public function GetTaskHistory()
{
$chain = new \SplStack();
$added = array();
// If we traverse in order, then we preserve the order that tasks
// made it to the TASK_FINISHED state, so long as we exclude
// duplicates.
foreach ($this->tasks as $task) {
if ($task->state() == self::TASK_FINISHED && !in_array($task, $added)) {
$chain->Unshift($task);
$added[] = $task;
}
}
return $chain;
}
