{-|
A WAI adapter to the HTML5 Server-Sent Events API.
If running through a proxy like Nginx you might need to add the
headers:
> [ ("X-Accel-Buffering", "no"), ("Cache-Control", "no-cache")]
There is a small example using these functions in the @example@ directory.
-}
module Network.Wai.EventSource (
ServerEvent(..),
eventSourceAppChan,
eventSourceAppIO,
eventStreamAppRaw
) where
import Data.Function (fix)
import Control.Concurrent.Chan (Chan, dupChan, readChan)
import Control.Monad.IO.Class (liftIO)
import Network.HTTP.Types (status200, hContentType)
import Network.Wai (Application, responseStream)
import Network.Wai.EventSource.EventStream
-- | Make a new WAI EventSource application reading events from
-- the given channel.
eventSourceAppChan :: Chan ServerEvent -> Application
eventSourceAppChan chan req sendResponse = do
chan' <- liftIO $ dupChan chan
eventSourceAppIO (readChan chan') req sendResponse
-- | Make a new WAI EventSource application reading events from
-- the given IO action.
eventSourceAppIO :: IO ServerEvent -> Application
eventSourceAppIO src _ sendResponse =
sendResponse $ responseStream
status200
[(hContentType, "text/event-stream")]
$ \sendChunk flush -> do
flush
fix $ \loop -> do
se <- src
case eventToBuilder se of
Nothing -> return ()
Just b -> sendChunk b >> flush >> loop
-- | Make a new WAI EventSource application with a handler that emits events.
--
-- @since 3.0.28
eventStreamAppRaw :: ((ServerEvent -> IO()) -> IO () -> IO ()) -> Application
eventStreamAppRaw handler _ sendResponse =
sendResponse $ responseStream
status200
[(hContentType, "text/event-stream")]
$ \sendChunk flush -> handler (sendEvent sendChunk) flush
where
sendEvent sendChunk event =
case eventToBuilder event of
Nothing -> return ()
Just b -> sendChunk b