plugin.php

<?php

/**
 * Plugin Name:   SimpleTOC - Table of Contents Block
 * Plugin URI:    https://marc.tv/simpletoc-wordpress-inhaltsverzeichnis-plugin-gutenberg/
 * Description:   SEO-friendly Table of Contents Gutenberg block. No JavaScript and no CSS means faster loading.
 * Version:       6.5.0
 * Author:        Marc Tönsing
 * Author URI:    https://toensing.com
 * Text Domain:   simpletoc
 * License: GPL   v2 or later
 * License URI:   http://www.gnu.org/licenses/gpl-2.0.html
 *
 */

require_once plugin_dir_path(__FILE__) . 'simpletoc-admin-settings.php';

/**
 * Prevents direct execution of the plugin file.
 * If a WordPress function does not exist, it means that the file has not been run by WordPress.
 */
if (!function_exists('add_filter')) {
    header('Status: 403 Forbidden');
    header('HTTP/1.1 403 Forbidden');
    exit;
}

/**
 * Registers the SimpleTOC block, adds a filter for plugin row meta, and sets script translations.
 *
 * This function registers the SimpleTOC block by specifying the build directory and render callback function.
 * It also sets the script translations for the block editor script and adds a filter for the plugin row meta.
 */
function register_simpletoc_block()
{

    if (function_exists('wp_set_script_translations')) {
        wp_set_script_translations('simpletoc-toc-editor-script', 'simpletoc');
    }

    add_filter('plugin_row_meta', __NAMESPACE__ . '\\simpletoc_plugin_meta', 10, 2);

    register_block_type(__DIR__ . '/build', [
    'render_callback' => __NAMESPACE__ . '\\render_callback_simpletoc'
    ]);
}

add_action('init', 'register_simpletoc_block');

/**
 * Inject potentially missing translations into the block-editor i18n
 * collection.
 *
 * This keeps the plugin backwards compatible, in case the user did not
 * update translations on their website (yet).
 *
 * @param string|false|null $translations JSON-encoded translation data. Default null.
 * @param string|false      $file         Path to the translation file to load. False if there isn't one.
 * @param string            $handle       Name of the script to register a translation domain to.
 * @param string            $domain       The text domain.
 *
 * @return string|false|null JSON string
 */
add_filter('load_script_translations', function ($translations, $file, $handle, $domain) {
    if ('simpletoc' === $domain && $translations) {
        // List of translations that we inject into the block-editor JS.
        $dynamic_translations = [
        'Table of Contents' => __('Table of Contents', 'simpletoc'),
        ];

        $changed = false;
        $obj = json_decode($translations, true);

        // Confirm that the translation JSON is valid.
        if (isset($obj['locale_data']) && isset($obj['locale_data']['messages'])) {
            $messages = $obj['locale_data']['messages'];

            // Inject dynamic translations, when needed.
            foreach ($dynamic_translations as $key => $locale) {
                if (empty($messages[$key])
                || !is_array($messages[$key])
                || !array_key_exists(0, $messages[$key])
                || $locale !== $messages[$key][0]
                ) {
                    $messages[$key] = [$locale];
                    $changed = true;
                }
            }

            // Only modify the translations string when locales did change.
            if ($changed) {
                $obj['locale_data']['messages'] = $messages;
                $translations = wp_json_encode($obj);
            }
        }
    }

    return $translations;
}, 10, 4);

/**
 * Sets the default value of translatable attributes.
 *
 * Values inside block.json are static strings that are not translated. This
 * filter inserts relevant translations i
 *
 * @param array $settings Array of determined settings for registering a block type.
 * @param array $metadata Metadata provided for registering a block type.
 *
 * @return array Modified settings array.
 */
add_filter('block_type_metadata_settings', function ($settings, $metadata) {
    if ('simpletoc/toc' === $metadata['name']) {
        $settings['attributes']['title_text']['default'] = __('Table of Contents', 'simpletoc');
    }

    return $settings;
}, 10, 2);

/**
 * Filter to add plugins to the TOC list for Rank Math plugin
 *
 * @param array TOC plugins.
 */
add_filter('rank_math/researches/toc_plugins', function ($toc_plugins) {
    $toc_plugins['simpletoc/plugin.php'] = 'SimpleTOC';
    return $toc_plugins;
});

/**
* Adds IDs to the headings of the provided post content using a recursive block structure.
* @param string $content The content to add IDs to
* @return string The content with IDs added to its headings
*/
function simpletoc_add_ids_to_content($content)
{

    $blocks = parse_blocks($content);

    $blocks = add_ids_to_blocks_recursive($blocks);

    $content = serialize_blocks($blocks);

    return $content;
}

add_filter('the_content', 'simpletoc_add_ids_to_content', 1);

/**
* Recursively adds IDs to the headings of a nested block structure.
* @param array $blocks The blocks to add IDs to
* @return array The blocks with IDs added to their headings
*/
function add_ids_to_blocks_recursive($blocks)
{

    foreach ($blocks as &$block) {
        if (isset($block['blockName']) && ($block['blockName'] === 'core/heading' || $block['blockName'] === 'generateblocks/headline') && isset($block['innerHTML']) && isset($block['innerContent']) && isset($block['innerContent'][0])) {
            $block['innerHTML'] = add_anchor_attribute($block['innerHTML']);
            $block['innerContent'][0] = add_anchor_attribute($block['innerContent'][0]);
        } elseif (isset($block['attrs']['ref'])) {
            // search in reusable blocks (this is not finished because I ran out of ideas.)
            // $reusable_block_id = $block['attrs']['ref'];
            // $reusable_block_content = parse_blocks(get_post($reusable_block_id)->post_content);
        } elseif (!empty($block['innerBlocks'])) {
            // search in groups
            $block['innerBlocks'] = add_ids_to_blocks_recursive($block['innerBlocks']);
        }
    }

    return $blocks;
}

/**
 * Renders a Table of Contents block for a post
 * @param array $attributes An array of attributes for the Table of Contents block
 * @return string The HTML output for the Table of Contents block
 */
function render_callback_simpletoc($attributes)
{
    $is_backend = defined('REST_REQUEST') && REST_REQUEST && 'edit' === filter_input(INPUT_GET, 'context');
    $title_text = $attributes['title_text'] ? esc_html(trim($attributes['title_text'])) : __('Table of Contents', 'simpletoc');
    $alignclass = !empty($attributes['align']) ? 'align' . $attributes['align'] : '';
    $className = !empty($attributes['className']) ? strip_tags($attributes['className']) : '';
    $title_level = $attributes['title_level'];

    $wrapper_enabled = apply_filters('simpletoc_wrapper_enabled', false) || get_option('simpletoc_wrapper_enabled') == 1 || get_option('simpletoc_accordion_enabled') == 1;

    $wrapper_attrs = get_block_wrapper_attributes(['class' => 'simpletoc']);
    $pre_html = (!empty($className) || $wrapper_enabled || $attributes['accordion'] || $attributes['wrapper']) ? '<div role="navigation" aria-label="' . __('Table of Contents', 'simpletoc') . '" ' . $wrapper_attrs . '>' : '';
    $post_html = (!empty($className) || $wrapper_enabled || $attributes['accordion'] || $attributes['wrapper']) ? '</div>' : '';

    $post = get_post();
    $blocks = !is_null($post) && !is_null($post->post_content) ? parse_blocks($post->post_content) : '';

    $headings = array_reverse(filter_headings_recursive($blocks));
    $headings = simpletoc_add_pagenumber($blocks, $headings);
    $headings_clean = array_map('trim', $headings);
    $toc_html = generate_toc($headings_clean, $attributes);

    if (empty($blocks)) {
        return get_empty_blocks_message($is_backend, $attributes, $title_level, $alignclass, $title_text, __('No blocks found.', 'simpletoc'), __('Save or update post first.', 'simpletoc'));
    }

    if (empty($headings_clean)) {
        return get_empty_blocks_message($is_backend, $attributes, $title_level, $alignclass, $title_text, __('No headings found.', 'simpletoc'), __('Save or update post first.', 'simpletoc'));
    }

    if (empty($toc_html)) {
        return get_empty_blocks_message($is_backend, $attributes, $title_level, $alignclass, $title_text, __('No headings found.', 'simpletoc'), __('Check minimal and maximum level block settings.', 'simpletoc'));
    }

    return $pre_html . $toc_html . $post_html;
}

/**
 * Generates an HTML message for empty blocks cases in the Table of Contents.
 *
 * @param bool   $is_backend    Indicates if the request is from the backend (i.e., the WordPress editor).
 * @param array  $attributes    An array of attributes for the Table of Contents block.
 * @param int    $title_level   The heading level for the Table of Contents title.
 * @param string $alignclass    The CSS class for alignment of the Table of Contents block.
 * @param string $title_text    The text for the Table of Contents title.
 * @param string $warning_text1 The first part of the warning message to be displayed.
 * @param string $warning_text2 The second part of the warning message to be displayed.
 *
 * @return string The HTML output for the empty blocks message.
 */
function get_empty_blocks_message($is_backend, $attributes, $title_level, $alignclass, $title_text, $warning_text1, $warning_text2)
{
    $html = '';

    if ($is_backend) {
        $html .= sprintf('<h%d class="simpletoc-title %s">%s</h%d>', $title_level, $alignclass, $title_text, $title_level);
        $html .= sprintf('<p class="components-notice is-warning %s">%s %s</p>', $alignclass, $warning_text1, $warning_text2);
    }

    return $html;
}

/**
* Adds page numbers to headings in the provided blocks array.
* @param array $blocks The array of blocks to process.
* @param array $headings The array of headings to add page numbers to.
* @return array The modified headings array with page numbers added.
*/
function simpletoc_add_pagenumber($blocks, $headings)
{
    $pages = 1;

    if (!is_array($blocks)) {
        return $headings;
    }

    foreach ($blocks as $block => $innerBlock) {
        // count nextpage blocks
        if (isset($blocks[$block]['blockName']) && $blocks[$block]['blockName'] === 'core/nextpage') {
            $pages++;
        }

        if (isset($blocks[$block]['blockName']) && $blocks[$block]["blockName"] === 'core/heading') {
            // make sure its a headline.
            foreach ($headings as $heading => &$innerHeading) {
                if ($innerHeading == $blocks[$block]["innerHTML"]) {
                    $innerHeading = preg_replace("/(<h1|<h2|<h3|<h4|<h5|<h6)/i", '$1 data-page="' . $pages . '"', $blocks[$block]["innerHTML"]);
                }
            }
        }
    }
    return $headings;
}

/**
* Return all headings with a recursive walk through all blocks.
* This includes groups and reusable block with groups within reusable blocks.
* @var array[] $blocks
* @return array[]
*/
function filter_headings_recursive($blocks)
{
    $arr = [];

    if (!is_array($blocks)) {
        return $arr;
    }

    // allow developers to ignore specific blocks
    $ignored_blocks = apply_filters('simpletoc_excluded_blocks', []);

    foreach ($blocks as $innerBlock) {
        if (is_array($innerBlock)) {
            // if block is ignored, skip
            if (isset($innerBlock['blockName']) && in_array($innerBlock['blockName'], $ignored_blocks)) {
                continue;
            }

            if (isset($innerBlock['attrs']['ref'])) {
                // search in reusable blocks
                $post = get_post($innerBlock['attrs']['ref']);
                if ($post) {
                    $e_arr = parse_blocks($post->post_content);
                    $arr = array_merge(filter_headings_recursive($e_arr), $arr);
                }
            } else {
                // search in groups
                $arr = array_merge(filter_headings_recursive($innerBlock), $arr);
            }
        } else {
            if (isset($blocks['blockName']) && ($blocks['blockName'] === 'core/heading') && $innerBlock !== 'core/heading') {
                // make sure it's a headline.
                if (preg_match("/(<h1|<h2|<h3|<h4|<h5|<h6)/i", $innerBlock)) {
                    $arr[] = $innerBlock;
                }
            }

            if (isset($blocks['blockName']) && ($blocks['blockName'] === 'generateblocks/headline') && $innerBlock !== 'core/heading') {
                // make sure it's a headline.
                if (preg_match("/(<h1|<h2|<h3|<h4|<h5|<h6)/i", $innerBlock)) {
                    $arr[] = $innerBlock;
                }
            }
        }
    }

    return $arr;
}

/**
* Sanitizes a string to be used as an anchor attribute in HTML by removing punctuation, non-breaking spaces, umlauts, and accents,
* and replacing whitespace and other characters with dashes.
* @param string $string The input string to be sanitized.
* @return string The sanitized string encoded for use in a URL.
*/
function simpletoc_sanitize_string($string)
{
    // remove punctuation
    $zero_punctuation = preg_replace("/\p{P}/u", "", $string);
    // remove non-breaking spaces
    $html_wo_nbs = str_replace("&nbsp;", " ", $zero_punctuation);
    // remove umlauts and accents
    $string_without_accents = remove_accents($html_wo_nbs);
    // Sanitizes a title, replacing whitespace and a few other characters with dashes.
    $sanitized_string = sanitize_title_with_dashes($string_without_accents);
    // Encode for use in an url
    $urlencoded = urlencode($sanitized_string);
    return $urlencoded;
}

/**
* Add additional plugin meta links to the SimpleTOC plugin page.
* @param array $links An array of plugin meta links.
* @param string $file The plugin file path.
* @return array The modified array of plugin meta links.
*/
function simpletoc_plugin_meta($links, $file)
{

    if (false !== strpos($file, 'simpletoc')) {
        $links = array_merge($links, array('<a href="https://wordpress.org/support/plugin/simpletoc">' . __('Support', 'simpletoc') . '</a>'));
        $links = array_merge($links, array('<a href="https://marc.tv/out/donate">' . __('Donate', 'simpletoc') . '</a>'));
        $links = array_merge($links, array('<a href="https://wordpress.org/support/plugin/simpletoc/reviews/#new-post">' . __('Write a review', 'simpletoc') . '&nbsp;⭐️⭐️⭐️⭐️⭐️</a>'));
    }

    return $links;
}

/**
* Adds an ID attribute to all Heading tags in the provided HTML.
* @param string $html The HTML content to modify
* @return string The modified HTML content with ID attributes added to the Heading tags
*/
function add_anchor_attribute($html)
{

    // remove non-breaking space entites from input HTML
    $html_wo_nbs = str_replace("&nbsp;", " ", $html);

    // Thank you Nick Diego
    if (!$html_wo_nbs) {
        return $html;
    }

    libxml_use_internal_errors(true);
    $dom = new \DOMDocument();
    @$dom->loadHTML('<?xml version="1.0" encoding="UTF-8"?>' . "\n" . $html_wo_nbs, LIBXML_HTML_NOIMPLIED | LIBXML_HTML_NODEFDTD);

    // use xpath to select the Heading html tags.
    $xpath = new \DOMXPath($dom);
    $tags = $xpath->evaluate("//*[self::h1 or self::h2 or self::h3 or self::h4 or self::h5 or self::h6]");

    // Loop through all the found tags
    foreach ($tags as $tag) {
        // if tag already has an attribute "id" defined, no need for creating a new one
        if (!empty($tag->getAttribute('id'))) {
            continue;
        }
        // Set id attribute
        $heading_text = trim(strip_tags($html));
        $anchor = simpletoc_sanitize_string($heading_text);
        $tag->setAttribute("id", $anchor);
    }

    // Save the HTML changes
    $content = $dom->saveHTML($dom->documentElement);

    return $content;
}

/**
* Generates a table of contents based on the provided headings and attributes
* @param array $headings An array of headings to include in the table of contents
* @param array $attributes An array of attributes to customize the output
* @return string The generated table of contents as HTML
*/
function generate_toc($headings, $attributes)
{
    $list = '';
    $html = '';
    $min_depth = 6;
    $initial_depth = 6;
    $align_class = isset($attributes['align']) ? 'align' . $attributes['align'] : '';
    $styles = $attributes['remove_indent'] ? 'style="padding-left:0;list-style:none;"' : '';
    $list_type = $attributes['use_ol'] ? 'ol' : 'ul';
    $global_absolut_urls_enabled = get_option('simpletoc_absolute_urls_enabled', false);
    $absolute_url = $attributes['use_absolute_urls'] || $global_absolut_urls_enabled ? get_permalink() : '';

    list($min_depth, $initial_depth) = find_min_depth($headings, $attributes);

    $item_count = 0;

    foreach ($headings as $line => $headline) {
        $this_depth = (int)$headings[$line][2];
        $next_depth = isset($headings[$line + 1][2]) ? (int)$headings[$line + 1][2] : '';
        $exclude_headline = should_exclude_headline($headline, $attributes, $this_depth);
        $title = trim(strip_tags($headline));
        $customId = extract_id($headline);
        $link = $customId ? $customId : simpletoc_sanitize_string($title);

        if (!$exclude_headline) {

            $item_count++;
            open_list($list, $list_type, $min_depth, $this_depth);
            $page = get_page_number_from_headline($headline);
            $list .= "<a href=\"" . $absolute_url . $page . "#" . $link . "\">" . $title . "</a>" . PHP_EOL;

        }
        close_list($list, $list_type, $min_depth, $attributes['min_level'], $attributes['max_level'], $next_depth, $line, count($headings) - 1, $initial_depth, $this_depth);

    }

    $html = add_accordion_start($html, $attributes, $item_count, $align_class);
    $html = add_hidden_markup_start($html, $attributes, $item_count, $align_class);
    $html = add_smooth($html, $attributes);


    // Add the table of contents list to the output if the list is not empty.
    if (!empty($list)) {
        $html_class = 'simpletoc-list';
        if (!empty($align_class)) {
            $html_class .= " $align_class";
        }

        $html_style = '';
        if (!empty($styles)) {
            $html_style = " $styles";
        }

        $html .= "<$list_type class=\"$html_class\"$html_style>\n$list</li></$list_type>";
    }

    $html = add_accordion_end($html, $attributes);
    $html = add_hidden_markup_end($html, $attributes);

    // return an emtpy string if stripped result is empty
    if (empty(trim(strip_tags($html)))) {
        $html = '';
    }

    return $html;
}

/**
* Finds the minimum depth level of headings in the provided array and adjusts it based on the provided attributes
* @param array $headings An array of headings to search through
* @param array $attributes An array of attributes to adjust the minimum depth level
* @return array An array containing the minimum depth level and the initial depth level
*/
function find_min_depth($headings, $attributes)
{
    $min_depth = 6;
    $initial_depth = 6;

    foreach ($headings as $line => $headline) {
        if ($min_depth > $headings[$line][2]) {
            $min_depth = (int)$headings[$line][2];
            $initial_depth = $min_depth;
        }
    }

    if ($attributes['min_level'] > $min_depth) {
        $min_depth = $attributes['min_level'];
        $initial_depth = $min_depth;
    }

    return [$min_depth, $initial_depth];
}

/**
* Determines if a given headline should be excluded based on the provided attributes
* @param string $headline The headline to check for exclusion
* @param array $attributes An array of attributes to use for exclusion
* @param int $this_depth The depth level of the headline
* @return bool True if the headline should be excluded, false otherwise
*/
function should_exclude_headline($headline, $attributes, $this_depth)
{
    $exclude_headline = false;
    preg_match('/class="([^"]+)"/', $headline, $matches);
    if (!empty($matches[1]) && strpos($matches[1], 'simpletoc-hidden') !== false) {
        $exclude_headline = true;
    }

    return ($this_depth > $attributes['max_level'] || $exclude_headline || $this_depth < $attributes['min_level']);
}

/**
* The open_list function appends a new list item to the global $list variable, adding necessary opening tags if needed to maintain the correct nesting of the list.
* @param string &$list The global list variable to append the new list item to.
* @param string $list_type The type of list to be created, either "ul" (unordered list) or "ol" (ordered list).
* @param int &$min_depth The minimum depth of headings that should be included in the table of contents.
* @param int $this_depth The depth of the current heading being processed.
* @return void The function modifies the input $list variable directly.
*/
function open_list(&$list, $list_type, &$min_depth, $this_depth)
{
    if ($this_depth == $min_depth) {
        $list .= "<li>";
    } else {
        for ($min_depth; $min_depth < $this_depth; $min_depth++) {
            $list .= "\n<" . $list_type . "><li>\n";
        }
    }
}

/**
* Closes an HTML list tag and updates the list string and minimum depth variable as necessary.
* @param string $list A reference to the list string being built.
* @param string $list_type The type of list tag being used (ul or ol).
* @param int $min_depth A reference to the minimum depth variable.
* @param int $min_depth Minimum depth setting, which is a low number like 1.
* @param int $max_depth Maximum depth setting, which is a high number like 6.
* @param int|null $next_depth The depth of the next list item, or null if this is the last item.
* @param int $line The index of the current list item.
* @param int $last_line The index of the last list item.
* @param int $initial_depth The initial depth of the list.
* @param int $this_depth The depth of the current list item.
* @return void
*/
function close_list(&$list, $list_type, &$min_depth, $min_level, $max_level, $next_depth, $line, $last_line, $initial_depth, $this_depth)
{
    if ($line !== $last_line) {
        $list .=  PHP_EOL;
        if($next_depth < $this_depth) {
            // Next heading goes back shallower in the ToC!
            if($next_depth >= $min_level) {
                // Next heading is within min depth bounds and WILL get ToC'd
                // Close this item and step back shallower in the ToC.
                for ($min_depth; $min_depth > $next_depth; $min_depth--) {
                    $list .= "</li>\n</" . $list_type . ">\n";
                }
            } else {
                // SKIP CLOSING! Next heading won't be included in the ToC at all.
            }
        } elseif($next_depth === $this_depth) {
            // Next heading is exactly as deep. Not going shallower or deeper in the ToC hierarchy.
            // E.g. this is h3, next is h3
            if ($next_depth < $min_level) {
                // E.g. this is h3, next is h3, min is h2
                // This heading didn't open a ToC item. Nothing to close.
            } else {
                // SKIP CLOSING! Next heading will open a new sub-list in the ToC.
                $list .= "</li>\n";
            }
        } else {
            // Next heading is deeper in the ToC.
            if ($next_depth <= $max_level) {
                // Next deeper heading is within bounds and will open a new sub-list. Leave this one open.
                // E.g. this is h3, next is h4, min is h2, max is h5
            } else {
                // Next heading is too deep and will be ignored. We'll close out coming up or finishing the ToC.
                // E.g. this is h3, next is h4, max is h3
            }
        }
    } else {
        // This is the last line of the ToC. Close out the whole thing.
        // IMPORTANT NOTE: The overall ToC list will be wrapped in a list element and closed out.
        for ($initial_depth; $initial_depth < $this_depth; $initial_depth++) {
            $list .= "</li>\n</" . $list_type . ">\n";
        }
    }
}

/**
* Adds smooth scrolling styles to the output HTML, if enabled by global option or block attribute.
* @param string $html The HTML string to which the styles will be added.
* @param array $attributes An array of block attributes.
* @return string The modified HTML string with the added smooth scrolling styles.
*/
function add_smooth($html, $attributes)
{
    // Add smooth scrolling styles, if enabled by global option or block attribute
    $isSmoothEnabled = $attributes['add_smooth'] || get_option('simpletoc_smooth_enabled') == 1;
    $html .= $isSmoothEnabled ? '<style>html { scroll-behavior: smooth; }</style>' : '';

    return $html;
}

/**
* Enqueues the necessary CSS and JS files for the accordion functionality on the frontend.
*/
function enqueue_accordion_frontend()
{
    wp_enqueue_script(
        'simpletoc-accordion',
        plugin_dir_url(__FILE__) . 'assets/accordion.js',
        array(),
        '6.4.3',
        true
    );

    wp_enqueue_style(
        'simpletoc-accordion',
        plugin_dir_url(__FILE__) . 'assets/accordion.css',
        array(),
        '6.4.3'
    );
}

function add_hidden_markup_start($html, $attributes, $itemcount, $alignclass) {
    $isHiddenEnabled = $attributes['hidden'];

    if ($isHiddenEnabled) {
        $titleText = esc_html(trim($attributes['title_text'])) ?: __('Table of Contents', 'simpletoc');
        $hiddenStart = '<details id="simpletoc-details" class="simpletoc" aria-labelledby="simpletoc-title">
        <summary style="cursor: pointer;">' . $titleText . '</summary>';
        $html .= $hiddenStart;
    }   

    // If there are no items in the table of contents, return an empty string
    if ($itemcount < 1) {
        return '';
    }

    return $html;
}

function add_hidden_markup_end($html, $attributes)
{
    $isHiddenEnabled = $attributes['hidden'];

    if ($isHiddenEnabled) {
        $html .= '</details>';
    }

    return $html;
}

/**
* Adds the opening HTML tag(s) for the accordion element and the table of contents title, if applicable.
* @param string $html The HTML string to add the opening tag(s) to
* @param array $attributes The attributes of the table of contents block
* @param int $itemcount The number of items in the table of contents
* @param string $alignclass The alignment class for the table of contents block
*/
function add_accordion_start($html, $attributes, $itemcount, $alignclass)
{
    // Check if accordion is enabled either through the function arguments or the options
    $isAccordionEnabled = $attributes['accordion'] || get_option('simpletoc_accordion_enabled') == 1;
    $isHiddenEnabled = $attributes['hidden'];
    $is_backend = defined('REST_REQUEST') && REST_REQUEST && 'edit' === filter_input(INPUT_GET, 'context');

    // Start and end HTML for accordion, if enabled
    $accordionStart = '';
    if ($isAccordionEnabled) {
        if(!$is_backend) {
            //enqueue_accordion_frontend();
        }
        $titleText = esc_html(trim($attributes['title_text'])) ?: __('Table of Contents', 'simpletoc');
        $accordionStart = '<h2 style="margin: 0;"><button type="button" aria-expanded="false" aria-controls="simpletoc-content-container" class="simpletoc-collapsible">' . $titleText . '<span class="simpletoc-icon" aria-hidden="true"></span></button></h2><div id="simpletoc-content-container" class="simpletoc-content">';
    }

    // Add the accordion start HTML to the output
    $html .= $accordionStart;

    // Add the table of contents title, if not hidden and not in accordion mode
    $showTitle = !$attributes['no_title'] && !$isAccordionEnabled && !$isHiddenEnabled;
    if ($showTitle) {
        $titleTag = $attributes['title_level'] > 0 ? "h{$attributes['title_level']}" : 'p';
        $html_class = 'simpletoc-title';

        if (!empty($alignclass)) {
            $html_class .= " $alignclass";
        }

        $html = "<$titleTag class=\"$html_class\">{$attributes["title_text"]}</$titleTag>\n";
    }

    // If there are no items in the table of contents, return an empty string
    if ($itemcount < 1) {
        return '';
    }

    return $html;
}

/**
* Adds the closing HTML tag(s) for the accordion element if the accordion is enabled.
* @param string $html The HTML string to add the closing tag(s) to
* @param array $attributes The attributes of the table of contents block
* @return string The modified HTML string with the closing tag(s) added
*/
function add_accordion_end($html, $attributes)
{
    // Check if accordion is enabled either through the function arguments or the options
    $isAccordionEnabled = $attributes['accordion'] || get_option('simpletoc_accordion_enabled') == 1;

    if ($isAccordionEnabled) {
        $html .= '</div>';
    }

    return $html;
}

/**
* Extracts the ID value from the provided heading HTML string.
* @param string $headline The heading HTML string to extract the ID value from
* @return mixed Returns the extracted ID value, or false if no ID value is found
*/
function extract_id($headline)
{
    $pattern = '/id="([^"]*)"/';
    preg_match($pattern, $headline, $matches);
    $idValue = $matches[1] ?? false;

    if ($idValue != false) {
        return  $idValue;
    }
}

/**
* Gets the page number from a headline string.
* @param string $headline The headline string.
* @return string The page number (in the format "X/") if it exists and is greater than 1, or an empty string otherwise.
*/
function get_page_number_from_headline($headline)
{
    $dom = new \DOMDocument();

    @$dom->loadHTML('<?xml version="1.0" encoding="UTF-8"?>' . "\n" . $headline, LIBXML_HTML_NOIMPLIED | LIBXML_HTML_NODEFDTD);

    $xpath = new \DOMXPath($dom);
    $nodes = $xpath->query('//*/@data-page');

    if (isset($nodes[0]) && $nodes[0]->nodeValue > 1) {
        $pageNumber = $nodes[0]->nodeValue . '/';
        return esc_html($pageNumber);
    } else {
        return '';
    }
}