search.module

<?php
// $Id$

/**
 * @file
 * Enables site-wide keyword searching.
 */

/**
 * Matches Unicode character classes to exclude from the search index.
 *
 * See: http://www.unicode.org/Public/UNIDATA/UCD.html#General_Category_Values
 *
 * The index only contains the following character classes:
 * Lu     Letter, Uppercase
 * Ll     Letter, Lowercase
 * Lt     Letter, Titlecase
 * Lo     Letter, Other
 * Nd     Number, Decimal Digit
 * No     Number, Other
 */
define('PREG_CLASS_SEARCH_EXCLUDE',
'\x{0}-\x{2f}\x{3a}-\x{40}\x{5b}-\x{60}\x{7b}-\x{bf}\x{d7}\x{f7}\x{2b0}-'.
'\x{385}\x{387}\x{3f6}\x{482}-\x{489}\x{559}-\x{55f}\x{589}-\x{5c7}\x{5f3}-'.
'\x{61f}\x{640}\x{64b}-\x{65e}\x{66a}-\x{66d}\x{670}\x{6d4}\x{6d6}-\x{6ed}'.
'\x{6fd}\x{6fe}\x{700}-\x{70f}\x{711}\x{730}-\x{74a}\x{7a6}-\x{7b0}\x{901}-'.
'\x{903}\x{93c}\x{93e}-\x{94d}\x{951}-\x{954}\x{962}-\x{965}\x{970}\x{981}-'.
'\x{983}\x{9bc}\x{9be}-\x{9cd}\x{9d7}\x{9e2}\x{9e3}\x{9f2}-\x{a03}\x{a3c}-'.
'\x{a4d}\x{a70}\x{a71}\x{a81}-\x{a83}\x{abc}\x{abe}-\x{acd}\x{ae2}\x{ae3}'.
'\x{af1}-\x{b03}\x{b3c}\x{b3e}-\x{b57}\x{b70}\x{b82}\x{bbe}-\x{bd7}\x{bf0}-'.
'\x{c03}\x{c3e}-\x{c56}\x{c82}\x{c83}\x{cbc}\x{cbe}-\x{cd6}\x{d02}\x{d03}'.
'\x{d3e}-\x{d57}\x{d82}\x{d83}\x{dca}-\x{df4}\x{e31}\x{e34}-\x{e3f}\x{e46}-'.
'\x{e4f}\x{e5a}\x{e5b}\x{eb1}\x{eb4}-\x{ebc}\x{ec6}-\x{ecd}\x{f01}-\x{f1f}'.
'\x{f2a}-\x{f3f}\x{f71}-\x{f87}\x{f90}-\x{fd1}\x{102c}-\x{1039}\x{104a}-'.
'\x{104f}\x{1056}-\x{1059}\x{10fb}\x{10fc}\x{135f}-\x{137c}\x{1390}-\x{1399}'.
'\x{166d}\x{166e}\x{1680}\x{169b}\x{169c}\x{16eb}-\x{16f0}\x{1712}-\x{1714}'.
'\x{1732}-\x{1736}\x{1752}\x{1753}\x{1772}\x{1773}\x{17b4}-\x{17db}\x{17dd}'.
'\x{17f0}-\x{180e}\x{1843}\x{18a9}\x{1920}-\x{1945}\x{19b0}-\x{19c0}\x{19c8}'.
'\x{19c9}\x{19de}-\x{19ff}\x{1a17}-\x{1a1f}\x{1d2c}-\x{1d61}\x{1d78}\x{1d9b}-'.
'\x{1dc3}\x{1fbd}\x{1fbf}-\x{1fc1}\x{1fcd}-\x{1fcf}\x{1fdd}-\x{1fdf}\x{1fed}-'.
'\x{1fef}\x{1ffd}-\x{2070}\x{2074}-\x{207e}\x{2080}-\x{2101}\x{2103}-\x{2106}'.
'\x{2108}\x{2109}\x{2114}\x{2116}-\x{2118}\x{211e}-\x{2123}\x{2125}\x{2127}'.
'\x{2129}\x{212e}\x{2132}\x{213a}\x{213b}\x{2140}-\x{2144}\x{214a}-\x{2b13}'.
'\x{2ce5}-\x{2cff}\x{2d6f}\x{2e00}-\x{3005}\x{3007}-\x{303b}\x{303d}-\x{303f}'.
'\x{3099}-\x{309e}\x{30a0}\x{30fb}-\x{30fe}\x{3190}-\x{319f}\x{31c0}-\x{31cf}'.
'\x{3200}-\x{33ff}\x{4dc0}-\x{4dff}\x{a015}\x{a490}-\x{a716}\x{a802}\x{a806}'.
'\x{a80b}\x{a823}-\x{a82b}\x{d800}-\x{f8ff}\x{fb1e}\x{fb29}\x{fd3e}\x{fd3f}'.
'\x{fdfc}-\x{fe6b}\x{feff}-\x{ff0f}\x{ff1a}-\x{ff20}\x{ff3b}-\x{ff40}\x{ff5b}-'.
'\x{ff65}\x{ff70}\x{ff9e}\x{ff9f}\x{ffe0}-\x{fffd}');

/**
 * Matches all 'N' Unicode character classes (numbers)
 */
define('PREG_CLASS_NUMBERS',
'\x{30}-\x{39}\x{b2}\x{b3}\x{b9}\x{bc}-\x{be}\x{660}-\x{669}\x{6f0}-\x{6f9}'.
'\x{966}-\x{96f}\x{9e6}-\x{9ef}\x{9f4}-\x{9f9}\x{a66}-\x{a6f}\x{ae6}-\x{aef}'.
'\x{b66}-\x{b6f}\x{be7}-\x{bf2}\x{c66}-\x{c6f}\x{ce6}-\x{cef}\x{d66}-\x{d6f}'.
'\x{e50}-\x{e59}\x{ed0}-\x{ed9}\x{f20}-\x{f33}\x{1040}-\x{1049}\x{1369}-'.
'\x{137c}\x{16ee}-\x{16f0}\x{17e0}-\x{17e9}\x{17f0}-\x{17f9}\x{1810}-\x{1819}'.
'\x{1946}-\x{194f}\x{2070}\x{2074}-\x{2079}\x{2080}-\x{2089}\x{2153}-\x{2183}'.
'\x{2460}-\x{249b}\x{24ea}-\x{24ff}\x{2776}-\x{2793}\x{3007}\x{3021}-\x{3029}'.
'\x{3038}-\x{303a}\x{3192}-\x{3195}\x{3220}-\x{3229}\x{3251}-\x{325f}\x{3280}-'.
'\x{3289}\x{32b1}-\x{32bf}\x{ff10}-\x{ff19}');

/**
 * Matches all 'P' Unicode character classes (punctuation)
 */
define('PREG_CLASS_PUNCTUATION',
'\x{21}-\x{23}\x{25}-\x{2a}\x{2c}-\x{2f}\x{3a}\x{3b}\x{3f}\x{40}\x{5b}-\x{5d}'.
'\x{5f}\x{7b}\x{7d}\x{a1}\x{ab}\x{b7}\x{bb}\x{bf}\x{37e}\x{387}\x{55a}-\x{55f}'.
'\x{589}\x{58a}\x{5be}\x{5c0}\x{5c3}\x{5f3}\x{5f4}\x{60c}\x{60d}\x{61b}\x{61f}'.
'\x{66a}-\x{66d}\x{6d4}\x{700}-\x{70d}\x{964}\x{965}\x{970}\x{df4}\x{e4f}'.
'\x{e5a}\x{e5b}\x{f04}-\x{f12}\x{f3a}-\x{f3d}\x{f85}\x{104a}-\x{104f}\x{10fb}'.
'\x{1361}-\x{1368}\x{166d}\x{166e}\x{169b}\x{169c}\x{16eb}-\x{16ed}\x{1735}'.
'\x{1736}\x{17d4}-\x{17d6}\x{17d8}-\x{17da}\x{1800}-\x{180a}\x{1944}\x{1945}'.
'\x{2010}-\x{2027}\x{2030}-\x{2043}\x{2045}-\x{2051}\x{2053}\x{2054}\x{2057}'.
'\x{207d}\x{207e}\x{208d}\x{208e}\x{2329}\x{232a}\x{23b4}-\x{23b6}\x{2768}-'.
'\x{2775}\x{27e6}-\x{27eb}\x{2983}-\x{2998}\x{29d8}-\x{29db}\x{29fc}\x{29fd}'.
'\x{3001}-\x{3003}\x{3008}-\x{3011}\x{3014}-\x{301f}\x{3030}\x{303d}\x{30a0}'.
'\x{30fb}\x{fd3e}\x{fd3f}\x{fe30}-\x{fe52}\x{fe54}-\x{fe61}\x{fe63}\x{fe68}'.
'\x{fe6a}\x{fe6b}\x{ff01}-\x{ff03}\x{ff05}-\x{ff0a}\x{ff0c}-\x{ff0f}\x{ff1a}'.
'\x{ff1b}\x{ff1f}\x{ff20}\x{ff3b}-\x{ff3d}\x{ff3f}\x{ff5b}\x{ff5d}\x{ff5f}-'.
'\x{ff65}');

/**
 * Matches all CJK characters that are candidates for auto-splitting
 * (Chinese, Japanese, Korean).
 * Contains kana and BMP ideographs.
 */
define('PREG_CLASS_CJK', '\x{3041}-\x{30ff}\x{31f0}-\x{31ff}\x{3400}-\x{4db5}'.
'\x{4e00}-\x{9fbb}\x{f900}-\x{fad9}');

/**
 * Implementation of hook_help().
 */
function search_help($section) {
  switch ($section) {
    case 'admin/help#search':
      $output = '<p>'. t('The search module adds the ability to search for content by keywords.  Search is often the only practical way to find content on a large site.  Search is useful for finding users and posts by searching on keywords.') .'</p>';
      $output .= '<p>'. t('The search engine works by maintaining an index of the words in your site\'s content. It indexes the posts and users.  You can adjust the settings to tweak the indexing behaviour. Note that the search requires cron to be set up correctly.  The index percentage sets the maximum amount of items that will be indexed in one cron run. Set this number lower if your cron is timing out or if PHP is running out of memory.') .'</p>';
      $output .= t('<p>You can</p>
<ul>
<li>read about how your site uses cron in the <a href="%admin-help-system">administer &gt;&gt; help &gt;&gt; system</a>.</li>
<li>run your <a href="%file-cron">cron.php</a>.</li>
<li>read about <a href="%external-http-drupal-org-node-23714">configuring cron jobs</a>.</li>
<li><a href="%admin-settings-search">administer &gt;&gt; settings &gt;&gt; search</a>.</ul>
', array('%admin-help-system' => url('admin/help/system'), '%file-cron' => 'cron.php', '%external-http-drupal-org-node-23714' => 'http://drupal.org/node/23714', '%admin-settings-search' => url('admin/settings/search')));
      $output .= '<p>'. t('For more information please read the configuration and customization handbook <a href="%search">Search page</a>.', array('%search' => 'http://www.drupal.org/handbook/modules/search/')) .'</p>';
      return $output;
    case 'admin/modules#description':
      return t('Enables site-wide keyword searching.');
    case 'admin/settings/search':
      return t('
<p>The search engine works by maintaining an index of the words in your site\'s content. You can adjust the settings below to tweak the indexing behaviour. Note that the search requires cron to be set up correctly.</p>
');
    case 'search#noresults':
      return t('<p><ul>
<li>Check if your spelling is correct.</li>
<li>Remove quotes around phrases to match each word individually: <em>"blue smurf"</em> will match less than <em>blue smurf</em>.</li>
<li>Consider loosening your query with <em>OR</em>: <em>blue smurf</em> will match less than <em>blue OR smurf</em>.</li>
</ul></p>');
  }
}

/**
 * Implementation of hook_perm().
 */
function search_perm() {
  return array('search content', 'administer search');
}

/**
 * Implementation of hook_block().
 */
function search_block($op = 'list', $delta = 0) {
  global $user;
  if ($op == 'list') {
    $blocks[0]['info'] = t('Search form');
    return $blocks;
  }
  else if ($op == 'view' && user_access('search content') && arg(0) != 'search') {
    $block['content'] = search_form('', '', null, '');
    $block['subject'] = t('Search');
    return $block;
  }
}

/**
 * Implementation of hook_menu().
 */
function search_menu($may_cache) {
  $items = array();

  if ($may_cache) {
    $items[] = array('path' => 'search', 'title' => t('search'),
      'callback' => 'search_view',
      'access' => user_access('search content'),
      'type' => MENU_SUGGESTED_ITEM);
    $items[] = array('path' => 'admin/settings/search/wipe', 'title' => t('Clear index'),
      'callback' => 'search_wipe_confirm',
      'access' => user_access('administer search'),
      'type' => MENU_CALLBACK);
  }
  else if (arg(0) == 'search') {
    // To remember the user's search keywords when switching across tabs,
    // we dynamically add the keywords to the search tabs' paths.
    $keys = search_get_keys();
    $keys = strlen($keys) ? '/'. $keys : '';
    foreach (module_list() as $name) {
      if (module_hook($name, 'search') && $title = module_invoke($name, 'search', 'name')) {
        $items[] = array('path' => 'search/'. $name . $keys, 'title' => $title,
          'callback' => 'search_view',
          'access' => user_access('search content'),
          'type' => MENU_LOCAL_TASK);
      }
    }
  }

  return $items;
}

/**
 * Implementation of hook_validate().
 */
function search_settings_form_validate($form_id, &$form) {
  if ($_POST['op'] == t('Re-index site')) {
    drupal_goto('admin/settings/search/wipe');
  }
  // If these settings change, the index needs to be rebuilt.
  if ((variable_get('minimum_word_size', 3) != $form['minimum_word_size']) ||
      (variable_get('overlap_cjk', true) != $form['overlap_cjk'])) {
    drupal_set_message(t('The index will be rebuilt.'));
    search_wipe();
  }
}

/**
 * Menu callback; displays the search module settings page.
 */
function search_settings() {
  // Collect some stats
  $remaining = 0;
  $total = 0;
  foreach (module_list() as $module) {
    if (module_hook($module, 'search')) {
      $status = module_invoke($module, 'search', 'status');
      $remaining += $status['remaining'];
      $total += $status['total'];
    }
  }
  $count = format_plural($remaining, 'There is 1 item left to index.', 'There are %count items left to index.');
  $percentage = ((int)min(100, 100 * ($total - $remaining) / max(1, $total))) . '%';
  $status = '<p><strong>'. t('%percentage of the site has been indexed.', array('%percentage' => $percentage)) .' '. $count .'</strong></p>';
  $form['status'] = array('#type' => 'fieldset', '#title' => t('Indexing status'));
  $form['status']['status'] = array('#type' => 'markup', '#value' => $status);
  $form['status']['wipe'] = array('#type' => 'submit', '#value' => t('Re-index site'));

  $items = drupal_map_assoc(array(10, 20, 50, 100, 200, 500));

  // Indexing throttle:
  $form['indexing_throttle'] = array('#type' => 'fieldset', '#title' => t('Indexing throttle'));
  $form['indexing_throttle']['search_cron_limit'] = array('#type' => 'select', '#title' => t('Items to index per cron run'), '#default_value' => variable_get('search_cron_limit', 100), '#options' => $items, '#description' => t('The maximum amount of items that will be indexed in one cron run. Set this number lower if your cron is timing out or if PHP is running out of memory.'));
  // Indexing settings:
  $form['indexing_settings'] = array('#type' => 'fieldset', '#title' => t('Indexing settings'));
  $form['indexing_settings']['info'] = array('#type' => 'markup', '#value' => '<em>'. t('<p>Changing the settings below will cause the site index to be rebuilt. The search index is not cleared but systematically updated to reflect the new settings. Searching will continue to work but new content won\'t be indexed until all existing content has been re-indexed.</p><p>The default settings should be appropriate for the majority of sites.</p>') .'</em>');
  $form['indexing_settings']['minimum_word_size'] = array('#type' => 'textfield', '#title' => t('Minimum word length to index'), '#default_value' => variable_get('minimum_word_size', 3), '#size' => 5, '#maxlength' => 3, '#description' => t('The number of characters a word has to be to be indexed. A lower setting means better search result ranking, but also a larger database. Each search query must contain at least one keyword that is this size (or longer).'));
  $form['indexing_settings']['remove_short'] = array('#type' => 'textfield', '#title' => t('Minimum word length to search for'), '#default_value' => variable_get('remove_short', 3), '#size' => 5, '#maxlength' => 3, '#description' => t('The number of characters a word has to be to be searched for, including wildcard characters.'));
  $form['indexing_settings']['overlap_cjk'] = array('#type' => 'checkbox', '#title' => t('Simple CJK handling'), '#default_value' => variable_get('overlap_cjk', true), '#description' => t('Whether to apply a simple Chinese/Japanese/Korean tokenizer based on overlapping sequences. Turn this off if you want to use an external preprocessor for this instead. Does not affect other languages.'));

  // Per module settings
  $form = array_merge($form, module_invoke_all('search', 'admin'));
  return $form;
}

/**
 * Menu callback: confirm wiping of the index.
 */
function search_wipe_confirm() {
  return confirm_form('search_wipe_confirm', $form, t('Are you sure you want to re-index the site?'),
                  'admin/forums', t(' The search index is not cleared but systematically updated to reflect the new settings. Searching will continue to work but new content won\'t be indexed until all existing content has been re-indexed. This action cannot be undone.'), t('Re-index site'), t('Cancel'));
}

/**
 * Handler for wipe confirmation
 */
function search_wipe_confirm_submit($form_id, &$form) {
  if ($form['confirm']) {
    search_wipe();
    drupal_set_message(t('The index will be rebuilt.'));
    drupal_goto('admin/settings/search');
  }
}

/**
 * Wipes a part of or the entire search index.
 *
 * @param $sid
 *  (optional) The SID of the item to wipe. If specified, $type must be passed
 *  too.
 * @param $type
 *  (optional) The type of item to wipe.
 */
function search_wipe($sid = NULL, $type = NULL) {
  if ($type == NULL && $sid == NULL) {
    module_invoke_all('search', 'reset');
  }
  else {
    db_query("DELETE FROM {search_dataset} WHERE sid = %d AND type = '%s'", $sid, $type);
    db_query("DELETE FROM {search_index} WHERE sid = %d AND type = '%s'", $sid, $type);
    db_query("DELETE FROM {search_index} WHERE fromsid = %d AND fromtype = '%s'", $sid, $type);
  }
}

/**
 * Marks a word as dirty (or retrieves the list of dirty words). This is used
 * during indexing (cron). Words which are dirty have outdated total counts in
 * the search_total table, and need to be recounted.
 */
function search_dirty($word = null) {
  static $dirty = array();
  if ($word !== null) {
    $dirty[$word] = true;
  }
  else {
    return $dirty;
  }
}

/**
 * Implementation of hook_cron().
 *
 * Fires hook_update_index() in all modules and cleans up dirty words (see
 * search_dirty).
 */
function search_cron() {
  // Update word index
  foreach (module_list() as $module) {
    module_invoke($module, 'update_index');
  }
  // Update word IDF (Inverse Document Frequency) counts for new/changed words
  foreach (search_dirty() as $word => $dummy) {
    // Get total count
    $total = db_result(db_query("SELECT SUM(score) FROM {search_index} WHERE word = '%s'", $word));
    // Apply Zipf's law to equalize the probability distribution
    $total = log10(1 + 1/(max(1, $total)));
    db_query("UPDATE {search_total} SET count = %f WHERE word = '%s'", $total, $word);
    if (!db_affected_rows()) {
      db_query("INSERT INTO {search_total} (word, count) VALUES ('%s', %f)", $word, $total);
    }
  }
  // Find words that were deleted from search_index, but are still in
  // search_total. We use a LEFT JOIN between the two tables and keep only the
  // rows which fail to join.
  $result = db_query("SELECT t.word AS realword, i.word FROM {search_total} t LEFT JOIN {search_index} i ON t.word = i.word WHERE i.word IS NULL");
  while ($word = db_fetch_object($result)) {
    db_query("DELETE FROM {search_total} WHERE word = '%s'", $word->realword);
  }
}

/**
 * Simplifies a string according to indexing rules.
 */
function search_simplify($text) {
  // Decode entities to UTF-8
  $text = decode_entities($text);

  // Lowercase
  $text = drupal_strtolower($text);

  // Call an external processor for word handling.
  search_preprocess($text);

  // Simple CJK handling
  if (variable_get('overlap_cjk', true)) {
    $text = preg_replace_callback('/['. PREG_CLASS_CJK .']+/u', 'search_expand_cjk', $text);
  }

  // To improve searching for numerical data such as dates, IP addresses
  // or version numbers, we consider a group of numerical characters
  // separated only by punctuation characters to be one piece.
  // This also means that searching for e.g. '20/03/1984' also returns
  // results with '20-03-1984' in them.
  // Readable regexp: ([number]+)[punctuation]+(?=[number])
  $text = preg_replace('/(['. PREG_CLASS_NUMBERS .']+)['. PREG_CLASS_PUNCTUATION .']+(?=['. PREG_CLASS_NUMBERS .'])/u', '\1', $text);

  // The dot, underscore and dash are simply removed. This allows meaningful
  // search behaviour with acronyms and URLs.
  $text = preg_replace('/[._-]+/', '', $text);

  // With the exception of the rules above, we consider all punctuation,
  // marks, spacers, etc, to be a word boundary.
  $text = preg_replace('/['. PREG_CLASS_SEARCH_EXCLUDE . ']+/u', ' ', $text);

  return $text;
}

/**
 * Basic CJK tokenizer. Simply splits a string into consecutive, overlapping
 * sequences of characters ('minimum_word_size' long).
 */
function search_expand_cjk($matches) {
  $min = variable_get('minimum_word_size', 3);
  $str = $matches[0];
  $l = drupal_strlen($str);
  // Passthrough short words
  if ($l <= $min) {
    return $str;
  }
  $tokens = ' ';
  // FIFO queue of characters
  $chars = array();
  // Begin loop
  for ($i = 0; $i < $l; ++$i) {
    // Grab next character
    $current = drupal_substr($str, 0, 1);
    $str = substr($str, strlen($current));
    $chars[] = $current;
    if ($i >= $min - 1) {
      $tokens .= implode('', $chars) .' ';
      array_shift($chars);
    }
  }
  return $tokens;
}

/**
 * Splits a string into tokens for indexing.
 */
function search_index_split($text) {
  static $last = null;
  static $lastsplit = null;

  if ($last == $text) {
    return $lastsplit;
  }
  // Process words
  $text = search_simplify($text);
  $words = explode(' ', $text);
  array_walk($words, '_search_index_truncate');

  // Save last keyword result
  $last = $text;
  $lastsplit = $words;

  return $words;
}

/**
 * Helper function for array_walk in search_index_split.
 */
function _search_index_truncate(&$text) {
  $text = truncate_utf8($text, 50);
}

/**
 * Invokes hook_search_preprocess() in modules.
 */
function search_preprocess(&$text) {
  foreach (module_implements('search_preprocess') as $module) {
    $text = module_invoke($module, 'search_preprocess', $text);
  }
}

/**
 * Update the full-text search index for a particular item.
 *
 * @param $sid
 *   A number identifying this particular item (e.g. node id).
 *
 * @param $type
 *   A string defining this type of item (e.g. 'node')
 *
 * @param $text
 *   The content of this item. Must be a piece of HTML text.
 *
 * @ingroup search
 */
function search_index($sid, $type, $text) {
  $minimum_word_size = variable_get('minimum_word_size', 4);

  // Link matching
  global $base_url;
  $node_regexp = '@href=[\'"]?(?:'. preg_quote($base_url, '@') .'/)?(?:\?q=)?/?((?![a-z]+:)[^\'">]+)[\'">]@i';

  // Multipliers for scores of words inside certain HTML tags.
  // Note: 'a' must be included for link ranking to work.
  $tags = array('h1' => 25,
                'h2' => 18,
                'h3' => 15,
                'h4' => 12,
                'h5' => 9,
                'h6' => 6,
                'u' => 3,
                'b' => 3,
                'i' => 3,
                'strong' => 3,
                'em' => 3,
                'a' => 10);

  // Strip off all ignored tags to speed up processing, but insert space before/after
  // them to keep word boundaries.
  $text = str_replace(array('<', '>'), array(' <', '> '), $text);
  $text = strip_tags($text, '<'. implode('><', array_keys($tags)) .'>');

  // Split HTML tags from plain text.
  $split = preg_split('/\s*<([^>]+?)>\s*/', $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).

  $tag = false; // Odd/even counter. Tag or no tag.
  $link = false; // State variable for link analyser
  $score = 1; // Starting score per word
  $accum = ' '; // Accumulator for cleaned up data
  $tagstack = array(); // Stack with open tags
  $tagwords = 0; // Counter for consecutive words
  $focus = 1; // Focus state

  $results = array(0 => array()); // Accumulator for words for index

  foreach ($split as $value) {
    if ($tag) {
      // Increase or decrease score per word based on tag
      list($tagname) = explode(' ', $value, 2);
      $tagname = drupal_strtolower($tagname);
      // Closing or opening tag?
      if ($tagname{0} == '/') {
        $tagname = substr($tagname, 1);
        // If we encounter unexpected tags, reset score to avoid incorrect boosting.
        if (!count($tagstack) || $tagstack[0] != $tagname) {
          $tagstack = array();
          $score = 1;
        }
        else {
          // Remove from tag stack and decrement score
          $score = max(1, $score - $tags[array_shift($tagstack)]);
        }
        if ($tagname == 'a') {
          $link = false;
        }
      }
      else {
        if ($tagstack[0] == $tagname) {
          // None of the tags we look for make sense when nested identically.
          // If they are, it's probably broken HTML.
          $tagstack = array();
          $score = 1;
        }
        else {
          // Add to open tag stack and increment score
          array_unshift($tagstack, $tagname);
          $score += $tags[$tagname];
        }
        if ($tagname == 'a') {
          // Check if link points to a node on this site
          if (preg_match($node_regexp, $value, $match)) {
            $path = drupal_get_normal_path($match[1]);
            if (preg_match('!(?:node|book)/(?:view/)?([0-9]+)!i', $path, $match)) {
              $linknid = $match[1];
              if ($linknid > 0) {
                // Note: ignore links to uncachable nodes to avoid redirect bugs.
                $node = db_fetch_object(db_query('SELECT n.title, n.nid, n.vid, r.format FROM {node} n INNER JOIN {node_revisions} r ON n.vid = r.vid WHERE n.nid = %d', $linknid));
                if (filter_format_allowcache($node->format)) {
                  $link = true;
                  $linktitle = $node->title;
                }
              }
            }
          }
        }
      }
      // A tag change occurred, reset counter.
      $tagwords = 0;
    }
    else {
      // Note: use of PREG_SPLIT_DELIM_CAPTURE above will introduce empty values
      if ($value != '') {
        if ($link) {
          // Check to see if the node link text is its URL. If so, we use the target node title instead.
          if (preg_match('!^https?://!i', $value)) {
            $value = $linktitle;
          }
        }
        $words = search_index_split($value);
        foreach ($words as $word) {
          // Add word to accumulator
          $accum .= $word .' ';
          $num = is_numeric($word);
          // Check wordlength
          if ($num || drupal_strlen($word) >= $minimum_word_size) {
            // Normalize numbers
            if ($num) {
              $word = (int)ltrim($word, '-0');
            }

            if ($link) {
              if (!isset($results[$linknid])) {
                $results[$linknid] = array();
              }
              $results[$linknid][$word] += $score * $focus;
            }
            else {
              $results[0][$word] += $score * $focus;
              // Focus is a decaying value in terms of the amount of unique words up to this point.
              // From 100 words and more, it decays, to e.g. 0.5 at 500 words and 0.3 at 1000 words.
              $focus = min(1, .01 + 3.5 / (2 + count($results[0]) * .015));
            }
          }
          $tagwords++;
          // Too many words inside a single tag probably mean a tag was accidentally left open.
          if (count($tagstack) && $tagwords >= 15) {
            $tagstack = array();
            $score = 1;
          }
        }
      }
    }
    $tag = !$tag;
  }

  search_wipe($sid, $type);

  // Insert cleaned up data into dataset
  db_query("INSERT INTO {search_dataset} (sid, type, data) VALUES (%d, '%s', '%s')", $sid, $type, $accum);

  // Insert results into search index
  foreach ($results[0] as $word => $score) {
    db_query("INSERT INTO {search_index} (word, sid, type, score) VALUES ('%s', %d, '%s', %d)", $word, $sid, $type, $score);
    search_dirty($word);
  }
  unset($results[0]);

  // Now insert links to nodes
  foreach ($results as $nid => $words) {
    foreach ($words as $word => $score) {
      db_query("INSERT INTO {search_index} (word, sid, type, fromsid, fromtype, score) VALUES ('%s', %d, '%s', %d, '%s', %d)", $word, $nid, 'node', $sid, $type, $score);
      search_dirty($word);
    }
  }
}

/**
 * Extract a module-specific search option from a search query. e.g. 'type:book'
 */
function search_query_extract($keys, $option) {
  if (preg_match('/(^| )'. $option .':([^ ]*)( |$)/i', $keys, $matches)) {
    return $matches[2];
  }
}

/**
 * Return a query with the given module-specific search option inserted in.
 * e.g. 'type:book'.
 */
function search_query_insert($keys, $option, $value = '') {
  if (search_query_extract($keys, $option)) {
    $keys = trim(preg_replace('/(^| )'. $option .':[^ ]*/i', '', $keys));
  }
  if ($value != '') {
    $keys .= ' '. $option .':'. $value;
  }
  return $keys;
}

/**
 * Parse a search query into SQL conditions.
 *
 * We build a query that matches the dataset bodies.
 */
function search_parse_query($text) {
  $keys = array('positive' => array(), 'negative' => array());

  // Tokenize query string
  preg_match_all('/ (-?)("[^"]+"|[^" ]+)/i', ' '. $text, $matches, PREG_SET_ORDER);

  if (count($matches) < 1) {
    return NULL;
  }

  // Classify tokens
  $or = false;
  foreach ($matches as $match) {
    $phrase = false;
    // Strip off quotes
    if ($match[2]{0} == '"') {
      $match[2] = substr($match[2], 1, -1);
      $phrase = true;
    }
    // Simplify keyword according to indexing rules
    $words = search_simplify($match[2]);
    // Re-explode in case simplification added more words, except when matching a phrase
    $words = $phrase ? array($words) : explode(' ', $words);
    // Negative matches
    if ($match[1] == '-') {
      $keys['negative'] = array_merge($keys['negative'], $words);
    }
    // OR operator: instead of a single keyword, we store an array of all
    // OR'd keywords.
    elseif ($match[2] == 'OR' && count($keys['positive'])) {
      $keys['positive'][] = array(array_pop($keys['positive']));
      $or = true;
      continue;
    }
    // Plain keyword
    else {
      if ($or) {
        // Add to last element (which is an array)
        $keys['positive'][count($keys['positive']) - 1] = array_merge($keys['positive'][count($keys['positive']) - 1], $words);
      }
      else {
        $keys['positive'] = array_merge($keys['positive'], $words);
      }
    }
    $or = false;
  }

  // Convert keywords into SQL statements.
  $scorewords = array();
  $query = array();
  $query2 = array();
  $arguments = array();
  $arguments2 = array();
  $matches = 0; // Counts the minimal number of words per item must match in the index.
  // Positive matches
  foreach ($keys['positive'] as $key) {
    // Group of ORed terms
    if (is_array($key) && count($key)) {
      $queryor = array();
      foreach ($key as $or) {
        $q = _search_parse_query($or, $scorewords);
        if ($q) {
          $queryor[] = $q;
          $arguments[] = $or;
        }
      }
      if (count($queryor)) {
        $query[] = '('. implode(' OR ', $queryor) .')';
      }
    }
    // Single ANDed term
    else {
      $q = _search_parse_query($key, $scorewords);
      if ($q) {
        $query[] = $q;
        $arguments[] = $key;
      }
    }
    $matches++;
  }
  foreach ($keys['negative'] as $key) {
    $q = _search_parse_query($key, $scorewords, true);
    if ($q) {
      $query[] = $q;
      $arguments[] = $key;
    }
  }
  // We separate word-index conditions because they are not needed in the
  // counting query.
  foreach ($scorewords as $word) {
    $query2[] = "i.word = '%s'";
    $arguments2[] = $word;
  }
  $query = implode(' AND ', $query);
  $query2 = implode(' OR ', $query2);
  return array($query, $arguments, $query2, $arguments2, $matches);
}

/**
 * Helper function for search_parse_query();
 */
function _search_parse_query(&$word, &$scores, $not = false) {
  // Determine the scorewords of this word/phrase
  if (!$not) {
    $split = explode(' ', $word);
    foreach ($split as $s) {
      $num = is_numeric($s);
      if ($num || drupal_strlen($s) >= variable_get('minimum_word_size', 4)) {
        $scores[] = $num ? ((int)ltrim($word, '-0')) : $s;
      }
    }
  }
  // Return matching snippet
  return "d.data ". ($not ? 'NOT ' : '') ."LIKE '%% %s %%'";
}

/**
 * Do a query on the full-text search index for a word or words.
 *
 * This function is normally only called by each module that support the
 * indexed search (and thus, implements hook_update_index()).
 *
 * Two queries are performed which can be extended by the caller.
 *
 * The first query selects a set of possible matches based on the search index
 * and any extra given restrictions. This is the classic "OR" search.
 *
 * SELECT i.type, i.sid, SUM(i.score*t.count) AS relevance
 * FROM {search_index} i
 * INNER JOIN {search_total} t ON i.word = t.word
 * $join1
 * WHERE $where1 AND (...)
 * GROUP BY i.type, i.sid
 *
 * The second query further refines this set by verifying advanced text
 * conditions (such as AND, negative or phrase matches), and orders the results
 * on a the column or expression 'score':
 *
 * SELECT i.type, i.sid, $select2
 * FROM temp_search_sids i
 * INNER JOIN {search_dataset} d ON i.sid = d.sid AND i.type = d.type
 * $join2
 * WHERE (...)
 * ORDER BY score DESC
 *
 * @param $keywords
 *   A search string as entered by the user.
 *
 * @param $type
 *   A string identifying the calling module.
 *
 * @param $join1
 *   (optional) Inserted into the JOIN part of the first SQL query.
 *   For example "INNER JOIN {node} n ON n.nid = i.sid".
 *
 * @param $where1
 *   (optional) Inserted into the WHERE part of the first SQL query.
 *   For example "(n.status > %d)".
 *
 * @param $arguments1
 *   (optional) Extra SQL arguments belonging to the first query.
 *
 * @param $select2
 *   (optional) Inserted into the SELECT pat of the second query. Must contain
 *   a column selected as 'score'.
 *   defaults to 'i.relevance AS score'
 *
 * @param $join2
 *   (optional) Inserted into the JOIN par of the second SQL query.
 *   For example "INNER JOIN {node_comment_statistics} n ON n.nid = i.sid"
 *
 * @param $arguments2
 *   (optional) Extra SQL arguments belonging to the second query parameter.
 *
 * @return
 *   An array of SIDs for the search results.
 *
 * @ingroup search
 */
function do_search($keywords, $type, $join1 = '', $where1 = '1', $arguments1 = array(), $select2 = 'i.relevance AS score', $join2 = '', $arguments2 = array()) {
  $query = search_parse_query($keywords);

  if ($query === NULL || $query[0] == '' || $query[2] == '') {
    return array();
  }

  // First pass: select all possible matching sids, doing a simple index-based OR matching on the keywords.
  // 'matches' is used to reject those items that cannot possibly match the query.
  $conditions = $where1 .' AND ('. $query[2] .") AND i.type = '%s'";
  $arguments = array_merge($arguments1, $query[3], array($type, $query[4]));
  $result = db_query_temporary("SELECT i.type, i.sid, SUM(i.score * t.count) AS relevance, COUNT(*) AS matches FROM {search_index} i INNER JOIN {search_total} t ON i.word = t.word $join1 WHERE $conditions GROUP BY i.type, i.sid HAVING COUNT(*) >= %d", $arguments, 'temp_search_sids');

  // Calculate maximum relevance, to normalize it
  $normalize = db_result(db_query('SELECT MAX(relevance) FROM temp_search_sids'));
  if (!$normalize) {
    return array();
  }
  $select2 = str_replace('i.relevance', '('. (1.0 / $normalize) .' * i.relevance)', $select2);

  // Second pass: only keep items that match the complicated keywords conditions (phrase search, negative keywords, ...)
  $conditions = '('. $query[0] .')';
  $arguments = array_merge($arguments2, $query[1]);
  $result = db_query_temporary("SELECT i.type, i.sid, $select2 FROM temp_search_sids i INNER JOIN {search_dataset} d ON i.sid = d.sid AND i.type = d.type $join2 WHERE $conditions ORDER BY score DESC", $arguments, 'temp_search_results');
  if (($count = db_result(db_query('SELECT COUNT(*) FROM temp_search_results'))) == 0) {
    return array();
  }
  $count_query = "SELECT $count";

  // Do actual search query
  $result = pager_query("SELECT * FROM temp_search_results", 10, 0, $count_query, $arguments);
  $results = array();
  while ($item = db_fetch_object($result)) {
    $results[] = $item->sid;
  }
  return $results;
}

/**
 * Helper function for grabbing search keys.
 */
function search_get_keys() {
  // Extract keys as remainder of path
  // Note: support old GET format of searches for existing links.
  $path = explode('/', $_GET['q'], 3);
  return count($path) == 3 ? $path[2] : $_REQUEST['keys'];
}

/**
 * Menu callback; presents the search form and/or search results.
 */
function search_view() {
  $type = arg(1);

  // Search form submits with POST but redirects to GET. This way we can keep
  // the search query URL clean as a whistle:
  // search/type/keyword+keyword
  if (isset($_POST['op'])) {
    if ($type == '') {
      $type = 'node';
    }
    $keys = module_invoke($type, 'search', 'post', $_POST['edit']['keys']);
    drupal_goto('search/'. drupal_urlencode($type) .'/'. drupal_urlencode(is_null($keys) ? $_POST['edit']['keys'] : $keys));
  }
  else if ($type == '') {
    // Note: search/node can not be a default tab because it would take on the
    // path of its parent (search). It would prevent remembering keywords when
    // switching tabs. This is why we drupal_goto to it from the parent instead.
    drupal_goto('search/node');
  }
  $keys = search_get_keys();

  if (user_access('search content')) {
    // Only perform search if there is non-whitespace search term:
    if (trim($keys)) {
      // Log the search keys:
      watchdog('search',
        t('Search: %keys (%type).', array('%keys' => theme('placeholder', $keys), '%type' => module_invoke($type, 'search', 'name'))),
        WATCHDOG_NOTICE,
        l(t('results'), 'search/'. drupal_urlencode($type) .'/'. drupal_urlencode($keys))
        );

      // Collect the search results:
      $results = search_data($keys, $type);

      if ($results) {
        $results = theme('box', t('Search results'), $results);
      }
      else {
        $results = theme('box', t('Your search yielded no results'), search_help('search#noresults'));
      }
    }
    else if (isset($_POST['edit'])) {
      form_set_error('keys', t('Please enter some keywords.'));
    }

    // Construct the search form.
    // Note, we do this last because of the form_set_error() above.
    $output = search_form(NULL, $keys, $type);

    $output .= $results;

    return $output;
  }
  else {
    drupal_access_denied();
  }
}

/**
 * @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 search.module, so this must be enabled
 * for all of the search features to work.
 *
 * There are three ways to interact with the search system:
 * - Specifically for searching nodes, you can implement nodeapi('update index')
 *   and nodeapi('search result'). However, note that the search system already
 *   indexes all visible output of a node, i.e. everything displayed normally
 *   by hook_view() and hook_nodeapi('view'). This is usually sufficient.
 *   You should only use this mechanism if you want additional, non-visible data
 *   to be indexed.
 * - Implement hook_search(). This will create a search tab for your module on
 *   the /search page with a simple keyword search form. You may optionally
 *   implement hook_search_item() to customize the display of your results.
 * - Implement hook_update_index(). This allows your module to use Drupal's
 *   HTML indexing mechanism for searching full text efficiently.
 *
 * If your module needs to provide a more complicated search form, then you need
 * to implement it yourself without hook_search(). In that case, you should
 * define it as a local task (tab) under the /search page (e.g. /search/mymodule)
 * so that users can easily find it.
 */

/**
 * Render a search form.
 *
 * @param $action
 *   Form action. Defaults to "search".
 * @param $keys
 *   The search string entered by the user, containing keywords for the search.
 * @param $type
 *   The type of search to render the node for. Must be the name of module
 *   which implements hook_search(). Defaults to 'node'.
 * @param $prompt
 *   A piece of text to put before the form (e.g. "Enter your keywords")
 * @return
 *   An HTML string containing the search form.
 */
function search_form($action = '', $keys = '', $type = null, $prompt = null) {

  if (!$action) {
    $action = url('search/'. $type);
  }
  if (is_null($prompt)) {
    $prompt = t('Enter your keywords');
  }

  $form = array();
  $form['#action'] = $action;
  $form['#attributes'] = array('class' => 'search-form');
  $form['basic'] = array('#type' => 'item', '#title' => $prompt);
  $form['basic']['inline'] = array('#type' => 'markup', '#prefix' => '<div class="container-inline">', '#suffix' => '</div>');
  $form['basic']['inline']['keys'] = array('#type' => 'textfield', '#title' => '', '#default_value' => $keys, '#size' => $prompt ? 40 : 30, '#maxlength' => 255);
  $form['basic']['inline']['submit'] = array('#type' => 'submit', '#value' => t('Search'));

  $form_module = module_invoke($type, 'search', 'form', $keys);
  if (is_array($form_module)) {
    $form = array_merge($form, $form_module);
  }

  return drupal_get_form('search_form', $form);
}

/**
 * Perform a standard search on the given keys, and return the formatted results.
 */
function search_data($keys = NULL, $type = 'node') {
  $output = '';

  if (isset($keys)) {
    if (module_hook($type, 'search')) {
      $results = module_invoke($type, 'search', 'search', $keys);
      if (is_array($results) && count($results)) {
        $output .= '<dl class="search-results">';
        foreach ($results as $entry) {
          $output .= theme('search_item', $entry, $type);
        }
        $output .= '</dl>';
        $output .= theme('pager', NULL, 15, 0);