69 lines
2.5 KiB
Haskell
69 lines
2.5 KiB
Haskell
{-# LANGUAGE TypeFamilies #-}
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{-# LANGUAGE OverloadedStrings #-}
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{-# LANGUAGE ScopedTypeVariables #-}
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{-# LANGUAGE DeriveDataTypeable #-}
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module Servant.API.Get where
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import Control.Monad.Trans.Either
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import Data.Aeson
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import Data.Proxy
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import Data.String.Conversions
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import Data.Typeable
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import Network.HTTP.Types
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import Network.Wai
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import Servant.Client
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import Servant.Common.BaseUrl
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import Servant.Common.Req
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import Servant.Docs
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import Servant.Server
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-- | Endpoint for simple GET requests. Serves the result as JSON.
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--
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-- Example:
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--
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-- > type MyApi = "books" :> Get [Book]
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data Get a
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deriving Typeable
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-- | When implementing the handler for a 'Get' endpoint,
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-- just like for 'Servant.API.Delete.Delete', 'Servant.API.Post.Post'
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-- and 'Servant.API.Put.Put', the handler code runs in the
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-- @EitherT (Int, String) IO@ monad, where the 'Int' represents
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-- the status code and the 'String' a message, returned in case of
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-- failure. You can quite handily use 'Control.Monad.Trans.EitherT.left'
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-- to quickly fail if some conditions are not met.
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--
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-- If successfully returning a value, we just require that its type has
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-- a 'ToJSON' instance and servant takes care of encoding it for you,
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-- yielding status code 200 along the way.
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instance ToJSON result => HasServer (Get result) where
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type Server (Get result) = EitherT (Int, String) IO result
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route Proxy action request respond
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| null (pathInfo request) && requestMethod request == methodGet = do
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e <- runEitherT action
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respond . succeedWith $ case e of
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Right output ->
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responseLBS ok200 [("Content-Type", "application/json")] (encode output)
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Left (status, message) ->
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responseLBS (mkStatus status (cs message)) [] (cs message)
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| null (pathInfo request) && requestMethod request /= methodGet =
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respond $ failWith WrongMethod
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| otherwise = respond $ failWith NotFound
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-- | If you have a 'Get' endpoint in your API, the client
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-- side querying function that is created when calling 'client'
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-- will just require an argument that specifies the scheme, host
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-- and port to send the request to.
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instance FromJSON result => HasClient (Get result) where
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type Client (Get result) = BaseUrl -> EitherT String IO result
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clientWithRoute Proxy req host =
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performRequestJSON methodGet req 200 host
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instance ToSample a => HasDocs (Get a) where
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docsFor Proxy (endpoint, action) =
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single endpoint' action'
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where endpoint' = endpoint & method .~ DocGET
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action' = action & response.respBody .~ sampleByteString p
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p = Proxy :: Proxy a
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