{-# LANGUAGE RecordWildCards #-}

module Network.GRPC.LowLevel.Server.Unregistered where

import           Control.Exception                                  (finally)
import           Data.ByteString                                    (ByteString)
import           Network.GRPC.LowLevel.Call                         (MethodName)
import           Network.GRPC.LowLevel.Call.Unregistered
import           Network.GRPC.LowLevel.CompletionQueue              (TimeoutSeconds)
import qualified Network.GRPC.LowLevel.CompletionQueue.Unregistered as U
import           Network.GRPC.LowLevel.GRPC
import           Network.GRPC.LowLevel.Op                           (OpRecvResult (..))
import qualified Network.GRPC.LowLevel.Op.Unregistered              as U
import           Network.GRPC.LowLevel.Server
import qualified Network.GRPC.Unsafe.Op                             as C

serverCreateCall :: Server -> TimeoutSeconds
                    -> IO (Either GRPCIOError ServerCall)
serverCreateCall Server{..} timeLimit =
  U.serverRequestCall internalServer serverCQ timeLimit

withServerCall :: Server -> TimeoutSeconds
                  -> (ServerCall -> IO (Either GRPCIOError a))
                  -> IO (Either GRPCIOError a)
withServerCall server timeout f = do
  createResult <- serverCreateCall server timeout
  case createResult of
    Left x -> return $ Left x
    Right call -> f call `finally` logDestroy call
      where logDestroy c = grpcDebug "withServerCall: destroying."
                           >> destroyServerCall c

-- | A handler for an unregistered server call; bytestring arguments are the
-- request body and response body respectively.
type ServerHandler
  =  ByteString -> MetadataMap -> MethodName
  -> IO (ByteString, MetadataMap, StatusDetails)

-- | Handle one unregistered call.
serverHandleNormalCall :: Server
                       -> TimeoutSeconds
                       -> MetadataMap -- ^ Initial server metadata.
                       -> ServerHandler
                       -> IO (Either GRPCIOError ())
serverHandleNormalCall s@Server{..} timeLimit srvMetadata f = do
  withServerCall s timeLimit $ \call -> do
    grpcDebug "serverHandleCall(U): starting batch."
    let recvOps = serverOpsGetNormalCall srvMetadata
    opResults <- U.runServerOps call serverCQ recvOps timeLimit
    case opResults of
      Left x -> do grpcDebug "serverHandleNormalCall(U): ops failed; aborting"
                   return $ Left x
      Right [OpRecvMessageResult (Just body)] -> do
        requestMeta <- serverCallGetMetadata call
        grpcDebug $ "got client metadata: " ++ show requestMeta
        methodName <- serverCallGetMethodName call
        hostName <- serverCallGetHost call
        grpcDebug $ "call_details host is: " ++ show hostName
        (respBody, respMetadata, details) <- f body requestMeta methodName
        let status = C.GrpcStatusOk
        let respOps = serverOpsSendNormalResponse
                        respBody respMetadata status details
        respOpsResults <- U.runServerOps call serverCQ respOps timeLimit
        case respOpsResults of
          Left x -> do grpcDebug "serverHandleNormalCall(U): resp failed."
                       return $ Left x
          Right _ -> grpcDebug "serverHandleNormalCall(U): ops done."
                     >> return (Right ())
      x -> error $ "impossible pattern match: " ++ show x