chamilo-lms/main/gradebook/lib/be/category.class.php

<?php


/**
 * Defines a gradebook Category object
 * @author Bert Stepp<EFBFBD>, Stijn Konings
 * @package dokeos.gradebook
 */
class Category implements GradebookItem
{

// PROPERTIES

	private $id;
	private $name;
	private $description;
	private $user_id;
	private $course_code;
	private $parent;
	private $weight;
	private $visible;


// CONSTRUCTORS

    function Category()
    {
    }


// GETTERS AND SETTERS

	public function get_id()
	{
		return $this->id;
	}

	public function get_name()
	{
		return $this->name;
	}

	public function get_description()
	{
		return $this->description;
	}

	public function get_user_id()
	{
		return $this->user_id;
	}

	public function get_course_code()
	{
		return $this->course_code;
	}

	public function get_parent_id()
	{
		return $this->parent;
	}

	public function get_weight()
	{
		return $this->weight;
	}

	public function is_visible()
	{
		return $this->visible;
	}

	public function set_id ($id)
	{
		$this->id = $id;
	}
	
	public function set_name ($name)
	{
		$this->name = $name;
	}
	
	public function set_description ($description)
	{
		$this->description = $description;
	}
	
	public function set_user_id ($user_id)
	{
		$this->user_id = $user_id;
	}
	
	public function set_course_code ($course_code)
	{
		$this->course_code = $course_code;
	}
	
	public function set_parent_id ($parent)
	{
		$this->parent = $parent;
	}
	
	public function set_weight ($weight)
	{
		$this->weight = $weight;
	}
	
	public function set_visible ($visible)
	{
		$this->visible = $visible;
	}


// CRUD FUNCTIONS

	/**
	 * Retrieve categories and return them as an array of Category objects
	 * @param $id category id
	 * @param $user_id user id (category owner)
	 * @param $course_code course code
	 * @param $parent_id parent category
	 * @param $visible visible
	 */
	public function load ($id = null, $user_id = null, $course_code = null, $parent_id = null, $visible = null)
	{
		if ($id == '0')
		{
			$cats = array();
			$cats[] = Category::create_root_category();
			return $cats;
		}
		
		$tbl_grade_categories = Database :: get_gradebook_table(TABLE_GRADEBOOK_CATEGORY);
		$sql='SELECT id,name,description,user_id,course_code,parent_id,weight,visible FROM '.$tbl_grade_categories;
		$paramcount = 0;
		if (isset ($id))
		{
			$sql.= ' WHERE id = '.$id;
			$paramcount ++;
		}
		if (isset ($user_id))
		{
			if ($paramcount != 0) $sql .= ' AND';
			else $sql .= ' WHERE';
			$sql .= ' user_id = '.$user_id;
			$paramcount ++;
		}
		if (isset ($course_code))
		{
			if ($paramcount != 0) $sql .= ' AND';
			else $sql .= ' WHERE';
			if ($course_code == '0') $sql .= ' course_code is null ';
			else $sql .= " course_code = '".$course_code."'";
			$paramcount ++;
		}
		if (isset ($parent_id))
		{
			if ($paramcount != 0) $sql .= ' AND';
			else $sql .= ' WHERE';
			$sql .= ' parent_id = '.$parent_id;
			$paramcount ++;
		}
		if (isset ($visible))
		{
			if ($paramcount != 0) $sql .= ' AND';
			else $sql .= ' WHERE';
			$sql .= ' visible = '.$visible;
			$paramcount ++;
		}
		
		$result = api_sql_query($sql, __FILE__, __LINE__);
		$allcat = Category::create_category_objects_from_mysql_result($result);
		return $allcat;
	}
	
	private function create_root_category()
	{
		$cat= new Category();
		$cat->set_id(0);
		$cat->set_name(get_lang('RootCat'));
		$cat->set_description(null);
		$cat->set_user_id(0);
		$cat->set_course_code(null);
		$cat->set_parent_id(null);
		$cat->set_weight(0);
		$cat->set_visible(1);
		return $cat;
	}
	
	private function create_category_objects_from_mysql_result($result)
	{
		$allcat=array();
		while ($data=mysql_fetch_array($result))
		{
			$cat= new Category();
			$cat->set_id($data['id']);
			$cat->set_name($data['name']);
			$cat->set_description($data['description']);
			$cat->set_user_id($data['user_id']);
			$cat->set_course_code($data['course_code']);
			$cat->set_parent_id($data['parent_id']);
			$cat->set_weight($data['weight']);
			$cat->set_visible($data['visible']);
			$allcat[]=$cat;
		}
		return $allcat;
	}

    /**
     * Insert this category into the database
     */
	public function add()
	{
		if (isset($this->name) && isset($this->user_id) && isset($this->weight) && isset($this->visible))
		{
			$tbl_grade_categories = Database :: get_gradebook_table(TABLE_GRADEBOOK_CATEGORY);
			$sql = 'INSERT INTO '.$tbl_grade_categories
					.' (name,user_id,weight,visible';
			if (isset($this->description)) $sql .= ',description';
			if (isset($this->course_code)) $sql .= ',course_code';
			if (isset($this->parent)) $sql .= ',parent_id';
			$sql .= ") VALUES ('".mysql_real_escape_string($this->get_name())."'"
					.','.$this->get_user_id()
					.','.$this->get_weight()
					.','.$this->is_visible();
			if (isset($this->description)) $sql .= ",'".mysql_real_escape_string($this->get_description())."'";
			if (isset($this->course_code)) $sql .= ",'".$this->get_course_code()."'";
			if (isset($this->parent)) $sql .= ','.$this->get_parent_id();
			$sql .= ')';

			api_sql_query($sql, __FILE__, __LINE__);
			$this->set_id(mysql_insert_id());
		}
		else
			die('Error in Category add: required field empty');
	}
	
	/**
	 * Update the properties of this category in the database
	 */
	public function save()
	{
		$tbl_grade_categories = Database :: get_gradebook_table(TABLE_GRADEBOOK_CATEGORY);
		$sql = 'UPDATE '.$tbl_grade_categories
			." SET name = '".mysql_real_escape_string($this->get_name())."'"
			.', description = ';
		if (isset($this->description))
			$sql .= "'".mysql_real_escape_string($this->get_description())."'";
		else
			$sql .= 'null';
		
		$sql .= ', user_id = '.$this->get_user_id()
			.', course_code = ';
		if (isset($this->course_code))
			$sql .= "'".$this->get_course_code()."'";
		else
			$sql .= 'null';
		
		$sql .=	', parent_id = ';
		if (isset ($this->parent))
			$sql .= $this->get_parent_id();
		else
			$sql .= 'null';
		
		$sql .= ', weight = '.$this->get_weight()
			.', visible = '.$this->is_visible()
			.' WHERE id = '.$this->id;

		api_sql_query($sql, __FILE__, __LINE__);
	}
	
	/**
	 * Delete this evaluation from the database
	 */
	public function delete()
	{
		$tbl_grade_categories = Database :: get_gradebook_table(TABLE_GRADEBOOK_CATEGORY);
		$sql = 'DELETE FROM '.$tbl_grade_categories.' WHERE id = '.$this->id;
		api_sql_query($sql, __FILE__, __LINE__);
	}


// OTHER FUNCTIONS

	/**
	 * Check if a category name (with the same parent category) already exists
	 * @param $name name to check (if not given, the name property of this object will be checked)
	 * @param $parent parent category
	 */
	public function does_name_exist($name, $parent)
	{
		if (!isset ($name))
		{
			$name = $this->name;
			$parent = $this->parent;
		}
		$tbl_grade_categories = Database :: get_gradebook_table(TABLE_GRADEBOOK_CATEGORY);
		$sql = 'SELECT count(id) AS number'
			 .' FROM '.$tbl_grade_categories
			 ." WHERE name = '".$name."'";

		if (api_is_allowed_to_create_course())
		{
			$parent = Category::load($parent);
			$code = $parent[0]->get_course_code();
			if (isset($code) && $code != '0')
			{
				$main_course_user_table = Database :: get_main_table(TABLE_MAIN_COURSE_USER);			
				$sql .= ' AND user_id IN ('
						.' SELECT user_id FROM '.$main_course_user_table
						." WHERE course_code = '".$code."'"
						.' AND status = '.COURSEMANAGER
						.')';
			}
			else
				$sql .= ' AND user_id = '.api_get_user_id();
		}
		else
			$sql .= ' AND user_id = '.api_get_user_id();

		if (!isset ($parent))
			$sql.= ' AND parent_id is null';
		else
			$sql.= ' AND parent_id = '.$parent;
			
    	$result = api_sql_query($sql, __FILE__, __LINE__);
		$number=mysql_fetch_row($result);
		return ($number[0] != 0);
	}
	
	/**
	 * Is this category a course ?
	 * A category is a course if it has a course code and no parent category.
	 */
    public function is_course()
    {
    	return (isset($this->course_code) && !empty($this->course_code)
    		&& (!isset($this->parent) || $this->parent == 0));
    }

	/**
	 * Calculate the score of this category
	 * @param $stud_id student id (default: all students - then the average is returned)
	 * @return	array (score sum, weight sum)
	 * 			or null if no scores available
	 */
	public function calc_score ($stud_id = null)
	{
		// get appropriate subcategories, evaluations and links
		
		$cats = $this->get_subcategories($stud_id);
		$evals = $this->get_evaluations($stud_id);
		$links = $this->get_links($stud_id);
		

		// calculate score
		
		$rescount = 0;
		$ressum = 0;
		$weightsum = 0;

		foreach ($cats as $cat)
		{
			$catres = $cat->calc_score ($stud_id);     // recursive call
			if (isset($catres) && $cat->get_weight() != 0)
			{
				$catweight = $cat->get_weight();
				$rescount++;
				$weightsum += $catweight;
				$ressum += (($catres[0]/$catres[1]) * $catweight);
			}
		}
		
		foreach ($evals as $eval)
		{
			$evalres = $eval->calc_score ($stud_id);
			if (isset($evalres) && $eval->get_weight() != 0)
			{
				$evalweight = $eval->get_weight();
				$rescount++;
				$weightsum += $evalweight;
				$ressum += (($evalres[0]/$evalres[1]) * $evalweight);
			}
		}
		
		foreach ($links as $link)
		{
			$linkres = $link->calc_score ($stud_id);
			if (isset($linkres) && $link->get_weight() != 0)
			{
				$linkweight = $link->get_weight();
				$rescount++;
				$weightsum += $linkweight;
				$ressum += (($linkres[0]/$linkres[1]) * $linkweight);
			}
		}


		if ($rescount == 0)
			return null;
		else
			return array ($ressum, $weightsum);
	}
	

	/**
	 * Delete this category and every subcategory, evaluation and result inside
	 */
	public function delete_all ()
	{
		$cats = Category::load(null, null, $this->course_code, $this->id, null);
		$evals = Evaluation::load(null, null, $this->course_code, $this->id, null);
		$links = LinkFactory::load(null,null,null,null,$this->course_code,$this->id,null);
		
		foreach ($cats as $cat)
		{
			$cat->delete_all();
			$cat->delete();
		}

		foreach ($evals as $eval)
			$eval->delete_with_results();

		foreach ($links as $link)
			$link->delete();
		
		$this->delete();
	}
	
	
	/**
	 * Return array of Category objects where a student is subscribed to.
	 * @param $stud_id student id
	 */
	public function get_root_categories_for_student ($stud_id)
	{
		// courses
		
		$main_course_user_table = Database :: get_main_table(TABLE_MAIN_COURSE_USER);			
		$tbl_grade_categories = Database :: get_gradebook_table(TABLE_GRADEBOOK_CATEGORY);

		$sql = 'SELECT *'
				.' FROM '.$tbl_grade_categories
				.' WHERE parent_id = 0';
		if (!api_is_allowed_to_create_course())
			$sql .= ' AND visible = 1';
		$sql .= ' AND course_code in'
				.' (SELECT course_code'
				.' FROM '.$main_course_user_table
				.' WHERE user_id = '.$stud_id
				.' AND status = '.STUDENT
				.')';

		if (api_is_allowed_to_create_course() && !api_is_platform_admin())
			$sql .= ' AND course_code in'
					.' (SELECT course_code'
					.' FROM '.$main_course_user_table
					.' WHERE user_id = '.api_get_user_id()
					.' AND status = '.COURSEMANAGER
					.')';


		$result = api_sql_query($sql, __FILE__, __LINE__);
		$cats = Category::create_category_objects_from_mysql_result($result);

		// course independent categories

		$cats = Category::get_independent_categories_with_result_for_student (0, $stud_id, $cats);

		return $cats;

	}
	
	/**
	 * Return array of Category objects where a teacher is admin for.
	 * @param $user_id user id (to return everything, use 'null' here)
	 */
	public function get_root_categories_for_teacher ($user_id)
	{
		if ($user_id == null)
			return Category::load(null,null,null,0);


		// courses
		
		$main_course_user_table = Database :: get_main_table(TABLE_MAIN_COURSE_USER);			
		$tbl_grade_categories = Database :: get_gradebook_table(TABLE_GRADEBOOK_CATEGORY);

		$sql = 'SELECT *'
				.' FROM '.$tbl_grade_categories
				.' WHERE parent_id = 0'
				.' AND course_code in'
				.' (SELECT course_code'
				.' FROM '.$main_course_user_table
				.' WHERE user_id = '.$user_id
				.' AND status = '.COURSEMANAGER
				.')';

		$result = api_sql_query($sql, __FILE__, __LINE__);
		$cats = Category::create_category_objects_from_mysql_result($result);

		// course independent categories

		$indcats = Category::load(null,$user_id,0,0);
		$cats = array_merge($cats, $indcats);

		return $cats;
	}
	
	
	/**
	 * Can this category be moved to somewhere else ?
	 * The root and courses cannot be moved.
	 */
	public function is_movable ()
	{
		return (!(!isset ($this->id) || $this->id == 0 || $this->is_course()));
	}
	
	/**
	 * Generate an array of possible categories where this category can be moved to.
	 * Notice: its own parent will be included in the list: it's up to the frontend
	 * to disable this element.
	 * @return array 2-dimensional array - every element contains 3 subelements (id, name, level)
	 */
	public function get_target_categories()
	{
		// the root or a course -> not movable
		if (!$this->is_movable())
		{
			return null;
		}
		// otherwise:
		// - course independent category
		//   -> movable to root or other independent categories
		// - category inside a course
		//   -> movable to root, independent categories or categories inside the course
		else
		{
			$user = (api_is_platform_admin() ? null : api_get_user_id());
			$targets = array();
			$level = 0;

			$root = array(0, get_lang('RootCat'), $level);
			$targets[] = $root;

			if (isset($this->course_code) && !empty($this->course_code))
			{
				$crscats = Category::load(null,null,$this->course_code,0);
				foreach ($crscats as $cat)
				{
					if ($this->can_be_moved_to_cat($cat))
					{
						$targets[] = array ($cat->get_id(), $cat->get_name(), $level+1);
						$targets = $this->add_target_subcategories($targets, $level+1, $cat->get_id());
					}
				}
			}

			$indcats = Category::load(null,$user,0,0);
			foreach ($indcats as $cat)
			{
				if ($this->can_be_moved_to_cat($cat))
				{
					$targets[] = array ($cat->get_id(), $cat->get_name(), $level+1);
					$targets = $this->add_target_subcategories($targets, $level+1, $cat->get_id());
				}
			}
			
			return $targets;
		}
	}
	
	/**
	 * Internal function used by get_target_categories()
	 */
	private function add_target_subcategories($targets, $level, $catid)
	{
		$subcats = Category::load(null,null,null,$catid);
		foreach ($subcats as $cat)
		{
			if ($this->can_be_moved_to_cat($cat))
			{
				$targets[] = array ($cat->get_id(), $cat->get_name(), $level+1);
				$targets = $this->add_target_subcategories($targets, $level+1, $cat->get_id());
			}
		}
		return $targets;
	}
	
	/**
	 * Internal function used by get_target_categories() and add_target_subcategories()
	 * Can this category be moved to the given category ?
	 * Impossible when origin and target are the same... children won't be processed
	 * either. (a category can't be moved to one of its own children)
	 */
	private function can_be_moved_to_cat ($cat)
	{
		return ($cat->get_id() != $this->get_id());
	}
	
	/**
	 * Move this category to the given category.
	 * If this category moves from inside a course to outside,
	 * its course code must be changed, as well as the course code
	 * of all underlying categories and evaluations. All links will
	 * be deleted as well !
	 */
	public function move_to_cat ($cat)
	{
		$this->set_parent_id($cat->get_id());
		if ($this->get_course_code() != $cat->get_course_code())
		{
			$this->set_course_code($cat->get_course_code());
			$this->apply_course_code_to_children();
		}
		$this->save();
	}
	
	/**
	 * Internal function used by move_to_cat()
	 */
	private function apply_course_code_to_children ()
	{
		$cats = Category::load(null, null, null, $this->id, null);
		$evals = Evaluation::load(null, null, null, $this->id, null);
		$links = LinkFactory::load(null,null,null,null,null,$this->id,null);
		
		foreach ($cats as $cat)
		{
			$cat->set_course_code($this->get_course_code());
			$cat->save();
			$cat->apply_course_code_to_children();
		}

		foreach ($evals as $eval)
		{
			$eval->set_course_code($this->get_course_code());
			$eval->save();
		}

		foreach ($links as $link)
			$link->delete();
	}
	
	
	
	/**
	 * Generate an array of all categories the user can navigate to
	 */
	public function get_tree ()
	{
		$targets = array();
		$level = 0;

		$root = array(0, get_lang('RootCat'), $level);
		$targets[] = $root;

		// course or platform admin
		if (api_is_allowed_to_create_course())
		{
			$user = (api_is_platform_admin() ? null : api_get_user_id());

			$cats = Category::get_root_categories_for_teacher($user);
			foreach ($cats as $cat)
			{
				$targets[] = array ($cat->get_id(), $cat->get_name(), $level+1);
				$targets = Category::add_subtree($targets, $level+1, $cat->get_id(),null);
			}
		}
		// student
		else
		{
			$cats = Category::get_root_categories_for_student(api_get_user_id());
			foreach ($cats as $cat)
			{
				$targets[] = array ($cat->get_id(), $cat->get_name(), $level+1);
				$targets = Category::add_subtree($targets, $level+1, $cat->get_id(), 1);
			}
		}
		
		return $targets;
	}

	/**
	 * Internal function used by get_tree()
	 */
	private function add_subtree ($targets, $level, $catid, $visible)
	{
		$subcats = Category::load(null,null,null,$catid,$visible);
		foreach ($subcats as $cat)
		{
			$targets[] = array ($cat->get_id(), $cat->get_name(), $level+1);
			$targets = Category::add_subtree($targets, $level+1, $cat->get_id(),$visible);
		}
		return $targets;
	}

	/**
	 * Generate an array of courses that a teacher hasn't created a category for.
	 * @return array 2-dimensional array - every element contains 2 subelements (code, title)
	 */
	public function get_not_created_course_categories ($user_id)
	{
		$tbl_main_courses = Database :: get_main_table(TABLE_MAIN_COURSE);
		$tbl_main_course_user = Database :: get_main_table(TABLE_MAIN_COURSE_USER);			
		$tbl_grade_categories = Database :: get_gradebook_table(TABLE_GRADEBOOK_CATEGORY);

		$sql = 'SELECT * FROM '.$tbl_main_courses.' cc, '.$tbl_main_course_user.' cu'
				.' WHERE cc.code = cu.course_code'
				.' AND cu.status = '.COURSEMANAGER;
		if (!api_is_platform_admin())
			$sql .= ' AND cu.user_id = '.$user_id;
		$sql .= ' AND cc.code NOT IN'
				.' (SELECT course_code FROM '.$tbl_grade_categories
				.' WHERE parent_id = 0'
//				.' AND user_id = '.$user_id
				.' AND course_code IS NOT null)';

		$result = api_sql_query($sql, __FILE__, __LINE__);

		$cats=array();
		while ($data=mysql_fetch_array($result))
		{
			$cats[] = array ($data['code'], $data['title']);
		}
		return $cats;
		
	}


	/**
	 * Apply the same visibility to every subcategory, evaluation and link
	 */
	public function apply_visibility_to_children ()
	{
		$cats = Category::load(null, null, null, $this->id, null);
		$evals = Evaluation::load(null, null, null, $this->id, null);
		$links = LinkFactory::load(null,null,null,null,null,$this->id,null);
		
		foreach ($cats as $cat)
		{
			$cat->set_visible($this->is_visible());
			$cat->save();
			$cat->apply_visibility_to_children();
		}

		foreach ($evals as $eval)
		{
			$eval->set_visible($this->is_visible());
			$eval->save();
		}

		foreach ($links as $link)
		{
			$link->set_visible($this->is_visible());
			$link->save();
		}
	}


	/**
	 * Check if a category contains evaluations with a result for a given student
	 */
	public function has_evaluations_with_results_for_student ($stud_id)
	{
		$evals = Evaluation::get_evaluations_with_result_for_student($this->id, $stud_id);
		if (count($evals) != 0)
		{
			return true;
		}
		else
		{
			$cats = Category::load(null, null, null, $this->id,
						api_is_allowed_to_create_course() ? null : 1);
			foreach ($cats as $cat)
			{
				if ($cat->has_evaluations_with_results_for_student ($stud_id))
					return true;
			}
			return false;
		}
	}

	/**
	 * Retrieve all categories inside a course independent category
	 * that should be visible to a student.
	 * @param $cat_id parent category
	 * @param $stud_id student id
	 * @param $cats optional: if defined, the categories will be added to this array
	 */
    public function get_independent_categories_with_result_for_student ($cat_id, $stud_id, $cats = array())
    {
    	$creator = (api_is_allowed_to_create_course() && !api_is_platform_admin()) ? api_get_user_id() : null;
    	
		$crsindcats = Category::load(null,$creator,'0',$cat_id,
						api_is_allowed_to_create_course() ? null : 1);
		foreach ($crsindcats as $crsindcat)
		{
			if ($crsindcat->has_evaluations_with_results_for_student($stud_id))
				$cats[] = $crsindcat;
		}
		return $cats;
    }



	/**
	 * Get appropriate subcategories visible for the user
	 * @param int $stud_id student id (default: all students)
	 */
	public function get_subcategories ($stud_id = null)
	{
		$cats = array();
		
		// 1 student
 		if (isset($stud_id))
		{
			// special case: this is the root
			if ($this->id == 0)
				return Category::get_root_categories_for_student ($stud_id);
			else
			{
				return Category::load(null,null,null,$this->id,
					api_is_allowed_to_create_course() ? null : 1);
			}
		}
		
		// all students
		else
		{
			// course admin
			if (api_is_allowed_to_create_course() && !api_is_platform_admin())
			{
				// root
				if ($this->id == 0)
					return $this->get_root_categories_for_teacher (api_get_user_id());
				// inside a course
				elseif (isset($this->course_code) && !empty($this->course_code))
					return Category::load(null, null, $this->course_code, $this->id, null);
				// course independent
				else
					return Category::load(null, api_get_user_id(), 0, $this->id, null);
			}
		
			// platform admin
			elseif (api_is_platform_admin())
				return Category::load(null, null, null, $this->id, null);
		}

		return array();
		
	}


	/**
	 * Get appropriate evaluations visible for the user
	 * @param int $stud_id student id (default: all students)
	 * @param boolean $recursive process subcategories (default: no recursion)
	 */
	public function get_evaluations ($stud_id = null, $recursive = false)
	{
		$evals = array();
		
		// 1 student
 		if (isset($stud_id))
		{
			// special case: this is the root
			if ($this->id == 0)
				$evals = Evaluation::get_evaluations_with_result_for_student(0,$stud_id);
			else
				$evals = Evaluation::load(null,null,null,$this->id,
					api_is_allowed_to_create_course() ? null : 1);
		}
		
		// all students
		else
		{
			// course admin
			if (api_is_allowed_to_create_course() && !api_is_platform_admin())
			{
				// root
				if ($this->id == 0)
					$evals = Evaluation::load(null, api_get_user_id(), null, $this->id, null);
				// inside a course
				elseif (isset($this->course_code) && !empty($this->course_code))
					$evals = Evaluation::load(null, null, $this->course_code, $this->id, null);
				// course independent
				else
					$evals = Evaluation::load(null, api_get_user_id(), null, $this->id, null);
			}
		
			// platform admin
			elseif (api_is_platform_admin())
				$evals = Evaluation::load(null, null, null, $this->id, null);
		}
		
		if ($recursive)
		{
			$subcats = $this->get_subcategories($stud_id);
			foreach ($subcats as $subcat)
			{
				$subevals = $subcat->get_evaluations($stud_id, true);
				//$this->debugprint($subevals);
				$evals = array_merge($evals, $subevals);
			}
		}
		
		return $evals;

	}

	/**
	 * Get appropriate links visible for the user
	 * @param int $stud_id student id (default: all students)
	 * @param boolean $recursive process subcategories (default: no recursion)
	 */
	public function get_links ($stud_id = null, $recursive = false)
	{
		$links = array();
		
		// no links in root or course independent categories
		if ($this->id == 0 || !isset($this->course_code) || empty($this->course_code))
			;
		
		// 1 student
 		elseif (isset($stud_id))
			$links = LinkFactory::load(null,null,null,null,$this->course_code,$this->id,
						api_is_allowed_to_create_course() ? null : 1);
		
		// all students -> only for course/platform admin
		elseif (api_is_allowed_to_create_course())
			$links = LinkFactory::load(null,null,null,null,$this->course_code,$this->id, null);
		
		if ($recursive)
		{
			$subcats = $this->get_subcategories($stud_id);
			foreach ($subcats as $subcat)
			{
				$sublinks = $subcat->get_links($stud_id, true);
				$links = array_merge($links, $sublinks);
			}
		}

		return $links;

	}


// Other methods implementing GradebookItem

	public function get_item_type()
	{
		return 'C';
	}

	public function get_date()
	{
		return null;
	}

	public function get_icon_name()
	{
		return 'cat';
	}


}
?>