/**
  * @task email
  */
 public function changePrimaryEmail(PhabricatorUser $user, PhabricatorUserEmail $email)
 {
     $actor = $this->requireActor();
     if (!$user->getID()) {
         throw new Exception("User has not been created yet!");
     }
     if (!$email->getID()) {
         throw new Exception("Email has not been created yet!");
     }
     $user->openTransaction();
     $user->beginWriteLocking();
     $user->reload();
     $email->reload();
     if ($email->getUserPHID() != $user->getPHID()) {
         throw new Exception("User does not own email!");
     }
     if ($email->getIsPrimary()) {
         throw new Exception("Email is already primary!");
     }
     if (!$email->getIsVerified()) {
         throw new Exception("Email is not verified!");
     }
     $old_primary = $user->loadPrimaryEmail();
     if ($old_primary) {
         $old_primary->setIsPrimary(0);
         $old_primary->save();
     }
     $email->setIsPrimary(1);
     $email->save();
     $log = PhabricatorUserLog::newLog($actor, $user, PhabricatorUserLog::ACTION_EMAIL_PRIMARY);
     $log->setOldValue($old_primary ? $old_primary->getAddress() : null);
     $log->setNewValue($email->getAddress());
     $log->save();
     $user->endWriteLocking();
     $user->saveTransaction();
     if ($old_primary) {
         $old_primary->sendOldPrimaryEmail($user, $email);
     }
     $email->sendNewPrimaryEmail($user);
     return $this;
 }