{-# LANGUAGE GeneralizedNewtypeDeriving #-}
{-# LANGUAGE MultiParamTypeClasses      #-}
{-# LANGUAGE StandaloneDeriving         #-}

module Network.GRPC.LowLevel.GRPC(
GRPC
, withGRPC
, GRPCIOError(..)
, throwIfCallError
, grpcDebug
, grpcDebug'
, threadDelaySecs
, C.MetadataMap(..)
, C.StatusDetails(..)
) where

import           Control.Concurrent     (threadDelay, myThreadId)
import           Control.Exception
import           Data.String            (IsString)
import           Data.ByteString        (ByteString)
import qualified Data.ByteString        as B
import qualified Data.Map               as M
import           Data.Typeable
import qualified Network.GRPC.Unsafe    as C
import qualified Network.GRPC.Unsafe.Op as C
import qualified Network.GRPC.Unsafe.Metadata as C
import           Proto3.Wire.Decode     (ParseError)

-- | Functions as a proof that the gRPC core has been started. The gRPC core
-- must be initialized to create any gRPC state, so this is a requirement for
-- the server and client create/start functions.
data GRPC = GRPC

withGRPC :: (GRPC -> IO a) -> IO a
withGRPC = bracket (C.grpcInit >> return GRPC)
                   (\_ -> grpcDebug "withGRPC: shutting down" >> C.grpcShutdown)

-- | Describes all errors that can occur while running a GRPC-related IO
-- action.
data GRPCIOError = GRPCIOCallError C.CallError
                   -- ^ Errors that can occur while the call is in flight. These
                   -- errors come from the core gRPC library directly.
                   | GRPCIOTimeout
                   -- ^ Indicates that we timed out while waiting for an
                   -- operation to complete on the 'CompletionQueue'.
                   | GRPCIOShutdown
                   -- ^ Indicates that the 'CompletionQueue' is shutting down
                   -- and no more work can be processed. This can happen if the
                   -- client or server is shutting down.
                   | GRPCIOShutdownFailure
                   -- ^ Thrown if a 'CompletionQueue' fails to shut down in a
                   -- reasonable amount of time.
                   | GRPCIOUnknownError
                   | GRPCIOBadStatusCode C.StatusCode C.StatusDetails

                   | GRPCIODecodeError ParseError
                   | GRPCIOInternalUnexpectedRecv String -- debugging description
                   | GRPCIOHandlerException String
  deriving (Eq, Show, Typeable)
instance Exception GRPCIOError

throwIfCallError :: C.CallError -> Either GRPCIOError ()
throwIfCallError C.CallOk = Right ()
throwIfCallError x = Left $ GRPCIOCallError x

grpcDebug :: String -> IO ()
{-# INLINE grpcDebug #-}
#ifdef DEBUG
grpcDebug = grpcDebug'
#else
grpcDebug _ = return ()
#endif

grpcDebug' :: String -> IO ()
{-# INLINE grpcDebug' #-}
grpcDebug' str = do
  tid <- myThreadId
  putStrLn $ "[" ++ show tid ++ "]: " ++ str

threadDelaySecs :: Int -> IO ()
threadDelaySecs = threadDelay . (* 10^(6::Int))