module Utils.Schedule
  ( fetchActiveTerms, fetchCourseEvents, fetchTutorials, fetchExamOccurrences
  ) where

import Import

import qualified Database.Esqueleto as E
import qualified Database.Esqueleto.Utils as E

import Utils.Course
import Utils.Tutorial

import Utils.Schedule.Types


fetchActiveTerms :: MonadHandler m => ReaderT SqlBackend m [E.Value TermId]
fetchActiveTerms = E.select $ E.from $ \term -> do
  E.where_ $ term E.^. TermActive
  return   $ term E.^. TermId

fetchCourseEvents :: MonadHandler m => Maybe UserId -> AuthTagActive -> UTCTime -> ReaderT SqlBackend m [ScheduleCourseEventInfo]
fetchCourseEvents muid ata now = E.select $ E.from $ \(course `E.InnerJoin` courseEvent) -> do
  E.on $ course E.^. CourseId E.==. courseEvent E.^. CourseEventCourse
  E.where_ $ courseEventShouldBeDisplayed muid course courseEvent
    E.&&.    mayViewCourse muid ata now course Nothing  -- should not be necessary, but let's be on the safe side
    E.&&. (  isCourseParticipant muid ata (course E.^. CourseId)
      E.||.  isCourseLecturer    muid ata (course E.^. CourseId)
    )
  return (course, courseEvent)

fetchTutorials :: MonadHandler m => Maybe UserId -> AuthTagActive -> UTCTime -> ReaderT SqlBackend m [ScheduleTutorialInfo]
fetchTutorials muid ata now = E.select $ E.from $ \(course `E.InnerJoin` tutorial) -> do
  E.on $ course E.^. CourseId E.==. tutorial E.^. TutorialCourse
  E.where_ $ tutorialShouldBeDisplayed muid course tutorial
    E.&&.    mayViewCourse muid ata now course Nothing  -- should not be necessary, but let's be on the safe side
    E.&&. (  isTutorialTutor       muid ata (tutorial E.^. TutorialId)
      E.||.  isTutorialParticipant muid ata (tutorial E.^. TutorialId)
    )
  return (course, tutorial)

fetchExamOccurrences :: MonadHandler m => Maybe UserId -> AuthTagActive -> UTCTime -> ReaderT SqlBackend m [ScheduleExamOccurrenceInfo]
fetchExamOccurrences muid ata now = E.select $ E.from $ \(course `E.InnerJoin` exam `E.InnerJoin` examOccurrence) -> do
    E.on $ course E.^. CourseId E.==. exam E.^. ExamCourse
    E.on $ exam E.^. ExamId E.==. examOccurrence E.^. ExamOccurrenceExam
    E.where_ $ isCourseLecturer muid ata (course E.^. CourseId)
      E.||. ( mayViewCourse muid ata now course Nothing  -- do NOT remove, this is actually necessary here!
                                                               -- (There can be exam participants that are 
                                                               --  not enrolled, me thinks)
        E.&&. E.maybe E.false (\visibleFrom -> visibleFrom E.<=. E.val now) (exam E.^. ExamVisibleFrom)  -- is the exam visible?
        E.&&. E.maybe E.false (\publishOcc  -> publishOcc  E.<=. E.val now) (exam E.^. ExamPublishOccurrenceAssignments)  -- are the exam occurrence assignments visible?
        E.&&. (E.exists $ E.from $ \examRegistration -> E.where_ $
                      examRegistration E.^. ExamRegistrationExam E.==. exam E.^. ExamId
                E.&&. E.just (examRegistration E.^. ExamRegistrationUser) E.==. E.val muid
                E.&&. E.maybe E.true (\registrationOccurrence -> registrationOccurrence E.==. examOccurrence E.^. ExamOccurrenceId) (examRegistration E.^. ExamRegistrationOccurrence)  -- if registered for a specific occurrence, get only this one, otherwise get every occurrence available
        )
      )
    return (course, exam, examOccurrence)


-- TODO: find better names

courseEventShouldBeDisplayed :: Maybe UserId -> E.SqlExpr (Entity Course) -> E.SqlExpr (Entity CourseEvent) -> E.SqlExpr (E.Value Bool)
courseEventShouldBeDisplayed (Just uid) _course _courseEvent = E.exists . E.from $ \user ->
  E.where_ $ user E.^. UserId E.==. E.val uid
    E.&&. (  -- TODO: also check whether there is a display opt-in/out for this course or course event
      user E.^. UserScheduleOccurrenceDisplayDefault
    )
courseEventShouldBeDisplayed _ _ _ = E.false

tutorialShouldBeDisplayed :: Maybe UserId -> E.SqlExpr (Entity Course) -> E.SqlExpr (Entity Tutorial) -> E.SqlExpr (E.Value Bool)
tutorialShouldBeDisplayed (Just uid) _course _tutorial = E.exists . E.from $ \user ->
  E.where_ $ user E.^. UserId E.==. E.val uid
    E.&&. (  -- TODO: also check whether there is a display opt-in/out for this course or tutorial
      user E.^. UserScheduleOccurrenceDisplayDefault
    )
tutorialShouldBeDisplayed _ _ _ = E.false