How to determine http vs https in nodejs / nextjs api handler - node.js

Question

In order to properly build my urls in my xml sitemaps and rss feeds I want to determine if the webpage is currently served over http or https, so it also works locally in development.
export default function handler(req, res) {
const host = req.headers.host;
const proto = req.connection.encrypted ? "https" : "http";
//construct url for xml sitemaps
}
With above code however also on Vercel it still shows as being served over http. I would expect it to run as https. Is there a better way to figure out http vs https?

Answer 1

As Next.js api routes run behind a proxy which is offloading to http the protocol is http.
By changing the code to the following I was able to first check at what protocol the proxy runs.
const proto = req.headers["x-forwarded-proto"];
However this will break the thing in development where you are not running behind a proxy, or a different way of deploying the solution that might also not involve a proxy. To support both use cases I eventually ended up with the following code.
const proto =
req.headers["x-forwarded-proto"] || req.connection.encrypted
? "https"
: "http";
Whenever the x-forwarded-proto header is not present (undefined) we fall back to req.connection.encrypted to determine if we should serve on http vs https.
Now it works on localhost as well a Vercel deployment.

Answer 2

my solution:
export const getServerSideProps: GetServerSideProps = async (context: any) => {
// Fetch data from external API
const reqUrl = context.req.headers["referer"];
const url = new URL(reqUrl);
console.log('====================================');
console.log(url.protocol); // http
console.log('====================================');
// const res = await fetch(`${origin}/api/projets`)
// const data = await res.json()
// Pass data to the page via props
return { props: { data } }
}