module Hasura.RQL.DML.Delete
  ( validateDeleteQWith
  , validateDeleteQ
  , AnnDelG(..)
  , traverseAnnDel
  , AnnDel
  , execDeleteQuery
  , runDelete
  ) where

import           Hasura.Prelude

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

import           Control.Monad.Trans.Control                  (MonadBaseControl)
import           Data.Aeson

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.Translate.Returning
import           Hasura.Backends.Postgres.Types.Table
import           Hasura.EncJSON
import           Hasura.RQL.DML.Internal
import           Hasura.RQL.DML.Types
import           Hasura.RQL.IR.Delete
import           Hasura.RQL.Types
import           Hasura.RQL.Types.Run
import           Hasura.Server.Version                        (HasVersion)
import           Hasura.Session


validateDeleteQWith
  :: (UserInfoM m, QErrM m, TableInfoRM 'Postgres m)
  => SessVarBldr 'Postgres m
  -> (ColumnType 'Postgres -> Value -> m S.SQLExp)
  -> DeleteQuery
  -> m (AnnDel 'Postgres)
validateDeleteQWith sessVarBldr prepValBldr
  (DeleteQuery tableName _ rqlBE mRetCols) = do
  tableInfo <- askTabInfoSource tableName
  let coreInfo = _tiCoreInfo tableInfo

  -- If table is view then check if it deletable
  mutableView tableName viIsDeletable
    (_tciViewInfo coreInfo) "deletable"

  -- Check if the role has delete permissions
  delPerm <- askDelPermInfo tableInfo

  -- Check if all dependent headers are present
  validateHeaders $ dpiRequiredHeaders delPerm

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

  let fieldInfoMap = _tciFieldInfoMap coreInfo
      allCols = getCols fieldInfoMap

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

  -- convert the where clause
  annSQLBoolExp <- withPathK "where" $
    convBoolExp fieldInfoMap selPerm rqlBE sessVarBldr tableName (valueParserWithCollectableType prepValBldr)

  resolvedDelFltr <- convAnnBoolExpPartialSQL sessVarBldr $
                     dpiFilter delPerm

  return $ AnnDel tableName
    (resolvedDelFltr, annSQLBoolExp)
    (mkDefaultMutFlds mAnnRetCols) allCols

  where
    selNecessaryMsg =
      "; \"delete\" is only allowed if the role "
      <> "has \"select\" permission as \"where\" can't be used "
      <> "without \"select\" permission on the table"

validateDeleteQ
  :: (QErrM m, UserInfoM m, CacheRM m)
  => DeleteQuery -> m (AnnDel 'Postgres, DS.Seq Q.PrepArg)
validateDeleteQ query = do
  let source = doSource query
  tableCache :: TableCache 'Postgres <- askTableCache source
  flip runTableCacheRT (source, tableCache) $ runDMLP1T $
    validateDeleteQWith sessVarFromCurrentSetting binRHSBuilder query

runDelete
  :: ( HasVersion, QErrM m, UserInfoM m, CacheRM m
     , HasServerConfigCtx m, MonadIO m
     , Tracing.MonadTrace m, MonadBaseControl IO m
     , MetadataM m
     )
  => Env.Environment
  -> DeleteQuery
  -> m EncJSON
runDelete env q = do
  sourceConfig <- askSourceConfig (doSource q)
  strfyNum <- stringifyNum . _sccSQLGenCtx <$> askServerConfigCtx
  validateDeleteQ q
    >>= runQueryLazyTx (_pscExecCtx sourceConfig) Q.ReadWrite
        . execDeleteQuery env strfyNum Nothing