data Task = Task {programToRun :: String, input :: String, continue :: String -> IO (Maybe Task)}

runTask :: Task -> IO (Either String Task)
runTask = undefined

addCont :: (String -> IO Task) -> Task -> Task
addCont f t1 = Task (programToRun t1) (input t1) (\result -> do
 task <- (continue t1) result
 case task of
  Nothing -> Just <$> f result
  Just task -> do 
    step <- runTask task
    case step of
      Left res -> Just <$> f res
      Right t2 -> return . Just $ (addCont f t2))
  

data Pipeline = Pipeline {steps :: Task}

makePipeline :: String -> Pipeline
makePipeline startingInput = Pipeline (Task "identityProgram" startingInput (\t -> return Nothing)) 

addStep :: Pipeline -> (String -> IO Task) -> Pipeline
addStep pipeline step = Pipeline ((addCont step) . steps $ pipeline)

run :: Pipeline -> IO ()
run pipeline = beginRun (steps pipeline)

beginRun :: Task -> IO ()
beginRun task = do
 result <- runTask task
 case result of
  Left finalResult -> putStrLn finalResult
  Right nextTask -> beginRun nextTask

examplePipeline :: Pipeline
examplePipeline = undefined

main = run examplePipeline