module Jobs.Handler.QueueNotification
  ( dispatchJobQueueNotification
  ) where

import Import

import Data.List (nub)

import Jobs.Types

import qualified Database.Esqueleto as E
import Utils.Sql
import Jobs.Queue

import qualified Data.Set as Set


dispatchJobQueueNotification :: Notification -> Handler ()
dispatchJobQueueNotification jNotification = runDBJobs . setSerializable $ do
  candidates <- hoist lift $ determineNotificationCandidates jNotification
  nClass <- hoist lift $ classifyNotification jNotification
  mapM_ (queueDBJob . flip JobSendNotification jNotification) $ do
    Entity uid User{userNotificationSettings} <- candidates
    guard $ notificationAllowed userNotificationSettings nClass
    return uid


determineNotificationCandidates :: Notification -> DB [Entity User]
determineNotificationCandidates NotificationSubmissionRated{..}
  = E.select . E.from $ \(user `E.InnerJoin` submissionUser) -> do
      E.on $ user E.^. UserId E.==. submissionUser E.^. SubmissionUserUser
      E.where_ $ submissionUser E.^. SubmissionUserSubmission E.==. E.val nSubmission
      return user
determineNotificationCandidates NotificationSheetActive{..}
  = E.select . E.from $ \(user `E.InnerJoin` courseParticipant `E.InnerJoin` sheet) -> do
      E.on $ sheet E.^. SheetCourse E.==. courseParticipant E.^. CourseParticipantCourse
      E.on $ user E.^. UserId E.==. courseParticipant E.^. CourseParticipantUser
      E.where_ $ sheet E.^. SheetId E.==. E.val nSheet
      return user
determineNotificationCandidates NotificationSheetSoonInactive{..}
  = E.select . E.from $ \(user `E.InnerJoin` courseParticipant `E.InnerJoin` sheet) -> do
      E.on $ sheet E.^. SheetCourse E.==. courseParticipant E.^. CourseParticipantCourse
      E.on $ user E.^. UserId E.==. courseParticipant E.^. CourseParticipantUser
      E.where_ $ sheet E.^. SheetId E.==. E.val nSheet
      return user
determineNotificationCandidates NotificationSheetInactive{..}
  = E.select . E.from $ \(user `E.InnerJoin` lecturer `E.InnerJoin` sheet) -> do
      E.on $ lecturer E.^. LecturerCourse E.==. sheet E.^. SheetCourse
      E.on $ lecturer E.^. LecturerUser   E.==. user E.^. UserId
      E.where_ $ sheet E.^. SheetId E.==. E.val nSheet
      return user
determineNotificationCandidates NotificationCorrectionsAssigned{..}
  = selectList [UserId ==. nUser] []
determineNotificationCandidates NotificationCorrectionsNotDistributed{nSheet}
  = E.select . E.from $ \(user `E.InnerJoin` lecturer `E.InnerJoin` sheet) -> do
      E.on $ lecturer E.^. LecturerCourse E.==. sheet E.^. SheetCourse
      E.on $ lecturer E.^. LecturerUser E.==. user E.^. UserId
      E.where_ $ sheet E.^. SheetId E.==. E.val nSheet
      return user
determineNotificationCandidates NotificationUserRightsUpdate{..} = do
  -- always send to affected user
  affectedUser <- selectList [UserId ==. nUser] []
  -- send to same-school admins only if there was an update
  currentAdminSchools <- setOf (folded . _entityVal . _userFunctionSchool) <$> selectList [UserFunctionUser ==. nUser, UserFunctionFunction ==. SchoolAdmin] []
  let oldAdminSchools = setOf (folded . filtered ((== SchoolAdmin) . view _1) . _2 . from _SchoolId) nOriginalRights
      newAdminSchools = currentAdminSchools `Set.difference` oldAdminSchools
  affectedAdmins <- E.select . E.from $ \(user `E.InnerJoin` admin) -> do
    E.on $ admin E.^. UserFunctionUser E.==. user E.^. UserId
    E.where_ $ admin E.^. UserFunctionSchool `E.in_` E.valList (Set.toList newAdminSchools)
         E.&&. admin E.^. UserFunctionFunction E.==. E.val SchoolAdmin
    return user
  return . nub $ affectedUser <> affectedAdmins
determineNotificationCandidates NotificationUserAuthModeUpdate{..}
  = selectList [UserId ==. nUser] []
determineNotificationCandidates notif@NotificationExamResult{..} = do
  lastExec <- fmap (fmap $ cronLastExecTime . entityVal) . getBy . UniqueCronLastExec . toJSON $ JobQueueNotification notif
  E.select . E.from $ \(examResult `E.InnerJoin` user) -> do
    E.on $ examResult E.^. ExamResultUser E.==. user E.^. UserId
    E.where_ $ examResult E.^. ExamResultExam E.==. E.val nExam
    whenIsJust lastExec $ \lastExec' ->
      E.where_ $ examResult E.^. ExamResultLastChanged E.>. E.val lastExec'
    return user


classifyNotification :: Notification -> DB NotificationTrigger
classifyNotification NotificationSubmissionRated{..} = do
  Sheet{sheetType} <- belongsToJust submissionSheet =<< getJust nSubmission
  return $ case sheetType of
    NotGraded -> NTSubmissionRated
    _other -> NTSubmissionRatedGraded
classifyNotification NotificationSheetActive{} = return NTSheetActive
classifyNotification NotificationSheetSoonInactive{} = return NTSheetSoonInactive
classifyNotification NotificationSheetInactive{} = return NTSheetInactive
classifyNotification NotificationCorrectionsAssigned{} = return NTCorrectionsAssigned
classifyNotification NotificationCorrectionsNotDistributed{} = return NTCorrectionsNotDistributed
classifyNotification NotificationUserRightsUpdate{} = return NTUserRightsUpdate
classifyNotification NotificationUserAuthModeUpdate{} = return NTUserAuthModeUpdate
classifyNotification NotificationExamResult{} = return NTExamResult