isSuperAdminCheck (Yesod Google Group question)

Foundation.hs

isAuthorized AssetR _ = isSuperAdmin
isAuthorized HomeR _ = isAuthenticated

-- | Are you logged in?
isAuthenticated :: Handler AuthResult
isAuthenticated = 
  do muid <- maybeAuthId
     return $
       case muid of
         Nothing -> Unauthorized "You must login to access this page"
         Just _ -> Authorized

-- | Are you a super admin
isSuperAdmin :: Handler AuthResult
isSuperAdmin = maybeAuthId >>= isSuperAdminCheck SuperAdmin

-- | Check that the user has the required role (using Esqueleto)
isSuperAdminCheck
  :: RoleType -> Maybe (Key User) -> Handler AuthResult
isSuperAdminCheck _ Nothing = 
  return $ Unauthorized "You need to be an administrator to access this area."
isSuperAdminCheck r (Just uid) = 
  runDB $
  do us <- 
       E.select $
       E.from $
       \(user `E.InnerJoin` userRole) -> 
         do E.on $
              userRole ^. UserRoleUserId E.==. user ^. UserId E.&&.
              E.isNothing (userRole ^. UserRoleDeletedAt) E.&&.
              userRole ^.
              UserRoleRoleType E.==.
              E.val r
            E.where_ (user ^. UserId E.==. E.val uid)
            return user
     case us of
       [users] -> return Authorized
       _ -> 
         return $
         Unauthorized "You need to be an administrator to access this area."