module Hasura.RQL.DML.Update
  ( runUpdate
  ) where

import           Hasura.Prelude

import qualified Data.Environment                             as Env
import qualified Data.HashMap.Strict                          as M
import qualified Data.Sequence                                as DS
import qualified Database.PG.Query                            as Q

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

import qualified Hasura.Backends.Postgres.SQL.DML             as S
import qualified Hasura.Tracing                               as Tracing

import           Hasura.Backends.Postgres.Connection
import           Hasura.Backends.Postgres.Execute.Mutation
import           Hasura.Backends.Postgres.SQL.Types
import           Hasura.Backends.Postgres.Translate.Returning
import           Hasura.EncJSON
import           Hasura.RQL.DML.Internal
import           Hasura.RQL.IR.Update
import           Hasura.RQL.Instances                         ()
import           Hasura.RQL.Types
import           Hasura.Server.Version                        (HasVersion)
import           Hasura.Session


convInc
  :: (QErrM m)
  => (PGColumnType -> Value -> m S.SQLExp)
  -> PGCol
  -> PGColumnType
  -> Value
  -> m (PGCol, S.SQLExp)
convInc f col colType val = do
  prepExp <- f colType val
  return (col, S.SEOpApp S.incOp [S.mkSIdenExp col, prepExp])

convMul
  :: (QErrM m)
  => (PGColumnType -> Value -> m S.SQLExp)
  -> PGCol
  -> PGColumnType
  -> Value
  -> m (PGCol, S.SQLExp)
convMul f col colType val = do
  prepExp <- f colType val
  return (col, S.SEOpApp S.mulOp [S.mkSIdenExp col, prepExp])

convSet
  :: (QErrM m)
  => (PGColumnType -> Value -> m S.SQLExp)
  -> PGCol
  -> PGColumnType
  -> Value
  -> m (PGCol, S.SQLExp)
convSet f col colType val = do
  prepExp <- f colType val
  return (col, prepExp)

convDefault :: (Monad m) => PGCol -> PGColumnType -> () -> m (PGCol, S.SQLExp)
convDefault col _ _ = return (col, S.SEUnsafe "DEFAULT")

convOp
  :: (UserInfoM m, QErrM m)
  => FieldInfoMap (FieldInfo 'Postgres)
  -> [PGCol]
  -> UpdPermInfo 'Postgres
  -> [(PGCol, a)]
  -> (PGCol -> PGColumnType -> a -> m (PGCol, S.SQLExp))
  -> m [(PGCol, S.SQLExp)]
convOp fieldInfoMap preSetCols updPerm objs conv =
  forM objs $ \(pgCol, a) -> do
    -- if column has predefined value then throw error
    when (pgCol `elem` preSetCols) $ throwNotUpdErr pgCol
    checkPermOnCol PTUpdate allowedCols pgCol
    colType <- askPGType fieldInfoMap pgCol relWhenPgErr
    res <- conv pgCol colType a
    -- build a set expression's entry
    withPathK (getPGColTxt pgCol) $ return res
  where
    allowedCols  = upiCols updPerm
    relWhenPgErr = "relationships can't be updated"
    throwNotUpdErr c = do
      roleName <- _uiRole <$> askUserInfo
      throw400 NotSupported $ "column " <> c <<> " is not updatable"
        <> " for role " <> roleName <<> "; its value is predefined in permission"

validateUpdateQueryWith
  :: (UserInfoM m, QErrM m, CacheRM m)
  => SessVarBldr 'Postgres m
  -> (PGColumnType -> Value -> m S.SQLExp)
  -> UpdateQuery
  -> m (AnnUpd 'Postgres)
validateUpdateQueryWith sessVarBldr prepValBldr uq = do
  let tableName = uqTable uq
  tableInfo <- withPathK "table" $ askTabInfo tableName
  let coreInfo = _tiCoreInfo tableInfo

  -- If it is view then check if it is updatable
  mutableView tableName viIsUpdatable
    (_tciViewInfo coreInfo) "updatable"

  -- Check if the role has update permissions
  updPerm <- askUpdPermInfo tableInfo

  -- Check if all dependent headers are present
  validateHeaders $ upiRequiredHeaders updPerm

  -- Check if select is allowed
  selPerm <- modifyErr (<> selNecessaryMsg) $
             askSelPermInfo tableInfo

  let fieldInfoMap = _tciFieldInfoMap coreInfo
      allCols = getCols fieldInfoMap
      preSetObj = upiSet updPerm
      preSetCols = M.keys preSetObj

  -- convert the object to SQL set expression
  setItems <- withPathK "$set" $
    convOp fieldInfoMap preSetCols updPerm (M.toList $ uqSet uq) $ convSet prepValBldr

  incItems <- withPathK "$inc" $
    convOp fieldInfoMap preSetCols updPerm (M.toList $ uqInc uq) $ convInc prepValBldr

  mulItems <- withPathK "$mul" $
    convOp fieldInfoMap preSetCols updPerm (M.toList $ uqMul uq) $ convMul prepValBldr

  defItems <- withPathK "$default" $
    convOp fieldInfoMap preSetCols updPerm ((,()) <$> uqDefault uq) convDefault

  -- convert the returning cols into sql returing exp
  mAnnRetCols <- forM mRetCols $ \retCols ->
    withPathK "returning" $ checkRetCols fieldInfoMap selPerm retCols

  resolvedPreSetItems <- M.toList <$>
                         mapM (convPartialSQLExp sessVarBldr) preSetObj

  let setExpItems = resolvedPreSetItems ++
                    setItems ++
                    incItems ++
                    mulItems ++
                    defItems

  when (null setExpItems) $
    throw400 UnexpectedPayload "atleast one of $set, $inc, $mul has to be present"

  -- convert the where clause
  annSQLBoolExp <- withPathK "where" $
    convBoolExp fieldInfoMap selPerm (uqWhere uq) sessVarBldr prepValBldr

  resolvedUpdFltr <- convAnnBoolExpPartialSQL sessVarBldr $
                     upiFilter updPerm
  resolvedUpdCheck <- fromMaybe gBoolExpTrue <$>
                        traverse (convAnnBoolExpPartialSQL sessVarBldr)
                          (upiCheck updPerm)

  return $ AnnUpd
    tableName
    (fmap UpdSet <$> setExpItems)
    (resolvedUpdFltr, annSQLBoolExp)
    resolvedUpdCheck
    (mkDefaultMutFlds mAnnRetCols)
    allCols
  where
    mRetCols = uqReturning uq
    selNecessaryMsg =
      "; \"update\" is only allowed if the role "
      <> "has \"select\" permission as \"where\" can't be used "
      <> "without \"select\" permission on the table"

validateUpdateQuery
  :: (QErrM m, UserInfoM m, CacheRM m)
  => UpdateQuery -> m (AnnUpd 'Postgres, DS.Seq Q.PrepArg)
validateUpdateQuery =
  runDMLP1T . validateUpdateQueryWith sessVarFromCurrentSetting binRHSBuilder

runUpdate
  :: ( HasVersion, QErrM m, UserInfoM m, CacheRM m
     , MonadTx m, HasSQLGenCtx m, MonadIO m
     , Tracing.MonadTrace m
     )
  => Env.Environment -> UpdateQuery -> m EncJSON
runUpdate env q = do
  strfyNum <- stringifyNum <$> askSQLGenCtx
  validateUpdateQuery q >>= execUpdateQuery env strfyNum Nothing