Servant Form Sample

servant_form_sample.hs

{-# LANGUAGE DataKinds                  #-}
{-# LANGUAGE DeriveGeneric              #-}
{-# LANGUAGE FlexibleInstances          #-}
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
{-# LANGUAGE MultiParamTypeClasses      #-}
{-# LANGUAGE OverloadedStrings          #-}
{-# LANGUAGE ScopedTypeVariables        #-}
{-# LANGUAGE TypeOperators              #-}

import GHC.Generics
import Control.Monad.IO.Class             -- liftIO
import Control.Monad.Trans.Except         -- Handler
import Data.Aeson.Types                   -- JSON
import Data.Aeson.Parser                  -- JSON
import Servant
import Network.Wai.Handler.Warp
import Web.Internal.FormUrlEncoded

data Req = Req { x  :: Int, y :: Int} deriving (Eq, Show, Generic)
data Res = Res { ret :: Int}          deriving (Eq, Show, Generic)

instance FromForm Req

instance ToJSON Res

type MyAPI =  "add" :> ReqBody '[FormUrlEncoded] Req :> Post '[JSON] Res

add' :: Req -> Handler Res
add' req =  do
  liftIO $ putStrLn $ logAdd (x req) (y req)
  return $ Res { ret = (x req) + (y req) }

logAdd :: Int -> Int -> String
logAdd f s = (show f) ++ "+" ++ (show s) ++ "=" ++ (show (f + s))

myServer :: Server MyAPI
myServer = add'

myProxy :: Proxy MyAPI
myProxy = Proxy

myApp :: Application
myApp = serve myProxy myServer

main :: IO ()
main = run 8081 myApp