IORef (Map UserId (TChan Text))

Connect.hs

getConnectR :: Handler ()
getConnectR = do
    mUserId <- maybeAuthId
    maybe notAuthenticated connectToWebSocket mUserId
    where connectToWebSocket :: UserId -> Handler ()
          connectToWebSocket userId = do
              webSockets (serverEventSocket userId)
              return () -- return 426 (https://httpstatuses.com/426) (https://stackoverflow.com/questions/42324473/http-1-1-426-upgrade-required)
          serverEventSocket :: UserId -> WebSocketsT Handler ()
          serverEventSocket userId = do
              wChan <- findOrCreateWChan userId
              rChan <- atomically $ dupTChan wChan
              forever $ atomically (readTChan rChan) >>= sendTextData
          findOrCreateWChan :: UserId -> WebSocketsT Handler (TChan Text)
          findOrCreateWChan userId = do
              ioRefChanDir <- channels <$> getYesod
              tChanDir <- readIORef ioRefChanDir
              let mTChan = lookup userId tChanDir
              maybe (createNewChan userId ioRefChanDir) return mTChan
          createNewChan :: UserId -> IORef (Map UserId (TChan Text)) -> WebSocketsT Handler (TChan Text)
          createNewChan userId ioRefChanDir = do
              tChan <- newBroadcastTChanIO
              atomicModifyIORef' ioRefChanDir (\dir -> (Map.insert userId tChan dir, tChan))