lightweight proxy made in node.js to avoid cors issues when working with holochain and React.js. Became useless with the usage of the "proxy" option in the "dna.json" file. Preserved for educational purposes since it handles several important concepts for begginers.

proxy.js

const http = require('http'),
	url = require('url')

const PORT = 3939

const allowedSources = [
	'::1',
	'localhost',
	/^127\.0\.0\.\d\d?\d?$/
]

function isAllowed(address) {
	for (var i = allowedSources.length - 1; i >= 0; i--) {
		let a = allowedSources[i]
		if( (typeof a === 'string' && a === address) || (a instanceof RegExp && a.test(address)) ) {
			return true
		}
	}
	return false
}


function postData(data,path) {
	return new Promise((succ,error) => {
		const postheaders = {
			'Content-Type' : 'application/json',
			'Content-Length' : Buffer.byteLength(data)
		}
		const optionspost = {
			host : 'localhost',
			port : 4141,
			path : path,
			method : 'POST',
			headers : postheaders
		}
		let result = ''
		let reqPost = http.request(optionspost, function(res) {
			res.on('data' , function( d ) { result += d })
			res.on('end'  , function( ) { succ(result) })
		})
		// write the json data
		reqPost.write(data)
		reqPost.end()
		reqPost.on('error', function(e) {
			error(e)
		})
	})
}

const server = http.createServer(async (req, res) => {
	if (!isAllowed(res.socket.remoteAddress)) {
		res.writeHead(400, {
			'Content-Length': 16,
			'Content-Type': 'text/plain'
		})
		res.end('400. Bad Request')
		return
	}
	res.setHeader('Access-Control-Allow-Origin', 'http://localhost:3000')
	let params = url.parse(req.url,true).query
	if (!params.path) {
		res.end('')
		return
	}
	const body = await postData( params.data , params.path )
	const content_length = body.length

	res.writeHead(200, {
		'Content-Length': content_length,
		'Content-Type': 'text/plain'
	})
 
	res.end(body)
})

function successServer() {
	console.log('Server is running on port 3939')
}

server.listen(PORT,successServer)

server.on('error', (e) => {
	if (e.code === 'EADDRINUSE') {
		console.log('Address in use, retrying...')
		setTimeout(() => {
			server.close()
			server.listen(PORT,successServer)
		}, 1000)
	}else{
		console.log('unknown error ' + e.code)
		console.log('Quitting...')
	}
})