Bot.hs

{-# LANGUAGE ExistentialQuantification #-}

import Conduit
import Data.Foldable

data Event = Event

data Command = Command

data Die = Die

-- | A bot is a mealy machine
data Bot m = forall x. Bot (x -> Event -> m (Either Die [Command], x)) (m x)

bot :: Bot IO
bot = Bot step start
  where
    start = undefined
    step = undefined

runBot :: Monad m => Bot m -> Conduit Event m Command
runBot (Bot step start) = lift start >>= go
  where
    go st = do
      eventOrEnd <- await
      case eventOrEnd of
        Nothing -> return ()
        Just event -> do
          (cmdOrDie, st') <- lift (step st event)
          case cmdOrDie of
            Left Die -> return ()
            Right cmds -> yieldMany cmds >> go st'

main :: IO ()
main = stdinC
  =$= linesUnboundedC
  =$= eventsC
  =$= runBot bot
  =$= commandsC
  =$= unlinesC
  $$ stdoutC
  where
    eventsC :: Conduit String IO Event
    eventsC = awaitForever (\_s -> undefined )

    commandsC :: Conduit Command IO String
    commandsC = awaitForever (\_c -> undefined )