servant/servant-examples/tutorial/T5.hs

38 lines
869 B
Haskell
Raw Normal View History

2015-05-06 15:07:49 +02:00
{-# LANGUAGE DataKinds #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE DeriveGeneric #-}
{-# LANGUAGE TypeOperators #-}
{-# LANGUAGE OverloadedStrings #-}
2015-05-10 13:39:18 +02:00
module T5 where
2015-05-06 15:07:49 +02:00
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