refactor(schedule): enhance course schedule opt toggle

src/Handler/Course/Show.hs

@@ -302,6 +302,13 @@ getCShowR tid ssh csh = do
   mayCreateEvents <- hasWriteAccessTo $ CourseR tid ssh csh CEventsNewR
   mayEdit <- hasWriteAccessTo $ CourseR tid ssh csh CEditR
 
+  let courseScheduleOptToggleValue User{userScheduleOccurrenceDisplayDefault} = maybe
+        ( userScheduleOccurrenceDisplayDefault
+          && ( is _Just registration )
+        )
+        (courseScheduleOptOpt . entityVal)
+        mCourseScheduleOpt
+
   let heading = [whamlet|
           $newline never
           ^{courseName course}

templates/course.hamlet

@@ -340,12 +340,12 @@ $#    $if NTop (Just 0) < NTop (courseCapacity course)
     <dd .deflist__dd>
       ^{tutorialTable}
 
-  $maybe (_, User{userScheduleOccurrenceDisplayDefault}) <- mbAuth
+  $maybe (_, user) <- mbAuth
     <dt .deflist__dt>
       _{MsgScheduleOptActions}
     <dd .deflist__dd>
-      <a .btn .btn-primary href=@{CourseR tid ssh csh (CScheduleOptSetR (not (maybe ((is _Just registration) && userScheduleOccurrenceDisplayDefault) (courseScheduleOptOpt . entityVal) mCourseScheduleOpt)))}>
-        _{bool MsgCourseScheduleOptIn MsgCourseScheduleOptOut (maybe ((is _Just registration) && userScheduleOccurrenceDisplayDefault) (courseScheduleOptOpt . entityVal) mCourseScheduleOpt)}
+      <a .btn .btn-primary href=@{CourseR tid ssh csh (CScheduleOptSetR (not (courseScheduleOptToggleValue user)))}>
+        _{bool MsgCourseScheduleOptIn MsgCourseScheduleOptOut (courseScheduleOptToggleValue user)}
       $if is _Just mCourseScheduleOpt
         <a .btn .btn-primary href=@{CourseR tid ssh csh CScheduleOptDelR}>
           _{MsgCourseScheduleOptDelete}