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<?php

/**

 * @file

 * Search query extender and helper functions.

 */

/**

 * Do a query on the full-text search index for a word or words.

 *

 * This function is normally only called by each module that supports the

 * indexed search (and thus, implements hook_update_index()).

 *

 * Results are retrieved in two logical passes. However, the two passes are

 * joined together into a single query. And in the case of most simple

 * queries the second pass is not even used.

 *

 * The first pass selects a set of all possible matches, which has the benefit

 * of also providing the exact result set for simple "AND" or "OR" searches.

 *

 * The second portion of the query further refines this set by verifying

 * advanced text conditions (such as negative or phrase matches).

 *

 * The used query object has the tag 'search_$module' and can be further

 * extended with hook_query_alter().

 */

class SearchQuery extends SelectQueryExtender {

  /**

   * The search query that is used for searching.

   *

   * @var string

   */

  protected $searchExpression;

  /**

   * Type of search (search module).

   *

   * This maps to the value of the type column in search_index, and is equal

   * to the machine-readable name of the module that implements

   * hook_search_info().

   *

   * @var string

   */

  protected $type;

  /**

   * Positive and negative search keys.

   *

   * @var array

   */

  protected $keys = array('positive' => array(), 'negative' => array());

  /**

   * Indicates whether the first pass query requires complex conditions (LIKE).

   *

   * @var boolean.

   */

  protected $simple = TRUE;

  /**

   * Conditions that are used for exact searches.

   *

   * This is always used for the second pass query but not for the first pass,

   * unless $this->simple is FALSE.

   *

   * @var DatabaseCondition

   */

  protected $conditions;

  /**

   * Indicates how many matches for a search query are necessary.

   *

   * @var int

   */

  protected $matches = 0;

  /**

   * Array of search words.

   *

   * These words have to match against {search_index}.word.

   *

   * @var array

   */

  protected $words = array();

  /**

   * Multiplier for the normalized search score.

   *

   * This value is calculated by the first pass query and multiplied with the

   * actual score of a specific word to make sure that the resulting calculated

   * score is between 0 and 1.

   *

   * @var float

   */

  protected $normalize;

  /**

   * Indicates whether the first pass query has been executed.

   *

   * @var boolean

   */

  protected $executedFirstPass = FALSE;

  /**

   * Stores score expressions.

   *

   * @var array

   *

   * @see addScore()

   */

  protected $scores = array();

  /**

   * Stores arguments for score expressions.

   *

   * @var array

   */

  protected $scoresArguments = array();

  /**

   * Stores multipliers for score expressions.

   *

   * @var array

   */

  protected $multiply = array();

  /**

   * Whether or not search expressions were ignored.

   *

   * The maximum number of AND/OR combinations exceeded can be configured to

   * avoid Denial-of-Service attacks. Expressions beyond the limit are ignored.

   *

   * @var boolean

   */

  protected $expressionsIgnored = FALSE;

  /**

   * Sets up the search query expression.

   *

   * @param $query

   *   A search query string, which can contain options.

   * @param $module

   *   The search module. This maps to {search_index}.type in the database.

   *

   * @return

   *   The SearchQuery object.

   */

  public function searchExpression($expression, $module) {

    $this->searchExpression = $expression;

    $this->type = $module;

    return $this;

  }

  /**

   * Applies a search option and removes it from the search query string.

   *

   * These options are in the form option:value,value2,value3.

   *

   * @param $option

   *   Name of the option.

   * @param $column

   *   Name of the database column to which the value should be applied.

   *

   * @return

   *   TRUE if a value for that option was found, FALSE if not.

   */

  public function setOption($option, $column) {

    if ($values = search_expression_extract($this->searchExpression, $option)) {

      $or = db_or();

      foreach (explode(',', $values) as $value) {

        $or->condition($column, $value);

      }

      $this->condition($or);

      $this->searchExpression = search_expression_insert($this->searchExpression, $option);

      return TRUE;

    }

    return FALSE;

  }

  /**

   * Parses the search query into SQL conditions.

   *

   * We build two queries that match the dataset bodies.

   */

  protected function parseSearchExpression() {

    // Matchs words optionally prefixed by a dash. A word in this case is

    // something between two spaces, optionally quoted.

    preg_match_all('/ (-?)("[^"]+"|[^" ]+)/i', ' ' .  $this->searchExpression , $keywords, PREG_SET_ORDER);

    if (count($keywords) ==  0) {

      return;

    }

    // Classify tokens.

    $or = FALSE;

    $warning = '';

    $limit_combinations = variable_get('search_and_or_limit', 7);

    // The first search expression does not count as AND.

    $and_count = -1;

    $or_count = 0;

    foreach ($keywords as $match) {

      if ($or_count && $and_count + $or_count >= $limit_combinations) {

        // Ignore all further search expressions to prevent Denial-of-Service

        // attacks using a high number of AND/OR combinations.

        $this->expressionsIgnored = TRUE;

        break;

      }

      $phrase = FALSE;

      // Strip off phrase quotes.

      if ($match[2]{0} == '"') {

        $match[2] = substr($match[2], 1, -1);

        $phrase = TRUE;

        $this->simple = FALSE;

      }

      // Simplify keyword according to indexing rules and external

      // preprocessors. Use same process as during search indexing, so it

      // will match search index.

      $words = search_simplify($match[2]);

      // Re-explode in case simplification added more words, except when

      // matching a phrase.

      $words = $phrase ? array($words) : preg_split('/ /', $words, -1, PREG_SPLIT_NO_EMPTY);

      // Negative matches.

      if ($match[1] == '-') {

        $this->keys['negative'] = array_merge($this->keys['negative'], $words);

      }

      // OR operator: instead of a single keyword, we store an array of all

      // OR'd keywords.

      elseif ($match[2] == 'OR' && count($this->keys['positive'])) {

        $last = array_pop($this->keys['positive']);

        // Starting a new OR?

        if (!is_array($last)) {

          $last = array($last);

        }

        $this->keys['positive'][] = $last;

        $or = TRUE;

        $or_count++;

        continue;

      }

      // AND operator: implied, so just ignore it.

      elseif ($match[2] == 'AND' || $match[2] == 'and') {

        $warning = $match[2];

        continue;

      }

      // Plain keyword.

      else {

        if ($match[2] == 'or') {

          $warning = $match[2];

        }

        if ($or) {

          // Add to last element (which is an array).

          $this->keys['positive'][count($this->keys['positive']) - 1] = array_merge($this->keys['positive'][count($this->keys['positive']) - 1], $words);

        }

        else {

          $this->keys['positive'] = array_merge($this->keys['positive'], $words);

          $and_count++;

        }

      }

      $or = FALSE;

    }

    // Convert keywords into SQL statements.

    $this->conditions = db_and();

    $simple_and = FALSE;

    $simple_or = FALSE;

    // Positive matches.

    foreach ($this->keys['positive'] as $key) {

      // Group of ORed terms.

      if (is_array($key) && count($key)) {

        $simple_or = TRUE;

        $any = FALSE;

        $queryor = db_or();

        foreach ($key as $or) {

          list($num_new_scores) = $this->parseWord($or);

          $any |= $num_new_scores;

          $queryor->condition('d.data', "% $or %", 'LIKE');

        }

        if (count($queryor)) {

          $this->conditions->condition($queryor);

          // A group of OR keywords only needs to match once.

          $this->matches += ($any > 0);

        }

      }

      // Single ANDed term.

      else {

        $simple_and = TRUE;

        list($num_new_scores, $num_valid_words) = $this->parseWord($key);

        $this->conditions->condition('d.data', "% $key %", 'LIKE');

        if (!$num_valid_words) {

          $this->simple = FALSE;

        }

        // Each AND keyword needs to match at least once.

        $this->matches += $num_new_scores;

      }

    }

    if ($simple_and && $simple_or) {

      $this->simple = FALSE;

    }

    // Negative matches.

    foreach ($this->keys['negative'] as $key) {

      $this->conditions->condition('d.data', "% $key %", 'NOT LIKE');

      $this->simple = FALSE;

    }

    if ($warning == 'or') {

      drupal_set_message(t('Search for either of the two terms with uppercase <strong>OR</strong>. For example, <strong>cats OR dogs</strong>.'));

    }

  }

  /**

   * Helper function for parseQuery().

   */

  protected function parseWord($word) {

    $num_new_scores = 0;

    $num_valid_words = 0;

    // Determine the scorewords of this word/phrase.

    $split = explode(' ', $word);

    foreach ($split as $s) {

      $num = is_numeric($s);

      if ($num || drupal_strlen($s) >= variable_get('minimum_word_size', 3)) {

        if (!isset($this->words[$s])) {

          $this->words[$s] = $s;

          $num_new_scores++;

        }

        $num_valid_words++;

      }

    }

    // Return matching snippet and number of added words.

    return array($num_new_scores, $num_valid_words);

  }

  /**

   * Executes the first pass query.

   *

   * This can either be done explicitly, so that additional scores and

   * conditions can be applied to the second pass query, or implicitly by

   * addScore() or execute().

   *

   * @return

   *   TRUE if search items exist, FALSE if not.

   */

  public function executeFirstPass() {

    $this->parseSearchExpression();

    if (count($this->words) == 0) {

      form_set_error('keys', format_plural(variable_get('minimum_word_size', 3), 'You must include at least one positive keyword with 1 character or more.', 'You must include at least one positive keyword with @count characters or more.'));

      return FALSE;

    }

    if ($this->expressionsIgnored) {

      drupal_set_message(t('Your search used too many AND/OR expressions. Only the first @count terms were included in this search.', array('@count' => variable_get('search_and_or_limit', 7))), 'warning');

    }

    $this->executedFirstPass = TRUE;

    if (!empty($this->words)) {

      $or = db_or();

      foreach ($this->words as $word) {

        $or->condition('i.word', $word);

      }

      $this->condition($or);

    }

    // Build query for keyword normalization.

    $this->join('search_total', 't', 'i.word = t.word');

    $this

      ->condition('i.type', $this->type)

      ->groupBy('i.type')

      ->groupBy('i.sid')

      ->having('COUNT(*) >= :matches', array(':matches' => $this->matches));

    // Clone the query object to do the firstPass query;

    $first = clone $this->query;

    // For complex search queries, add the LIKE conditions to the first pass query.

    if (!$this->simple) {

      $first->join('search_dataset', 'd', 'i.sid = d.sid AND i.type = d.type');

      $first->condition($this->conditions);

    }

    // Calculate maximum keyword relevance, to normalize it.

    $first->addExpression('SUM(i.score * t.count)', 'calculated_score');

    $this->normalize = $first

      ->range(0, 1)

      ->orderBy('calculated_score', 'DESC')

      ->execute()

      ->fetchField();

    if ($this->normalize) {

      return TRUE;

    }

    return FALSE;

  }

  /**

   * Adds a custom score expression to the search query.

   *

   * Score expressions are used to order search results. If no calls to

   * addScore() have taken place, a default keyword relevance score will be

   * used. However, if at least one call to addScore() has taken place, the

   * keyword relevance score is not automatically added.

   *

   * Also note that if you call orderBy() directly on the query, search scores

   * will not automatically be used to order search results. Your orderBy()

   * expression can reference 'calculated_score', which will be the total

   * calculated score value.

   *

   * @param $score

   *   The score expression, which should evaluate to a number between 0 and 1.

   *   The string 'i.relevance' in a score expression will be replaced by a

   *   measure of keyword relevance between 0 and 1.

   * @param $arguments

   *   Query arguments needed to provide values to the score expression.

   * @param $multiply

   *   If set, the score is multiplied with this value. However, all scores

   *   with multipliers are then divided by the total of all multipliers, so

   *   that overall, the normalization is maintained.

   *

   * @return object

   *   The updated query object.

   */

  public function addScore($score, $arguments = array(), $multiply = FALSE) {

    if ($multiply) {

      $i = count($this->multiply);

      // Modify the score expression so it is multiplied by the multiplier,

      // with a divisor to renormalize.

      $score = "CAST(:multiply_$i AS DECIMAL) * COALESCE(( " . $score . "), 0) / CAST(:total_$i AS DECIMAL)";

      // Add an argument for the multiplier. The :total_$i argument is taken

      // care of in the execute() method, which is when the total divisor is

      // calculated.

      $arguments[':multiply_' . $i] = $multiply;

      $this->multiply[] = $multiply;

    }

    $this->scores[] = $score;

    $this->scoresArguments += $arguments;

    return $this;

  }

  /**

   * Executes the search.

   *

   * If not already done, this executes the first pass query. Then the complex

   * conditions are applied to the query including score expressions and

   * ordering.

   *

   * @return

   *   FALSE if the first pass query returned no results, and a database result

   *   set if there were results.

   */

  public function execute()

  {

    if (!$this->executedFirstPass) {

      $this->executeFirstPass();

    }

    if (!$this->normalize) {

      return new DatabaseStatementEmpty();

    }

    // Add conditions to query.

    $this->join('search_dataset', 'd', 'i.sid = d.sid AND i.type = d.type');

    $this->condition($this->conditions);

    if (empty($this->scores)) {

      // Add default score.

      $this->addScore('i.relevance');

    }

    if (count($this->multiply)) {

      // Re-normalize scores with multipliers by dividing by the total of all

      // multipliers. The expressions were altered in addScore(), so here just

      // add the arguments for the total.

      $i = 0;

      $sum = array_sum($this->multiply);

      foreach ($this->multiply as $total) {

        $this->scoresArguments[':total_' . $i] = $sum;

        $i++;

      }

    }

    // Replace the pseudo-expression 'i.relevance' with a measure of keyword

    // relevance in all score expressions, using string replacement. Careful

    // though! If you just print out a float, some locales use ',' as the

    // decimal separator in PHP, while SQL always uses '.'. So, make sure to

    // set the number format correctly.

    $relevance = number_format((1.0 / $this->normalize), 10, '.', '');

    $this->scores = str_replace('i.relevance', '(' . $relevance . ' * i.score * t.count)', $this->scores);

    // Add all scores together to form a query field.

    $this->addExpression('SUM(' . implode(' + ', $this->scores) . ')', 'calculated_score', $this->scoresArguments);

    // If an order has not yet been set for this query, add a default order

    // that sorts by the calculated sum of scores.

    if (count($this->getOrderBy()) == 0) {

      $this->orderBy('calculated_score', 'DESC');

    }

    // Add tag and useful metadata.

    $this

      ->addTag('search_' . $this->type)

      ->addMetaData('normalize', $this->normalize)

      ->fields('i', array('type', 'sid'));

    return $this->query->execute();

  }

  /**

   * Builds the default count query for SearchQuery.

   *

   * Since SearchQuery always uses GROUP BY, we can default to a subquery. We

   * also add the same conditions as execute() because countQuery() is called

   * first.

   */

  public function countQuery() {

    // Clone the inner query.

    $inner = clone $this->query;

    // Add conditions to query.

    $inner->join('search_dataset', 'd', 'i.sid = d.sid AND i.type = d.type');

    $inner->condition($this->conditions);

    // Remove existing fields and expressions, they are not needed for a count

    // query.

    $fields =& $inner->getFields();

    $fields = array();

    $expressions =& $inner->getExpressions();

    $expressions = array();

    // Add the sid as the only field and count them as a subquery.

    $count = db_select($inner->fields('i', array('sid')), NULL, array('target' => 'slave'));

    // Add the COUNT() expression.

    $count->addExpression('COUNT(*)');

    return $count;

  }

}