Implement onConnect

[jmatsushita]

Description of the change

This PR allows to use the "connect" event which can be useful to implement an http proxy server. Following the example from the nodeJS documentation https://nodejs.org/api/http.html#http_event_connect

respond :: Request -> Response -> Effect Unit
respond req res = do
  setStatusCode res 200
  setHeader res "Content-Type" "text/plain"

main :: Effect Unit
main = do
  proxy <- createServer respond
  listen proxy { hostname: "localhost", port: 3030, backlog: Nothing} $ void do
    log "Listening on port 3030"
    onConnect proxy $ \req clientSocket head -> void do
      log (requestMethod req <> " " <> requestURL req)
      logShow $ requestHeaders req
      let url = parse $ "http://" <> requestURL req
      logShow url 
      case (toMaybe url.port), (toMaybe url.hostname) of
        Just stringPort, Just host -> case fromString stringPort of
          Just port -> do
            serverSocket <- Socket.createConnectionTCP port host do
                infoShow $ "CONNECT " <> host

            Socket.onConnect serverSocket do
              -- infoShow { _message: "Socket connected" }
              void $ Socket.writeString clientSocket 
                ("HTTP/1.1 200 Connection Established\r\n" <>
                "Proxy-agent: Node.js-Proxy\r\n" <>
                "\r\n") UTF8 $ pure unit
              void $ Socket.write serverSocket head $ pure unit
              void $ Socket.onData serverSocket $ case _ of
                Left buffer -> void $ Socket.write clientSocket buffer $ pure unit
                Right string -> void $ Socket.writeString clientSocket string UTF8 $ pure unit
              void $ Socket.onData clientSocket $ case _ of
                Left buffer -> void $ Socket.write serverSocket buffer $ pure unit
                Right string -> void $ Socket.writeString serverSocket string UTF8 $ pure unit
            Socket.onError serverSocket \err -> do
              infoShow { _message: "Server had an error", err }
            Socket.onError clientSocket \err -> do
              infoShow { _message: "Client had an error", err }
          _ -> log "port is not a string"
        _,_ -> log "port or hosts error"

No tests yet!

---

Checklist:

• Added the change to the changelog's "Unreleased" section with a reference to this PR (e.g. "- Made a change (#0000)")
• Linked any existing issues or proposals that this pull request should close
• Updated or added relevant documentation
• Added a test for the contribution (if applicable)

[JordanMartinez]

Not sure what the CI error was, but I've restarted it.

Code looks fine otherwise.

[thomashoneyman]

The test failure is just that the tests don't terminate (which we should fix!). See also:

• Ensure that tests terminate #35
• Disable tests in CI #39