FilterAutoP.php

<?php

namespace Drupal\filter\Plugin\Filter;

use Drupal\Core\StringTranslation\TranslatableMarkup;
use Drupal\filter\Attribute\Filter;
use Drupal\filter\FilterProcessResult;
use Drupal\filter\Plugin\FilterBase;
use Drupal\filter\Plugin\FilterInterface;

/**
 * Provides a filter to convert line breaks to HTML.
 */
class FilterAutoP extends FilterBase {
  
  /**
   * {@inheritdoc}
   */
  public function process($text, $langcode) {
    // All block level tags.
    $block = '(?:table|thead|tfoot|caption|col|colgroup|tbody|tr|td|th|div|dl|dd|dt|ul|ol|li|pre|select|option|form|map|area|blockquote|address|math|input|p|h[1-6]|fieldset|legend|hr|article|aside|details|figcaption|figure|footer|header|hgroup|menu|nav|section|summary)';
    // Split at opening and closing PRE, SCRIPT, STYLE, OBJECT, IFRAME tags and
    // comments. We don't apply any processing to the contents of these tags to
    // avoid messing up code. We look for matched pairs and allow basic nesting.
    // For example,
    // "processed<pre>ignored<script>ignored</script>ignored</pre>processed".
    $chunks = preg_split('@(<!--.*?-->|</?(?:pre|script|style|object|iframe|drupal-media|svg|!--)[^>]*>)@i', $text, -1, PREG_SPLIT_DELIM_CAPTURE);
    // Note: PHP ensures the array consists of alternating delimiters and
    // literals and begins and ends with a literal (inserting NULL as required).
    $ignore = FALSE;
    $ignore_tag = '';
    $output = '';
    foreach ($chunks as $i => $chunk) {
      if ($i % 2) {
        if (str_starts_with($chunk, '<!--')) {
          // Nothing to do, this is a comment.
          $output .= $chunk;
          continue;
        }
        // Opening or closing tag?
        $open = $chunk[1] != '/';
        [$tag] = preg_split('/[ >]/', substr($chunk, 2 - $open), 2);
        if (!$ignore) {
          if ($open) {
            $ignore = TRUE;
            $ignore_tag = $tag;
          }
        }
        elseif (!$open && $ignore_tag == $tag) {
          $ignore = FALSE;
          $ignore_tag = '';
        }
      }
      elseif (!$ignore) {
        // Skip if the next chunk starts with Twig theme debug.
        // @see twig_render_template()
        if (isset($chunks[$i + 1]) && $chunks[$i + 1] === '<!-- THEME DEBUG -->') {
          $chunk = rtrim($chunk, "\n");
          $output .= $chunk;
          continue;
        }
        // Skip if the preceding chunk was the end of a Twig theme debug.
        // @see \Drupal\Core\Template\TwigThemeEngine::renderTemplate()
        if (isset($chunks[$i - 1])) {
          if (str_starts_with($chunks[$i - 1], '<!-- BEGIN OUTPUT from ') || str_starts_with($chunks[$i - 1], '<!-- 💡 BEGIN CUSTOM TEMPLATE OUTPUT from ')) {
            $chunk = ltrim($chunk, "\n");
            $output .= $chunk;
            continue;
          }
        }
        // Just to make things a little easier, pad the end.
        $chunk = preg_replace('|\\n*$|', '', $chunk) . "\n\n";
        $chunk = preg_replace('|<br />\\s*<br />|', "\n\n", $chunk);
        // Space things out a little.
        $chunk = preg_replace('!(<' . $block . '[^>]*>)!', "\n\$1", $chunk);
        // Space things out a little.
        $chunk = preg_replace('!(</' . $block . '>)!', "\$1\n\n", $chunk);
        // Take care of duplicates.
        $chunk = preg_replace("/\n\n+/", "\n\n", $chunk);
        $chunk = preg_replace('/^\\n|\\n\\s*\\n$/', '', $chunk);
        // Make paragraphs, including one at the end.
        $chunk = '<p>' . preg_replace('/\\n\\s*\\n\\n?(.)/', "</p>\n<p>\$1", $chunk) . "</p>\n";
        // Problem with nested lists.
        $chunk = preg_replace("|<p>(<li.+?)</p>|", "\$1", $chunk);
        $chunk = preg_replace('|<p><blockquote([^>]*)>|i', "<blockquote\$1><p>", $chunk);
        $chunk = str_replace('</blockquote></p>', '</p></blockquote>', $chunk);
        // Under certain strange conditions it could create a P of entirely
        // whitespace.
        $chunk = preg_replace('|<p>\\s*</p>\\n?|', '', $chunk);
        $chunk = preg_replace('!<p>\\s*(</?' . $block . '[^>]*>)!', "\$1", $chunk);
        $chunk = preg_replace('!(</?' . $block . '[^>]*>)\\s*</p>!', "\$1", $chunk);
        // Make line breaks.
        $chunk = preg_replace('|(?<!<br />)\\s*\\n|', "<br />\n", $chunk);
        $chunk = preg_replace('!(</?' . $block . '[^>]*>)\\s*<br />!', "\$1", $chunk);
        $chunk = preg_replace('!<br />(\\s*</?(?:p|li|div|dl|dd|dt|th|pre|td|ul|ol)>)!', '$1', $chunk);
        $chunk = preg_replace('/&([^#])(?![A-Za-z0-9]{1,8};)/', '&amp;$1', $chunk);
      }
      $output .= $chunk;
    }
    return new FilterProcessResult($output);
  }
  
  /**
   * {@inheritdoc}
   */
  public function tips($long = FALSE) {
    if ($long) {
      return $this->t('Lines and paragraphs are automatically recognized. The &lt;br /&gt; line break, &lt;p&gt; paragraph and &lt;/p&gt; close paragraph tags are inserted automatically. If paragraphs are not recognized simply add a couple of blank lines.');
    }
    else {
      return $this->t('Lines and paragraphs break automatically.');
    }
  }

}