{-# OPTIONS_GHC -fno-warn-orphans #-}
{-# LANGUAGE UndecidableInstances #-}

module Hasura.Backends.Postgres.Instances.Transport
  ( runPGMutationTransaction
  ) where

import           Hasura.Prelude

import qualified Data.Aeson                                 as J
import qualified Data.ByteString                            as B
import qualified Data.HashMap.Strict.InsOrd                 as OMap
import qualified Database.PG.Query                          as Q
import qualified Language.GraphQL.Draft.Syntax              as G

import           Control.Monad.Morph                        (hoist)
import           Data.Text.Extended

import qualified Hasura.Backends.Postgres.Execute.LiveQuery as PGL
import qualified Hasura.GraphQL.Execute.Query               as EQ
import qualified Hasura.Logging                             as L
import qualified Hasura.Tracing                             as Tracing

import           Hasura.Backends.Postgres.SQL.Value
import           Hasura.EncJSON
import           Hasura.GraphQL.Execute.Backend
import           Hasura.GraphQL.Execute.LiveQuery.Plan
import           Hasura.GraphQL.Logging
import           Hasura.GraphQL.Transport.Backend
import           Hasura.GraphQL.Transport.HTTP.Protocol
import           Hasura.RQL.Types
import           Hasura.Server.Types                        (RequestId)
import           Hasura.Session
import           Hasura.Tracing


instance Backend ('Postgres pgKind) => BackendTransport ('Postgres pgKind) where
  runDBQuery = runPGQuery
  runDBMutation = runPGMutation
  runDBSubscription = runPGSubscription
  runDBQueryExplain = runPGQueryExplain


runPGQuery
  :: ( MonadIO m
     , MonadError QErr m
     , MonadQueryLog m
     , MonadTrace m
     )
  => RequestId
  -> GQLReqUnparsed
  -> G.Name
  -> UserInfo
  -> L.Logger L.Hasura
  -> SourceConfig ('Postgres pgKind)
  -> Tracing.TraceT (LazyTxT QErr IO) EncJSON
  -> Maybe (EQ.PreparedSql pgKind)
  -> m (DiffTime, EncJSON)
  -- ^ Also return the time spent in the PG query; for telemetry.
runPGQuery reqId query fieldName _userInfo logger sourceConfig tx genSql = do
  -- log the generated SQL and the graphql query
  logQueryLog logger $ mkQueryLog query fieldName genSql reqId
  withElapsedTime $ trace ("Postgres Query for root field " <>> fieldName) $
    Tracing.interpTraceT id $ hoist (runQueryTx $ _pscExecCtx sourceConfig) tx

runPGMutation
  :: ( MonadIO m
     , MonadError QErr m
     , MonadQueryLog m
     , MonadTrace m
     )
  => RequestId
  -> GQLReqUnparsed
  -> G.Name
  -> UserInfo
  -> L.Logger L.Hasura
  -> SourceConfig ('Postgres pgKind)
  -> Tracing.TraceT (LazyTxT QErr IO) EncJSON
  -> Maybe (EQ.PreparedSql pgKind)
  -> m (DiffTime, EncJSON)
  -- ^ Also return 'Mutation' when the operation was a mutation, and the time
  -- spent in the PG query; for telemetry.
runPGMutation reqId query fieldName userInfo logger sourceConfig tx _genSql =  do
  -- log the graphql query
  logQueryLog logger $ mkQueryLog query fieldName Nothing reqId
  ctx <- Tracing.currentContext
  withElapsedTime $ trace ("Postgres Mutation for root field " <>> fieldName) $
    Tracing.interpTraceT (
      liftEitherM . liftIO . runExceptT
      . runLazyTx (_pscExecCtx sourceConfig) Q.ReadWrite
      . withTraceContext ctx
      . withUserInfo userInfo
      ) tx

runPGSubscription
  :: ( MonadIO m
     )
  => SourceConfig ('Postgres pgKind)
  -> MultiplexedQuery ('Postgres pgKind)
  -> [(CohortId, CohortVariables)]
  -> m (DiffTime, Either QErr [(CohortId, B.ByteString)])
runPGSubscription sourceConfig query variables = withElapsedTime
  $ runExceptT
  $ runQueryTx (_pscExecCtx sourceConfig)
  $ PGL.executeMultiplexedQuery query variables

runPGQueryExplain
  :: forall pgKind m
   . ( MonadIO m
     , MonadError QErr m
     )
  => DBStepInfo ('Postgres pgKind)
  -> m EncJSON
runPGQueryExplain (DBStepInfo _ sourceConfig _ action) =
  -- All Postgres transport functions use the same monad stack: the ExecutionMonad defined in the
  -- matching instance of BackendExecute. However, Explain doesn't need tracing! Rather than
  -- introducing a separate "ExplainMonad", we simply use @runTraceTWithReporter@ to remove the
  -- TraceT.
  runQueryTx (_pscExecCtx sourceConfig) $ runTraceTWithReporter noReporter "explain" $ action


mkQueryLog
  :: GQLReqUnparsed
  -> G.Name
  -> Maybe (EQ.PreparedSql pgKind)
  -> RequestId
  -> QueryLog
mkQueryLog gqlQuery fieldName preparedSql requestId =
  QueryLog gqlQuery ((fieldName,) <$> generatedQuery) requestId QueryLogKindDatabase
  where
    generatedQuery = preparedSql <&> \(EQ.PreparedSql query args _) ->
      GeneratedQuery (Q.getQueryText query) (J.toJSON $ pgScalarValueToJson . snd <$> args)


-- ad-hoc transaction optimisation
-- see Note [Backwards-compatible transaction optimisation]

runPGMutationTransaction
  :: ( MonadIO m
     , MonadError QErr m
     , MonadQueryLog m
     , MonadTrace m
     )
  => RequestId
  -> GQLReqUnparsed
  -> UserInfo
  -> L.Logger L.Hasura
  -> SourceConfig ('Postgres pgKind)
  -> InsOrdHashMap G.Name (DBStepInfo ('Postgres pgKind))
  -> m (DiffTime, InsOrdHashMap G.Name EncJSON)
runPGMutationTransaction reqId query userInfo logger sourceConfig mutations = do
  logQueryLog logger $ mkQueryLog query $$(G.litName "transaction") Nothing reqId
  ctx <- Tracing.currentContext
  withElapsedTime $ do
    Tracing.interpTraceT (
      liftEitherM . liftIO . runExceptT
      . runLazyTx (_pscExecCtx sourceConfig) Q.ReadWrite
      . withTraceContext ctx
      . withUserInfo userInfo
      ) $ flip OMap.traverseWithKey mutations \fieldName dbsi ->
            trace ("Postgres Mutation for root field " <>> fieldName) $ dbsiAction dbsi