<?php

/**
 * @file
 */

use Drupal\Component\Utility\Html;
use Drupal\Component\Utility\Unicode;
use Drupal\search\SearchTextProcessorInterface;

/**
 * Implements hook_theme_suggestions_HOOK().
 */
function search_theme_suggestions_search_result(array $variables): array {
  return ['search_result__' . $variables['plugin_id']];
}

/**
 * Implements hook_preprocess_HOOK() for block templates.
 */
function search_preprocess_block(&$variables): void {
  if ($variables['plugin_id'] == 'search_form_block') {
    $variables['attributes']['role'] = 'search';
  }
}

/**
 * @defgroup search Search interface
 * @{
 * The Drupal search interface manages a global search mechanism.
 *
 * Modules may plug into this system to provide searches of different types of
 * data. Most of the system is handled by the Search module, so this must be
 * enabled for all of the search features to work.
 *
 * There are two ways to interact with the search system:
 * - Specifically for searching nodes, you can implement
 *   hook_node_update_index() and hook_node_search_result(). However, note that
 *   the search system already indexes all visible output of a node; i.e.,
 *   everything displayed normally during node viewing. This is
 *   usually sufficient. You should only use this mechanism if you want
 *   additional, non-visible data to be indexed.
 * - Define a plugin implementing \Drupal\search\Plugin\SearchInterface and
 *   annotated as \Drupal\search\Annotation\SearchPlugin. This will create a
 *   search page type that users can use to set up one or more search pages.
 *   Each of these corresponds to a tab on the /search page, which can be
 *   used to perform searches. You will also need to implement the execute()
 *   method from the interface to perform the search. A base class is provided
 *   in \Drupal\search\Plugin\SearchPluginBase. For more information about
 *   plugins, see the @link plugin_api Plugin API topic. @endlink
 *
 * If your module needs to provide a more complicated search form, then you need
 * to implement it yourself. In that case, you may wish to define it as a local
 * task (tab) under the /search page (e.g. /search/my_module) so that users can
 * easily find it.
 *
 * @see plugin_api
 * @see annotation
 */

/**
 * Returns snippets from a piece of text, with search keywords highlighted.
 *
 * Used for formatting search results. All HTML tags will be stripped from
 * $text.
 *
 * @param string $keys
 *   A string containing a search query.
 * @param string $text
 *   The text to extract fragments from.
 * @param string|null $langcode
 *   Language code for the language of $text, if known.
 *
 * @return array
 *   A render array containing HTML for the excerpt.
 */
function search_excerpt($keys, $text, $langcode = NULL): array {
  // We highlight around non-indexable or CJK characters.
  $boundary_character = '[' . Unicode::PREG_CLASS_WORD_BOUNDARY . SearchTextProcessorInterface::PREG_CLASS_CJK . ']';
  $preceded_by_boundary = '(?<=' . $boundary_character . ')';
  $followed_by_boundary = '(?=' . $boundary_character . ')';

  // Extract positive keywords and phrases.
  preg_match_all('/ ("([^"]+)"|(?!OR)([^" ]+))/', ' ' . $keys, $matches);
  $keys = array_merge($matches[2], $matches[3]);

  // Prepare text by stripping HTML tags and decoding HTML entities.
  $text = strip_tags(str_replace(['<', '>'], [' <', '> '], $text));
  $text = Html::decodeEntities($text);
  $text_length = strlen($text);

  // Make a list of unique keywords that are actually found in the text,
  // which could be items in $keys or replacements that are equivalent through
  // \Drupal\search\SearchTextProcessorInterface::analyze().
  $temp_keys = [];
  foreach ($keys as $key) {
    $key = _search_find_match_with_simplify($key, $text, $boundary_character, $langcode);
    if (isset($key)) {
      // Quote slashes so they can be used in regular expressions.
      $temp_keys[] = preg_quote($key, '/');
    }
  }
  // Several keywords could have simplified down to the same thing, so pick
  // out the unique ones.
  $keys = array_unique($temp_keys);

  // Extract fragments of about 60 characters around keywords, bounded by word
  // boundary characters. Try to reach 256 characters, using second occurrences
  // if necessary.
  $ranges = [];
  $length = 0;
  $look_start = [];
  $remaining_keys = $keys;

  while ($length < 256 && !empty($remaining_keys)) {
    $found_keys = [];
    foreach ($remaining_keys as $key) {
      if ($length >= 256) {
        break;
      }

      // Remember where we last found $key, in case we are coming through a
      // second time.
      if (!isset($look_start[$key])) {
        $look_start[$key] = 0;
      }

      // See if we can find $key after where we found it the last time. Since
      // we are requiring a match on a word boundary, make sure $text starts
      // and ends with a space.
      $matches = [];
      if (preg_match('/' . $preceded_by_boundary . $key . $followed_by_boundary . '/iu', ' ' . $text . ' ', $matches, PREG_OFFSET_CAPTURE, $look_start[$key])) {
        $found_position = $matches[0][1];
        $look_start[$key] = $found_position + 1;
        // Keep track of which keys we found this time, in case we need to
        // pass through again to find more text.
        $found_keys[] = $key;

        // Locate a space before and after this match, leaving about 60
        // characters of context on each end.
        $before = strpos(' ' . $text, ' ', max(0, $found_position - 61));
        if ($before !== FALSE && $before <= $found_position) {
          if ($text_length > $found_position + 60) {
            $after = strrpos(substr($text, 0, $found_position + 60), ' ', $found_position);
          }
          else {
            $after = $text_length;
          }
          if ($after !== FALSE && $after > $found_position) {
            // Account for the spaces we added.
            $before = max($before - 1, 0);
            if ($before < $after) {
              // Save this range.
              $ranges[$before] = $after;
              $length += $after - $before;
            }
          }
        }
      }
    }
    // Next time through this loop, only look for keys we found this time,
    // if any.
    $remaining_keys = $found_keys;
  }

  if (empty($ranges)) {
    // We didn't find any keyword matches, so just return the first part of the
    // text. We also need to re-encode any HTML special characters that we
    // entity-decoded above.
    return [
      '#plain_text' => Unicode::truncate($text, 256, TRUE, TRUE),
    ];
  }

  // Sort the text ranges by starting position.
  ksort($ranges);

  // Collapse overlapping text ranges into one. The sorting makes it O(n).
  $new_ranges = [];
  $max_end = 0;
  foreach ($ranges as $this_from => $this_to) {
    $max_end = max($max_end, $this_to);
    if (!isset($working_from)) {
      // This is the first time through this loop: initialize.
      $working_from = $this_from;
      $working_to = $this_to;
      continue;
    }
    if ($this_from <= $working_to) {
      // The ranges overlap: combine them.
      $working_to = max($working_to, $this_to);
    }
    else {
      // The ranges do not overlap: save the working range and start a new one.
      $new_ranges[$working_from] = $working_to;
      $working_from = $this_from;
      $working_to = $this_to;
    }
  }
  // Save the remaining working range.
  $new_ranges[$working_from] = $working_to;

  // Fetch text within the combined ranges we found.
  $out = [];
  foreach ($new_ranges as $from => $to) {
    $out[] = substr($text, $from, $to - $from);
  }

  // Combine the text chunks with "…" separators. The "…" needs to be
  // translated. Let translators have the … separator text as one chunk.
  $ellipses = explode('@excerpt', t('… @excerpt … @excerpt …'));
  $text = (isset($new_ranges[0]) ? '' : $ellipses[0]) . implode($ellipses[1], $out) . (($max_end < strlen($text) - 1) ? $ellipses[2] : '');
  $text = Html::escape($text);

  // Highlight keywords. Must be done at once to prevent conflicts ('strong'
  // and '<strong>').
  $text = trim(preg_replace('/' . $preceded_by_boundary . '(?:' . implode('|', $keys) . ')' . $followed_by_boundary . '/iu', '<strong>\0</strong>', ' ' . $text . ' '));
  return [
    '#markup' => $text,
    '#allowed_tags' => ['strong'],
  ];
}

/**
 * @} End of "defgroup search".
 */

/**
 * Finds an appropriate keyword in text.
 *
 * @param string $key
 *   The keyword to find.
 * @param string $text
 *   The text to search for the keyword.
 * @param string $boundary
 *   Regular expression for the boundary character class (characters that
 *   indicate spaces between words).
 * @param string|null $langcode
 *   Language code for the language of $text, if known.
 *
 * @return string|null
 *   A segment of $text that is between word boundary characters that either
 *   matches $key directly, or matches $key when both this text segment and
 *   $key are processed by
 *   \Drupal\search\SearchTextProcessorInterface::analyze(). If a matching text
 *   segment is not located, NULL is returned.
 */
function _search_find_match_with_simplify($key, $text, $boundary, $langcode = NULL) {
  $preceded_by_boundary = '(?<=' . $boundary . ')';
  $followed_by_boundary = '(?=' . $boundary . ')';

  // See if $key appears as-is. When testing, make sure $text starts/ends with
  // a space, because we require $key to be surrounded by word boundary
  // characters.
  $temp = trim($key);
  if ($temp == '') {
    return NULL;
  }
  if (preg_match('/' . $preceded_by_boundary . preg_quote($temp, '/') . $followed_by_boundary . '/iu', ' ' . $text . ' ')) {
    return $temp;
  }

  // See if there is a match after lower-casing and removing diacritics in
  // both, which should preserve the string length.
  $new_text = mb_strtolower($text);
  $new_text = \Drupal::service('transliteration')->removeDiacritics($new_text);
  $new_key = mb_strtolower($temp);
  $new_key = \Drupal::service('transliteration')->removeDiacritics($new_key);
  if (preg_match('/' . $preceded_by_boundary . preg_quote($new_key, '/') . $followed_by_boundary . '/u', ' ' . $new_text . ' ')) {
    $position = mb_strpos($new_text, $new_key);
    return mb_substr($text, $position, mb_strlen($new_key));
  }

  // Run both text and key through text processor.
  /** @var \Drupal\search\SearchTextProcessorInterface $text_processor */
  $text_processor = \Drupal::service('search.text_processor');
  $simplified_key = trim($text_processor->analyze($key, $langcode));
  $simplified_text = trim($text_processor->analyze($text, $langcode));
  if ($simplified_key == '' || $simplified_text == '' || !str_contains($simplified_text, $simplified_key)) {
    // The simplified keyword and text do not match at all, or are empty.
    return NULL;
  }

  // Split $text into words, keeping track of where the word boundaries are.
  $words = preg_split('/' . $boundary . '+/u', $text, -1, PREG_SPLIT_OFFSET_CAPTURE);
  // Add an entry pointing to the end of the string, for the loop below.
  $words[] = ['', strlen($text)];

  // Using a binary search, find the earliest possible ending position in
  // $text where it will still match the keyword after applying
  // \Drupal\search\SearchTextProcessorInterface::analyze().
  $start_index = 0;
  $start_pos = $words[$start_index][1];
  $min_end_index = 1;
  $max_end_index = count($words) - 1;
  while ($max_end_index > $min_end_index) {
    // Check the index half way between min and max. See if we ended there,
    // if we would still have a match.
    $proposed_end_index = floor(($max_end_index + $min_end_index) / 2);
    $proposed_end_pos = $words[$proposed_end_index][1];
    // Since the split was done with preg_split(), the positions are byte counts
    // not character counts, so use substr() not mb_substr() here.
    $trial_text = trim($text_processor->analyze(substr($text, $start_pos, $proposed_end_pos - $start_pos), $langcode));
    if (str_contains($trial_text, $simplified_key)) {
      // The proposed endpoint is fine, text still matches.
      $max_end_index = $proposed_end_index;
    }
    else {
      // The proposed endpoint index is too early, so the earliest possible
      // OK ending point would be the next index.
      $min_end_index = $proposed_end_index + 1;
    }
  }

  // Now do the same for the starting position: using a binary search, find the
  // latest possible starting position in $text where it will still match the
  // keyword after applying
  // \Drupal\search\SearchTextProcessorInterface::analyze().
  $end_index = $min_end_index;
  $end_pos = $words[$end_index][1];
  $min_start_index = 0;
  $max_start_index = $end_index - 1;
  while ($max_start_index > $min_start_index) {
    // Check the index half way between min and max. See if we started there,
    // if we would still have a match.
    $proposed_start_index = ceil(($max_start_index + $min_start_index) / 2);
    $proposed_start_pos = $words[$proposed_start_index][1];
    // Since the split was done with preg_split(), the positions are byte counts
    // not character counts, so use substr() not mb_substr() here.
    $trial_text = trim($text_processor->analyze(substr($text, $proposed_start_pos, $end_pos - $proposed_start_pos), $langcode));
    if (str_contains($trial_text, $simplified_key)) {
      // The proposed start point is fine, text still matches.
      $min_start_index = $proposed_start_index;
    }
    else {
      // The proposed start point index is too late, so the latest possible
      // OK starting point would be the previous index.
      $max_start_index = $proposed_start_index - 1;
    }
  }
  $start_index = $max_start_index;

  // Return the matching text. We need to use substr() here and not the
  // mb_substr() function, because the indices in $words came from preg_split(),
  // so they are Unicode-safe byte positions, not character positions.
  return trim(substr($text, $words[$start_index][1], $words[$end_index][1] - $words[$start_index][1]));
}