135 lines
4 KiB
Haskell
135 lines
4 KiB
Haskell
{-# LANGUAGE DataKinds #-}
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{-# LANGUAGE PolyKinds #-}
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{-# LANGUAGE TypeFamilies #-}
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{-# LANGUAGE DeriveGeneric #-}
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{-# LANGUAGE TypeOperators #-}
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{-# LANGUAGE FlexibleInstances #-}
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{-# LANGUAGE OverloadedStrings #-}
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{-# LANGUAGE QuasiQuotes #-}
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{-# OPTIONS_GHC -fno-warn-orphans #-}
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import Control.Concurrent (forkIO, killThread)
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import Control.Monad.Trans.Either
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import Data.Aeson
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import Data.Monoid
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import Data.Proxy
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import Data.Text
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import GHC.Generics
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import Network.Wai
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import Network.Wai.Handler.Warp
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import Servant.API
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import Servant.Client
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import Servant.Docs
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import Servant.Server
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-- * Example
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-- | A greet message data type
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newtype Greet = Greet { msg :: Text }
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deriving (Generic, Show)
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instance FromJSON Greet
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instance ToJSON Greet
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-- We add some useful annotations to our captures,
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-- query parameters and request body to make the docs
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-- really helpful.
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instance ToCapture (Capture "name" Text) where
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toCapture _ = DocCapture "name" "name of the person to greet"
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instance ToCapture (Capture "greetid" Text) where
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toCapture _ = DocCapture "greetid" "identifier of the greet msg to remove"
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instance ToParam (QueryParam "capital" Bool) where
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toParam _ =
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DocQueryParam "capital"
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["true", "false"]
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"Get the greeting message in uppercase (true) or not (false). Default is false."
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Normal
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instance ToSample Greet where
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toSample = Just $ Greet "Hello, haskeller!"
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-- API specification
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type TestApi =
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-- GET /hello/:name?capital={true, false} returns a Greet as JSON
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"hello" :> Capture "name" Text :> QueryParam "capital" Bool :> Get Greet
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-- POST /greet with a Greet as JSON in the request body,
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-- returns a Greet as JSON
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:<|> "greet" :> ReqBody Greet :> Post Greet
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-- DELETE /greet/:greetid
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:<|> "greet" :> Capture "greetid" Text :> Delete
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testApi :: Proxy TestApi
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testApi = Proxy
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-- Server-side handlers.
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--
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-- There's one handler per endpoint, which, just like in the type
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-- that represents the API, are glued together using :<|>.
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--
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-- Each handler runs in the 'EitherT (Int, String) IO' monad.
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server :: Server TestApi
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server = helloH :<|> postGreetH :<|> deleteGreetH
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where helloH name Nothing = helloH name (Just False)
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helloH name (Just False) = return . Greet $ "Hello, " <> name
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helloH name (Just True) = return . Greet . toUpper $ "Hello, " <> name
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postGreetH greet = return greet
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deleteGreetH _ = return ()
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-- Client-side querying functions
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--
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-- They're all derived automatically from the type, and glued together
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-- with :<|> just like in the type and for the server handlers, except
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-- that we don't have to implement them!
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clientApi :: Client TestApi
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clientApi = client testApi
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getGreet :: Text -> Maybe Bool -> BaseUrl -> EitherT String IO Greet
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postGreet :: Greet -> BaseUrl -> EitherT String IO Greet
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deleteGreet :: Text -> BaseUrl -> EitherT String IO ()
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getGreet :<|> postGreet :<|> deleteGreet = clientApi
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-- Turn the server into a WAI app. 'serve' is provided by servant,
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-- more precisely by the Servant.Server module.
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test :: Application
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test = serve testApi server
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-- Generate the data that lets us have API docs. This
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-- is derived from the type as well as from
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-- the 'ToCapture', 'ToParam' and 'ToSample' instances from above.
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docsGreet :: API
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docsGreet = docs testApi
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-- Run the server.
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--
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-- 'run' comes from Network.Wai.Handler.Warp
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runTestServer :: Port -> IO ()
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runTestServer port = run port test
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-- Put this all to work!
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main :: IO ()
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main = do
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-- we start the server, binding it to port 8001
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tid <- forkIO $ runTestServer 8001
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-- we tell the client where to find it
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let uri = BaseUrl Http "localhost" 8001
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-- we run a couple of requests against the server
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print =<< runEitherT (getGreet "alp" (Just True) uri)
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print =<< runEitherT (getGreet "alp" (Just False) uri)
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let g = Greet "yo"
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print =<< runEitherT (postGreet g uri)
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print =<< runEitherT (deleteGreet "blah" uri)
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killThread tid
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putStrLn "\n---------\n"
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-- we print the markdown docs
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putStrLn $ markdown docsGreet
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