application/x-www-form-urlencoded for servant

gistfile1.hs

data FormUrlEncoded deriving Typeable

class ToFormUrlEncoded a where
  toFormUrlEncoded :: a -> [(ByteString, ByteString)]

class FromFormUrlEncoded a where
  fromFormUrlEncoded :: [(ByteString, ByteString)] -> Either String a

instance ToFormUrlEncoded [(ByteString, ByteString)] where
  toFormUrlEncoded = id

instance FromFormUrlEncoded [(ByteString, ByteString)] where
  fromFormUrlEncoded = return

-- | @application/x-www-form-urlencoded@
instance Accept FormUrlEncoded where
    contentType _ = "application" M.// "x-www-form-urlencoded"

instance ToFormUrlEncoded a => MimeRender FormUrlEncoded a where
    toByteString _ = Text.encodeUtf8 . Text.pack
                   . exportParams
                   . map (Text.unpack . Text.decodeUtf8 *** Text.unpack . Text.decodeUtf8)
                   . toFormUrlEncoded

instance FromFormUrlEncoded a => MimeUnrender FormUrlEncoded a where
    fromByteString _ x = do
      x' <- either (const Nothing) (Just . Text.unpack) . Text.decodeUtf8' $ x
      x'' <- importParams x'
      either (const Nothing) Just . fromFormUrlEncoded . map (Text.encodeUtf8 . Text.pack *** Text.encodeUtf8 . Text.pack) $ x''