<?php

/**
 * @file
 * Implements a drop-in replacement for the flag_node class.
 * Maintains flag counts not by re-counting rows from flag_content on every update
 * but through in-/decrementing the counter values
 *
 * @link http://drupal.org/node/719616
 */
 
 
/**
 * PUT THIS HOOK FUNCTION INTO YOUR MAIN MODULE FILE
 * Then select the new type during flag creation (or change "content_type" of existing flags in db)
 * You might also want to derive your own flag class from this
 *
 * Implements hook_flag_definitions().
 */
/*
function mymodule_flag_definitions(){
  return array(
    'node_inccount' => array(
        'title' => t('Nodes (using inc/dec counter)'),
        'description' => t("Nodes are a Drupal site's primary content."),
        'handler' => 'flag_node_inccount'
    ),
  );
}
*/
 
class flag_node_inccount extends flag_node {
  
  /**
  * @see flag_flag::_flag
  */
  function _flag($content_id, $uid, $sid) {
    $transaction = db_transaction();
    $fcid = parent::_flag($content_id, $uid, $sid);
    if ($fcid) {
      $this->_increase_count($content_id);
    }
    return $fcid;
  }

  /**
  * @see flag_flag::_unflag
  */
  function _unflag($content_id, $uid, $sid) {
    $transaction = db_transaction();
    $fcid = parent::_unflag($content_id, $uid, $sid);
    if ($fcid) {
      $this->_decrease_count($content_id);
    }
    return $fcid;
  }
  
  /**
  * @see flag_flag::_update_count
  */
  function _update_count($content_id) {
    // do nothing
  }
  
 /**
  * Increases the flag count for this content.
  *
  * @param $content_id
  *   For which item should the count be increased.
  *
  * @param $number
  *   Increase by this number (default 1).
  *
  * @protected
  */
  function _increase_count($content_id, $number = 1) {
    if (!db_update('flag_counts')
         ->expression('count', "count + $number")
         ->condition('fid', $this->fid)
         ->condition('content_id', $content_id)
         ->execute()
    ){
        db_insert('flag_counts')->fields(array(
          'fid' => $this->fid,
          'content_type' => $this->content_type,
          'content_id' => $content_id,
          'count' => $number))
        ->execute();
    }
  }

 /**
  * Decreases the flag count for this content.
  *
  * @param $content_id
  *   For which item should the count be descreased.
  *
  * @param $number
  *   Decrease by this number (default 1).
  *
  * @protected
  */
  function _decrease_count($content_id, $number = 1) {
    if (!db_delete('flag_counts')
         ->condition('fid', $this->fid)
         ->condition('content_id', $content_id)
         ->condition('count',$number,'<=')
         ->execute()
    ){
       db_update('flag_counts')
       ->expression('count', "count - $number")
       ->condition('fid', $this->fid)
       ->condition('content_id', $content_id)
       ->execute();
    }
  }
  
}
?>