feat(guess-user): add option to limit query

src/Handler/Exam/Users.hs

@@ -979,7 +979,7 @@ postEUsersR tid ssh csh examn = do
                       , GuessUserSurname <$> csvEUserSurname
                       , GuessUserFirstName <$> csvEUserFirstName
                       ]
-                guess <- maybe (throwM ExamUserCsvExceptionNoMatchingUser) return =<< guessUser criteria
+                guess <- maybe (throwM ExamUserCsvExceptionNoMatchingUser) return =<< guessUser criteria (Just 2)  -- we're only interested in at most one match, but want to throw an error on multiple matches
                 pid <- either (const $ throwM ExamUserCsvExceptionMultipleMatchingUsers) (return . entityKey) guess
                 (,) <$> exists [CourseParticipantCourse ==. examCourse, CourseParticipantUser ==. pid, CourseParticipantState ==. CourseParticipantActive] <*> pure pid
 

src/Handler/ExternalExam/Correct.hs

@@ -81,25 +81,7 @@ postEECorrectR tid ssh coursen examn = do
               , GuessUserSurname        (ident :: UserSurname)
               , GuessUserFirstName      (ident :: UserFirstName)
               ]
-        in  lift (guessUser pdnf) >>= return . maybe [] (either NonEmpty.toList pure)  -- TODO add and use option to E.limit query in guessUser (see deprecated query below)
-
-    -- TODO remove
-    --userMatches <- 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
-    --    E.||. (case mUserIdent of
-    --             Just userIdent -> 
-    --                     user E.^. UserSurname         E.==.       E.val userIdent
-    --               E.||. user E.^. UserSurname        `E.hasInfix` E.val userIdent
-    --               E.||. user E.^. UserFirstName       E.==.       E.val userIdent
-    --               E.||. user E.^. UserFirstName      `E.hasInfix` E.val userIdent
-    --               E.||. user E.^. UserDisplayName     E.==.       E.val userIdent
-    --               E.||. user E.^. UserDisplayName    `E.hasInfix` E.val userIdent
-    --               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
+        in  lift (guessUser pdnf $ Just $ maxCountUserMatches+1) >>= return . maybe [] (either NonEmpty.toList pure)
 
     if
       | is _Nothing ciqResults, is _Nothing ciqGrade -> do

src/Handler/Utils/ExternalExam/Users.hs

@@ -498,7 +498,7 @@ makeExternalExamUsersTable mode (Entity eeId ExternalExam{..}) = do
                 , GuessUserSurname <$> csvEUserSurname
                 , GuessUserFirstName <$> csvEUserFirstName
                 ]
-          maybe (throwM ExamUserCsvExceptionNoMatchingUser) return =<< guessUser criteria
+          maybe (throwM ExamUserCsvExceptionNoMatchingUser) return =<< guessUser criteria (Just 1)  -- we're only interested in at most one match
     externalExamUsersDBTableValidator = def
       & defaultSorting (bool id (SortAscBy "is-synced" :) (mode == EEUMGrades) [SortAscBy "user-name"])
       & defaultPagesize PagesizeAll

src/Handler/Utils/Users.hs

@@ -14,6 +14,7 @@ import Auth.LDAP (campusUserMatr')
 import Crypto.Hash (hashlazy)
 
 import Data.ByteArray (constEq)
+import Data.Maybe (fromJust)
 import qualified Data.List.NonEmpty as NonEmpty (fromList)
 
 import qualified Data.Aeson as JSON
@@ -69,8 +70,12 @@ matchesName (repack -> haystack) (repack -> needle)
       ]
 
 
-guessUser :: PredDNF GuessUserInfo -> DB (Maybe (Either (NonEmpty (Entity User)) (Entity User)))
-guessUser (((Set.toList . toNullable) <$>) . Set.toList . dnfTerms -> criteria) = $cachedHereBinary criteria $ go False
+guessUser :: PredDNF GuessUserInfo  -- ^ guessing criteria
+          -> Maybe Int64  -- ^ Should the query be limited to a maximum number of results?
+          -> DB (Maybe (Either (NonEmpty (Entity User)) (Entity User)))  -- ^ Just (Left _) in case of multiple results, 
+                                                                         --   Just (Right _) in case of single result, and
+                                                                         --   Nothing in case of no result
+guessUser (((Set.toList . toNullable) <$>) . Set.toList . dnfTerms -> criteria) mQueryLimit = $cachedHereBinary criteria $ go False
   where
     asWords :: Text -> [Text]
     asWords = filter (not . Text.null) . Text.words . Text.strip
@@ -86,6 +91,7 @@ guessUser (((Set.toList . toNullable) <$>) . Set.toList . dnfTerms -> criteria)
     go didLdap = do
       let retrieveUsers = E.select . E.from $ \user -> do
             E.where_ . E.or $ map (E.and . map (toSql user)) criteria
+            when (is _Just mQueryLimit) $ (E.limit . fromJust) mQueryLimit
             return user
       users <- retrieveUsers
       let users' = sortBy (flip closeness) users