https://github.com/athanclark/websockets-simple

A simple wrapper around the websockets library.
https://github.com/athanclark/websockets-simple

algebraic-data-types api haskell websocket

Last synced: 7 months ago
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A simple wrapper around the websockets library.

• Host: GitHub
• URL: https://github.com/athanclark/websockets-simple
• Owner: athanclark
• License: bsd-3-clause
• Created: 2017-05-06T08:26:07.000Z (about 9 years ago)
• Default Branch: master
• Last Pushed: 2019-10-06T19:17:58.000Z (over 6 years ago)
• Last Synced: 2024-04-25T23:02:07.900Z (about 2 years ago)
• Topics: algebraic-data-types, api, haskell, websocket
• Language: Haskell
• Size: 49.8 KB
• Stars: 1
• Watchers: 3
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

          
# websockets-simple

Provides for a slightly more composable structure for websocket apps:

```haskell

data Input = Increment | Decrement

  deriving (FromJSON)

data Output = Value Int

  deriving (ToJSON)

myApp :: MonadBaseControl IO m => m (WebSocketsApp m Input Output)

myApp = do

  countRef <- liftIO $ newIORef 0

  emitter <- liftIO $ newIORef (Nothing :: Async ())

  let killEmitter = do

        mThread <- liftIO $ readIORef emitter

        case mThread of

          Nothing -> pure ()

          Just thread -> cancel thread

  pure WebSocketsApp

    { onOpen = \WebSocketsAppParams{send} ->

        liftBaseWith $ \runInBase -> do

          thread <- async $ forever $ do

            count <- readIORef countRef

            runInBase $ send $ Value count

            threadDelay 1000000 -- every second, emit the current value

          writeIORef emitter (Just thread)

    , onReceive = \WebSocketsAppParams{send,close} x -> do

        count <- liftIO $

          ( modifyIORef countRef $ case x of

              Increment -> (+ 1)

              Decrement -> (-) 1

          ) *> readIORef countRef

        if count >= 10 || count <= -10

          then close

          else send (Value count)

    , onClose = \mReason -> do

        killEmitter

        case mReason of

          Nothing -> liftIO $ writeIORef countRef 0

          Just _ -> pure ()

    }

```