servant/servant-examples/tutorial/T2.hs

{-# LANGUAGE DataKinds     #-}
{-# LANGUAGE DeriveGeneric #-}
{-# LANGUAGE TypeFamilies  #-}
{-# LANGUAGE TypeOperators #-}
module T2 where

import           Data.Aeson
import           Data.Time.Calendar
import           GHC.Generics
import           Network.Wai
import           Servant

data User = User
  { name              :: String
  , age               :: Int
  , email             :: String
  , registration_date :: Day
  } deriving (Eq, Show, Generic)

-- orphan ToJSON instance for Day. necessary to derive one for User
instance ToJSON Day where
  -- display a day in YYYY-mm-dd format
  toJSON d = toJSON (showGregorian d)

instance ToJSON User

type UserAPI = "users" :> Get '[JSON] [User]
          :<|> "albert" :> Get '[JSON] User
          :<|> "isaac" :> Get '[JSON] User

isaac :: User
isaac = User "Isaac Newton" 372 "isaac@newton.co.uk" (fromGregorian 1683 3 1)

albert :: User
albert = User "Albert Einstein" 136 "ae@mc2.org" (fromGregorian 1905 12 1)

users :: [User]
users = [isaac, albert]

userAPI :: Proxy UserAPI
userAPI = Proxy

server :: Server UserAPI
server = return users
    :<|> return albert
    :<|> return isaac

app :: Application
app = serve userAPI server