servant/servant-examples/tutorial/T5.hs
Julian K. Arni 6eb7add53a stylish haskell changes
And import fix.
2015-08-18 00:07:12 +02:00

37 lines
960 B
Haskell

{-# LANGUAGE DataKinds #-}
{-# LANGUAGE DeriveGeneric #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE TypeOperators #-}
module T5 where
import Control.Monad.IO.Class
import Control.Monad.Trans.Either
import Data.Aeson
import GHC.Generics
import Network.Wai
import Servant
import System.Directory
type IOAPI = "myfile.txt" :> Get '[JSON] FileContent
ioAPI :: Proxy IOAPI
ioAPI = Proxy
newtype FileContent = FileContent
{ content :: String }
deriving Generic
instance ToJSON FileContent
server :: Server IOAPI
server = do
exists <- liftIO (doesFileExist "myfile.txt")
if exists
then liftIO (readFile "myfile.txt") >>= return . FileContent
else left custom404Err
where custom404Err = err404 { errBody = "myfile.txt just isn't there, please leave this server alone." }
app :: Application
app = serve ioAPI server