{-# LANGUAGE ImpredicativeTypes #-}

data Request
data Response
type Application = forall a. Request -> (Response -> IO a) -> IO a
type Middleware = Application -> Application

middleware1, middleware2, middleware3 :: Middleware
middleware1 _ = undefined
middleware2 _ = undefined
middleware3 _ = undefined

middlewares :: Middleware
middlewares app = foldl' @[] @Application (flip ($)) app $
  [ middleware1
  , middleware2
  , middleware3
  ]

main = pure ()