[ws] add options to transform client and server streams

[GertSallaerts]

A "light" alternative to #991. This simply allows us to pass in two options: createWsClientTransformStream and/or createWsServerTransformStream. Implementation of parsing and/or transforming the messages is left up to the user.

It's also a solution to #1203

[fanfare]

Is there any progress with this? I'd really like to implement this in something I'm working on, but can't really figure out how to manipulate the frames after a connection has been established.

[brickbite]

hi @GertSallaerts, wondering if you have an example of the function that returns a duplex stream (and an example of the duplex stream implementation). I'm testing this locally and trying to get it to work, but figuring out streams at the moment.

[GertSallaerts]

@brickbite the logic to set this up is not that straightforward so I created a separate repo for it. You can find it here: https://github.com/GertSallaerts/ws-transform-stream

I've not had time to complete the documentation or test the code yet, but I hope it can help you in the right direction.

It will probably be something along these lines for use with node-http-proxy

const http = require('http');
const { createProxyServer } = require('http-proxy');
const WsTransformStream = require('@gertt/ws-transform-stream');

const server = http.createServer();
const proxy = createProxyServer({});

function transform(message) {
    return message.toUpperCase();
}

function createWsClientTransformStream(req) {
    return WsTransformStream.fromUpgradeRequest(req, { transform });
};

server.on('upgrade', (req, socket, head) => {
    proxy.ws(req, socket, head, {
        /* ...yourOptions, */
        createWsClientTransformStream,
    });
});

server.listen(3000);

[brickbite]

@GertSallaerts thank you very much for the reference, I'll see if I can make anything of it

[fanfare]

Yes! can confirm it works. thanks so much @GertSallaerts

[GertSallaerts]

@fanfare @brickbite I published it on NPM as well in case you guys are interested in using it as a library. You're welcome to report any issues or suggestions on the GitHub repo.

[kindermax]

Hi, do you have any plans to merge this PR? This is quite a useful feature.

[claudio-viola]

merge please