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Created July 22, 2011 15:50
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{-# LANGUAGE DeriveDataTypeable #-}
module Main where
{-
Example FRP/zeromq app.
The idea is that messages come into a zeromq socket in the form "id state". The state is of each id is tracked until it's complete.
-}
import Control.Monad
import Data.ByteString.Char8 as C (unpack)
import Data.Map as M
import Data.Maybe
import Reactive.Banana
import System.Environment (getArgs)
import System.ZMQ
data Msg = Msg {mid :: String, state :: String}
deriving (Show, Typeable)
type IdMap = Map String String
-- | Deserialize a string to a Maybe Msg
fromString :: String -> Maybe Msg
fromString s =
case words s of
(x:y:[]) -> Just $ Msg x y
_ -> Nothing
-- | Map a message to a partial operation on a map
-- If the 'state' of the message is "complete" the operation is a delete
-- otherwise it's an insert
toMap :: Msg -> IdMap -> IdMap
toMap msg = case msg of
Msg id_ "complete" -> delete id_
_ -> insert (mid msg) (state msg)
main :: IO ()
main = do
(socketHandle,runSocket) <- newAddHandler
args <- getArgs
let sockAddr = case args of
[s] -> s
_ -> "tcp://127.0.0.1:9999"
putStrLn ("Socket: " ++ sockAddr)
network <- compile $ do
recvd <- fromAddHandler socketHandle
let
-- Filter out the Nothings
justs = filterE isJust recvd
-- Accumulate the partially applied toMap operations
counter = accumE M.empty $ (toMap . fromJust <$> justs)
-- Print the contents
reactimate $ fmap print counter
actuate network
-- Get a socket and kick off the eventloop
withContext 1 $ \ctx ->
withSocket ctx Sub $ \sub -> do
connect sub sockAddr
subscribe sub ""
linkSocketHandler sub runSocket
-- | Recieve a message, deserialize it to a 'Msg' and call the action with the message
linkSocketHandler :: Socket a -> (Maybe Msg -> IO ()) -> IO ()
linkSocketHandler s runner = forever $ do
receive s [] >>= runner . fromString . C.unpack
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