RunPause.hs

{-----------------------------------------------------------------------------
    reactive-banana
    
    Example: Run and pause an event network
------------------------------------------------------------------------------}
import Control.Monad (when)
import Data.Maybe (isJust, fromJust)
import Data.List (nub)
import System.Random
import System.IO
import Debug.Trace
import Data.IORef

import Reactive.Banana as R


main :: IO ()
main = do
    displayHelpMessage
    sources <- (,) <$> newAddHandler <*> newAddHandler
    network <- setupNetwork sources
    run network
    eventLoop sources network

displayHelpMessage :: IO ()
displayHelpMessage = mapM_ putStrLn $
    "Commands are:":
    "   count   - send counter event":
    "   pause   - pause event network":
    "   run     - run   event network":
    "   quit    - quit the program":
    "":
    []

-- Read commands and fire corresponding events 
eventLoop :: (EventSource (),EventSource EventNetwork) -> EventNetwork -> IO ()
eventLoop (escounter, espause) network = loop
    where
    loop = do
        putStr "> "
        hFlush stdout
        s <- getLine
        case s of
            "count" -> fire escounter ()
            "pause" -> fire espause network
            "run"   -> run network
            "quit"  -> return ()
            _       -> putStrLn $ s ++ " - unknown command"
        when (s /= "quit") loop

{-----------------------------------------------------------------------------
    Event sources
------------------------------------------------------------------------------}
-- Event Sources - allows you to register event handlers
-- Your GUI framework should provide something like this for you
type EventSource a = (AddHandler a, a -> IO ())

addHandler :: EventSource a -> AddHandler a
addHandler = fst

fire :: EventSource a -> a -> IO ()
fire = snd

{-----------------------------------------------------------------------------
    Program logic
------------------------------------------------------------------------------}
-- Set up the program logic in terms of events and behaviors.
setupNetwork :: (EventSource (),EventSource EventNetwork) -> IO EventNetwork
setupNetwork (escounter, espause) = compile $ do
    ecounter <- fromAddHandler (addHandler escounter)
    epause   <- fromAddHandler (addHandler espause  )
    
    let ecount = accumE 0 ((+1) <$ ecounter)
    
    reactimate $ fmap print ecount
    reactimate $ fmap pause epause