Show how to implement proper CORS support in Stardog (stardog.com) using a Node.js example

testCORS.js

/* ISSUE: Stardog (up to v1.1.3) does not properly support CORS[1] interaction.
    The issue is two-fold:
    1) Stardog tries to authenticated the OPTIONS "pre-flight" request.
    2) Stardog doesn't return CORS headers, hence can only be accessed 
       by browser web apps running in a different domain via a proxy.

Effected browsers: Firefox and IE*. Safari and Chrome work due to a bug in webkit (see [2]).

Expected behavior: Stardog MUST NOT try to authenticate the pre-flight request, it SHOULD rather return 
proper CORS headers. [4]

As pers CORS spec: if the pre-flight request fails (response code != 200), the original request will not be sent.
For security reasons, browsers will not send any authentication information or custom HTTP headers in the pre-flight request.

[1] https://dvcs.w3.org/hg/cors/raw-file/tip/Overview.html 
[2] https://bugzilla.mozilla.org/show_bug.cgi?id=778548
[3] https://bugzilla.mozilla.org/show_bug.cgi?id=778548#c5
[4] https://dvcs.w3.org/hg/cors/raw-file/tip/Overview.html#preflight-request

This is an example implementation to demostrate how should Stardog work in a CORS scenario 

Run it:

> node testCORS.js

*/

var http = require('http');

/* Always add these CORS headers to the response */
function addCORSHeaders(res) {
    res.setHeader("Access-Control-Allow-Headers","accept, Authorization,  origin, sd-connection-string");
    res.setHeader("Access-Control-Allow-Methods","OPTIONS, GET");
    res.setHeader("Access-Control-Allow-Origin","*");
}

var server = http.createServer(function(req, res){
    console.log('Connection');
    /* Browsers will send a "pre-flight" HTTP request and scan the response for CORS headers. 
       The pre-flight OPTIONS request MUST NOT be authenticated.
    */
  if (req.method == "OPTIONS") {
		console.log('Preflight request OPTIONS received');
		
		res.setHeader('Content-Type', 'text/plain')
		addCORSHeaders(res);
		
		res.writeHead(200);
		
		res.end();	
	} else {
	    /* Regular requests MAY be authenticated. */
		if (req.headers['authorization']) {
		    console.log('Authorization header received: '+req.headers['authorization']);
		    res.setHeader('Content-Type', 'application/sparql-results+json')
			addCORSHeaders(res);

			res.writeHead(200);
    		res.write(JSON.stringify({"head": {"vars": [ "name" ]}, "results": {
						"bindings": [
							{"name": { "type": "literal", "xml:lang": "en", "value": "DMP-BDT310 3D Blu-ray Player" }}, 
							{"name": { "type": "literal", "xml:lang": "en", "value": "DVP-SR350"}}]}}));
    		
			res.end();
		} else {
		    res.setHeader('Content-Type', 'text/plain')
		    res.setHeader('WWW-Authenticate','BASIC realm="Stardog"');
			addCORSHeaders(res);

			res.writeHead(401);
			res.end();
		}
		    
	}
});

server.listen('8088');
console.log("HTTP Server started on http://localhost:8088");