Can we make this library more abstract?

[krutoo]

Hi, i want to use this library with not only IncomingMessage instances.

Node.js 16+ has Fetch API now and it has global constructors such as Request, Response, Headers and other.

Also i see that implementation of this library uses only headers field from req parameter.

Idea 1

Maybe we can make this library more abstract, for example we can make next interface changes:

// it is just a variant of interface
declare function accepts(getHeader: (headerName: string) => string | null): Accepts

With this interface we can use this library with instance of any class:

const req1 = new IncomingMessage(/* ... */);
const result1 = accepts(headerName => req1.getHeader(headerName));

const req2 = new Request(/* ... */)
const result2 = accepts(headerName => req2.headers.get(headerName))

Idea 2

Incoming message already has getHeader method, we can make interface like:

declare function accepts(req: Pick<IncomingMessage, 'getHeader'>): Accepts

And then we can use it now too for IncomingMessage:

const req = new IncomingMessage(/* ... */);

// no changes in usage
const accept = accepts(req);

And also we can use it easy with Request instance or any other request value:

const req = new Request(/* ... */);

// easy making wrapper object for use with Request
const accept = accepts({
  getHeader: headerName => req.headers.get(headerName)
});

Idea 3

Maybe we can make just TypeScript types of this library more abstract, for example:

declare function accepts(req: Pick<IncomingMessage, 'headers'>): Accepts