class Style

class Style extends CKEditor5PluginDefault implements CKEditor5PluginConfigurableInterface, CKEditor5PluginElementsSubsetInterface {
    use CKEditor5PluginConfigurableTrait;
    
    /**
     * {@inheritdoc}
     */
    public function buildConfigurationForm(array $form, FormStateInterface $form_state) {
        $form['styles'] = [
            '#title' => $this->t('Styles'),
            '#type' => 'textarea',
            '#description' => $this->t('A list of classes that will be provided in the "Style" dropdown. Enter one or more classes on each line in the format: element.classA.classB|Label. Example: h1.title|Title. Advanced example: h1.fancy.title|Fancy title.<br />These styles should be available in your theme\'s CSS file.'),
        ];
        if (!empty($this->configuration['styles'])) {
            $as_selectors = '';
            foreach ($this->configuration['styles'] as $style) {
                [
                    $tag,
                    $classes,
                ] = self::getTagAndClasses(HTMLRestrictions::fromString($style['element']));
                $as_selectors .= sprintf("%s.%s|%s\n", $tag, implode('.', $classes), $style['label']);
            }
            $form['styles']['#default_value'] = $as_selectors;
        }
        return $form;
    }
    
    /**
     * Gets the tag and classes for a parsed style element.
     *
     * @param \Drupal\ckeditor5\HTMLRestrictions $style_element
     *   A parsed style element.
     *
     * @return array
     *   An array containing two values:
     *   - a HTML tag name
     *   - a list of classes
     *
     * @internal
     */
    public static function getTagAndClasses(HTMLRestrictions $style_element) : array {
        $tag = array_keys($style_element->getAllowedElements())[0];
        $classes = array_keys($style_element->getAllowedElements()[$tag]['class']);
        return [
            $tag,
            $classes,
        ];
    }
    
    /**
     * {@inheritdoc}
     */
    public function validateConfigurationForm(array &$form, FormStateInterface $form_state) {
        // Match the config schema structure at ckeditor5.plugin.ckeditor5_style.
        $form_value = $form_state->getValue('styles');
        [
            $styles,
            $invalid_lines,
        ] = self::parseStylesFormValue($form_value);
        if (!empty($invalid_lines)) {
            $line_numbers = array_keys($invalid_lines);
            $form_state->setError($form['styles'], $this->formatPlural(count($invalid_lines), 'Line @line-number does not contain a valid value. Enter a valid CSS selector containing one or more classes, followed by a pipe symbol and a label.', 'Lines @line-numbers do not contain a valid value. Enter a valid CSS selector containing one or more classes, followed by a pipe symbol and a label.', [
                '@line-number' => reset($line_numbers),
                '@line-numbers' => implode(', ', $line_numbers),
            ]));
        }
        $form_state->setValue('styles', $styles);
    }
    
    /**
     * Parses the line-based (for form) style configuration.
     *
     * @param string $form_value
     *   A string containing >=1 lines with on each line a CSS selector targeting
     *   1 tag with >=1 classes, a pipe symbol and a label. An example of a single
     *   line: `p.foo.bar|Foo bar paragraph`.
     *
     * @return array
     *   The parsed equivalent: a list of arrays with each containing:
     *   - label: the label after the pipe symbol, with whitespace trimmed
     *   - element: the CKEditor 5 element equivalent of the tag + classes
     *
     * @internal
     */
    private static function parseStylesFormValue(string $form_value) : array {
        $invalid_lines = [];
        $lines = explode("\n", $form_value);
        $styles = [];
        foreach ($lines as $index => $line) {
            if (empty(trim($line))) {
                continue;
            }
            // Parse the line.
            [
                $selector,
                $label,
            ] = array_map('trim', explode('|', $line));
            // Validate the selector.
            $selector_matches = [];
            // @see https://www.w3.org/TR/CSS2/syndata.html#:~:text=In%20CSS%2C%20identifiers%20(including%20element,hyphen%20followed%20by%20a%20digit
            if (!preg_match('/^([a-z][0-9a-zA-Z\\-]*)((\\.[a-zA-Z0-9\\x{00A0}-\\x{FFFF}\\-_]+)+)$/u', $selector, $selector_matches)) {
                $invalid_lines[$index + 1] = $line;
                continue;
            }
            // Parse selector into tag + classes and normalize.
            $tag = $selector_matches[1];
            $classes = array_filter(explode('.', $selector_matches[2]));
            $normalized = HTMLRestrictions::fromString(sprintf('<%s class="%s">', $tag, implode(' ', $classes)));
            $styles[] = [
                'label' => $label,
                'element' => $normalized->toCKEditor5ElementsArray()[0],
            ];
        }
        return [
            $styles,
            $invalid_lines,
        ];
    }
    
    /**
     * {@inheritdoc}
     */
    public function submitConfigurationForm(array &$form, FormStateInterface $form_state) {
        $this->configuration['styles'] = $form_state->getValue('styles');
    }
    
    /**
     * {@inheritdoc}
     */
    public function defaultConfiguration() {
        return [
            'styles' => [],
        ];
    }
    
    /**
     * {@inheritdoc}
     */
    public function getElementsSubset() : array {
        return array_column($this->configuration['styles'], 'element');
    }
    
    /**
     * {@inheritdoc}
     */
    public function getDynamicPluginConfig(array $static_plugin_config, EditorInterface $editor) : array {
        $definitions = [];
        foreach ($this->configuration['styles'] as $style) {
            [
                $tag,
                $classes,
            ] = self::getTagAndClasses(HTMLRestrictions::fromString($style['element']));
            // Transform configured styles to the configuration structure expected by
            // the CKEditor 5 Style plugin.
            $definitions[] = [
                'name' => $style['label'],
                'element' => $tag,
                'classes' => $classes,
            ];
        }
        return [
            'style' => [
                'definitions' => $definitions,
            ],
        ];
    }

}