{-# LANGUAGE FlexibleInstances    #-}
{-# LANGUAGE UndecidableInstances #-}
-- Copyright (c) 2019 The DAML Authors. All rights reserved.
-- SPDX-License-Identifier: Apache-2.0

module Development.IDE.LSP.Server
  ( ReactorMessage(..)
  , ReactorChan
  , ServerM(..)
  , requestHandler
  , notificationHandler
  ) where
import           Control.Monad.IO.Unlift       (MonadUnliftIO)
import           Control.Monad.Reader
import           Development.IDE.Core.Shake
import           Development.IDE.Core.Tracing
import           Ide.Types                     (HasTracing, traceWithSpan)
import           Language.LSP.Protocol.Message
import           Language.LSP.Server           (Handlers, LspM)
import qualified Language.LSP.Server           as LSP
import           Language.LSP.VFS
import           UnliftIO.Chan

data ReactorMessage
  = ReactorNotification (IO ())
  | ReactorRequest SomeLspId (IO ()) (ResponseError -> IO ())

type ReactorChan = Chan ReactorMessage
newtype ServerM c a = ServerM { unServerM :: ReaderT (ReactorChan, IdeState) (LspM c) a }
  deriving (Functor, Applicative, Monad, MonadReader (ReactorChan, IdeState), MonadIO, MonadUnliftIO, LSP.MonadLsp c)

requestHandler
  :: forall (m :: Method ClientToServer Request) c. (HasTracing (MessageParams m)) =>
     SMethod m
  -> (IdeState -> MessageParams m -> LspM c (Either ResponseError (MessageResult m)))
  -> Handlers (ServerM c)
requestHandler m k = LSP.requestHandler m $ \TRequestMessage{_method,_id,_params} resp -> do
  st@(chan,ide) <- ask
  env <- LSP.getLspEnv
  let resp' :: Either ResponseError (MessageResult m) -> LspM c ()
      resp' = flip (runReaderT . unServerM) st . resp
      trace x = otTracedHandler "Request" (show _method) $ \sp -> do
        traceWithSpan sp _params
        x
  writeChan chan $ ReactorRequest (SomeLspId _id) (trace $ LSP.runLspT env $ resp' =<< k ide _params) (LSP.runLspT env . resp' . Left)

notificationHandler
  :: forall (m :: Method ClientToServer Notification) c. (HasTracing (MessageParams m)) =>
     SMethod m
  -> (IdeState -> VFS -> MessageParams m -> LspM c ())
  -> Handlers (ServerM c)
notificationHandler m k = LSP.notificationHandler m $ \TNotificationMessage{_params,_method}-> do
  (chan,ide) <- ask
  env <- LSP.getLspEnv
  -- Take a snapshot of the VFS state on every notification
  -- We only need to do this here because the VFS state is only updated
  -- on notifications
  vfs <- LSP.getVirtualFiles
  let trace x = otTracedHandler "Notification" (show _method) $ \sp -> do
        traceWithSpan sp _params
        x
  writeChan chan $ ReactorNotification (trace $ LSP.runLspT env $ k ide vfs _params)