Deny location based access to nodes

Question

I need to restrict access to a node based on the distance of the current user to a location attached to the node (with Location module). The distance to decide, if access is allowed is node based and stored in a field of the node. Currently I achive this feature with hook_node_access(). I get the current location of the user through the Smart IP module and are able to calculate the distance by passing the coordinates of the user and the node to location_distance_between(), which is provided by the Location module.

Because hook_node_access() isn't considered by Views I think about accomplishing this feature with hook_node_access_records() and hook_node_grants(). Since the distance is dynamically, I have no idea how to achive this. In my understanding hook_node_grants() is called before the database query, so I have no chance to get the distance right?

Any ideas?

Thanks, Daniel

Answer 1

Option 1

I use the Geofield module, which provides a similar function to the Location module. It provides the concept of a proximity filter. This allows you to implement views such as "show all nodes within 50km of specified point". I don't know whether the Location module has a similar function, or whether you might be willing to change modules. The Smart IP module claims some Views integration but D6 only, so you might need a bit of code to integrate with views.

This approach would not use access control at all - so that if the user specifically navigated by URL to a far away node, they would still see it.

Option 2

If you definitely want access control, then I think you will have to give up exact distances. You could divide your target area into regions, maybe around 50-500 of them - most simply using a simple grid. In your hook_node_access_records, you decide which regions are close enough to the node (calculate distance to the region centre). Finally in hook_node_grants, you need code to take the output of the Smart IP module and calculate which region it is in, and set the appropriate grant.

If you need some more help with the details of either approach, feel free to edit your question to say which approach you prefer, what you have working and where you are stuck.

Answer 2

Ok I got it with a little work around.

I use hook_views_query_alter() to get all the distances of the relevant nodes. So I build an own query like this:

function mymodule_views_query_alter(&$view, &$query) {
  if($view->name === 'my_view' && $view->current_display === 'my_display') {
    // build the query to get the distances
    $location_query = db_select($query->table_queue['node']['table'], $query->table_queue['node']['alias']);
    $location_query->leftJoin('location_instance', 'li', $query->table_queue['node']['alias'] . '.vid = li.vid');
    $location_query->leftJoin('location', 'l', 'li.lid = l.lid');
    $location_query->leftJoin('field_data_field_distance', 'd', $query->table_queue['node']['alias'] . '.nid = d.entity_id');
    $location_query->fields('l', array('latitude', 'longitude'))
    ->fields('d', array('field_distance_value'))
    ->fields($query->table_queue['node']['alias'], array('nid'));

    // consider all filters which were set in the views ui
    foreach ($query->where[1]['conditions'] as $condition) {
      $location_query->condition($condition['field'], $condition['value'], $condition['operator']);

    }

    // execute the query
    $result = $location_query->execute()->fetchAll();
    // go through all results to check the distance
    foreach($result as $node) {
      // do the calculation of the distance
      // ...
      // check if distance is close enough
      if($distance <= $node->field_distance_value) {
        $nids[] = $node->nid;
      }
    }

    // remove all conditions from the views query, because we already used them
    unset($query->where[1]['conditions']);

    // let views just load all the relevant NIDs
    $query->where[1]['conditions'][0] = array(
      'field' => $query->table_queue['node']['alias'] . '.nid',
      'value' => $nids,
      'operator' => 'in',
    );
  }
}

Well, in this way I anticipate the Views query and change it, so that Views just needs to load the NIDs which were required.