Akka Stream Flow in Eta

Main.hs

{-# LANGUAGE MagicHash, TypeOperators, MultiParamTypeClasses, TypeFamilies, DataKinds, FlexibleContexts, OverloadedStrings, ScopedTypeVariables #-}

import Java

import Data.Char
import Data.Dynamic
import Data.Typeable

data {-# CLASS "akka.japi.function.Function" #-} Function t r = Function (Object# (Function t r))
  deriving Class

foreign import java unsafe "@wrapper apply"
  applyFunction :: (t <: Object, r <: Object) => (t -> Java (Function t r) r) -> Function t r


data {-# CLASS "akka.stream.javadsl.Flow" #-} Flow i o m = Flow (Object# (Flow i o m))
  deriving Class

data {-# CLASS "akka.NotUsed" #-} NotUsed = NotUsed (Object# NotUsed)
  deriving Class

-- public static <I,O> Flow<I,O,NotUsed> fromFunction(Function<I,O> f)
foreign import java unsafe "@static akka.stream.javadsl.Flow.fromFunction" flowFromFunction :: (t <: Object) => Function t t -> IO (Flow t t NotUsed)


main :: IO ()
main = do
  flow <- flowFromFunction $ applyFunction f
  return ()
  where f = \(_ :: JString) -> return ("anonymous class" :: JString)