CLearnLesson::DeleteRecursiveLikeHardlinks

static function DeleteRecursiveLikeHardlinks ($in_data)
{
	list ($root_lesson_id, $simulate, $check_permissions, $user_id) =
		self::_funcDelete_ParseOptions($in_data);

	// list of lessons, which are candidates to be removed
	$arCandidatesToRemove = array();

	// Build list of all descendants (excluded duplicated)
	$oTree = self::GetTree($root_lesson_id);
	$arDescendantsList = $oTree->GetLessonsIdListInTree();

	// Transform list: add list of immediate parents to every candidate
	foreach ($arDescendantsList as $lesson_id)
	{
		$arParents = array();
		$arEdges = self::ListImmediateParents($lesson_id);

		foreach ($arEdges as $arEdgeData)
			$arParents[] = (int) $arEdgeData['PARENT_LESSON'];

		$arCandidatesToRemove[(int) $lesson_id] = $arParents;
	}

	// Now, move out parents of root lesson, because they mustn't be checked below.
	$arCandidatesToRemove[$root_lesson_id] = array();

	// Withdraw lessons, which has ancestors not among candidates to be removed
	do
	{
		$lessonsWithdrawn = 0;	// count of withdrawn lessons

		foreach ($arCandidatesToRemove as $lesson_id => $arParents)
		{
			// Check that all parents are from candidates to be removed;
			// otherwise $lesson_id must be withdrew from candidates
			foreach ($arParents as $parent_lesson_id)
			{
				if ( ! array_key_exists((int) $parent_lesson_id, $arCandidatesToRemove) )
				{
					unset($arCandidatesToRemove[(int) $lesson_id]);
					$lessonsWithdrawn++;
					break;	// we don't need to check other parents for this lesson anymore
				}
			}
		}
	}
	while ($lessonsWithdrawn > 0);

	// Now, broke edges and remove lessons.
	// Broke edges to lessons in $arCandidatesToRemove list only.
	foreach ($arCandidatesToRemove as $lesson_id => $arParents)
	{
		try
		{
			self::Delete(
				array(
					'lesson_id'         => $lesson_id,
					'simulate'          => $simulate,
					'check_permissions' => $check_permissions,
					'user_id'           => $user_id
					)
				);
		}
		catch (LearnException $e)
		{
			if ($e->GetCode() === LearnException::EXC_ERR_LL_UNREMOVABLE_CL)
				;	// course cannot be removed - ignore this error
			elseif ($e->GetCode() === LearnException::EXC_ERR_ALL_ACCESS_DENIED)
			{
				// if lesson not exists - ignore error (lesson to be deleted is already removed)
				$rsLesson = self::GetListUni(
					array(),
					array('LESSON_ID' => $lesson_id, 'CHECK_PERMISSIONS' => 'N'),
					array('LESSON_ID'),
					self::GET_LIST_ALL
				);

				if ( ! $rsLesson->fetch() )
				{
					;	// ignore this situation, it's OK
				}
				else
				{
					// bubble exception
					throw new LearnException ($e->GetMessage(), $e->GetCode());
				}
			}
			else
			{
				// bubble exception
				throw new LearnException ($e->GetMessage(), $e->GetCode());
			}
		}
	}
}