module Hasura.RQL.DML.Select
  ( selectP2
  , convSelectQuery
  , asSingleRowJsonResp
  , module Hasura.RQL.DML.Select.Internal
  , runSelect
  )
where

import           Data.Aeson.Types
import           Instances.TH.Lift              ()

import qualified Data.HashSet                   as HS
import qualified Data.List.NonEmpty             as NE
import qualified Data.Sequence                  as DS

import           Hasura.EncJSON
import           Hasura.Prelude
import           Hasura.RQL.DML.Internal
import           Hasura.RQL.DML.Select.Internal
import           Hasura.RQL.Types
import           Hasura.SQL.Types

import qualified Database.PG.Query              as Q
import qualified Hasura.SQL.DML                 as S

convSelCol :: (UserInfoM m, QErrM m, CacheRM m)
           => FieldInfoMap FieldInfo
           -> SelPermInfo
           -> SelCol
           -> m [ExtCol]
convSelCol _ _ (SCExtSimple cn) =
  return [ECSimple cn]
convSelCol fieldInfoMap _ (SCExtRel rn malias selQ) = do
  -- Point to the name key
  let pgWhenRelErr = "only relationships can be expanded"
  relInfo <- withPathK "name" $
    askRelType fieldInfoMap rn pgWhenRelErr
  let (RelInfo _ _ _ relTab _) = relInfo
  (rfim, rspi) <- fetchRelDet rn relTab
  resolvedSelQ <- resolveStar rfim rspi selQ
  return [ECRel rn malias resolvedSelQ]
convSelCol fieldInfoMap spi (SCStar wildcard) =
  convWildcard fieldInfoMap spi wildcard

convWildcard
  :: (UserInfoM m, QErrM m, CacheRM m)
  => FieldInfoMap FieldInfo
  -> SelPermInfo
  -> Wildcard
  -> m [ExtCol]
convWildcard fieldInfoMap selPermInfo wildcard =
  case wildcard of
  Star         -> return simpleCols
  (StarDot wc) -> (simpleCols ++) <$> (catMaybes <$> relExtCols wc)
  where
    cols = spiCols selPermInfo
    pgCols = map pgiColumn $ getCols fieldInfoMap
    relColInfos = getRels fieldInfoMap

    simpleCols = map ECSimple $ filter (`HS.member` cols) pgCols

    mkRelCol wc relInfo = do
      let relName = riName relInfo
          relTab  = riRTable relInfo
      relTabInfo <- fetchRelTabInfo relTab
      mRelSelPerm <- askPermInfo' PASelect relTabInfo

      forM mRelSelPerm $ \rspi -> do
        rExtCols <- convWildcard (_tciFieldInfoMap $ _tiCoreInfo relTabInfo) rspi wc
        return $ ECRel relName Nothing $
          SelectG rExtCols Nothing Nothing Nothing Nothing

    relExtCols wc = mapM (mkRelCol wc) relColInfos

resolveStar :: (UserInfoM m, QErrM m, CacheRM m)
            => FieldInfoMap FieldInfo
            -> SelPermInfo
            -> SelectQ
            -> m SelectQExt
resolveStar fim spi (SelectG selCols mWh mOb mLt mOf) = do
  procOverrides <- fmap (concat . catMaybes) $ withPathK "columns" $
    indexedForM selCols $ \selCol -> case selCol of
    (SCStar _) -> return Nothing
    _          -> Just <$> convSelCol fim spi selCol
  everything <- case wildcards of
    [] -> return []
    _  -> convWildcard fim spi $ maximum wildcards
  let extCols = unionBy equals procOverrides everything
  return $ SelectG extCols mWh mOb mLt mOf
  where
    wildcards = lefts $ map mkEither selCols

    mkEither (SCStar wc) = Left wc
    mkEither selCol      = Right selCol

    equals (ECSimple x) (ECSimple y)   = x == y
    equals (ECRel x _ _) (ECRel y _ _) = x == y
    equals _ _                         = False

convOrderByElem
  :: (UserInfoM m, QErrM m, CacheRM m)
  => SessVarBldr m
  -> (FieldInfoMap FieldInfo, SelPermInfo)
  -> OrderByCol
  -> m AnnObCol
convOrderByElem sessVarBldr (flds, spi) = \case
  OCPG fldName -> do
    fldInfo <- askFieldInfo flds fldName
    case fldInfo of
      FIColumn colInfo -> do
        checkSelOnCol spi (pgiColumn colInfo)
        let ty = pgiType colInfo
        if isScalarColumnWhere isGeoType ty
          then throw400 UnexpectedPayload $ mconcat
           [ fldName <<> " has type 'geometry'"
           , " and cannot be used in order_by"
           ]
          else return $ AOCPG $ pgiColumn colInfo
      FIRelationship _ -> throw400 UnexpectedPayload $ mconcat
        [ fldName <<> " is a"
        , " relationship and should be expanded"
        ]
      FIComputedField _ -> throw400 UnexpectedPayload $ mconcat
        [ fldName <<> " is a"
        , " computed field and can't be used in 'order_by'"
        ]
  OCRel fldName rest -> do
    fldInfo <- askFieldInfo flds fldName
    case fldInfo of
      FIColumn _ -> throw400 UnexpectedPayload $ mconcat
        [ fldName <<> " is a Postgres column"
        , " and cannot be chained further"
        ]
      FIComputedField _ -> throw400 UnexpectedPayload $ mconcat
        [ fldName <<> " is a"
        , " computed field and can't be used in 'order_by'"
        ]
      FIRelationship relInfo -> do
        when (riType relInfo == ArrRel) $
          throw400 UnexpectedPayload $ mconcat
          [ fldName <<> " is an array relationship"
          ," and can't be used in 'order_by'"
          ]
        (relFim, relSpi) <- fetchRelDet (riName relInfo) (riRTable relInfo)
        resolvedSelFltr <- convAnnBoolExpPartialSQL sessVarBldr $ spiFilter relSpi
        AOCObj relInfo resolvedSelFltr <$>
          convOrderByElem sessVarBldr (relFim, relSpi) rest

convSelectQ
  :: (UserInfoM m, QErrM m, CacheRM m, HasSQLGenCtx m)
  => FieldInfoMap FieldInfo  -- Table information of current table
  -> SelPermInfo   -- Additional select permission info
  -> SelectQExt     -- Given Select Query
  -> SessVarBldr m
  -> (PGColumnType -> Value -> m S.SQLExp)
  -> m AnnSimpleSel
convSelectQ fieldInfoMap selPermInfo selQ sessVarBldr prepValBldr = do

  annFlds <- withPathK "columns" $
    indexedForM (sqColumns selQ) $ \case
    (ECSimple pgCol) -> do
      colInfo <- convExtSimple fieldInfoMap selPermInfo pgCol
      return (fromPGCol pgCol, mkAnnColField colInfo Nothing)
    (ECRel relName mAlias relSelQ) -> do
      annRel <- convExtRel fieldInfoMap relName mAlias
                relSelQ sessVarBldr prepValBldr
      return ( fromRel $ fromMaybe relName mAlias
             , either FObj FArr annRel
             )

  -- let spiT = spiTable selPermInfo

  -- Convert where clause
  wClause <- forM (sqWhere selQ) $ \be ->
    withPathK "where" $
    convBoolExp fieldInfoMap selPermInfo be sessVarBldr prepValBldr

  annOrdByML <- forM (sqOrderBy selQ) $ \(OrderByExp obItems) ->
    withPathK "order_by" $ indexedForM obItems $ mapM $
    convOrderByElem sessVarBldr (fieldInfoMap, selPermInfo)

  let annOrdByM = NE.nonEmpty =<< annOrdByML

  -- validate limit and offset values
  withPathK "limit" $ mapM_ onlyPositiveInt mQueryLimit
  withPathK "offset" $ mapM_ onlyPositiveInt mQueryOffset

  resolvedSelFltr <- convAnnBoolExpPartialSQL sessVarBldr $
                     spiFilter selPermInfo

  let tabFrom = FromTable $ spiTable selPermInfo
      tabPerm = TablePerm resolvedSelFltr mPermLimit
      tabArgs = TableArgs wClause annOrdByM mQueryLimit
                (S.intToSQLExp <$> mQueryOffset) Nothing

  strfyNum <- stringifyNum <$> askSQLGenCtx
  return $ AnnSelG annFlds tabFrom tabPerm tabArgs strfyNum

  where
    mQueryOffset = sqOffset selQ
    mQueryLimit = sqLimit selQ
    mPermLimit = spiLimit selPermInfo

convExtSimple
  :: (UserInfoM m, QErrM m)
  => FieldInfoMap FieldInfo
  -> SelPermInfo
  -> PGCol
  -> m PGColumnInfo
convExtSimple fieldInfoMap selPermInfo pgCol = do
  checkSelOnCol selPermInfo pgCol
  askPGColInfo fieldInfoMap pgCol relWhenPGErr
  where
    relWhenPGErr = "relationships have to be expanded"

convExtRel
  :: (UserInfoM m, QErrM m, CacheRM m, HasSQLGenCtx m)
  => FieldInfoMap FieldInfo
  -> RelName
  -> Maybe RelName
  -> SelectQExt
  -> SessVarBldr m
  -> (PGColumnType -> Value -> m S.SQLExp)
  -> m (Either ObjSel ArrSel)
convExtRel fieldInfoMap relName mAlias selQ sessVarBldr prepValBldr = do
  -- Point to the name key
  relInfo <- withPathK "name" $
    askRelType fieldInfoMap relName pgWhenRelErr
  let (RelInfo _ relTy colMapping relTab _) = relInfo
  (relCIM, relSPI) <- fetchRelDet relName relTab
  annSel <- convSelectQ relCIM relSPI selQ sessVarBldr prepValBldr
  case relTy of
    ObjRel -> do
      when misused $ throw400 UnexpectedPayload objRelMisuseMsg
      return $ Left $ AnnRelG (fromMaybe relName mAlias) colMapping annSel
    ArrRel ->
      return $ Right $ ASSimple $ AnnRelG (fromMaybe relName mAlias)
               colMapping annSel
  where
    pgWhenRelErr = "only relationships can be expanded"
    misused      =
      or [ isJust (sqWhere selQ)
         , isJust (sqLimit selQ)
         , isJust (sqOffset selQ)
         , isJust (sqOrderBy selQ)
         ]
    objRelMisuseMsg =
      mconcat [ "when selecting an 'obj_relationship' "
              , "'where', 'order_by', 'limit' and 'offset' "
              , " can't be used"
              ]

convSelectQuery
  :: (UserInfoM m, QErrM m, CacheRM m, HasSQLGenCtx m)
  => SessVarBldr m
  -> (PGColumnType -> Value -> m S.SQLExp)
  -> SelectQuery
  -> m AnnSimpleSel
convSelectQuery sessVarBldr prepArgBuilder (DMLQuery qt selQ) = do
  tabInfo     <- withPathK "table" $ askTabInfo qt
  selPermInfo <- askSelPermInfo tabInfo
  let fieldInfo = _tciFieldInfoMap $ _tiCoreInfo tabInfo
  extSelQ <- resolveStar fieldInfo selPermInfo selQ
  validateHeaders $ spiRequiredHeaders selPermInfo
  convSelectQ fieldInfo selPermInfo
    extSelQ sessVarBldr prepArgBuilder

selectP2 :: JsonAggSelect -> (AnnSimpleSel, DS.Seq Q.PrepArg) -> Q.TxE QErr EncJSON
selectP2 jsonAggSelect (sel, p) =
  encJFromBS . runIdentity . Q.getRow
  <$> Q.rawQE dmlTxErrorHandler (Q.fromBuilder selectSQL) (toList p) True
  where
    selectSQL = toSQL $ mkSQLSelect jsonAggSelect sel

asSingleRowJsonResp :: Q.Query -> [Q.PrepArg] -> Q.TxE QErr EncJSON
asSingleRowJsonResp query args =
  encJFromBS . runIdentity . Q.getRow
  <$> Q.rawQE dmlTxErrorHandler query args True

phaseOne
  :: (QErrM m, UserInfoM m, CacheRM m, HasSQLGenCtx m)
  => SelectQuery -> m (AnnSimpleSel, DS.Seq Q.PrepArg)
phaseOne =
  runDMLP1T . convSelectQuery sessVarFromCurrentSetting binRHSBuilder

phaseTwo :: (MonadTx m) => (AnnSimpleSel, DS.Seq Q.PrepArg) -> m EncJSON
phaseTwo =
  liftTx . selectP2 JASMultipleRows

runSelect
  :: (QErrM m, UserInfoM m, CacheRM m, HasSQLGenCtx m, MonadTx m)
  => SelectQuery -> m EncJSON
runSelect q =
  phaseOne q >>= phaseTwo