feat(exam-correct): limit number of matching users (BE)

src/Handler/Exam/Correct.hs

@@ -21,6 +21,13 @@ import Utils.Exam
 minNeedleLength :: Int
 minNeedleLength = 3
 
+-- TODO use according to description
+-- TODO maybe renders minNeedleLength unnecessary?
+-- TODO maybe also perform user and ldap lookups if there are fewer results than this number? (TODO add user as exam participant if not already participant)
+-- | Maximum number of participant matches to show. Also serves as an upper limit to the number of query results from participant lookups.
+maxCountUserMatches :: Integral a => a
+maxCountUserMatches = 10
+
 
 getECorrectR :: TermId -> SchoolId -> CourseShorthand -> ExamName -> Handler Html
 getECorrectR tid ssh csh examn = do
@@ -67,7 +74,6 @@ postECorrectR tid ssh csh examn = do
     guardMExceptT (maybe True ((>= minNeedleLength) . length) $ euid ^? _Left) $ 
       CorrectInterfaceResponseFailure Nothing <$> (getMessageRender <*> pure MsgExamCorrectErrorNeedleTooShort)
 
-
     participantMatches <- lift . E.select . E.from $ \(examRegistration `E.InnerJoin` user) -> do
       E.on $ examRegistration E.^. ExamRegistrationUser E.==. user E.^. UserId
       E.where_ $ examRegistration E.^. ExamRegistrationExam E.==. E.val eId
@@ -86,6 +92,7 @@ postECorrectR tid ssh csh examn = do
                         E.||. user E.^. UserMatrikelnummer E.==. E.val mUserIdent
                         E.||. user E.^. UserMatrikelnummer `E.hasInfix` E.val mUserIdent
             Nothing -> E.val False)
+      E.limit $ maxCountUserMatches+1
       return user
 
     if
@@ -185,9 +192,10 @@ postECorrectR tid ssh csh examn = do
 
       -- on match with multiple exam participants, answer with 400 and a set of all matches
       | otherwise -> do
-        users <- traverse userToResponse participantMatches
+        users <- traverse userToResponse $ take maxCountUserMatches participantMatches
         return CorrectInterfaceResponseAmbiguous
           { ciraMessage = mr MsgExamCorrectErrorMultipleMatchingParticipants
+          , ciraHasMore = length participantMatches > maxCountUserMatches
           , ciraUsers   = Set.fromList users
           }
   

src/Handler/ExternalExam/Correct.hs

@@ -15,10 +15,17 @@ import Handler.Utils.ExternalExam
 
 import Utils.Exam
 
+
 -- | Minimum length of a participant identifier. Identifiers that are shorter would result in too many query results and are therefor rejected.
 minNeedleLength :: Int
 minNeedleLength = 3  -- TODO rethink
 
+-- TODO use according to description
+-- TODO maybe renders minNeedleLength unnecessary?
+-- | Maximum number of user matches to show. Also serves as an upper limit to the number of query results from user and/or ldap lookups.
+maxCountUserMatches :: Integral a => a
+maxCountUserMatches = 10
+
 
 getEECorrectR :: TermId -> SchoolId -> CourseName -> ExamName -> Handler Html
 getEECorrectR tid ssh coursen examn = do
@@ -66,6 +73,7 @@ postEECorrectR tid ssh coursen examn = do
     guardMExceptT (maybe True ((>= minNeedleLength) . length) $ euid ^? _Left) $
       CorrectInterfaceResponseFailure Nothing <$> (getMessageRender <*> pure MsgExamCorrectErrorNeedleTooShort)
 
+    -- TODO additionally call guessUser if this query produces too few results
     matches <- lift . E.select . E.from $ \user -> do
       let mUserIdent = euid ^? _Left
       E.where_ $ either (const E.false) (\uid -> user E.^. UserId E.==. E.val uid) euid
@@ -80,6 +88,7 @@ postEECorrectR tid ssh coursen examn = do
                    E.||. user E.^. UserMatrikelnummer  E.==.       E.val mUserIdent
                    E.||. user E.^. UserMatrikelnummer `E.hasInfix` E.val mUserIdent
                  Nothing -> E.false)
+      E.limit $ maxCountUserMatches+1
       return user
 
     if
@@ -134,9 +143,10 @@ postEECorrectR tid ssh coursen examn = do
         }
 
       | otherwise -> do
-        users <- traverse userToResponse matches
+        users <- traverse userToResponse $ take maxCountUserMatches matches
         return CorrectInterfaceResponseAmbiguous
           { ciraUsers   = Set.fromList users
+          , ciraHasMore = length matches > maxCountUserMatches
           , ciraMessage = mr MsgExamCorrectErrorMultipleMatchingParticipants  -- TODO use new msg
           }
 

src/Utils/Exam.hs

@@ -42,6 +42,7 @@ data CorrectInterfaceResponse
     }
   | CorrectInterfaceResponseAmbiguous
     { ciraUsers      :: Set CorrectInterfaceUser
+    , ciraHasMore    :: Bool
     , ciraMessage    :: Text
     }
   | CorrectInterfaceResponseFailure