farmOS/modules/farm/farm_group/farm_group.module

<?php
/**
 * @file
 * Code for the Farm Group feature.
 */

include_once 'farm_group.features.inc';

/**
 * Implements hook_farm_ui_entities().
 */
function farm_group_farm_ui_entities() {
  return array(
    'farm_asset' => array(
      'group' => array(
        'label' => t('Group'),
        'label_plural' => t('Groups'),
        'view' => 'farm_groups',
      ),
    ),
  );
}

/**
 * Load groups that an asset is a member of.
 *
 * @param FarmAsset $asset
 *   The farm_asset object to look for.
 * @param int $time
 *   Unix timestamp limiter. Only logs before this time will be included.
 *   Defaults to the current time. Set to 0 to load the absolute last.
 * @param bool $done
 *   Whether or not to only show logs that are marked as "done".
 *   Defaults to TRUE.
 *
 * @return array
 *   Returns an array of groups that the asset is a member of.
 */
function farm_group_asset_membership(FarmAsset $asset, $time = REQUEST_TIME, $done = TRUE) {
  $groups = array();

  // Load the log using our helper function.
  $log = farm_group_asset_latest_membership($asset, $time, $done);

  // If no groups are specified, bail.
  if (empty($log->field_farm_group[LANGUAGE_NONE])) {
    return $groups;
  }

  // Iterate through the referenced groups and load them.
  if (!empty($log->field_farm_group[LANGUAGE_NONE])) {
    foreach ($log->field_farm_group[LANGUAGE_NONE] as $group_reference) {
      if (!empty($group_reference['target_id'])) {
        $group = farm_asset_load($group_reference['target_id']);
        if (!empty($group)) {
          $groups[] = $group;
        }
      }
    }
  }
  return $groups;
}

/**
 * Load an asset's latest log that defines a group membership.
 *
 * @param FarmAsset $asset
 *   The farm_asset object to look for.
 * @param int $time
 *   Unix timestamp limiter. Only logs before this time will be included.
 *   Defaults to the current time. Set to 0 to load the absolute last.
 * @param bool $done
 *   Whether or not to only show logs that are marked as "done". Defaults to
 *   TRUE.
 *
 * @return Log|bool
 *   Returns a log entity. FALSE if something goes wrong.
 */
function farm_group_asset_latest_membership(FarmAsset $asset, $time = REQUEST_TIME, $done = TRUE) {

  /**
   * Please read the comments in farm_group_asset_membership_query() to
   * understand how this works, and to be aware of the limitations and
   * responsibilities we have in this function with regard to sanitizing query
   * inputs.
   */

  // If the asset doesn't have an ID (for instance if it is new and hasn't been
  // saved yet), bail.
  if (empty($asset->id)) {
    return FALSE;
  }

  // Make a query for loading the latest group membership log.
  $query = farm_group_asset_membership_query($asset->id, $time, $done);

  // Execute the query and gather the log id.
  $result = $query->execute();
  $log_id = $result->fetchField();

  // If a log id exists, load and return it.
  if (!empty($log_id)) {
    return log_load($log_id);
  }
  return FALSE;
}

/**
 * Build a query to find group membership logs of a specific asset.
 *
 * @param int|string $asset_id
 *   The asset id to search for. This can either be a specific id, or a field
 *   alias string from another query (ie: 'mytable.assetid'). For an example
 *   of field alias string usage, see the Views relationship handler code in
 *   farm_group_handler_relationship_membership::query().
 * @param int $time
 *   Unix timestamp limiter. Only logs before this time will be included.
 *   Defaults to the current time. Set to 0 to load the absolute last.
 * @param bool $done
 *   Whether or not to only show logs that are marked as "done". Defaults to
 *   TRUE.
 * @param bool $single
 *   Whether or not to limit the query to a single result. Defaults to TRUE.
 *
 * @return \SelectQuery
 *   Returns a SelectQuery object.
 */
function farm_group_asset_membership_query($asset_id, $time = REQUEST_TIME, $done = TRUE, $single = TRUE) {

  /**
   * Please read the comments in farm_log_asset_query() to understand how this
   * works, and to be aware of the limitations and responsibilities we have in
   * this function with regard to sanitizing query inputs.
   */

  // Use the farm_log_asset_query() helper function to start a query object.
  $query = farm_log_asset_query($asset_id, $time, $done, $single);

  // Join in the log's "group" field, and filter to only include logs that have
  // a "group" value defined.
  $query->join('field_data_field_farm_group', 'ss_fdffg', "ss_fdffg.entity_type = 'log' AND ss_fdffg.entity_id = ss_log.id AND ss_fdffg.deleted = 0");
  $query->where('ss_fdffg.field_farm_group_target_id IS NOT NULL');

  // Add the log ID field.
  $query->addField('ss_log', 'id');

  // Return the query object.
  return $query;
}

/**
 * Recursively check for circular group membership.
 *
 * @param FarmAsset $group
 *   The group that the asset will be added to.
 * @params FarmAsset $asset
 *   The asset being considered for membership in the group.
 *
 * @return bool
 *   Returns TRUE if a circular dependency would exist if the asset became a
 *   member of the group, FALSE otherwise.
 */
function farm_group_circular_membership(FarmAsset $group, FarmAsset $asset) {

  // A group can't be inside itself. This is primarily how we will check for
  // circular membership, along with recursively checking parent groups below.
  if ($group->id == $asset->id) {
    return TRUE;
  }

  // Check to see if the group is a member of other groups.
  $parent_groups = farm_group_asset_membership($group);

  // If no parent groups were found, no circular membership can exist.
  if (empty($parent_groups)) {
    return FALSE;
  }

  // Iterate through the parent groups and recurse into them to check if the
  // new asset will create a circular membership anywhere down the line.
  foreach ($parent_groups as $parent_group) {
    if (farm_group_circular_membership($parent_group, $asset)) {
      return TRUE;
    }
  }

  // Ok we're good! No circular memberships detected!
  return FALSE;
}