is supported.
        // Merely checking the existence of the array key is sufficient; this
        // plugin does not set or need any additional attributes.
        // @see \Drupal\filter\Plugin\FilterInterface::getHTMLRestrictions()
        $intersect = array_intersect([
          'h2',
          'h3',
          'h4',
          'h5',
          'h6',
        ], array_keys($allowed_elements));
        // Do not return the 'codeBlock' toolbar item, not even when `<pre>` is
        // allowed in the text format. This ensures that SmartDefaultSettings:
        // - first adds the `code` toolbar item (for inline `<code>`)
        // - then adds `codeBlock` toolbar item (for code blocks: `<pre><code>`)
        // @see https://www.drupal.org/project/drupal/issues/3263384#comment-14446315
        return count($intersect) > 0 ? [
          'heading',
        ] : NULL;
      case 'Table':
        return [
          'insertTable',
        ];
      case 'Source':
        return [
          'sourceEditing',
        ];
      case 'Strike':
        return [
          'strikethrough',
        ];
      case 'Cut':
      case 'Copy':
      case 'Paste':
      case 'PasteText':
      case 'PasteFromWord':
      case 'Maximize':
      case '-':
        // @see https://www.drupal.org/project/ckeditor5/issues/3211049#comment-14167764
        return NULL;
      case 'ShowBlocks':
        return [
          'showBlocks',
        ];
      // @see \Drupal\ckeditor5\Plugin\CKEditor5Plugin\RemoveFormat
      case 'RemoveFormat':
        return [
          'removeFormat',
        ];
      // @see \Drupal\ckeditor\Plugin\CKEditorPlugin\StylesCombo
      case 'Styles':
        return [
          'style',
        ];
      // @see \Drupal\ckeditor5\Plugin\CKEditor5Plugin\specialCharacters
      case 'SpecialChar':
        return [
          'specialCharacters',
        ];
      // @see \Drupal\ckeditor\Plugin\CKEditorPlugin\Language
      case 'Language':
        return [
          'textPartLanguage',
        ];
      // @see \Drupal\media_library\Plugin\CKEditorPlugin\DrupalMediaLibrary
      case 'DrupalMediaLibrary':
        return [
          'drupalMedia',
        ];
      default:
        throw new \OutOfBoundsException();
    }
  }
  
  /**
   * {@inheritdoc}
   */
  public function mapCKEditor4SettingsToCKEditor5Configuration(string $cke4_plugin_id, array $cke4_plugin_settings) : ?array {
    switch ($cke4_plugin_id) {
      // @see \Drupal\ckeditor\Plugin\CKEditorPlugin\StylesCombo
      case 'stylescombo':
        if (!isset($cke4_plugin_settings['styles'])) {
          $styles = [];
        }
        else {
          [$styles] = Style::parseStylesFormValue($cke4_plugin_settings['styles']);
        }
        return [
          'ckeditor5_style' => [
            'styles' => $styles,
          ],
        ];
      // @see \Drupal\ckeditor\Plugin\CKEditorPlugin\Language
      case 'language':
        // Identical configuration.
        return [
          'ckeditor5_language' => $cke4_plugin_settings,
        ];
      default:
        throw new \OutOfBoundsException();
    }
  }
  
  /**
   * {@inheritdoc}
   */
  public function computeCKEditor5PluginSubsetConfiguration(string $cke5_plugin_id, FilterFormatInterface $text_format) : ?array {
    switch ($cke5_plugin_id) {
      case 'ckeditor5_heading':
        $restrictions = $text_format->getHtmlRestrictions();
        if ($restrictions === FALSE) {
          // The default is to allow all headings, which makes sense when there
          // are no restrictions.
          // @see \Drupal\ckeditor5\Plugin\CKEditor5Plugin\Heading::DEFAULT_CONFIGURATION
          return NULL;
        }
        // Otherwise, only enable headings that allowed by the restrictions.
        $configuration = [];
        foreach (range(1, 6) as $index) {
          // Merely checking the existence of the array key is sufficient; this
          // plugin does not set or need any additional attributes.
          // @see \Drupal\filter\Plugin\FilterInterface::getHTMLRestrictions()
          if (array_key_exists("h{$index}", $restrictions['allowed'])) {
            $configuration['enabled_headings'][] = "heading{$index}";
          }
        }
        return $configuration;
      case 'ckeditor5_alignment':
        $alignment_classes_to_types = [
          'text-align-left' => 'left',
          'text-align-right' => 'right',
          'text-align-center' => 'center',
          'text-align-justify' => 'justify',
        ];
        $restrictions = $text_format->getHtmlRestrictions();
        if ($restrictions === FALSE) {
          // The default is to allow all alignments. This makes sense when there
          // are no restrictions.
          // @see \Drupal\ckeditor5\Plugin\CKEditor5Plugin\Alignment::DEFAULT_CONFIGURATION
          return NULL;
        }
        // Otherwise, enable alignment types based on the provided restrictions.
        // I.e. if a tag is found with a text-align-{alignment type} class,
        // activate that alignment type.
        $configuration = [];
        foreach ($restrictions['allowed'] as $tag) {
          $classes = isset($tag['class']) && is_array($tag['class']) ? $tag['class'] : [];
          foreach (array_keys($classes) as $class) {
            if (isset($alignment_classes_to_types[$class])) {
              $configuration['enabled_alignments'][] = $alignment_classes_to_types[$class];
            }
          }
        }
        if (isset($configuration['enabled_alignments'])) {
          $configuration['enabled_alignments'] = array_unique($configuration['enabled_alignments']);
        }
        return $configuration;
      case 'ckeditor5_list':
        $restrictions = $text_format->getHtmlRestrictions();
        if ($restrictions === FALSE) {
          // The default is to allow a reversed list and a start index, which makes sense when there
          // are no restrictions.
          // @see \Drupal\ckeditor5\Plugin\CKEditor5Plugin\ListPlugin::default_configuration()
          return NULL;
        }
        $configuration = [];
        $configuration['properties']['reversed'] = !empty($restrictions['allowed']['ol']['reversed']);
        $configuration['properties']['startIndex'] = !empty($restrictions['allowed']['ol']['start']);
        return $configuration;
      case 'media_media':
        $restrictions = $text_format->getHtmlRestrictions();
        if ($restrictions === FALSE) {
          // The default is to not allow the user to override the default view mode.
          // @see \Drupal\ckeditor5\Plugin\CKEditor5Plugin\Media::defaultConfiguration()
          return NULL;
        }
        $configuration = [];
        // Check if data-view-mode is allowed.
        $configuration['allow_view_mode_override'] = !empty($restrictions['allowed']['drupal-media']['data-view-mode']);
        return $configuration;
      case 'ckeditor5_style':
        // @see mapCKEditor4SettingsToCKEditor5Configuration()
        return NULL;
      default:
        throw new \OutOfBoundsException();
    }
  }

}