Use with Express on server

[tvedtorama]

Hi,

I wanted to test the webrtc-swarm library and needed a signalhub server for that purpose.

I was not sure the server.js file would work nicely alongside my existing setup, so I made a version that produces an Express router. The code is just a quick mock up, but it works for my purpose:

(Note: Code is in Typescript)

import * as express from 'express'
const collect = require('stream-collector')
const pump = require('pump')
const iterate = require('random-iterate')
const limiter = require('size-limit-stream')
const eos = require('end-of-stream')

const flushHeaders = function (res) {
	if (res.flushHeaders) {
		res.flushHeaders()
	} else {
		if (!res._header) res._implicitHeader()
		res._send('')
	}
}

/** Set up a signalhub logic primarliy for webrtc-swarm, allowing the client to send and receive
 * on channels "all" and "user-specific" (the uuid).
 *
 * Code migrated from https://github.com/mafintosh/signalhub/blob/master/server.js
 */
export const getHubRouter = function (opts: { maxBroadcasts?: number, rootName: string }) {
	let channels = {}
	let maxBroadcasts = (opts && opts.maxBroadcasts) || Infinity
	let subs = 0

	const router = express.Router()

	const findName = (req: express.Request) => req.params["app"] + "/" + req.params["channel"]

	/** channel = "app/channel" */
	const getAppChannel = function (channel: string) {
		if (channels[channel]) return channels[channel]
		const sub = { name: channel, subscribers: [], heartbeat: null }
		sub.heartbeat = setInterval(heartbeater(sub), 30 * 1000)
		channels[channel] = sub
		return channels[channel]
	}

	router.post("/v1/:app/:channel", (req, res) => {
		collect(pump(req, limiter(64 * 1024)), function (err, data) {
			if (err) return res.end()
			const name = findName(req)
			if (!channels[name]) return res.end()
			const channel = getAppChannel(name)

			data = Buffer.concat(data).toString()

			let ite = iterate(channel.subscribers)
			let next
			let cnt = 0

			while ((next = ite()) && cnt++ < maxBroadcasts) {
				next.write('data: ' + data + '\n\n')
			}

			res.end()
		})
	})

	router.get("/v1/:app/:channel", (req, res) => {
		res.setHeader('Content-Type', 'text/event-stream; charset=utf-8')

		const name = findName(req)
		const app = name.split('/')[0]
		const channelNames = name.slice(app.length + 1)

		channelNames.split(',').forEach(function (channelName) {
			const channel = getAppChannel(app + '/' + channelName)
			channel.subscribers.push(res)
			subs++
			eos(res, function () {
				subs--
				let i = channel.subscribers.indexOf(res)
				if (i > -1) channel.subscribers.splice(i, 1)
				if (!channel.subscribers.length && channel === channels[channel.name]) {
					clearInterval(channel.heartbeat)
					delete channels[channel.name]
				}
			})
		})

		flushHeaders(res)
	})
	return router
}

function heartbeater(sub) {
	return function () {
		for (let i = 0; i < sub.subscribers.length; i++) {
			sub.subscribers[i].write(':heartbeat signal\n\n')
		}
	}
}

Then i hooked it up this way:

	app.use('/signalhub/', getHubRouter({rootName: '/signalhub/'})) // No body parser!

	// Existing setup...
	app.use(bodyParser.urlencoded({ extended: true }))
	app.use(bodyParser.json())

	app.use('/', eventRouter)
	app.use('/', router)