<?php
/**
* Implementation of hook_help().
*/
function term_merge_help($section) {
  switch($section) {
    case 'admin/modules#description':
      return t('Allows site admins to associate nodes with a foster term when a term is deleted.');
  }
}

/**
* Implementation of hook_form_alter().
*/
function term_merge_form_alter($form_id, &$form) {
  switch($form_id) {
    case 'taxonomy_term_confirm_delete':
      $tid = arg(4);
      if(is_numeric($tid)) {
        $term_nodes = taxonomy_term_count_nodes($tid);
        if($term_nodes > 0) {
          $nids = array();
          $term_nodes = _term_merge_select_nodes($tid);
          while ($node = db_fetch_object($term_nodes)) {
            $nids[] = $node->nid;
          }

          $term = taxonomy_get_term($tid);
          $children = taxonomy_get_tree($term->vid, $tid);

          foreach ($children as $child) {
            $exclude[] = $child->tid;
          }
          $exclude[] = $tid;

          $form['foster'] = _taxonomy_term_select(t('Foster term(s)'), 'foster', -1, $term->vid, t('One or more nodes are using this term. If you select one or more terms from the list above, these nodes will be associated with the selected terms.'), 1, NULL, $exclude);

          $form['#submit']['term_merge_term_delete_submit'] = array($nids);
        }
      }
      break;
    }
}

function term_merge_term_delete_submit($form_id, $form_values, $nids) {
  if(isset($form_values['foster'])) {
    $foster = $form_values['foster'];
    if (count($foster)>0) {
      while (list($tid, $object) = each($foster)) {
        $foster[$tid] = taxonomy_get_term($tid);
      }
      reset($foster);
      foreach($nids as $nid) { 
        $node = node_load($nid);
        $terms = $node->taxonomy;
        while (list($tid,$object) = each($foster)) {
          $terms[$tid] = $object;
        }
        reset($foster);

        // note for 6.x: taxonomy_node_save was changed to take a $node object instead of $nid
        taxonomy_node_save($nid, $terms);
        drupal_set_message(t('Assigned foster terms to node %title.', array('%title' => theme('placeholder', check_plain($node->title)))));
      }
    }
  }
}

function _term_merge_select_nodes($tid) {
  // I would have liked to use taxonomy_select_nodes() instead, but that function
  // either uses a pager, or returns only the latest n nodes, and we need all of them 
  // (including unpublished nodes)

  // generate an array of descendant term IDs to the right depth.
  $descendant_tids = array();

  $term = taxonomy_get_term($tid);
  $tree = taxonomy_get_tree($term->vid, $tid, -1, NULL);
  $descendant_tids[] = array_merge(array($tid), array_map('_taxonomy_get_tid_from_term', $tree));

  $str_tids = implode(',', call_user_func_array('array_merge', $descendant_tids));
  $sql = 'SELECT DISTINCT(n.nid), n.sticky, n.title, n.created FROM {node} n INNER JOIN {term_node} tn ON n.nid = tn.nid WHERE tn.tid IN ('. $str_tids .')';

  $result = db_query(db_rewrite_sql($sql));

  return $result;
} 

?>