From dac786f300cd35b7d40fafe29399d36435c068c8 Mon Sep 17 00:00:00 2001
From: jamiesensei <jamiesensei>
Date: Thu, 19 Apr 2007 08:57:54 +0000
Subject: [PATCH] MDL-9437 lib/listlib.php for displaying and editing a nested
 list of items.  And changes to question\category.php to use the new lists.

---
 lang/en_utf8/error.php      |  10 +-
 lang/en_utf8/question.php   |   3 +-
 lib/listlib.php             | 606 ++++++++++++++++++++++++++++++++++++
 question/category.php       |  53 ++--
 question/category_class.php | 406 ++++++++----------------
 5 files changed, 776 insertions(+), 302 deletions(-)
 create mode 100644 lib/listlib.php

diff --git a/lang/en_utf8/error.php b/lang/en_utf8/error.php
index 3e11952a76..77cabf26cf 100644
--- a/lang/en_utf8/error.php
+++ b/lang/en_utf8/error.php
@@ -1,4 +1,4 @@
-<?PHP // $Id$ 
+<?PHP // $Id$
       // error.php - created with Moodle 1.7 beta + (2006101003)
 
 
@@ -40,6 +40,14 @@ $string['invalidmd5'] = 'Invalid md5';
 $string['invalidrequest'] = 'Invalid request';
 $string['invalidrole'] = 'Invalid role';
 $string['invalidxmlfile'] = '\"$a\" is not a valid XML file';
+$string['listnopeers'] = 'No peers of item found.';
+$string['listnoitem'] = 'Item not found.';
+$string['listnochildren'] = 'No children of item found.';
+$string['listupdatefail'] = 'DB operation failed when editing list hierarchy.';
+$string['listcantmoveup'] = 'Failed to move the item up, it is the first of it\'s peers.';
+$string['listcantmovedown'] = 'Failed to move item down, it is the last of it\'s peers.';
+$string['listcantmoveleft'] = 'Failed to move item left, it has no parent.';
+$string['listcantmoveright'] = 'Failed to move item right, their is no peer to make it a child of. Move it below another peer and then you can move it right.';
 $string['loginasonecourse'] = 'You can not enter this course.<br /> You have to terminate the \"Login as\" session before entering any other course.';
 $string['loginasnoenrol'] = 'You can not use enrol or unenrol when in course \"Login as\" session.';
 $string['missingfield'] = 'Field \"$a\" is missing';
diff --git a/lang/en_utf8/question.php b/lang/en_utf8/question.php
index e50e5afa94..5fbeba3808 100644
--- a/lang/en_utf8/question.php
+++ b/lang/en_utf8/question.php
@@ -9,5 +9,6 @@ $string['questionbank'] = 'Question bank';
 $string['questiondoesnotexist'] = 'This question does not exist';
 $string['unknownquestiontype'] = 'Unknown question type: $a.';
 $string['fractionsnomax'] = 'One of the answers should have a score of 100%% so it is possible to get full marks for this question.';
-
+$string['makechildof'] = "Make Child of '\$a'";
+$string['maketoplevelitem'] = 'Move to top level';
 ?>
diff --git a/lib/listlib.php b/lib/listlib.php
new file mode 100644
index 0000000000..9789a32636
--- /dev/null
+++ b/lib/listlib.php
@@ -0,0 +1,606 @@
+<?php // $Id$
+
+///////////////////////////////////////////////////////////////////////////
+//                                                                       //
+// NOTICE OF COPYRIGHT                                                   //
+//                                                                       //
+// Moodle - Modular Object-Oriented Dynamic Learning Environment         //
+//          http://moodle.com                                            //
+//                                                                       //
+// Copyright (C) 2007       Jamie Pratt  http://jamiep.org               //
+//                                                                       //
+// This program is free software; you can redistribute it and/or modify  //
+// it under the terms of the GNU General Public License as published by  //
+// the Free Software Foundation; either version 2 of the License, or     //
+// (at your option) any later version.                                   //
+//                                                                       //
+// This program is distributed in the hope that it will be useful,       //
+// but WITHOUT ANY WARRANTY; without even the implied warranty of        //
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         //
+// GNU General Public License for more details:                          //
+//                                                                       //
+//          http://www.gnu.org/copyleft/gpl.html                         //
+//                                                                       //
+///////////////////////////////////////////////////////////////////////////
+
+/**
+ * Classes for displaying and editing a nested list of items.
+ *
+ * Handles functionality for :
+ *
+ *    Construction of nested list from db records with some key pointing to a parent id.
+ *    Display of list with or without editing icons with optional pagination.
+ *    Reordering of items works across pages.
+ *    Processing of editing actions on list.
+ *
+ * @author Jamie Pratt
+ * @version  $Id$
+ * @license http://www.gnu.org/copyleft/gpl.html GNU Public License
+ * @package moodlecore
+ */
+
+
+class moodle_list{
+    var $attributes;
+    var $listitemclassname = 'list_item';
+    /**
+     * An array of $listitemclassname objects.
+     *
+     * @var array
+     */
+    var $items = array();
+    /**
+     * ol / ul
+     *
+     * @var string
+     */
+    var $type;
+    /**
+     *
+     * @var list_item or derived class
+     */
+    var $parentitem;
+    var $table;
+    var $fieldnamesparent = 'parent';
+    var $sortby = 'parent, sortorder, name';
+    /**
+     * Records from db, only used in top level list.
+     *
+     * @var array
+     */
+    var $records = array();
+
+    var $editable;
+
+    /**
+     * Key is child id, value is parent.
+     *
+     * @var array
+     */
+    var $childparent;
+
+//------------------------------------------------------
+//vars used for pagination.
+    var $page = 0;// 0 means no pagination
+    var $firstitem = 1;
+    var $lastitem = 999999;
+    var $topcount;
+    var $pagecount;
+//------------------------------------------------------
+    var $pageurl;
+    var $pageparams = array();
+
+    var $str;
+    /**
+     * Constructor function
+     *
+     * @param string $type
+     * @param string $attributes
+     * @param boolean $editable
+     * @param integer $page if 0 no pagination.
+     * @return moodle_list
+     */
+    function moodle_list($type='ul', $attributes='', $editable = false, $page = 0){
+        $this->editable = $editable;
+        $this->attributes = $attributes;
+        $this->type = $type;
+        $this->page = $page;
+        $this->pageurl = strip_querystring(qualified_me());//default
+        if (!empty($this->page)){
+            $this->add_page_params(array('page' => $this->page));
+        }
+    }
+    /**
+     * Add an array of params to the params for this page.
+     *
+     * @param unknown_type $params
+     */
+    function add_page_params($params){
+        $this->pageparams = $params + $this->pageparams;
+    }
+
+    /**
+     * Get url and query string for an action on this page (get_url() + sesskey)
+     *
+     * @param array $overrideparams an array of params which override $this->pageparams
+     * @return string
+     */
+    function get_action_url($overrideparams = array()){
+        global $USER;
+
+        $arr = array();
+        $paramarray = $overrideparams + $this->pageparams + array('sesskey'=>$USER->sesskey);
+        foreach ($paramarray as $key => $val){
+           $arr[] = urlencode($key)."=".urlencode($val);
+        }
+        $params = implode($arr, "&amp;");
+
+        return $this->pageurl.'?'.$params;
+    }
+
+    /**
+     * Get url and query string for this page
+     *
+     * @param array $overrideparams an array of params which override $this->pageparams
+     * @return string
+     */
+    function get_url($overrideparams = array()){
+
+        $arr = array();
+        $paramarray = $overrideparams + $this->pageparams;
+        foreach ($paramarray as $key => $val){
+           $arr[] = urlencode($key)."=".urlencode($val);
+        }
+        $params = implode($arr, "&amp;");
+
+        return $this->pageurl.'?'.$params;
+    }
+
+    /**
+     * Returns html string.
+     *
+     * @param integer $indent depth of indentation.
+     */
+    function to_html($indent=0, $extraargs=array()){
+        if (count($this->items)){
+            $tabs = str_repeat("\t", $indent);
+            $html = $tabs.'<'.$this->type.((!empty($this->attributes))?(' '.$this->attributes):'').">\n";
+            $first = true;
+            $itemiter = 1;
+            $lastitem = '';
+
+            foreach ($this->items as $item){
+                $last = (count($this->items) == $itemiter);
+                if ($itemiter >= $this->firstitem && $itemiter <= $this->lastitem ){
+                    if ($this->editable){
+                        $item->set_icon_html($first, $last, $lastitem);
+                    }
+                    $html .= "$tabs\t<li".((!empty($item->attributes))?(' '.$item->attributes):'').">";
+                    $html .= $item->to_html($indent+1, $extraargs);
+                    $html .= "</li>\n";
+                }
+                $first = false;
+                $lastitem = $item;
+                $itemiter++;
+            }
+            $html .= $tabs."</".$this->type.">\n";
+        } else {
+            $html = '';
+        }
+        return $html;
+    }
+
+    /**
+     * Recurse down the tree and find an item by it's id.
+     *
+     * @param integer $id
+     * @return list_item *copy* or null if item is not found
+     */
+    function find_item($id, $suppresserror = false){
+        if (isset($this->items)){
+            foreach ($this->items as $key => $child){
+                if ($child->id == $id){
+                    return $this->items[$key];
+                }
+            }
+            foreach (array_keys($this->items) as $key){
+                $thischild =& $this->items[$key];
+                $ref = $thischild->children->find_item($id, true);//error always reported at top level
+                if ($ref !== null){
+                    return $ref;
+                }
+            }
+        }
+
+        if (!$suppresserror){
+            print_error('listnoitem');
+        }
+        return null;
+    }
+
+
+
+    function add_item(&$item){
+        $this->items[] =& $item;
+    }
+
+    function set_parent(&$parent){
+        $this->parentitem =& $parent;
+    }
+
+
+    /**
+     * Produces a hierarchical tree of list items from a flat array of records.
+     * 'parent' field is expected to point to a parent record.
+     * records are already sorted.
+     * If the parent field doesn't point to another record in the array then this is
+     * a top level list
+     *
+     * @param array $records
+     * @param string $listitemclassname
+     * @param integer $itemsperpage no of top level items.
+     */
+    function list_from_records($itemsperpage = 25){
+        $this->get_records();
+        $records = $this->records;
+        $page = $this->page;
+        if (!empty($page)) {
+            $this->firstitem = ($page-1) * $itemsperpage + 1;
+            $this->lastitem = $this->firstitem + $itemsperpage - 1;
+        }
+        $itemiter = 1;
+        //make a simple array which is easier to search
+        $this->childparent = array();
+        foreach ($records as $record){
+            $this->childparent[$record->id] = $record->parent;
+        }
+        //create top level list items and they're responsible for creating their children
+        foreach ($records as $record){
+            if (!array_key_exists($record->parent, $this->childparent)){
+                //if this record is not a child of another record then
+
+                //make list item for top level for all items
+                //we need the info about the top level items for reordering peers.
+                $newlistitem =& new $this->listitemclassname($record, $this);
+                if ($itemiter >= $this->firstitem && $itemiter <= $this->lastitem ){
+                    //but don't recurse down the tree for items that are not on this page
+                    $newlistitem->create_children($records, $this->childparent, $record->id);
+                }
+                $itemiter++;
+            }
+        }
+        $this->topcount = $itemiter - 1;
+        $this->pagecount = (integer) ceil( $this->topcount / QUESTION_PAGE_LENGTH );
+    }
+
+    /**
+     * Should be overriden to return an array of records of list items.
+     *
+     */
+    function get_records() {
+    }
+
+    /**
+     * display list of page numbers for navigation
+     */
+    function display_page_numbers() {
+        if (!empty($this->page) && ($this->pagecount>1)){
+            echo "<div class=\"paging\">".get_string('page').":\n";
+            foreach (range(1,$this->pagecount) as $currentpage) {
+                if ($this->page == $currentpage) {
+                    echo " $currentpage \n";
+                }
+                else {
+                    echo "<a href=\"".$this->get_url(array('page'=>$currentpage))."\">";
+                    echo " $currentpage </a>\n";
+                }
+            }
+            echo "</div>";
+        }
+    }
+
+    /**
+     * Returns an array of ids of peers of an item.
+     *
+     * @param    int itemid - if given, restrict records to those with this parent id.
+     * @return   array peer ids
+     */
+    function get_items_peers($itemid) {
+        $itemref = $this->find_item($itemid);
+        $peerids = $itemref->parentlist->get_child_ids();
+        return $peerids;
+    }
+
+    /**
+     * Returns an array of ids of child items.
+     *
+     * @return   array peer ids
+     */
+    function get_child_ids() {
+        $childids = array();
+        foreach ($this->items as $child){
+           $childids[] = $child->id;
+        }
+        return $childids;
+    }
+
+    /**
+     * Move a record up or down
+     *
+     * @param string $direction up / down
+     * @param integer $id
+     */
+    function move_item_up_down($direction, $id) {
+        $peers = $this->get_items_peers($id);
+        $itemkey = array_search($id, $peers);
+        switch ($direction) {
+            case 'down' :
+                if (isset($peers[$itemkey+1])){
+                    $olditem = $peers[$itemkey+1];
+                    $peers[$itemkey+1] = $id;
+                    $peers[$itemkey] = $olditem;
+                } else {
+                    print_error('listcantmoveup');
+
+                }
+                break;
+
+            case 'up' :
+                if (isset($peers[$itemkey-1])){
+                    $olditem = $peers[$itemkey-1];
+                    $peers[$itemkey-1] = $id;
+                    $peers[$itemkey] = $olditem;
+                } else {
+                    print_error('listcantmovedown');
+                }
+                break;
+        }
+        $this->reorder_peers($peers);
+    }
+    function reorder_peers($peers){
+        foreach ($peers as $key => $peer) {
+            if (! set_field("{$this->table}", "sortorder", $key, "id", $peer)) {
+                print_error('listupdatefail');
+            }
+        }
+    }
+    function move_item_left($id) {
+        $item = $this->find_item($id);
+        if (!isset($item->parentlist->parentitem->parentlist)){
+            print_error('listcantmoveleft');
+        } else {
+            $newpeers = $this->get_items_peers($item->parentlist->parentitem->id);
+            if (isset($item->parentlist->parentitem->parentlist->parentitem)){
+                $newparent = $item->parentlist->parentitem->parentlist->parentitem->id;
+            } else {
+                $newparent = 0; // top level item
+            }
+            if (!set_field("{$this->table}", "parent", $newparent, "id", $item->id)) {
+                print_error('listupdatefail');
+            } else {
+                $oldparentkey = array_search($item->parentlist->parentitem->id, $newpeers);
+                $neworder = array_merge(array_slice($newpeers, 0, $oldparentkey+1), array($item->id), array_slice($newpeers, $oldparentkey+1));
+                $this->reorder_peers($neworder);
+            }
+        }
+    }
+    /**
+     * Make item with id $id the child of the peer that is just above it in the sort order.
+     *
+     * @param integer $id
+     */
+    function move_item_right($id) {
+        $peers = $this->get_items_peers($id);
+        $itemkey = array_search($id, $peers);
+        if (!isset($peers[$itemkey-1])){
+            print_error('listcantmoveright');
+        } else {
+            if (!set_field("{$this->table}", "parent", $peers[$itemkey-1], "id", $peers[$itemkey])) {
+                print_error('listupdatefail');
+            } else {
+                $newparent = $this->find_item($peers[$itemkey-1]);
+                if (isset($newparent->children)){
+                    $newpeers = $newparent->children->get_child_ids();
+                }
+                if ($newpeers){
+                    $newpeers[] = $peers[$itemkey];
+                    $this->reorder_peers($newpeers);
+                }
+            }
+        }
+    }
+
+    /**
+     * process any actions.
+     *
+     * @param integer $left id of item to move left
+     * @param integer $right id of item to move right
+     * @param integer $moveup id of item to move up
+     * @param integer $movedown id of item to move down
+     * @return unknown
+     */
+    function process_actions($left, $right, $moveup, $movedown){
+        if (!empty($left)) {
+            $this->move_item_left($left);
+        } else if (!empty($right)) {
+            $this->move_item_right($right);
+        } else if (!empty($moveup)) {
+            $this->move_item_up_down('up', $moveup);
+            if ($moveup == $this->items[$this->firstitem -1]->id){//redirect to page that item has been moved to.
+                $this->page --;
+                $this->add_page_params(array('page'=>$this->page));
+            }
+        } else if (!empty($movedown)) {
+            $this->move_item_up_down('down', $movedown);
+            if ($movedown == $this->items[$this->lastitem -1]->id){//redirect to page that item has been moved to.
+                $this->page ++;
+                $this->add_page_params(array('page'=>$this->page));
+            }
+        } else {
+            return false;
+        }
+
+        redirect($this->get_url());
+    }
+}
+
+class list_item{
+    /**
+     * id of record, used if list is editable
+     *
+     * @var integer
+     */
+    var $id;
+    /**
+     * name of this item, used if list is editable
+     *
+     * @var string
+     */
+    var $name;
+    /**
+     * The object or string representing this item.
+     *
+     * @var mixed
+     */
+    var $item;
+    var $fieldnamesname = 'name';
+    var $attributes;
+    var $iconhtml = '';
+    /**
+     *
+     * @var moodle_list
+     */
+    var $parentlist;
+    /**
+     * Set if there are any children of this listitem.
+     *
+     * @var moodle_list
+     */
+    var $children;
+    /**
+     * Constructor
+     *
+     * @param mixed $item fragment of html for list item or record
+     * @param string $attributes attributes for li tag
+     * @return list_item
+     */
+    function list_item($item, &$parent, $attributes=''){
+        $this->item = $item;
+        if (is_object($this->item)) {
+            $this->id = $this->item->id;
+            $this->name = $this->item->{$this->fieldnamesname};
+        }
+        $this->set_parent($parent);
+        $this->attributes = $attributes;
+        $parentlistclass = get_class($parent);
+        $this->children =& new $parentlistclass($parent->type, $parent->attributes, $parent->editable, $parent->page);
+        $this->children->add_page_params($parent->pageparams);
+        $this->children->pageurl = $parent->pageurl;
+        $this->children->set_parent($this);
+    }
+    /**
+     * Output the html just for this item. Called by to_html which adds html for children.
+     *
+     */
+    function item_html($extraargs = array()){
+        if (is_string($this->item)){
+            $html = $this->item;
+        } elseif (is_object($this->item)) {
+            //for debug purposes only. You should create a sub class to
+            //properly handle the record
+            $html = join(', ', (array)$this->item);
+        }
+        return $html;
+    }
+    /**
+     * Returns html
+     *
+     * @param integer $indent
+     * @param array $extraargs any extra data that is needed to print the list item
+     *                            may be used by sub class.
+     * @return string html
+     */
+    function to_html($indent=0, $extraargs = array()){
+        $tabs = str_repeat("\t", $indent);
+
+        if (isset($this->children)){
+            $childrenhtml = $this->children->to_html($indent+1, $extraargs);
+        } else {
+            $childrenhtml = '';
+        }
+        return $this->item_html($extraargs).$this->iconhtml.(($childrenhtml !='')?("\n".$childrenhtml):'');
+    }
+
+    function set_icon_html($first, $last, &$lastitem){
+        global $CFG;
+        $strmoveup = get_string('moveup');
+        $strmovedown = get_string('movedown');
+        $pixpath = $CFG->pixpath;
+        $icons = '&nbsp;';
+        if (!empty($this->parentlist->page)) {
+            $pagelink="&amp;page={$this->parentlist->page}";
+        } else {
+            $pagelink="";
+        }
+        if (isset($this->parentlist->parentitem)) {
+            $parentitem =& $this->parentlist->parentitem;
+            if (isset($parentitem->parentlist->parentitem)){
+                $action = get_string('makechildof', 'question', $parentitem->parentlist->parentitem->name);
+            } else {
+                $action = get_string('maketoplevelitem', 'question');
+            }
+            $icons .= '<a title="' . $action .'" href="'.$this->parentlist->get_action_url().'&amp;left=' . $this->id .'">
+                <img src="' . $pixpath . '/t/left.gif" class="iconsmall" alt="' . $action. '" /></a> ';
+        } else {
+            $icons .=  '<img src="' . $pixpath . '/spacer.gif" class="iconsmall" alt="" />';
+        }
+
+        if (!$first) {
+            $icons .= '<a title="' . $strmoveup .'" href="'.$this->parentlist->get_action_url().'&amp;moveup=' . $this->id .'">
+                <img src="' . $pixpath . '/t/up.gif" class="iconsmall" alt="' . $strmoveup. '" /></a> ';
+        } else {
+            $icons .=  '<img src="' . $pixpath . '/spacer.gif" class="iconsmall" alt="" />';
+        }
+
+        if (!$last) {
+            $icons .= '<a title="' . $strmovedown .'" href="'.$this->parentlist->get_action_url().'&amp;movedown=' . $this->id .'">
+                 <img src="' . $pixpath . '/t/down.gif" class="iconsmall" alt="' .$strmovedown. '" /></a> ';
+        } else {
+            $icons .=  '<img src="' . $pixpath . '/spacer.gif" class="iconsmall" alt="" />';
+        }
+
+        if (!empty($lastitem)) {
+            $makechildof = get_string('makechildof', 'question', $lastitem->name);
+            $icons .= '<a title="' . $makechildof .'" href="'.$this->parentlist->get_action_url().'&amp;right=' . $this->id .'">
+                <img src="' . $pixpath . '/t/right.gif" class="iconsmall" alt="' . $makechildof. '" /></a> ';
+        } else {
+            $icons .=  '<img src="' . $pixpath . '/spacer.gif" class="iconsmall" alt="" />';
+        }
+
+        $this->iconhtml = $icons;
+    }
+    /**
+     * Recurse down tree creating list_items, called from moodle_list::list_from_records
+     *
+     * @param array $records
+     * @param array $children
+     * @param integer $thisrecordid
+     */
+    function create_children(&$records, &$children, $thisrecordid){
+        //keys where value is $thisrecordid
+        $thischildren = array_keys($children, $thisrecordid);
+        if (count($thischildren)){
+            foreach ($thischildren as $child){
+                $thisclass = get_class($this);
+                $newlistitem =& new $thisclass($records[$child], $this->children, $this->attributes);
+                $newlistitem->create_children($records, $children, $records[$child]->id);
+            }
+        }
+    }
+    function set_parent(&$parent){
+        $this->parentlist =& $parent;
+        $parent->add_item($this);
+    }
+
+}
+?>
\ No newline at end of file
diff --git a/question/category.php b/question/category.php
index 265972c4af..761127340c 100644
--- a/question/category.php
+++ b/question/category.php
@@ -14,36 +14,41 @@
 
     // get values from form
     $param = new stdClass();
-    $id = required_param('id',PARAM_INT);   // course id
-    $param->moveup = optional_param('moveup',0,PARAM_INT);
-    $param->movedown = optional_param('movedown',0,PARAM_INT);
-    $param->hide = optional_param('hide',0,PARAM_INT);
-    $param->delete = optional_param('delete',0,PARAM_INT);
-    $param->confirm = optional_param('confirm',0,PARAM_INT);
-    $param->cancel = optional_param('cancel','',PARAM_ALPHA);
-    $param->move = optional_param('move',0,PARAM_INT);
-    $param->moveto = optional_param('moveto',0,PARAM_INT);
-    $param->publish = optional_param('publish',0,PARAM_INT);
-    $param->addcategory = optional_param('addcategory','',PARAM_NOTAGS);
-    $param->edit = optional_param('edit',0,PARAM_INT);
-    $param->updateid = optional_param('updateid',0,PARAM_INT);
-    $param->page = optional_param('page',1,PARAM_INT);
+
+    $id = required_param('id', PARAM_INT);   // course id
+    $param->page = optional_param('page', 1, PARAM_INT);
+
+    $param->moveup = optional_param('moveup', 0, PARAM_INT);
+    $param->movedown = optional_param('movedown', 0, PARAM_INT);
+    $param->left = optional_param('left', 0, PARAM_INT);
+    $param->right = optional_param('right', 0, PARAM_INT);
+    $param->hide = optional_param('hide', 0, PARAM_INT);
+    $param->delete = optional_param('delete', 0, PARAM_INT);
+    $param->confirm = optional_param('confirm', 0, PARAM_INT);
+    $param->cancel = optional_param('cancel', '', PARAM_ALPHA);
+    $param->move = optional_param('move', 0, PARAM_INT);
+    $param->moveto = optional_param('moveto', 0, PARAM_INT);
+    $param->publish = optional_param('publish', 0, PARAM_INT);
+    $param->addcategory = optional_param('addcategory', '', PARAM_NOTAGS);
+    $param->edit = optional_param('edit', 0, PARAM_INT);
+    $param->updateid = optional_param('updateid', 0, PARAM_INT);
 
     if (! $course = get_record("course", "id", $id)) {
         error("Course ID is incorrect");
     }
-    
+
     $context = get_context_instance(CONTEXT_COURSE, $id);
-    
+
     require_login($course->id, false);
     require_capability('moodle/question:managecategory', $context);
 
-    $qcobject = new question_category_object();
-    $qcobject->set_course($course);
+    $qcobject = new question_category_object($param->page);
 
-    // Page header
-    // TODO: generalise this to any activity
-    if (isset($SESSION->modform->instance) and $quiz = get_record('quiz', 'id', $SESSION->modform->instance)) {
+    if ($qcobject->editlist->process_actions($param->left, $param->right, $param->moveup, $param->movedown)) {
+            //processing of these actions is handled in the method and page redirects.
+    } else if (isset($SESSION->modform->instance) and $quiz = get_record('quiz', 'id', $SESSION->modform->instance)) {
+        // Page header
+        // TODO: generalise this to any activity
         $strupdatemodule = has_capability('moodle/course:manageactivities', get_context_instance(CONTEXT_COURSE, $course->id))
             ? update_module_button($SESSION->modform->cmid, $course->id, get_string('modulename', 'quiz'))
             : "";
@@ -72,10 +77,6 @@
             } else {
                 $qcobject->delete_category($param->delete);
             }
-        } else if (!empty($param->moveup)) {
-            $qcobject->move_category_up_down('up', $param->moveup);
-        } else if (!empty($param->movedown)) {
-            $qcobject->move_category_up_down('down', $param->movedown);
         } else if (!empty($param->hide)) {
             $qcobject->publish_category(false, $param->hide);
         } else if (!empty($param->move)) {
@@ -102,7 +103,7 @@
     }
 
     // display the user interface
-    $qcobject->display_user_interface($param->page);
+    $qcobject->display_user_interface();
 
     print_footer($course);
 ?>
diff --git a/question/category_class.php b/question/category_class.php
index 49ce7af4a6..566df1f44d 100644
--- a/question/category_class.php
+++ b/question/category_class.php
@@ -8,34 +8,110 @@
  */
 
 // number of categories to display on page
-define( "PAGE_LENGTH",25 );
+define("QUESTION_PAGE_LENGTH", 25);
+
+require_once("$CFG->libdir/listlib.php");
+
+class question_category_list extends moodle_list {
+    var $table = "question_categories";
+    var $listitemclassname = 'question_category_list_item';
+    function question_category_list($type='ul', $attributes='', $editable = false, $page = 0){
+        parent::moodle_list($type, $attributes, $editable, $page);
+    }
+    function get_records() {
+        global $COURSE, $CFG;
+        $categories = get_records($this->table, 'course', "{$COURSE->id}", $this->sortby);
+
+        $catids = array_keys($categories);
+        $select = "WHERE category IN ('".join("', '", $catids)."') AND hidden='0' AND parent='0'";
+        $questioncounts = get_records_sql_menu('SELECT category, COUNT(*) FROM '. $CFG->prefix . 'question' .' '. $select.' GROUP BY category');
+        foreach ($categories as $categoryid => $category){
+            if (isset($questioncounts[$categoryid])){
+                $categories[$categoryid]->questioncount = $questioncounts[$categoryid];
+            } else {
+                $categories[$categoryid]->questioncount = 0;
+            }
+        }
+        $this->records = $categories;
+    }
+}
+
+class question_category_list_item extends list_item {
+
+
+    function item_html($extraargs = array()){
+        global $CFG;
+        $pixpath = $CFG->pixpath;
+        $str = $extraargs['str'];
+        $category = $this->item;
+
+        $linkcss = $category->publish ? ' class="published" ' : ' class="unpublished" ';
+
+        if (!empty($parent->page)) {
+            $pagelink="&amp;page=".$parent->page;
+        } else {
+            $pagelink="";
+        }
+
+        /// Each section adds html to be displayed as part of this list item
+
+        $item = '<a ' . $linkcss . ' title="' . $str->edit. '" href="'.$this->parentlist->get_action_url().'&amp;edit=' . $this->id .'">
+            <img src="' . $pixpath . '/t/edit.gif" class="iconsmall"
+            alt="' .$str->edit. '" /> ' . $category->name . '('.$category->questioncount.')'. '</a>';
+
+        $item .= '&nbsp;'. $category->info;
+
+
+        if (!empty($category->publish)) {
+            $item .= '<a title="' . $str->hide . '" href="'.$this->parentlist->get_action_url().'&amp;hide=' . $this->id .'">
+              <img src="' . $pixpath . '/t/hide.gif" class="iconsmall" alt="' .$str->hide. '" /></a> ';
+        } else {
+            $item .= '<a title="' . $str->publish . '" href="'.$this->parentlist->get_action_url().'&amp;publish=' . $this->id .'">
+              <img src="' . $pixpath . '/t/show.gif" class="iconsmall" alt="' .$str->publish. '" /></a> ';
+        }
+
+        if ($category->id != $extraargs['defaultcategory']->id) {
+            $item .=  '<a title="' . $str->delete . '"href="'.$this->parentlist->get_action_url().'&amp;delete=' . $this->id .'">
+                    <img src="' . $pixpath . '/t/delete.gif" class="iconsmall" alt="' .$str->delete. '" /></a> ';
+        }
+
+        return $item;
+
+
+    }
+
+}
+
 
 /**
  * Class representing question categories
- * 
+ *
  * @package questionbank
  */
 class question_category_object {
 
     var $str;
     var $pixpath;
-    var $edittable;
+    /**
+     * Nested list to display categories.
+     *
+     * @var question_category_list
+     */
+    var $editlist;
     var $newtable;
     var $tab;
     var $tabsize = 3;
     var $categories;
     var $categorystrings;
     var $defaultcategory;
-    var $course;
-    var $topcount;
 
     /**
      * Constructor
      *
      * Gets necessary strings and sets relevant path information
      */
-    function question_category_object() {
-        global $CFG;
+    function question_category_object($page) {
+        global $CFG, $COURSE;
 
         $this->tab = str_repeat('&nbsp;', $this->tabsize);
 
@@ -62,39 +138,31 @@ class question_category_object {
         $this->str->page           = get_string('page');
         $this->pixpath = $CFG->pixpath;
 
-    }
+        $this->editlist = new question_category_list('ul', '', true, $page);
+        $this->editlist->add_page_params(array('id'=>$COURSE->id));
+        $this->initialize();
 
-    /**
-     * Sets the course for this object
-     *
-     * @param object course
-     */
-    function set_course($course) {
-        $this->course = $course;
     }
 
+
+
     /**
      * Displays the user interface
      *
-     * @param object modform
-     * @param int $page page number to display (0=don't paginate)
      */
-    function display_user_interface($page=0) {
-        $this->initialize();
+    function display_user_interface() {
+
+        /// Interface for editing existing categories
+        print_heading_with_help($this->str->editcategories, 'categories', 'quiz');
+        $this->output_edit_list();
 
+
+        echo '<br />';
         /// Interface for adding a new category:
         print_heading_with_help($this->str->addcategory, 'categories_edit', 'quiz');
         $this->output_new_table();
         echo '<br />';
 
-        /// Interface for editing existing categories
-        print_heading_with_help($this->str->editcategories, 'categories', 'quiz');
-        $this->output_edit_table($page);
-        if ($this->topcount>PAGE_LENGTH) {
-            $this->display_page_numbers($page);
-        }
-        echo '<br />';
-
     }
 
 
@@ -102,60 +170,34 @@ class question_category_object {
      * Initializes this classes general category-related variables
      */
     function initialize() {
+        global $COURSE, $CFG;
 
         /// Get the existing categories
-        if (!$this->defaultcategory = get_default_question_category($this->course->id)) {
+        if (!$this->defaultcategory = get_default_question_category($COURSE->id)) {
             error("Error: Could not find or make a category!");
         }
 
-        $this->categories = $this->get_question_categories(null, "parent, sortorder, name ASC");
+        $this->editlist->list_from_records(QUESTION_PAGE_LENGTH);
 
-        $this->categories = $this->arrange_categories($this->categories);
+        $this->categories = $this->editlist->records;
 
         // create the array of id=>full_name strings
         $this->categorystrings = $this->expanded_category_strings($this->categories);
 
-        // for pagination calculate number of 'top' categories and hence number of pages
-        // (pagination only based on top categories)
-        $count = 0;
-        foreach( $this->categories as $category ) {
-            if ($category->parent==0) {
-                ++$count;
-            }
-        }
-        $this->topcount = $count;
-        $this->pagecount = (integer) ceil( $count / PAGE_LENGTH );
-    }
-
-    /**
-     * display list of page numbers for navigation
-     */
-    function display_page_numbers( $page=0 ) {
-        global $USER;
 
-        echo "<div class=\"paging\">{$this->str->page}:\n";
-        foreach (range(1,$this->pagecount) as $currentpage) {
-            if ($page == $currentpage) {
-                echo " $currentpage \n";
-            }
-            else {
-                echo "<a href=\"category.php?id={$this->course->id}&amp;page=$currentpage&amp;sesskey={$USER->sesskey}\">";
-                echo " $currentpage </a>\n";
-            }
-        }
-        echo "</div>";
     }
 
+
     /**
      * Outputs a table to allow entry of a new category
      */
     function output_new_table() {
-        global $USER;
+        global $USER, $COURSE;
         $publishoptions[0] = get_string("no");
         $publishoptions[1] = get_string("yes");
 
         $this->newtable->head  = array ($this->str->parent, $this->str->category, $this->str->categoryinfo, $this->str->publish, $this->str->action);
-        $this->newtable->width = 200;
+        $this->newtable->width = '200';
         $this->newtable->data[] = array();
         $this->newtable->tablealign = 'center';
 
@@ -191,79 +233,32 @@ class question_category_object {
         echo '<form action="category.php" method="post">';
         echo '<fieldset class="invisiblefieldset" style="display: block">';
         echo "<input type=\"hidden\" name=\"sesskey\" value=\"$USER->sesskey\" />";
-        echo '<input type="hidden" name="id" value="'. $this->course->id . '" />';
+        echo '<input type="hidden" name="id" value="'. $COURSE->id . '" />';
         echo '<input type="hidden" name="addcategory" value="true" />';
         print_table($this->newtable);
         echo '</fieldset>';
         echo '</form>';
     }
 
+
     /**
-     * Outputs a table to allow editing/rearranging of existing categories
+     * Outputs a list to allow editing/rearranging of existing categories
      *
      * $this->initialize() must have already been called
      *
-     * @param object course
      * @param int $page page to display (0=do not paginate)
      */
-    function output_edit_table($page=0) {
-        $this->edittable->head  = array ($this->str->category, $this->str->categoryinfo, $this->str->questions, $this->str->publish,
-                                    $this->str->delete, $this->str->order, $this->str->parent);
-        $this->edittable->width = 200;
-        $this->edittable->tablealign = 'center';
-
-        $courses = $this->course->shortname;
-
-        // if pagination required work out range
-        if (!empty($page)) {
-            $firstcat = ($page-1) * PAGE_LENGTH + 1;
-            $lastcat = $firstcat + PAGE_LENGTH - 1;
-        }
-        else {
-            $firstcat = 1;
-            $lastcat = $this->topcount;
-        }
-//echo "$firstcat $lastcat $page"; die;
-        $this->build_edit_table_body($this->categories, $page, $firstcat, $lastcat);
-        print_table($this->edittable);
-    }
-    
-    /**
-     * Recursively builds up the edit-categories table body
-     *
-     * @param array categories contains category objects in  a tree representation
-     * @param mixed courses String with shortname of course | array containing courseid=>shortname
-     * @param int depth controls the indenting
-     */
-    function build_edit_table_body($categories, $page = 0, $firstcat = 1, $lastcat = 99999, $depth = 0) {
-        $countcats = count($categories);
-        $count = 0;
-        $first = true;
-        $last = false;
-        $topcount = 0;
-
-        foreach ($categories as $category) {
-            $count++;
-            if ($count == $countcats) {
-                $last = true;
-            }
-            // check if this category is on the display page
-            if ($depth==0) {
-                $topcount++;
-                if (($topcount<$firstcat) or ($topcount>$lastcat)) {
-                    continue;
-                }
-            }
-            $up = $first ? false : true;
-            $down = $last ? false : true;
-            $first = false;
-            $this->edit_question_category_row($category, $depth, $up, $down, $page);
-            if (isset($category->children)) {
-                $this->build_edit_table_body($category->children, $page, $firstcat, $lastcat, $depth + 1);
-            }
-        }
+    function output_edit_list() {
+        print_box_start('boxwidthwide boxaligncenter generalbox');
+        echo $this->editlist->to_html(0, array('str'=>$this->str,
+                                'defaultcategory' => $this->defaultcategory));
+        print_box_end();
+        echo $this->editlist->display_page_numbers();
+
     }
 
+
+
     /**
      * gets all the courseids for the given categories
      *
@@ -281,99 +276,11 @@ class question_category_object {
         return $courseids;
     }
 
-    /**
-     * Constructs each row of the edit-categories table
-     *
-     * @param object category
-     * @param int depth controls the indenting
-     * @param string shortname short name of the course
-     * @param boolean up can it be moved up?
-     * @param boolean down can it be moved down?
-     * @param int page page number
-     */
-    function edit_question_category_row($category, $depth, $up = false, $down = false, $page = 0) {
-        global $USER;
-        $fill = str_repeat($this->tab, $depth);
-
-        $linkcss = $category->publish ? ' class="published" ' : ' class="unpublished" ';
-
-        if (!empty($page)) {
-            $pagelink="&amp;page=$page";
-        }
-        else {
-            $pagelink="";
-        }
-
-        /// Each section below adds a data cell to this table row
-
-        $this->edittable->align["$category->id.name"] =  "left";
-        $this->edittable->wrap["$category->id.name"] = "nowrap";
-        $row["$category->id.name"] = '<a ' . $linkcss . ' title="' . $this->str->edit. '" href="category.php?id=' . $this->course->id .
-            '&amp;edit=' . $category->id . '&amp;sesskey='.$USER->sesskey.$pagelink.'"><img src="' . $this->pixpath . '/t/edit.gif" class="iconsmall" 
-            alt="' .$this->str->edit. '" /> ' . $fill . $category->name . '</a>';
-
-        $this->edittable->align["$category->id.info"] =  "left";
-        $this->edittable->wrap["$category->id.info"] = "nowrap";
-        $row["$category->id.info"] = '<a ' . $linkcss . ' title="' . $this->str->edit .'" href="category.php?id=' . $this->course->id .
-            '&amp;edit=' . $category->id . '&amp;sesskey='.$USER->sesskey.$pagelink.'">' . $category->info . '</a>';
-
-        $this->edittable->align["$category->id.qcount"] = "center";
-        $row["$category->id.qcount"] = $category->questioncount;
-
-        $this->edittable->align["$category->id.publish"] =  "center";
-        $this->edittable->wrap["$category->id.publish"] = "nowrap";
-        if (!empty($category->publish)) {
-              $row["$category->id.publish"] = '<a title="' . $this->str->hide . '" href="category.php?id=' . $this->course->id . '&amp;hide=' . $category->id .
-              '&amp;sesskey='.$USER->sesskey.$pagelink.'"><img src="' . $this->pixpath . '/t/hide.gif" class="iconsmall" alt="' .$this->str->hide. '" /></a> ';
-        } else {
-            $row["$category->id.publish"] = '<a title="' . $this->str->publish . '" href="category.php?id=' . $this->course->id . '&amp;publish=' . $category->id .
-                 '&amp;sesskey='.$USER->sesskey.$pagelink.'"><img src="' . $this->pixpath . '/t/show.gif" class="iconsmall" alt="' .$this->str->publish. '" /></a> ';
-        }
-
-        if ($category->id != $this->defaultcategory->id) {
-            $this->edittable->align["$category->id.delete"] =  "center";
-            $this->edittable->wrap["$category->id.delete"] = "nowrap";
-            $row["$category->id.delete"] =  '<a title="' . $this->str->delete . '" href="category.php?id=' . $this->course->id .
-                    '&amp;delete=' . $category->id . '&amp;sesskey='.$USER->sesskey.$pagelink.'"><img src="' . $this->pixpath . '/t/delete.gif" class="iconsmall" alt="' .$this->str->delete. '" /></a> ';
-        } else {
-            $row["$category->id.delete"] = '';
-        }
-
-        $this->edittable->align["$category->id.order"] =  "left";
-        $this->edittable->wrap["$category->id.order"] = "nowrap";
-        $icons = '';
-        if ($up) {
-            $icons .= '<a title="' . $this->str->moveup .'" href="category.php?id=' . $this->course->id . '&amp;moveup=' . $category->id . '&amp;sesskey='.$USER->sesskey.$pagelink.'">
-                <img src="' . $this->pixpath . '/t/up.gif" class="iconsmall" alt="' . $this->str->moveup. '" /></a> ';
-        }
-        if ($down) {
-            $icons .= '<a title="' . $this->str->movedown .'" href="category.php?id=' . $this->course->id . '&amp;movedown=' . $category->id . '&amp;sesskey='.$USER->sesskey.$pagelink.'">
-                 <img src="' . $this->pixpath . '/t/down.gif" class="iconsmall" alt="' .$this->str->movedown. '" /></a> ';
-        }
-        $row["$category->id.order"]= $icons;
 
-        $this->edittable->align["$category->id.moveto"] =  "left";
-        $this->edittable->wrap["$category->id.moveto"] = "nowrap";
-        if ($category->id != $this->defaultcategory->id) {
-            $viableparents = $this->categorystrings;
-            $this->set_viable_parents($viableparents, $category);
-            $viableparents = array(0=>$this->str->top) + $viableparents;
 
-            $row["$category->id.moveto"] = popup_form ("category.php?id={$this->course->id}&amp;move={$category->id}&amp;sesskey=$USER->sesskey$pagelink&amp;moveto=",
-               $viableparents, "moveform{$category->id}", "$category->parent", "", "", "", true);
-        } else {
-            $row["$category->id.moveto"]='---';
-        }
-
-
-        $this->edittable->data[$category->id] = $row;
-    }
-
-
-    function edit_single_category($categoryid,$page=1) {
+    function edit_single_category($categoryid, $page=1) {
     /// Interface for adding a new category
-        global $USER;
-        $this->initialize();
+        global $USER, $COURSE;
 
         /// Interface for editing existing categories
         if ($category = get_record("question_categories", "id", $categoryid)) {
@@ -382,20 +289,20 @@ class question_category_object {
             helpbutton("categories_edit", $this->str->editcategory, "quiz");
             echo '</h2>';
             echo '<table width="100%"><tr><td>';
-            $this->output_edit_single_table($category,$page);
+            $this->output_edit_single_table($category, $page);
             echo '</td></tr></table>';
             echo '<p><div align="center"><form action="category.php" method="get">
                 <div>
                 <input type="hidden" name="sesskey" value="'.$USER->sesskey.'" />
-                <input type="hidden" name="id" value="' . $this->course->id . '" />
+                <input type="hidden" name="id" value="' . $COURSE->id . '" />
                 <input type="submit" value="' . $this->str->cancel . '" />
                 </div>
                 </form>
                 </div></p>';
-            print_footer($this->course);
+            print_footer($COURSE);
             exit;
         } else {
-            error("Category $categoryid not found", "category.php?id={$this->course->id}");
+            error("Category $categoryid not found", "category.php?id={$COURSE->id}");
         }
     }
 
@@ -406,7 +313,7 @@ class question_category_object {
      * @param int page current page
      */
     function output_edit_single_table($category, $page=1) {
-        global $USER;
+        global $USER, $COURSE;
         $publishoptions[0] = get_string("no");
         $publishoptions[1] = get_string("yes");
         $strupdate = get_string('update');
@@ -450,7 +357,7 @@ class question_category_object {
         echo '<p><form action="category.php" method="post">';
         echo '<fieldset class="invisiblefieldset">';
         echo "<input type=\"hidden\" name=\"sesskey\" value=\"$USER->sesskey\" />";
-        echo '<input type="hidden" name="id" value="'. $this->course->id . '" />';
+        echo '<input type="hidden" name="id" value="'. $COURSE->id . '" />';
         echo '<input type="hidden" name="updateid" value="' . $category->id . '" />';
         echo "<input type=\"hidden\" name=\"page\" value=\"$page\" />";
         print_table($edittable);
@@ -480,55 +387,6 @@ class question_category_object {
         return $categorystrings;
     }
 
-    /**
-     * Arranges the categories into a hierarchical tree
-     *
-     * If a category has children, it's "children" property holds an array of children
-     * The questioncount for each category is also calculated
-     *
-     * @param    array records a flat list of the categories
-     * @return   array categorytree a hierarchical list of the categories
-     */
-    function arrange_categories($records) {
-    //TODO: get the question count for all records with one sql statement: select category, count(*) from question group by category
-        $levels = array();
-
-        // build a levels array, which places each record according to it's depth from the top level
-        $parents = array(0);
-        while (!empty($parents)) {
-            $children = array();
-            foreach ($records as $record) {
-                if (in_array($record->parent, $parents)) {
-                    $children[] = $record->id;
-                }
-            }
-            if (!empty($children)) {
-                $levels[] = $children;
-            }
-            $parents = $children;
-        }
-        // if there is no hierarchy (e.g., if all records have parent == 0), set level[0] to these keys
-        if (empty($levels)) {
-            $levels[0] = array_keys($records);
-        }
-
-        // build a hierarchical array that depicts the parent-child relationships of the categories
-        $categorytree = array();
-        for ($index = count($levels) - 1; $index >= 0; $index--) {
-            foreach($levels[$index] as $key) {
-                $parentkey = $records[$key]->parent;
-                if (!($records[$key]->questioncount = count_records('question', 'category', $records[$key]->id, 'hidden', 0, 'parent', '0'))) {
-                    $records[$key]->questioncount = 0;
-                }
-                if ($parentkey == 0) {
-                    $categorytree[$key] = $records[$key];
-                } else {
-                    $records[$parentkey]->children[$key] = $records[$key];
-                }
-            }
-        }
-        return $categorytree;
-    }
 
     /**
      * Sets the viable parents
@@ -557,11 +415,11 @@ class question_category_object {
      * @return   array categories
      */
     function get_question_categories($parent=null, $sort="sortorder ASC") {
-
+        global $COURSE;
         if (is_null($parent)) {
-            $categories = get_records('question_categories', 'course', "{$this->course->id}", $sort);
+            $categories = get_records('question_categories', 'course', "{$COURSE->id}", $sort);
         } else {
-            $select = "parent = '$parent' AND course = '{$this->course->id}'";
+            $select = "parent = '$parent' AND course = '{$COURSE->id}'";
             $categories = get_records_select('question_categories', $select, $sort);
         }
         return $categories;
@@ -574,18 +432,18 @@ class question_category_object {
      * @param    int destcategoryid id of category which will inherit the orphans of deletecat
      */
     function delete_category($deletecat, $destcategoryid = null) {
-        global $USER;
+        global $USER, $COURSE;
 
         if (!$category = get_record("question_categories", "id", $deletecat)) {  // security
-            error("No such category $deletecat!", "category.php?id={$this->course->id}");
+            error("No such category $deletecat!", "category.php?id={$COURSE->id}");
         }
 
         if (!is_null($destcategoryid)) { // Need to move some questions before deleting the category
             if (!$category2 = get_record("question_categories", "id", $destcategoryid)) {  // security
-                error("No such category $destcategoryid!", "category.php?id={$this->course->id}");
+                error("No such category $destcategoryid!", "category.php?id={$COURSE->id}");
             }
             if (! set_field('question', 'category', $destcategoryid, 'category', $deletecat)) {
-                error("Error while moving questions from category '" . format_string($category->name) . "' to '$category2->name'", "category.php?id={$this->course->id}");
+                error("Error while moving questions from category '" . format_string($category->name) . "' to '$category2->name'", "category.php?id={$COURSE->id}");
             }
 
         } else {
@@ -601,14 +459,14 @@ class question_category_object {
                 echo "<p><div align=\"center\"><form action=\"category.php\" method=\"get\">";
                 echo '<fieldset class="invisiblefieldset">';
                 echo "<input type=\"hidden\" name=\"sesskey\" value=\"$USER->sesskey\" />";
-                echo "<input type=\"hidden\" name=\"id\" value=\"{$this->course->id}\" />";
+                echo "<input type=\"hidden\" name=\"id\" value=\"{$COURSE->id}\" />";
                 echo "<input type=\"hidden\" name=\"delete\" value=\"$category->id\" />";
                 choose_from_menu($categorystrings, "confirm", "", "");
                 echo "<input type=\"submit\" value=\"". get_string("categorymoveto", "quiz") . "\" />";
                 echo "<input type=\"submit\" name=\"cancel\" value=\"{$this->str->cancel}\" />";
                 echo '</fieldset>';
                 echo "</form></div></p>";
-                print_footer($this->course);
+                print_footer($COURSE);
                 exit;
             }
         }
@@ -617,7 +475,7 @@ class question_category_object {
         if ($childcats = get_records("question_categories", "parent", $category->id)) {
             foreach ($childcats as $childcat) {
                 if (! set_field("question_categories", "parent", $category->parent, "id", $childcat->id)) {
-                    error("Could not update a child category!", "category.php?id={$this->course->id}");
+                    error("Could not update a child category!", "category.php?id={$COURSE->id}");
                 }
             }
         }
-- 
2.39.5