/**
  * @return Planning_Milestone[]
  */
 private function getPlanningMilestonesForTimePeriod(Planning $planning)
 {
     $user = $this->request->getCurrentUser();
     switch ($this->request->get('period')) {
         case self::PAST_PERIOD:
             return $this->milestone_factory->getPastMilestones($user, $planning, self::NUMBER_PAST_MILESTONES_SHOWN);
         case self::FUTURE_PERIOD:
             return $this->milestone_factory->getAllFutureMilestones($user, $planning);
         default:
             return $this->milestone_factory->getAllCurrentMilestones($user, $planning);
     }
 }