<?php
// $Id$

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

/**
 * 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 CJK (Chinese, Japanese, Korean) letter-like characters.
 *
 * This list is derived from the "East Asian Scripts" section of
 * http://www.unicode.org/charts/index.html, as well as a comment on
 * http://unicode.org/reports/tr11/tr11-11.html listing some character
 * ranges that are reserved for additional CJK ideographs.
 *
 * The character ranges do not include numbers, punctuation, or symbols, since
 * these are handled separately in search. Note that radicals and strokes are
 * considered symbols. (See
 * http://www.unicode.org/Public/UNIDATA/extracted/DerivedGeneralCategory.txt)
 *
 * @see search_expand_cjk()
 */
define('PREG_CLASS_CJK', '\x{1100}-\x{11FF}\x{3040}-\x{309F}\x{30A1}-\x{318E}' .
  '\x{31A0}-\x{31B7}\x{31F0}-\x{31FF}\x{3400}-\x{4DBF}\x{4E00}-\x{9FCF}' .
  '\x{A000}-\x{A48F}\x{A4D0}-\x{A4FD}\x{A960}-\x{A97F}\x{AC00}-\x{D7FF}' .
  '\x{F900}-\x{FAFF}\x{FF21}-\x{FF3A}\x{FF41}-\x{FF5A}\x{FF66}-\x{FFDC}' .
  '\x{20000}-\x{2FFFD}\x{30000}-\x{3FFFD}');

/**
 * Implements hook_help().
 */
function search_help($path, $arg) {
  switch ($path) {
    case 'admin/help#search':
      $output = '';
      $output .= '<h3>' . t('About') . '</h3>';
      $output .= '<p>' . t('The Search module provides the ability to index and search for content by exact keywords, and for users by username or e-mail. For more information, see the online handbook entry for <a href="@search-module">Search module</a>.', array('@search-module' => 'http://drupal.org/handbook/modules/search/', '@search' => url('search'))) . '</p>';
      $output .= '<h3>' . t('Uses') . '</h3>';
      $output .= '<dl>';
      $output .= '<dt>' . t('Searching content and users') . '</dt>';
      $output .= '<dd>' . t('Users with <em>Use search</em> permission can use the search block and <a href="@search">Search page</a>. Users with the <em>View published content</em> permission can search for content containing exact keywords. Users with the <em>View user profiles</em> permission can search for users containing the keyword anywhere in the user name, and users with the <em>Administer users</em> permission can search for users by email address. Additionally, users with <em>Use advanced search</em> permission can find content using more complex search methods and filtering by choosing the <em>Advanced search</em> option on the <a href="@search">Search page</a>.', array('@search' => url('search'))) . '</dd>';
      $output .= '<dt>' . t('Indexing content with cron') . '</dt>';
      $output .= '<dd>' . t('To provide keyword searching, the search engine maintains an index of words found in the content and its fields, along with text added to your content by other modules (such as comments from the core Comment module, and taxonomy terms from the core Taxonomy module). To build and maintain this index, a correctly configured <a href="@cron">cron maintenance task</a> is required. Users with <em>Administer search</em> permission can further configure the cron settings on the <a href="@searchsettings">Search settings page</a>.', array('@cron' => 'http://drupal.org/cron', '@searchsettings' => url('admin/config/search/settings'))) . '</dd>';
      $output .= '<dt>' . t('Content reindexing') . '</dt>';
      $output .= '<dd>' . t('Content-related actions on your site (creating, editing, or deleting content and comments) automatically cause affected content items to be marked for indexing or reindexing at the next cron run. When content is marked for reindexing, the previous content remains in the index until cron runs, at which time it is replaced by the new content. Unlike content-related actions, actions related to the structure of your site do not cause affected content to be marked for reindexing. Examples of structure-related actions that affect content include deleting or editing taxonomy terms, enabling or disabling modules that add text to content (such as Taxonomy, Comment, and field-providing modules), and modifying the fields or display parameters of your content types. If you take one of these actions and you want to ensure that the search index is updated to reflect your changed site structure, you can mark all content for reindexing by clicking the "Re-index site" button on the <a href="@searchsettings">Search settings page</a>. If you have a lot of content on your site, it may take several cron runs for the content to be reindexed.', array('@searchsettings' => url('admin/config/search/settings'))) . '</dd>';
      $output .= '<dt>' . t('Configuring search settings') . '</dt>';
      $output .= '<dd>' . t('Indexing behavior can be adjusted using the <a href="@searchsettings">Search settings page</a>. Users with <em>Administer search</em> permission can control settings such as the <em>Number of items to index per cron run</em>, <em>Indexing settings</em> (word length), <em>Active search modules</em>, and <em>Content ranking</em>, which lets you adjust the priority in which indexed content is returned in results.', array('@searchsettings' => url('admin/config/search/settings'))) . '</dd>';
      $output .= '<dt>' . t('Search block') . '</dt>';
      $output .= '<dd>' . t('The Search module includes a default <em>Search form</em> block, which can be enabled and configured on the <a href="@blocks">Blocks administration page</a>. The block is available to users with the <em>Search content</em> permission.', array('@blocks' => url('admin/structure/block'))) . '</dd>';
      $output .= '<dt>' . t('Extending Search module') . '</dt>';
      $output .= '<dd>' . t('By default, the Search module only supports exact keyword matching in content searches. You can modify this behavior by installing a language-specific stemming module for your language (such as <a href="http://drupal.org/project/porterstemmer">Porter Stemmer</a> for American English), which allows words such as walk, walking, and walked to be matched in the Search module. Another approach is to use a third-party search technology with stemming or partial word matching features built in, such as <a href="http://drupal.org/project/apachesolr">Apache Solr</a> or <a href="http://drupal.org/project/sphinx">Sphinx</a>. These and other <a href="@contrib-search">search-related contributed modules</a> can be downloaded by visiting Drupal.org.', array('@contrib-search' => 'http://drupal.org/project/modules?filters=tid%3A105')) . '</dd>';
      $output .= '</dl>';
      return $output;
    case 'admin/config/search/settings':
      return '<p>' . t('The search engine maintains an index of words found in your site\'s content. To build and maintain this index, a correctly configured <a href="@cron">cron maintenance task</a> is required. Indexing behavior can be adjusted using the settings below.', array('@cron' => url('admin/reports/status'))) . '</p>';
    case 'search#noresults':
      return t('<ul>
<li>Check if your spelling is correct.</li>
<li>Remove quotes around phrases to search for each word individually. <em>bike shed</em> will often show more results than <em>&quot;bike shed&quot;</em>.</li>
<li>Consider loosening your query with <em>OR</em>. <em>bike OR shed</em> will often show more results than <em>bike shed</em>.</li>
</ul>');
  }
}

/**
 * Implements hook_init().
 */
function search_init() {
  drupal_add_css(drupal_get_path('module', 'search') . '/search.css', array('preprocess' => TRUE));
}

/**
 * Implements hook_theme().
 */
function search_theme() {
  return array(
    'search_block_form' => array(
      'render element' => 'form',
      'template' => 'search-block-form',
    ),
    'search_result' => array(
      'variables' => array('result' => NULL, 'type' => NULL),
      'file' => 'search.pages.inc',
      'template' => 'search-result',
    ),
    'search_results' => array(
      'variables' => array('results' => NULL, 'type' => NULL),
      'file' => 'search.pages.inc',
      'template' => 'search-results',
    ),
  );
}

/**
 * Implements hook_permission().
 */
function search_permission() {
  return array(
    'administer search' => array(
      'title' => t('Administer search'),
    ),
    'search content' => array(
      'title' => t('Use search'),
    ),
    'use advanced search' => array(
      'title' => t('Use advanced search'),
    ),
  );
}

/**
 * Implements hook_block_info().
 */
function search_block_info() {
  $blocks['form']['info'] = t('Search form');
  // Not worth caching.
  $blocks['form']['cache'] = DRUPAL_NO_CACHE;
  return $blocks;
}

/**
 * Implements hook_block_view().
 */
function search_block_view($delta = '') {
  if (user_access('search content')) {
    $block['content'] = drupal_get_form('search_block_form');
    return $block;
  }
}

/**
 * Implements hook_menu().
 */
function search_menu() {
  $items['search'] = array(
    'title' => 'Search',
    'page callback' => 'search_view',
    'access arguments' => array('search content'),
    'type' => MENU_SUGGESTED_ITEM,
    'file' => 'search.pages.inc',
  );
  $items['admin/config/search/settings'] = array(
    'title' => 'Search settings',
    'description' => 'Configure relevance settings for search and other indexing options.',
    'page callback' => 'drupal_get_form',
    'page arguments' => array('search_admin_settings'),
    'access arguments' => array('administer search'),
    'type' => MENU_NORMAL_ITEM,
    'weight' => -10,
    'file' => 'search.admin.inc',
  );
  $items['admin/config/search/settings/reindex'] = array(
    'title' => 'Clear index',
    'page callback' => 'drupal_get_form',
    'page arguments' => array('search_reindex_confirm'),
    'access arguments' => array('administer search'),
    'type' => MENU_CALLBACK,
    'file' => 'search.admin.inc',
  );

  // Add paths for searching. We add each module search path twice: once without
  // and once with %menu_tail appended. The reason for this is that we want to
  // preserve keywords when switching tabs, and also to have search tabs
  // highlighted properly. The only way to do that within the Drupal menu
  // system appears to be having two sets of tabs. See discussion on issue
  // http://drupal.org/node/245103 for details.

  drupal_static_reset('search_get_info');
  if ($active = variable_get('search_active_modules', array('node', 'user'))) {
    foreach (array_intersect_key(search_get_info(), array_flip($active)) as $module => $search_info) {
      $path = 'search/' . $search_info['path'];
      $items[$path] = array(
        'title' => $search_info['title'],
        'page callback' => 'search_view',
        'page arguments' => array($module),
        'access callback' => '_search_menu_access',
        'access arguments' => array($module),
        'type' => $module == 'node' ? MENU_DEFAULT_LOCAL_TASK : MENU_LOCAL_TASK,
        'file' => 'search.pages.inc',
        'weight' => $module == 'node' ? -10 : 0,
      );
      $items["$path/%menu_tail"] = array(
        'title' => $search_info['title'],
        'page callback' => 'search_view',
        'page arguments' => array($module),
        'access callback' => '_search_menu_access',
        'access arguments' => array($module),
        // The default local task points to its parent, but this item points to
        // where it should so it should not be changed.
        'type' => MENU_LOCAL_TASK,
        'file' => 'search.pages.inc',
        'weight' => 0,
        // These tabs are not subtabs.
        'tab_root' => 'search/node/%',
        // These tabs need to display at the same level.
        'tab_parent' => 'search',
      );
    }
  }
  return $items;
}

/**
 * Get information about all available search hooks.
 */
function search_get_info() {
  $search_hooks = &drupal_static(__FUNCTION__);

  if (!isset($search_hooks)) {
    foreach (module_implements('search_info') as $module) {
      $search_hooks[$module] = call_user_func($module . '_search_info');
      // Use module name as the default.
      $search_hooks[$module] += array('title' => $module, 'path' => $module);
    }
  }
  return $search_hooks;
}

/**
 * Access callback for search tabs.
 */
function _search_menu_access($name) {
  return user_access('search content') && (!function_exists($name . '_search_access') || module_invoke($name, 'search_access'));
}

/**
 * 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 $type
 *  (optional) The type of item to wipe.
 */
function search_reindex($sid = NULL, $type = NULL, $reindex = FALSE) {
  if ($type == NULL && $sid == NULL) {
    module_invoke_all('search_reset');
  }
  else {
    db_delete('search_dataset')
      ->condition('sid', $sid)
      ->condition('type', $type)
      ->execute();
    db_delete('search_index')
      ->condition('sid', $sid)
      ->condition('type', $type)
      ->execute();
    // Don't remove links if re-indexing.
    if (!$reindex) {
      db_delete('search_node_links')
        ->condition('sid', $sid)
        ->condition('type', $type)
        ->execute();
    }
  }
}

/**
 * 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) {
  $dirty = &drupal_static(__FUNCTION__, array());
  if ($word !== NULL) {
    $dirty[$word] = TRUE;
  }
  else {
    return $dirty;
  }
}

/**
 * Implements hook_cron().
 *
 * Fires hook_update_index() in all modules and cleans up dirty words (see
 * search_dirty).
 */
function search_cron() {
  // We register a shutdown function to ensure that search_total is always up
  // to date.
  drupal_register_shutdown_function('search_update_totals');

  foreach(variable_get('search_active_modules', array('node', 'user')) as $module) {
    // Update word index
    module_invoke($module, 'update_index');
  }
}

/**
 * This function is called on shutdown to ensure that search_total is always
 * up to date (even if cron times out or otherwise fails).
 */
function search_update_totals() {
  // Update word IDF (Inverse Document Frequency) counts for new/changed words.
  foreach (search_dirty() as $word => $dummy) {
    // Get total count
    $total = db_query("SELECT SUM(score) FROM {search_index} WHERE word = :word", array(':word' => $word), array('target' => 'slave'))->fetchField();
    // Apply Zipf's law to equalize the probability distribution.
    $total = log10(1 + 1/(max(1, $total)));
    db_merge('search_total')
      ->key(array('word' => $word))
      ->fields(array('count' => $total))
      ->execute();
  }
  // 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", array(), array('target' => 'slave'));
  $or = db_or();
  foreach ($result as $word) {
    $or->condition('word', $word->realword);
  }
  if (count($or) > 0) {
    db_delete('search_total')
      ->condition($or)
      ->execute();
  }
}

/**
 * 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_invoke_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);

  // Multiple dot and dash groups are word boundaries and replaced with space.
  // No need to use the unicode modifer here because 0-127 ASCII characters
  // can't match higher UTF-8 characters as the leftmost bit of those are 1.
  $text = preg_replace('/[.-]{2,}/', ' ', $text);

  // The dot, underscore and dash are simply removed. This allows meaningful
  // search behavior with acronyms and URLs. See unicode note directly above.
  $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_UNICODE_WORD_BOUNDARY . ']+/u', ' ', $text);

  return $text;
}

/**
 * Splits CJK (Chinese, Japanese, Korean) text into tokens.
 *
 * The Search module matches exact words, where a word is defined to be a
 * sequence of characters delimited by spaces or punctuation. CJK languages are
 * written in long strings of characters, though, not split up into words. So
 * in order to allow search matching, we split up CJK text into tokens
 * consisting of consecutive, overlapping sequences of characters whose length
 * is equal to the 'minimum_word_size' variable. This tokenizing is only done if
 * the 'overlap_cjk' variable is TRUE.
 *
 * @param $matches
 *   This function is a callback for preg_replace_callback(), which is called
 *   from search_simplify(). So, $matches is an array of regular expression
 *   matches, which means that $matches[0] contains the matched text -- a string
 *   of CJK characters to tokenize.
 *
 * @return
 *   Tokenized text, starting and ending with a space character.
 */
function search_expand_cjk($matches) {
  $min = variable_get('minimum_word_size', 3);
  $str = $matches[0];
  $length = drupal_strlen($str);
  // If the text is shorter than the minimum word size, don't tokenize it.
  if ($length <= $min) {
    return ' ' . $str . ' ';
  }
  $tokens = ' ';
  // Build a FIFO queue of characters.
  $chars = array();
  for ($i = 0; $i < $length; $i++) {
    // Add the next character off the beginning of the string to the queue.
    $current = drupal_substr($str, 0, 1);
    $str = substr($str, strlen($current));
    $chars[] = $current;
    if ($i >= $min - 1) {
      // Make a token of $min characters, and add it to the token string.
      $tokens .= implode('', $chars) . ' ';
      // Shift out the first character in the queue.
      array_shift($chars);
    }
  }
  return $tokens;
}

/**
 * Splits a string into tokens for indexing.
 */
function search_index_split($text) {
  $last = &drupal_static(__FUNCTION__);
  $lastsplit = &drupal_static(__FUNCTION__ . ':lastsplit');

  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_invoke_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', 3);

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

  // Multipliers for scores of words inside certain HTML tags. The weights are stored
  // in a variable so that modules can overwrite the default weights.
  // Note: 'a' must be included for link ranking to work.
  $tags = variable_get('search_tag_weights', 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 analyzer
  $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') {
          $link = FALSE;
        }
      }
      else {
        if (isset($tagstack[0]) && $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) {
                $node = db_query('SELECT title, nid, vid FROM {node} WHERE nid = :nid', array(':nid' => $linknid), array('target' => 'slave'))->fetchObject();
                $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');
            }

            // Links score mainly for the target.
            if ($link) {
              if (!isset($results[$linknid])) {
                $results[$linknid] = array();
              }
              $results[$linknid][] = $word;
              // Reduce score of the link caption in the source.
              $focus *= 0.2;
            }
            // Fall-through
            if (!isset($results[0][$word])) {
              $results[0][$word] = 0;
            }
            $results[0][$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_reindex($sid, $type, TRUE);

  // Insert cleaned up data into dataset
  db_insert('search_dataset')
    ->fields(array(
      'sid' => $sid,
      'type' => $type,
      'data' => $accum,
      'reindex' => 0,
    ))
    ->execute();

  // Insert results into search index
  foreach ($results[0] as $word => $score) {
    // If a word already exists in the database, its score gets increased
    // appropriately. If not, we create a new record with the appropriate
    // starting score.
    db_merge('search_index')
      ->key(array(
        'word' => $word,
        'sid' => $sid,
        'type' => $type,
      ))
      ->fields(array('score' => $score))
      ->expression('score', 'score + :score', array(':score' => $score))
      ->execute();
    search_dirty($word);
  }
  unset($results[0]);

  // Get all previous links from this item.
  $result = db_query("SELECT nid, caption FROM {search_node_links} WHERE sid = :sid AND type = :type", array(
    ':sid' => $sid,
    ':type' => $type
  ), array('target' => 'slave'));
  $links = array();
  foreach ($result as $link) {
    $links[$link->nid] = $link->caption;
  }

  // Now store links to nodes.
  foreach ($results as $nid => $words) {
    $caption = implode(' ', $words);
    if (isset($links[$nid])) {
      if ($links[$nid] != $caption) {
        // Update the existing link and mark the node for reindexing.
        db_update('search_node_links')
          ->fields(array('caption' => $caption))
          ->condition('sid', $sid)
          ->condition('type', $type)
          ->condition('nid', $nid)
          ->execute();
        search_touch_node($nid);
      }
      // Unset the link to mark it as processed.
      unset($links[$nid]);
    }
    elseif ($sid != $nid || $type != 'node') {
      // Insert the existing link and mark the node for reindexing, but don't
      // reindex if this is a link in a node pointing to itself.
      db_insert('search_node_links')
        ->fields(array(
          'caption' => $caption,
          'sid' => $sid,
          'type' => $type,
          'nid' => $nid,
        ))
        ->execute();
      search_touch_node($nid);
    }
  }
  // Any left-over links in $links no longer exist. Delete them and mark the nodes for reindexing.
  foreach ($links as $nid => $caption) {
    db_delete('search_node_links')
      ->condition('sid', $sid)
      ->condition('type', $type)
      ->condition('nid', $nid)
      ->execute();
    search_touch_node($nid);
  }
}

/**
 * Change a node's changed timestamp to 'now' to force reindexing.
 *
 * @param $nid
 *   The nid of the node that needs reindexing.
 */
function search_touch_node($nid) {
  db_update('search_dataset')
    ->fields(array('reindex' => REQUEST_TIME))
    ->condition('type', 'node')
    ->condition('sid', $nid)
    ->execute();
}

/**
 * Implements hook_node_update_index().
 */
function search_node_update_index($node) {
  // Transplant links to a node into the target node.
  $result = db_query("SELECT caption FROM {search_node_links} WHERE nid = :nid", array(':nid' => $node->nid), array('target' => 'slave'));
  $output = array();
  foreach ($result as $link) {
    $output[] = $link->caption;
  }
  if (count($output)) {
    return '<a>(' . implode(', ', $output) . ')</a>';
  }
}

/**
 * Implements hook_node_update().
 */
function search_node_update($node) {
  // Reindex the node when it is updated. The node is automatically indexed
  // when it is added, simply by being added to the node table.
  search_touch_node($node->nid);
}

/**
 * Implements hook_comment_insert().
 */
function search_comment_insert($comment) {
  // Reindex the node when comments are added.
  search_touch_node($comment->nid);
}

/**
 * Implements hook_comment_update().
 */
function search_comment_update($comment) {
  // Reindex the node when comments are changed.
  search_touch_node($comment->nid);
}

/**
 * Implements hook_comment_delete().
 */
function search_comment_delete($comment) {
  // Reindex the node when comments are deleted.
  search_touch_node($comment->nid);
}

/**
 * Implements hook_comment_publish().
 */
function search_comment_publish($comment) {
  // Reindex the node when comments are published.
  search_touch_node($comment->nid);
}

/**
 * Implements hook_comment_unpublish().
 */
function search_comment_unpublish($comment) {
  // Reindex the node when comments are unpublished.
  search_touch_node($comment->nid);
}

/**
 * Extract a module-specific search option from a search query. e.g. 'type:book'
 */
function search_expression_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_expression_insert($keys, $option, $value = '') {
  if (search_expression_extract($keys, $option)) {
    $keys = trim(preg_replace('/(^| )' . $option . ':[^ ]*/i', '', $keys));
  }
  if ($value != '') {
    $keys .= ' ' . $option . ':' . $value;
  }
  return $keys;
}

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

/**
 * @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 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
 *   by hook_view() and hook_node_view(). This is usually sufficient. You should
 *   only use this mechanism if you want additional, non-visible data to be
 *   indexed.
 * - Implement hook_search_info(). This will create a search tab for your module on
 *   the /search page with a simple keyword search form. You will also need to
 *   implement hook_search_execute() to perform the search.
 * - 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_info(). 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 $action
 *   Form action. Defaults to "search/$type". This will be run through url().
 * @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 $prompt
 *   A piece of text to put before the form (e.g. "Enter your keywords")
 * @return
 *   An HTML string containing the search form.
 */
function search_form($form, &$form_state, $action = '', $keys = '', $type = NULL, $prompt = NULL) {
  if (!$action) {
    $action = 'search/' . $type;
  }
  if (is_null($prompt)) {
    $prompt = t('Enter your keywords');
  }

  $form['#action'] = url($action);
  // Record the $action for later use in redirecting.
  $form_state['action'] = $action;
  $form['#attributes']['class'][] = 'search-form';
  $form['module'] = array('#type' => 'value', '#value' => $type);
  $form['basic'] = array('#type' => 'container', '#attributes' => array('class' => array('container-inline')));
  $form['basic']['keys'] = array(
    '#type' => 'textfield',
    '#title' => $prompt,
    '#default_value' => $keys,
    '#size' => $prompt ? 40 : 20,
    '#maxlength' => 255,
  );
  // processed_keys is used to coordinate keyword passing between other forms
  // that hook into the basic search form.
  $form['basic']['processed_keys'] = array('#type' => 'value', '#value' => array());
  $form['basic']['submit'] = array('#type' => 'submit', '#value' => t('Search'));

  return $form;
}

/**
 * Form builder; Output a search form for the search block's search box.
 *
 * @ingroup forms
 * @see search_box_form_submit()
 * @see search-theme-form.tpl.php
 * @see search-block-form.tpl.php
 */
function search_box($form, &$form_state, $form_id) {
  $form[$form_id] = array(
    '#type' => 'textfield',
    '#size' => 15,
    '#default_value' => '',
    '#attributes' => array('title' => t('Enter the terms you wish to search for.')),
  );
  $form['actions'] = array('#type' => 'actions');
  $form['actions']['submit'] = array('#type' => 'submit', '#value' => t('Search'));
  $form['#submit'][] = 'search_box_form_submit';

  return $form;
}

/**
 * Process a block search form submission.
 */
function search_box_form_submit($form, &$form_state) {
  // The search form relies on control of the redirect destination for its
  // functionality, so we override any static destination set in the request,
  // for example by drupal_access_denied() or drupal_not_found()
  // (see http://drupal.org/node/292565).
  if (isset($_GET['destination'])) {
    unset($_GET['destination']);
  }

  $form_id = $form['form_id']['#value'];
  $form_state['redirect'] = 'search/node/' . trim($form_state['values'][$form_id]);
}

/**
 * Process variables for search-block-form.tpl.php.
 *
 * The $variables array contains the following arguments:
 * - $form
 *
 * @see search-block-form.tpl.php
 */
function template_preprocess_search_block_form(&$variables) {
  $variables['search'] = array();
  $hidden = array();
  // Provide variables named after form keys so themers can print each element independently.
  foreach (element_children($variables['form']) as $key) {
    $type = $variables['form'][$key]['#type'];
    if ($type == 'hidden' || $type == 'token') {
      $hidden[] = drupal_render($variables['form'][$key]);
    }
    else {
      $variables['search'][$key] = drupal_render($variables['form'][$key]);
    }
  }
  // Hidden form elements have no value to themers. No need for separation.
  $variables['search']['hidden'] = implode($hidden);
  // Collect all form elements to make it easier to print the whole form.
  $variables['search_form'] = implode($variables['search']);
}

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

  if (isset($keys)) {
    if (module_hook($type, 'search_execute')) {
      $results = module_invoke($type, 'search_execute', $keys);
      if (module_hook($type, 'search_page')) {
        return module_invoke($type, 'search_page', $results);
      }
      else {
        return theme('search_results', array('results' => $results, 'type' => $type));
      }
    }
  }
}

/**
 * Returns snippets from a piece of text, with certain keywords highlighted.
 * Used for formatting search results.
 *
 * @param $keys
 *   A string containing a search query.
 *
 * @param $text
 *   The text to extract fragments from.
 *
 * @return
 *   A string containing HTML for the excerpt.
 */
function search_excerpt($keys, $text) {
  // We highlight around non-indexable or CJK characters.
  $boundary = '(?:(?<=[' . PREG_CLASS_UNICODE_WORD_BOUNDARY . PREG_CLASS_CJK . '])|(?=[' . PREG_CLASS_UNICODE_WORD_BOUNDARY . PREG_CLASS_CJK . ']))';

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

  // Prepare text
  $text = ' ' . strip_tags(str_replace(array('<', '>'), array(' <', '> '), $text)) . ' ';
  array_walk($keys, '_search_excerpt_replace');
  $workkeys = $keys;

  // Extract a fragment per keyword for at most 4 keywords.
  // First we collect ranges of text around each keyword, starting/ending
  // at spaces.
  // If the sum of all fragments is too short, we look for second occurrences.
  $ranges = array();
  $included = array();
  $length = 0;
  while ($length < 256 && count($workkeys)) {
    foreach ($workkeys as $k => $key) {
      if (strlen($key) == 0) {
        unset($workkeys[$k]);
        unset($keys[$k]);
        continue;
      }
      if ($length >= 256) {
        break;
      }
      // Remember occurrence of key so we can skip over it if more occurrences
      // are desired.
      if (!isset($included[$key])) {
        $included[$key] = 0;
      }
      // Locate a keyword (position $p), then locate a space in front (position
      // $q) and behind it (position $s)
      if (preg_match('/' . $boundary . $key . $boundary . '/iu', $text, $match, PREG_OFFSET_CAPTURE, $included[$key])) {
        $p = $match[0][1];
        if (($q = strpos($text, ' ', max(0, $p - 60))) !== FALSE) {
          $end = substr($text, $p, 80);
          if (($s = strrpos($end, ' ')) !== FALSE) {
            $ranges[$q] = $p + $s;
            $length += $p + $s - $q;
            $included[$key] = $p + 1;
          }
          else {
            unset($workkeys[$k]);
          }
        }
        else {
          unset($workkeys[$k]);
        }
      }
      else {
        unset($workkeys[$k]);
      }
    }
  }

  // If we didn't find anything, return the beginning.
  if (count($ranges) == 0) {
    return truncate_utf8($text, 256, TRUE, TRUE);
  }

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

  // Now we collapse overlapping text ranges into one. The sorting makes it O(n).
  $newranges = array();
  foreach ($ranges as $from2 => $to2) {
    if (!isset($from1)) {
      $from1 = $from2;
      $to1 = $to2;
      continue;
    }
    if ($from2 <= $to1) {
      $to1 = max($to1, $to2);
    }
    else {
      $newranges[$from1] = $to1;
      $from1 = $from2;
      $to1 = $to2;
    }
  }
  $newranges[$from1] = $to1;

  // Fetch text
  $out = array();
  foreach ($newranges as $from => $to) {
    $out[] = substr($text, $from, $to - $from);
  }
  $text = (isset($newranges[0]) ? '' : '... ') . implode(' ... ', $out) . ' ...';

  // Highlight keywords. Must be done at once to prevent conflicts ('strong' and '<strong>').
  $text = preg_replace('/' . $boundary . '(' . implode('|', $keys) . ')' . $boundary . '/iu', '<strong>\0</strong>', $text);
  return $text;
}

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

/**
 * Helper function for array_walk in search_except.
 */
function _search_excerpt_replace(&$text) {
  $text = preg_quote($text, '/');
}

function search_forms() {
  $forms['search_block_form']= array(
    'callback' => 'search_box',
    'callback arguments' => array('search_block_form'),
  );
  return $forms;
}
