/**
  * @param Portfolio $portfolio
  * @param User|null $user
  * @param bool      $isAdmin
  *
  * @return string|null
  */
 public function getOpeningMode(Portfolio $portfolio, $user, $isAdmin = false)
 {
     $openingMode = null;
     if (null !== $user) {
         if ($user === $portfolio->getUser() || $isAdmin) {
             $openingMode = self::PORTFOLIO_OPENING_MODE_EDIT;
         } elseif ($portfolio->hasGuide($user)) {
             $openingMode = self::PORTFOLIO_OPENING_MODE_EVALUATE;
         } elseif ($this->visibleToUser($portfolio, $user)) {
             $openingMode = self::PORTFOLIO_OPENING_MODE_VIEW;
         }
     } elseif (Portfolio::VISIBILITY_EVERYBODY === $portfolio->getVisibility()) {
         $openingMode = self::PORTFOLIO_OPENING_MODE_VIEW;
     }
     return $openingMode;
 }