<?php

/**
 * @file
 * The non-volatile object cache is used to store an object while it is
 * being edited, so that we don't have to save until we're completely
 * done. The cache should be 'cleaned' on a regular basis, meaning to
 * remove old objects from the cache, but otherwise the data in this
 * cache must remain stable, as it includes unsaved changes.
 */

/**
 * Get an object from the non-volatile ctools cache.
 *
 * This function caches in memory as well, so that multiple calls to this
 * will not result in multiple database reads.
 *
 * @param $obj
 *   A 128 character or less string to define what kind of object is being
 *   stored; primarily this is used to prevent collisions.
 * @param $name
 *   The name of the object being stored.
 * @param $skip_cache
 *   Deprecated in favor of drupal_static*
 *   Skip the memory cache, meaning this must be read from the db again.
 * @param $sid
 *   The session id, allowing someone to use Session API or their own solution;
 *   defaults to session_id().
 *
 * @return
 *   The data that was cached.
 */
function ctools_object_cache_get($obj, $name, $skip_cache = FALSE, $sid = NULL) {
  $cache = &drupal_static(__FUNCTION__, array());
  $key = "$obj:$name";
  if ($skip_cache) {
    unset($cache[$key]);
  }

  if (!$sid) {
    $sid = session_id();
  }

  if (!array_key_exists($key, $cache)) {
    $data = db_query('SELECT * FROM {ctools_object_cache} WHERE sid = :session_id AND obj = :object AND name = :name', array(
      ':session_id' => $sid,
      ':object' => $obj,
      ':name' => md5($name),
    ))->fetchObject();
    if ($data) {
      $cache[$key] = unserialize($data->data);
    }
  }
  return isset($cache[$key]) ? $cache[$key] : NULL;
}

/**
 * Store an object in the non-volatile ctools cache.
 *
 * @param $obj
 *   A 128 character or less string to define what kind of object is being
 *   stored; primarily this is used to prevent collisions.
 * @param $name
 *   The name of the object being stored.
 * @param $cache
 *   The object to be cached. This will be serialized prior to writing.
 * @param $sid
 *   The session id, allowing someone to use Session API or their own solution;
 *   defaults to session_id().
 */
function ctools_object_cache_set($obj, $name, $cache, $sid = NULL) {
  // Store the CTools session id in the user session to force a
  // session for anonymous users in Drupal 7 and Drupal 6 Pressflow.
  // see http://drupal.org/node/562374, http://drupal.org/node/861778
  if (empty($GLOBALS['user']->uid) && empty($_SESSION['ctools_session_id'])) {
    $_SESSION['ctools_hold_session'] = TRUE;
  }

  ctools_object_cache_clear($obj, $name, $sid);

  if (!$sid) {
    $sid = session_id();
  }

  db_insert('ctools_object_cache')
    ->fields(array(
      'sid' => $sid,
      'obj' => $obj,
      'name' => md5($name),
      'data' => serialize($cache),
      'updated' => REQUEST_TIME,
    ))
    ->execute();
}

/**
 * Remove an object from the non-volatile ctools cache.
 *
 * @param $obj
 *   A 128 character or less string to define what kind of object is being
 *   stored; primarily this is used to prevent collisions.
 * @param $name
 *   The name of the object being removed.
 * @param $sid
 *   The session id, allowing someone to use Session API or their own solution;
 *   defaults to session_id().
 */
function ctools_object_cache_clear($obj, $name, $sid = NULL) {
  if (!$sid) {
    $sid = session_id();
  }

  db_delete('ctools_object_cache')
    ->condition('sid', $sid)
    ->condition('obj', $obj)
    ->condition('name', md5($name))
    ->execute();
  // Ensure the static cache is emptied of this obj:name set.
  drupal_static_reset('ctools_object_cache_get');
}

/**
 * Determine if another user has a given object cached.
 *
 * This is very useful for 'locking' objects so that only one user can
 * modify them.
 *
 * @param $obj
 *   A 128 character or less string to define what kind of object is being
 *   stored; primarily this is used to prevent collisions.
 * @param $name
 *   The name of the object being removed.
 * @param $sid
 *   The session id, allowing someone to use Session API or their own solution;
 *   defaults to session_id().
 *
 * @return
 *   An object containing the UID and updated date if found; NULL if not.
 */
function ctools_object_cache_test($obj, $name, $sid = NULL) {

  if (!$sid) {
    $sid = session_id();
  }

  return db_query('SELECT s.uid, c.updated FROM {ctools_object_cache} c INNER JOIN {sessions} s ON c.sid = s.sid WHERE s.sid <> :session_id AND c.obj = :obj AND c.name = :name ORDER BY c.updated ASC', array(
    ':session_id' => $sid,
    ':obj' => $obj,
    ':name' => md5($name),
  ))->fetchObject();
}

/**
 * Get the cache status of a group of objects.
 *
 * This is useful for displaying lock status when listing a number of objects
 * an an administration UI.
 *
 * @param $obj
 *   A 128 character or less string to define what kind of object is being
 *   stored; primarily this is used to prevent collisions.
 * @param $names
 *   An array of names of objects
 *
 * @return
 *   An array of objects containing the UID and updated date for each name found.
 */
function ctools_object_cache_test_objects($obj, $names) {
  array_walk($names, 'md5');
  return db_query("SELECT c.name, s.uid, c.updated FROM {ctools_object_cache} c INNER JOIN {sessions} s ON c.sid = s.sid WHERE c.obj = :obj AND c.name IN (:names) ORDER BY c.updated ASC", array(':obj' => $obj, ':names' => $names))
    ->fetchAllAssoc('name');
}

/**
 * Remove an object from the non-volatile ctools cache for all session IDs.
 *
 * This is useful for clearing a lock.
 *
 * @param $obj
 *   A 128 character or less string to define what kind of object is being
 *   stored; primarily this is used to prevent collisions.
 * @param $name
 *   The name of the object being removed.
 */
function ctools_object_cache_clear_all($obj, $name) {
  db_delete('ctools_object_cache')
    ->condition('obj', $obj)
    ->condition('name', md5($name))
    ->execute();
  // Ensure the static cache is emptied of this obj:name set.
  $cache = &drupal_static('ctools_object_cache_get', array());
  unset($cache["$obj:$name"]);
}

/**
 * Remove all objects in the object cache that are older than the
 * specified age.
 *
 * @param $age
 *   The minimum age of objects to remove, in seconds. For example, 86400 is
 *   one day. Defaults to 7 days.
 */
function ctools_object_cache_clean($age = NULL) {
  if (empty($age)) {
    // 7 days.
    $age = 86400 * 7;
  }
  db_delete('ctools_object_cache')
    ->condition('updated', REQUEST_TIME - $age, '<')
    ->execute();
}
