{-# LANGUAGE NoImplicitPrelude #-}
{-# LANGUAGE RecordWildCards #-}
{-# LANGUAGE NamedFieldPuns #-}
{-# LANGUAGE ViewPatterns #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE TupleSections #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE LambdaCase #-}
{-# LANGUAGE TemplateHaskell #-}
{-# LANGUAGE DeriveGeneric, DeriveDataTypeable #-}
{-# LANGUAGE TypeOperators #-}
{-# LANGUAGE PartialTypeSignatures #-}


module Handler.Utils.Submission
  ( AssignSubmissionException(..)
  , assignSubmissions
  , submissionFileSource, submissionFileQuery
  , submissionMultiArchive 
  , SubmissionSinkException(..)
  , sinkSubmission
  ) where

import Import hiding ((.=), joinPath)

import Control.Lens
import Control.Lens.Extras (is)
import Utils.Lens

import Control.Monad.State hiding (forM_, mapM_,foldM)
import qualified Control.Monad.Random as Rand

import Data.Maybe

import qualified Data.List as List
import Data.Set (Set)
import qualified Data.Set as Set
import Data.Map (Map, (!?))
import qualified Data.Map as Map

import Data.CaseInsensitive (CI)
import qualified Data.CaseInsensitive as CI

import Data.Monoid (Monoid, Any(..))
import Generics.Deriving.Monoid (memptydefault, mappenddefault)

import Handler.Utils.Rating
import Handler.Utils.Zip

import qualified Database.Esqueleto as E

import qualified Data.Conduit.List as Conduit
import Data.Conduit.ResumableSink

import System.FilePath


data AssignSubmissionException = NoCorrectorsByProportion
  deriving (Typeable, Show)

instance Exception AssignSubmissionException

-- | Assigns all submissions according to sheet corrector loads
assignSubmissions :: SheetId -- ^ Sheet do distribute to correction
                  -> Maybe (Set SubmissionId) -- ^ Optionally restrict submission to consider
                  -> YesodDB UniWorX ( Set SubmissionId -- ^ assigned submissions
                                     , Set SubmissionId -- ^ unassigend submissions (no tutors by load)
                                     )
assignSubmissions sid restriction = do
    correctors <- selectList [SheetCorrectorSheet ==. sid] []
    let corrsGroup = filter hasTutorialLoad correctors -- needed as List within Esqueleto
    let corrsProp  = filter hasPositiveLoad correctors
    let countsToLoad' :: UserId -> Bool
        countsToLoad' uid = -- refactor by simply using Map.(!)
          fromMaybe (error "Called `countsToLoad'` on entity not element of `corrsGroup`") $
          Map.lookup uid loadMap
        loadMap :: Map UserId Bool
        loadMap = Map.fromList [(sheetCorrectorUser,b) | Entity _ SheetCorrector{ sheetCorrectorLoad = (Load {byTutorial = Just b}), .. } <- corrsGroup]

    subs <- E.select . E.from $ \(submission `E.LeftOuterJoin` user) -> do
        let tutors = E.subList_select . E.from $ \(submissionUser `E.InnerJoin` tutorialUser `E.InnerJoin` tutorial) -> do
              -- Uncomment next line for equal chance between tutors, irrespective of the number of students per tutor per submission group
              -- E.distinctOn [E.don $ tutorial E.^. TutorialTutor] $ do
                E.on (tutorial       E.^. TutorialId         E.==. tutorialUser E.^. TutorialUserTutorial)
                E.on (submissionUser E.^. SubmissionUserUser E.==. tutorialUser E.^. TutorialUserUser)
                E.where_ (tutorial   E.^. TutorialTutor `E.in_` E.valList (map (sheetCorrectorUser . entityVal) corrsGroup))
                return $ tutorial E.^. TutorialTutor
        E.on $ user E.?. UserId `E.in_` E.justList tutors
        E.where_ $ submission E.^. SubmissionSheet E.==. E.val sid
             E.&&. maybe (E.val True) (submission E.^. SubmissionId `E.in_`) (E.valList . Set.toList <$> restriction)
        E.orderBy [E.rand] -- randomize for fair tutor distribution
        return (submission E.^. SubmissionId, user) -- , listToMaybe tutors)

    queue <- liftIO . Rand.evalRandIO . sequence . repeat $ Rand.weightedMay [ (sheetCorrectorUser, byProportion sheetCorrectorLoad) | Entity _ SheetCorrector{..} <- corrsProp]

    let subTutor' :: Map SubmissionId (Maybe UserId)
        subTutor' = Map.fromListWith (<|>) $ map (over (_2.traverse) entityKey . over _1 E.unValue) subs

    subTutor <- fmap fst . flip execStateT (Map.empty, queue) . forM_ (Map.toList subTutor') $ \case
      (smid, Just tutid) -> do
        _1 %= Map.insert smid tutid
        when (any ((== tutid) . sheetCorrectorUser . entityVal) corrsProp && countsToLoad' tutid) $
          _2 %= List.delete (Just tutid)
      (smid, Nothing) -> do
        (q:qs) <- use _2
        _2 .= qs
        case q of
          Just q  -> _1 %= Map.insert smid q
          Nothing -> return () -- NOTE: throwM NoCorrectorsByProportion

    forM_ (Map.toList subTutor) $ \(smid, tutid) -> update smid [SubmissionRatingBy =. Just tutid]
        
    let assignedSubmissions   = Map.keysSet subTutor
        unassigendSubmissions = Map.keysSet subTutor' \\ assignedSubmissions
    return (assignedSubmissions, unassigendSubmissions)
    where
      hasPositiveLoad = (> 0)  . byProportion . sheetCorrectorLoad . entityVal
      hasTutorialLoad = isJust . byTutorial   . sheetCorrectorLoad . entityVal


submissionFileSource :: SubmissionId -> Source (YesodDB UniWorX) (Entity File)
submissionFileSource = E.selectSource . E.from . submissionFileQuery

submissionFileQuery :: SubmissionId -> E.SqlExpr (Entity SubmissionFile) `E.InnerJoin` E.SqlExpr (Entity File)
                        -> E.SqlQuery (E.SqlExpr (Entity File))
submissionFileQuery submissionID (sf `E.InnerJoin` f) = E.distinctOnOrderBy [E.asc $ f E.^. FileTitle] $ do
  E.on (f E.^. FileId E.==. sf E.^. SubmissionFileFile)
  E.where_ $ sf E.^. SubmissionFileSubmission E.==. E.val submissionID
  E.where_ . E.not_ $ sf E.^. SubmissionFileIsDeletion -- TODO@gk: won't work as intended! Fix with refactor
  E.orderBy [E.desc $ sf E.^. SubmissionFileIsUpdate]  -- E.desc returns corrector updated data first
  return f

submissionMultiArchive :: Set SubmissionId -> Handler TypedContent
submissionMultiArchive (Set.toList -> ids) = do
  (dbrunner, cleanup) <- getDBRunner

  ratedSubmissions <- runDBRunner dbrunner $ do
    submissions <- selectList [ SubmissionId <-. ids ] []
    forM submissions $ \s@(Entity submissionId _) -> maybe (invalidArgs ["Invalid submission numbers"]) (return . (, s)) =<< getRating submissionId
  
  (<* cleanup) . respondSource "application/zip" . transPipe (runDBRunner dbrunner) $ do
    let
      fileEntitySource' :: (Rating, Entity Submission) -> Source (YesodDB UniWorX) File
      fileEntitySource' (rating, Entity submissionID Submission{..}) = do
        cID <- encrypt submissionID

        let
          directoryName = CI.foldedCase $ ciphertext (cID :: CryptoFileNameSubmission)
              
          fileEntitySource = do
            submissionFileSource submissionID =$= Conduit.map entityVal
            yieldM (ratingFile cID rating)

          withinDirectory f@File{..} = f { fileTitle = directoryName </> fileTitle }

        lastEditMb <- lift $ selectList [SubmissionEditSubmission ==. submissionID] [Desc SubmissionEditTime, LimitTo 1]
        lastEditTime <- case lastEditMb of
          [(submissionEditTime.entityVal -> time)] -> return time
          _other -> liftIO getCurrentTime
        yield $ File
          { fileModified = lastEditTime
          , fileTitle = directoryName
          , fileContent = Nothing
          }

        fileEntitySource =$= mapC withinDirectory
          
    mapM_ fileEntitySource' ratedSubmissions =$= produceZip def =$= Conduit.map toFlushBuilder





data SubmissionSinkState = SubmissionSinkState
  { sinkSeenRating :: Any
  , sinkSubmissionTouched :: Any
  , sinkFilenames :: Set FilePath
  } deriving (Show, Eq, Generic, Typeable)

instance Monoid SubmissionSinkState where
  mempty = memptydefault
  mappend = mappenddefault

data SubmissionSinkException = DuplicateFileTitle FilePath
                             | DuplicateRating
                             | RatingWithoutUpdate
                             | ForeignRating
  deriving (Typeable, Show)

instance Exception SubmissionSinkException

sinkSubmission :: UserId
               -> Either SheetId SubmissionId
               -> Bool -- ^ Is this a correction
               -> Sink SubmissionContent (YesodDB UniWorX) SubmissionId
-- ^ Replace the currently saved files for the given submission (either
--   corrected files or original ones, depending on arguments) with the supplied
--   'SubmissionContent'.
--
-- Files that don't occur in the 'SubmissionContent' but are in the database
-- are deleted (or marked as deleted in the case of this being a correction).
--
-- A 'Submission' is created if no 'SubmissionId' is supplied
sinkSubmission userId mExists isUpdate = do
  sId <- lift $ case mExists of
    Left sheetId -> do
      let
        submissionSheet         = sheetId
        submissionRatingPoints  = Nothing
        submissionRatingComment = Nothing
        submissionRatingBy      = Nothing
        submissionRatingTime    = Nothing
      sId <- insert Submission{..}
      -- now <- liftIO getCurrentTime
      -- insert $ SubmissionEdit userId now sId -- This is done automatically during 'sinkSubmission'' iff the given submission is nonempty
      return sId
    Right sId -> return sId

  sId <$ sinkSubmission' sId isUpdate
  where
    tell = modify . mappend

    sinkSubmission' :: SubmissionId
                    -> Bool -- ^ Is this a correction
                    -> Sink SubmissionContent (YesodDB UniWorX) ()
    sinkSubmission' submissionId isUpdate = lift . finalize <=< execStateLC mempty . Conduit.mapM_ $ \case
      Left file@(File{..}) -> do
        $logDebugS "sinkSubmission" . tshow $ (submissionId, fileTitle)
        
        alreadySeen <- gets (Set.member fileTitle . sinkFilenames)
        when alreadySeen . throwM $ DuplicateFileTitle fileTitle
        tell $ mempty{ sinkFilenames = Set.singleton fileTitle  }

        otherVersions <- lift . E.select . E.from $ \(sf `E.InnerJoin` f) -> do
          E.on $ sf E.^. SubmissionFileFile E.==. f E.^. FileId
          E.where_ $ sf E.^. SubmissionFileSubmission E.==. E.val submissionId
          -- E.where_ $ sf E.^. SubmissionFileIsUpdate E.==. E.val isUpdate
          E.where_ $ f E.^. FileTitle E.==. E.val fileTitle -- 'Zip.hs' normalises filenames already, so this should work
          return (f, sf)

        let collidingFiles = [ t | t@(_, Entity _ sf) <- otherVersions
                                 , submissionFileIsUpdate sf == isUpdate
                                 ]
            underlyingFiles = [ t | t@(_, Entity _ sf) <- otherVersions
                                  , submissionFileIsUpdate sf == False
                                  ]
            anyChanges
              | not (null collidingFiles)  = any (/~ file) [ f | (Entity _ f, _) <- collidingFiles ]
              | otherwise                  = True
            matchesUnderlying
              | not (null underlyingFiles) = all (~~ file) [ f | (Entity _ f, Entity _ _sf) <- underlyingFiles ]
              | otherwise                  = False
            undoneDeletion = any submissionFileIsDeletion [ sf | (_, Entity _ sf) <- collidingFiles ]
  
        when anyChanges $ do
          touchSubmission
          when (not $ null collidingFiles) $
            lift $ deleteCascadeWhere [ FileId <-. [ fId | (Entity fId _, _) <- collidingFiles ] ]
          lift $ case () of
            _ | matchesUnderlying
              , isUpdate
                -> return ()
            _   -> do
              fileId <- insert file
              insert_ $ SubmissionFile
                { submissionFileSubmission = submissionId
                , submissionFileFile = fileId
                , submissionFileIsUpdate = isUpdate
                , submissionFileIsDeletion = False
                }
        when undoneDeletion $ do
          touchSubmission
          lift $ deleteWhere [ SubmissionFileId <-. [ sfId | (_, Entity sfId sf) <- collidingFiles, submissionFileIsDeletion sf ] ]
  
      Right (submissionId', Rating'{..}) -> do
        $logDebugS "sinkSubmission" $ tshow submissionId'

        unless (submissionId' == submissionId) $ throwM ForeignRating
        
        alreadySeen <- gets $ getAny . sinkSeenRating
        when alreadySeen $ throwM DuplicateRating
        tell $ mempty{ sinkSeenRating = Any True }

        unless isUpdate $ throwM RatingWithoutUpdate

        Submission{..} <- lift $ getJust submissionId

        let anyChanges = or $ 
              [ submissionRatingPoints /= ratingPoints
              , submissionRatingComment /= ratingComment
              ]
        -- 'ratingTime' is ignored for consistency with 'File's:
        -- 
        -- 'fileModified' is simply stored and never inspected while
        -- 'submissionChanged' is always set to @now@.

        when anyChanges $ do
          touchSubmission
          lift $ update submissionId
            [ SubmissionRatingPoints =. ratingPoints
            , SubmissionRatingComment =. ratingComment
            ]
      where
        a /~ b = not $ a ~~ b

        (~~) :: File -> File -> Bool
        (~~) a b
          | isUpdate  = fileTitle a == fileTitle b && fileContent a == fileContent b
          | otherwise = a == b
        -- The Eq Instance for File compares modification time exactly even
        -- though zip archives have very limited accuracy and range regarding
        -- timestamps.
        -- We thus expect to replace files a little more often than is actually
        -- necessary.
        -- This was done on the premise that changes in file modification time
        -- break file identity under upload and re-download.
        --
        -- The check whether the new version matches the underlying file is
        -- more lenient, considering only filename and -content.

        touchSubmission :: StateT SubmissionSinkState (YesodDB UniWorX) ()
        touchSubmission = do
          alreadyTouched <- gets $ getAny . sinkSubmissionTouched
          when (not alreadyTouched) $ do
            now <- liftIO getCurrentTime
            lift $ case isUpdate of
              False -> insert_ $ SubmissionEdit userId now submissionId
              True  -> update submissionId [ SubmissionRatingBy =. Just userId, SubmissionRatingTime =. Just now ]
            tell $ mempty{ sinkSubmissionTouched = Any True }

        finalize :: SubmissionSinkState -> YesodDB UniWorX ()
        finalize SubmissionSinkState{..} = do
          missingFiles <- E.select . E.from $ \(sf `E.InnerJoin` f) -> E.distinctOnOrderBy [E.asc $ f E.^. FileTitle] $ do
            E.on $ sf E.^. SubmissionFileFile E.==. f E.^. FileId
            E.where_ $ sf E.^. SubmissionFileSubmission E.==. E.val submissionId
            when (not isUpdate) $
              E.where_ $ sf E.^. SubmissionFileIsUpdate E.==. E.val isUpdate
            E.where_ $ f E.^. FileTitle `E.notIn` E.valList (Set.toList sinkFilenames)
            E.orderBy [E.desc $ sf E.^. SubmissionFileIsUpdate]

            return (f, sf)

          case isUpdate of
            False -> deleteCascadeWhere [ FileId <-. [ fileId | (Entity fileId _, _) <- missingFiles ] ]
            True  -> forM_ missingFiles $ \(Entity fileId File{..}, Entity sfId SubmissionFile{..}) -> do
              shadowing <- E.select . E.from $ \(sf `E.InnerJoin` f) -> do
                E.on $ sf E.^. SubmissionFileFile E.==. f E.^. FileId
                E.where_ $ sf E.^. SubmissionFileSubmission E.==. E.val submissionId
                E.where_ $ sf E.^. SubmissionFileIsUpdate E.==. E.val (not isUpdate)
                E.where_ $ f E.^. FileTitle E.==. E.val fileTitle
                return $ f E.^. FileId

              case (shadowing, submissionFileIsUpdate) of
                ([], _) -> deleteCascade fileId
                (E.Value f:_, False) -> do
                  insert_ $ SubmissionFile
                    { submissionFileSubmission = submissionId
                    , submissionFileFile = f
                    , submissionFileIsUpdate = True
                    , submissionFileIsDeletion = True
                    }
                (E.Value f:_, True) -> do
                  update sfId [ SubmissionFileFile =. f, SubmissionFileIsDeletion =. True ]
                  deleteCascade fileId

          when (isUpdate && not (getAny sinkSeenRating)) $
            update submissionId
              [ SubmissionRatingTime =. Nothing
              , SubmissionRatingPoints =. Nothing
              , SubmissionRatingBy =. Nothing
              , SubmissionRatingComment =. Nothing
              ]

sinkMultiSubmission :: UserId
                    -> Bool {-^ Are these corrections -}
                    -> Sink SubmissionContent (YesodDB UniWorX) (Set SubmissionId)
               
-- ^ Expects all supplied 'SubmissionContent' to contain an encrypted 'SubmissionId' and replaces the currently saved files for the respective submissions (either corrected files or original ones, depending on arguments) with the supplied 'SubmissionContent'.
--
-- Files that don't occur in the 'SubmissionContent' but are in the database are deleted (or marked as deleted in the case of this being a correction).
sinkMultiSubmission userId isUpdate = do
  let
    feed :: SubmissionId
         -> SubmissionContent
         -> StateT
              (Map SubmissionId (ResumableSink SubmissionContent (YesodDB UniWorX) SubmissionId))
              (YesodDB UniWorX)
              ()
    feed sId val = do
      mSink <- gets $ Map.lookup sId
      sink <- case mSink of
        Just sink -> return sink
        Nothing -> do
          -- Submission{..} <- lift $ get404 sId
          return . newResumableSink $ sinkSubmission userId (Right sId) isUpdate
      sink' <- lift $ yield val ++$$ sink
      case sink' of
        Left _ -> error "sinkSubmission returned prematurely"
        Right nSink -> modify $ Map.insert sId nSink
  sinks <- execStateLC Map.empty . awaitForever $ \case
    v@(Right (sId, _)) -> lift $ feed sId v
    (Left f@File{..})  -> do
      let
        tryDecrypt :: FilePath -> _ (Either CryptoIDError SubmissionId)
        tryDecrypt (CI.mk -> ciphertext) = try $ decrypt (CryptoID{..} :: CryptoFileNameSubmission)
        acc (Just cID, fp) segment = return (Just cID, fp ++ [segment])
        acc (Nothing , fp) segment = do
          msId <- tryDecrypt segment
          return . either (const id) (set _1 . Just) msId $ (Nothing, fp)
      (msId, (joinPath -> fileTitle')) <- foldM acc (Nothing, []) $ splitDirectories fileTitle
      lift . maybe (const $ return ()) feed msId $ Left f{ fileTitle = fileTitle' }
  fmap Map.keysSet . lift $ mapM (void . closeResumableSink) sinks