{-# LANGUAGE DataKinds #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE KindSignatures #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE TypeOperators #-}
module Servant.Server.Internal.RoutingApplicationSpec (spec) where

import Prelude ()
import Prelude.Compat

import Control.Exception hiding (Handler)
import Control.Monad.Trans.Resource (register)
import Control.Monad.IO.Class
import Data.IORef
import Data.Proxy
import GHC.TypeLits (Symbol, KnownSymbol, symbolVal)
import Servant
import Servant.Server.Internal.RoutingApplication
import Network.Wai (defaultRequest)
import Test.Hspec
import Test.Hspec.Wai (request, shouldRespondWith, with)

import qualified Data.Text as T

import System.IO.Unsafe (unsafePerformIO)

data TestResource x
    = TestResourceNone
    | TestResource x
    | TestResourceFreed
    | TestResourceError
  deriving (Eq, Show)

-- Let's not write to the filesystem
delayedTestRef :: IORef (TestResource String)
delayedTestRef = unsafePerformIO $ newIORef TestResourceNone

fromTestResource :: a -> (b -> a) -> TestResource b -> a
fromTestResource _ f (TestResource x) = f x
fromTestResource x _ _                = x

initTestResource :: IO ()
initTestResource = writeIORef delayedTestRef TestResourceNone

writeTestResource :: String -> IO ()
writeTestResource x = modifyIORef delayedTestRef $ \r -> case r of
    TestResourceNone -> TestResource x
    _                -> TestResourceError

freeTestResource :: IO ()
freeTestResource = modifyIORef delayedTestRef $ \r -> case r of
    TestResource _ -> TestResourceFreed
    _              -> TestResourceError

delayed :: DelayedIO () -> RouteResult (Handler ()) -> Delayed () (Handler ())
delayed body srv = Delayed
  { capturesD = \() -> return ()
  , methodD   = return ()
  , authD     = return ()
  , acceptD   = return ()
  , contentD  = return ()
  , paramsD   = return ()
  , headersD   = return ()
  , bodyD     = \() -> do
      liftIO (writeTestResource "hia" >> putStrLn "garbage created")
      _ <- register (freeTestResource >> putStrLn "garbage collected")
      body
  , serverD   = \() () () () _body _req -> srv
  }

simpleRun :: Delayed () (Handler ())
          -> IO ()
simpleRun d = fmap (either ignoreE id) . try $
  runAction d () defaultRequest (\_ -> return ()) (\_ -> FailFatal err500)

  where ignoreE :: SomeException -> ()
        ignoreE = const ()

-------------------------------------------------------------------------------
-- Combinator example
-------------------------------------------------------------------------------

-- | This data types writes 'sym' to 'delayedTestRef'.
data Res (sym :: Symbol)

instance (KnownSymbol sym, HasServer api ctx) => HasServer (Res sym :> api) ctx where
    type ServerT (Res sym :> api) m = IORef (TestResource String) -> ServerT api m
    route Proxy ctx server = route (Proxy :: Proxy api) ctx $
        addBodyCheck server (return ()) check
      where
        sym  = symbolVal (Proxy :: Proxy sym)
        check () = do
            liftIO $ writeTestResource sym
            _ <- register freeTestResource
            return delayedTestRef

type ResApi = "foobar" :> Res "foobar" :> Get '[PlainText] T.Text

resApi :: Proxy ResApi
resApi = Proxy

resServer :: Server ResApi
resServer ref = liftIO $ fmap (fromTestResource "<wrong>" T.pack)  $ readIORef ref

-------------------------------------------------------------------------------
-- Spec
-------------------------------------------------------------------------------

spec :: Spec
spec = do
  describe "Delayed" $ do
    it "actually runs clean up actions" $ do
      liftIO initTestResource
      _ <- simpleRun $ delayed (return ()) (Route $ return ())
      res <- readIORef delayedTestRef
      res `shouldBe` TestResourceFreed
    it "even with exceptions in serverD" $ do
      liftIO initTestResource
      _ <- simpleRun $ delayed (return ()) (Route $ throw DivideByZero)
      res <- readIORef delayedTestRef
      res `shouldBe` TestResourceFreed
    it "even with routing failure in bodyD" $ do
      liftIO initTestResource
      _ <- simpleRun $ delayed (delayedFailFatal err500) (Route $ return ())
      res <- readIORef delayedTestRef
      res `shouldBe` TestResourceFreed
    it "even with exceptions in bodyD" $ do
      liftIO initTestResource
      _ <- simpleRun $ delayed (liftIO $ throwIO DivideByZero) (Route $ return ())
      res <- readIORef delayedTestRef
      res `shouldBe` TestResourceFreed
  describe "ResApi" $
    with (return $ serve resApi resServer) $ do
      it "writes and cleanups resources" $ do
        liftIO initTestResource
        request "GET" "foobar" [] "" `shouldRespondWith` "foobar"
        liftIO $ do
          res <- readIORef delayedTestRef
          res `shouldBe` TestResourceFreed
