servant/servant-examples/tutorial/T2.hs

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{-# LANGUAGE DataKinds #-}
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{-# LANGUAGE DeriveGeneric #-}
{-# LANGUAGE TypeFamilies #-}
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{-# LANGUAGE TypeOperators #-}
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module T2 where
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import Data.Aeson
import Data.Time.Calendar
import GHC.Generics
import Network.Wai
import Servant
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data User = User
{ name :: String
, age :: Int
, email :: String
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, 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