Functions typing (server code)

Taking this example on how to build a Function in JS from the docs:

export default async ({ req, res, log }) => {

    switch (req.query.type) {
        case 'empty': 
            return res.empty();
        case 'json':
            return res.json({"type": "This is a JSON response"});
        case 'redirect':
            return res.redirect("https://appwrite.io", 301);
        case 'html':
            return res.send(
                "<h1>This is an HTML response</h1>", 200, {
                    "content-type": "text/html"
                });
        default:
            return res.send("This is a text response");
    }
}

I wonder if there's some documentation on the typing of req, res and log? Or even better a dependency I can pull in for it... I actually develop in TypeScript and use Bun for execution, and not having any typing is hard. E.g. can I pass a status code to res.json()? Which parameter would it be? Will it always be the second one? Can I always send headers on the third parameter? What's the fourth parameter?

I found a comment in one of the projects, which hints to types, but it's a comment (not code or types) and it's not complete: https://github.com/appwrite/functions-starter/blob/main/node-18.0/src/index.js