Network.JavaScript.Services

Web Services

data Engine

An Engine is a handle to a specific JavaScript engine

Constructors

Engine

Fields

• sendJavaScript :: JavaScript -> IO ()
• genNonce :: IO Int
• replyBox :: Int -> IO (Either Value [Value])
• eventChan :: STM (Value, UTCTime)

start :: (Engine -> IO ()) -> Application -> Application

This accepts WebSocket requests, calls the callback with an Engine that can be used to access JavaScript.

addListener :: Engine -> (Value -> IO ()) -> IO ThreadId

Add a listener for events. There can be many. non-blocking.

From JavaScript, you can call event(..) to send values to this listener. Any valid JSON value can be sent.

listen :: Engine -> IO Value

listen for the next event. blocking.

From JavaScript, you can call event(..) to send values to this listener. Any valid JSON value can be sent.

readEventChan :: Engine -> STM (Value, UTCTime)

readEventChan uses STM to read the next event.

From JavaScript, you can call event(..) to send values to this channel. Any valid JSON value can be sent.

type Application = Request -> (Response -> IO ResponseReceived) -> IO ResponseReceived

The WAI application.

Note that, since WAI 3.0, this type is structured in continuation passing style to allow for proper safe resource handling. This was handled in the past via other means (e.g., ResourceT). As a demonstration:

app :: Application
app req respond = bracket_
    (putStrLn "Allocating scarce resource")
    (putStrLn "Cleaning up")
    (respond $ responseLBS status200 [] "Hello World")