Alternative Query Attempt

src/Handler/Course.hs

@@ -649,6 +649,31 @@ validateCourse CourseForm{..} =
 --------------------
 -- CourseUserTable
 
+
+userTableQuery' :: CourseId ->  E.Esqueleto query expr backend =>
+                         E.LeftOuterJoin
+                           (E.LeftOuterJoin
+                              (E.InnerJoin
+                                 (expr (Entity User)) (expr (Entity CourseParticipant)))
+                              (expr (Maybe (Entity CourseUserNote))))
+                           (E.InnerJoin
+                              (E.InnerJoin
+                                 (expr (Maybe (Entity StudyFeatures)))
+                                 (expr (Maybe (Entity StudyDegree))))
+                              (expr (Maybe (Entity StudyTerms))))
+                         -> query (expr (Entity User), expr (E.Value UTCTime),
+                                   expr (E.Value (Maybe (Key CourseUserNote))),
+                                   (expr (Maybe (Entity StudyFeatures)), expr (Maybe (Entity StudyDegree)), expr (Maybe (Entity StudyTerms))))
+userTableQuery' cid ((user `E.InnerJoin` participant) `E.LeftOuterJoin` note `E.LeftOuterJoin` _studyFeatures@(features `E.InnerJoin` degree `E.InnerJoin` terms)) = do
+  E.on $ participant E.^. CourseParticipantField E.==. features E.?. StudyFeaturesId
+  --(features, degree, terms) <- studyFeaturesQuery (participant E.^. CourseParticipantField) studyFeatures
+  E.on $ terms  E.?. StudyTermsId  E.==. features E.?. StudyFeaturesField
+  E.on $ degree E.?. StudyDegreeId E.==. features E.?. StudyFeaturesDegree
+  E.on $ E.just (participant E.^. CourseParticipantUser) E.==. note E.?. CourseUserNoteUser
+  E.on $         participant E.^. CourseParticipantUser  E.==. user E.^. UserId
+  E.where_ $ participant E.^. CourseParticipantCourse E.==. E.val cid
+  return (user, participant E.^. CourseParticipantRegistration, note E.?. CourseUserNoteId, (features,degree,terms))
+
 type UserTableExpr   = (E.SqlExpr (Entity User) `E.InnerJoin` E.SqlExpr (Entity CourseParticipant)) `E.LeftOuterJoin` E.SqlExpr (Maybe (Entity CourseUserNote))
 type UserTableWhere  = UserTableExpr -> E.SqlExpr (E.Value Bool)
 type UserTableData   = DBRow (Entity User, UTCTime, Maybe CourseUserNoteId)

src/Handler/Utils/Database.hs

@@ -1,6 +1,7 @@
 module Handler.Utils.Database
   ( getSchoolsOf
   , makeSchoolDictionaryDB, makeSchoolDictionary
+  , studyFeaturesQuery, studyFeaturesQuery'
   ) where
 
 import Import
@@ -29,3 +30,25 @@ getSchoolsOf uid uschool uuser = fmap (Import.map E.unValue) $ E.select $ E.from
   E.where_ $ urights E.^. uuser   E.==. E.val uid
   E.orderBy [E.asc $ school E.^.SchoolName]
   return $ school E.^. SchoolName
+
+
+studyFeaturesQuery :: E.Esqueleto query expr backend
+  => expr (E.Value (Maybe StudyFeaturesId)) -- ^ query is filtered by StudyFeatureId
+  -> (expr (Entity StudyFeatures)) `E.InnerJoin` (expr (Entity StudyDegree)) `E.InnerJoin` (expr (Entity StudyTerms))
+  -> query (expr (Entity StudyFeatures), expr (Entity StudyDegree), expr (Entity StudyTerms))
+studyFeaturesQuery sfId (features `E.InnerJoin` degree `E.InnerJoin` terms) = do
+  E.on $ terms  E.^. StudyTermsId  E.==. features E.^. StudyFeaturesField
+  E.on $ degree E.^. StudyDegreeId E.==. features E.^. StudyFeaturesDegree
+  E.where_ $ (E.just (features E.^. StudyFeaturesId)) E.==. sfId
+  return (features, degree, terms)
+
+-- | Variant of @studyFeaturesQuery@ to be used in outer joins
+studyFeaturesQuery' :: E.Esqueleto query expr backend
+  => expr (E.Value (Maybe StudyFeaturesId)) -- ^ query is filtered by StudyFeatureId
+  -> (expr (Maybe (Entity StudyFeatures)) `E.InnerJoin` (expr (Maybe (Entity StudyDegree))) `E.InnerJoin` (expr (Maybe (Entity StudyTerms))))
+  -> query (expr (Maybe (Entity StudyFeatures)), expr (Maybe (Entity StudyDegree)), expr (Maybe (Entity StudyTerms)))
+studyFeaturesQuery' sfId (features `E.InnerJoin` degree `E.InnerJoin` terms) = do
+  E.on $ terms  E.?. StudyTermsId  E.==. features E.?. StudyFeaturesField
+  E.on $ degree E.?. StudyDegreeId E.==. features E.?. StudyFeaturesDegree
+  E.where_ $ features E.?. StudyFeaturesId E.==. sfId
+  return (features, degree, terms)

src/Handler/Utils/Table/Cells.hs

@@ -41,9 +41,11 @@ maybeCell =flip foldMap
 ---------------------
 -- Icon cells
 
+-- | Maybe display a tickmark/checkmark icon
 tickmarkCell :: (IsDBTable m a) => Bool -> DBCell m a
 tickmarkCell = cell . toWidget . hasTickmark
 
+-- | Maybe display comment icon linking a given URL or show nothing at all
 commentCell :: IsDBTable m a => Maybe (Route UniWorX) -> DBCell m a
 commentCell Nothing     = mempty
 commentCell (Just link) = anchorCell link icon