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();
        }
    }

}