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

{-# LANGUAGE DuplicateRecordFields #-}
{-# LANGUAGE GADTs                 #-}
{-# LANGUAGE KindSignatures        #-}
{-# LANGUAGE RankNTypes            #-}
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.Server          (Handlers, LspM)
import qualified Language.LSP.Server          as LSP
import           Language.LSP.Types
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 FromClient Request) c. (HasTracing (MessageParams m)) =>
     SMethod m
  -> (IdeState -> MessageParams m -> LspM c (Either ResponseError (ResponseResult m)))
  -> Handlers (ServerM c)
requestHandler m k = LSP.requestHandler m $ \RequestMessage{_method,_id,_params} resp -> do
  st@(chan,ide) <- ask
  env <- LSP.getLspEnv
  let 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 FromClient Notification) c. (HasTracing (MessageParams m)) =>
     SMethod m
  -> (IdeState -> VFS -> MessageParams m -> LspM c ())
  -> Handlers (ServerM c)
notificationHandler m k = LSP.notificationHandler m $ \NotificationMessage{_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)