{-# LANGUAGE DataKinds           #-}
{-# LANGUAGE GADTs               #-}
{-# LANGUAGE LambdaCase          #-}
{-# LANGUAGE OverloadedStrings   #-}
{-# LANGUAGE RankNTypes          #-}
{-# LANGUAGE RecordWildCards     #-}
{-# LANGUAGE ScopedTypeVariables #-}

module Network.GRPC.HighLevel.Server.Unregistered where

import           Control.Concurrent
import           Control.Concurrent.Async                  (async, wait)
import           Control.Arrow
import qualified Control.Exception                         as CE
import           Control.Monad
import           Data.Foldable                             (find)
import           Data.Protobuf.Wire.Class
import           Network.GRPC.HighLevel.Server
import           Network.GRPC.LowLevel
import qualified Network.GRPC.LowLevel.Call.Unregistered   as U
import qualified Network.GRPC.LowLevel.Server.Unregistered as U

dispatchLoop :: Server
             -> MetadataMap
             -> [Handler 'Normal]
             -> [Handler 'ClientStreaming]
             -> [Handler 'ServerStreaming]
             -> [Handler 'BiDiStreaming]
             -> IO ()
dispatchLoop s md hN hC hS hB =
  forever $ U.withServerCallAsync s $ \sc ->
    case findHandler sc allHandlers of
      Just (AnyHandler ah) -> case ah of
        UnaryHandler _ h        -> unaryHandler sc h
        ClientStreamHandler _ h -> csHandler sc h
        ServerStreamHandler _ h -> ssHandler sc h
        BiDiStreamHandler _ h   -> bdHandler sc h
      Nothing                   -> unknownHandler sc
  where
    allHandlers = map AnyHandler hN ++ map AnyHandler hC
                  ++ map AnyHandler hS ++ map AnyHandler hB

    findHandler sc = find ((== U.callMethod sc) . anyHandlerMethodName)

    unaryHandler :: (Message a, Message b) => U.ServerCall -> ServerHandler a b -> IO ()
    unaryHandler sc h =
      handleError $
        U.serverHandleNormalCall' s sc md $ \_sc' bs ->
          convertServerHandler h (const bs <$> U.convertCall sc)

    csHandler :: (Message a, Message b) => U.ServerCall -> ServerReaderHandler a b -> IO ()
    csHandler sc = handleError . U.serverReader s sc md . convertServerReaderHandler

    ssHandler :: (Message a, Message b) => U.ServerCall -> ServerWriterHandler a b -> IO ()
    ssHandler sc = handleError . U.serverWriter s sc md . convertServerWriterHandler

    bdHandler :: (Message a, Message b) => U.ServerCall -> ServerRWHandler a b -> IO ()
    bdHandler sc = handleError . U.serverRW s sc md . convertServerRWHandler

    unknownHandler :: U.ServerCall -> IO ()
    unknownHandler sc = void $ U.serverHandleNormalCall' s sc md $ \_ _ ->
      return (mempty, mempty, StatusNotFound, StatusDetails "unknown method")

    handleError :: IO a -> IO ()
    handleError = (handleCallError . left herr =<<) . CE.try
      where herr (e :: CE.SomeException) = GRPCIOHandlerException (show e)

serverLoop :: ServerOptions -> IO ()
serverLoop ServerOptions{..} = do
  -- We run the loop in a new thread so that we can kill the serverLoop thread.
  -- Without this fork, we block on a foreign call, which can't be interrupted.
  tid <- async $ withGRPC $ \grpc ->
    withServer grpc config $ \server -> do
      dispatchLoop server
                   optInitialMetadata
                   optNormalHandlers
                   optClientStreamHandlers
                   optServerStreamHandlers
                   optBiDiStreamHandlers
  wait tid
  where
    config = ServerConfig
      { host                             = "localhost"
      , port                             = optServerPort
      , methodsToRegisterNormal          = []
      , methodsToRegisterClientStreaming = []
      , methodsToRegisterServerStreaming = []
      , methodsToRegisterBiDiStreaming   = []
      , serverArgs                       =
          [CompressionAlgArg GrpcCompressDeflate | optUseCompression]
          ++
          [ UserAgentPrefix optUserAgentPrefix
          , UserAgentSuffix optUserAgentSuffix
          ]
      }