How to use multiple handlers for the same route depending on accept header?

[Grafcube]

Summary

Say I have the route /user with two handlers. I want to use get_user_data if the accept header is set to application/json and user_page otherwise. How do I do this?

My current set up uses a separate router with ValidateRequestHeaderLayer for multiple routes and those same routes are defined again outside that nested router. The problem is that it panics because the route has already been registered.

let apub_router = Router::new()
    .route("/user/:id", get(get_user))
    .route_layer(ValidateRequestHeaderLayer::accept(FEDERATION_CONTENT_TYPE));

let app = Router::new()
    .leptos_routes_with_context( // This generates /user/:id which conflicts with `apub_router`
        &uiconf.leptos_options,
        routes,
        {
            let state = instance_metadata.clone();
            move || provide_context(state.clone())
        },
        App,
    )
    .with_state(uiconf.leptos_options.clone())
    .nest("/", apub_router)

Any help is appreciated!

axum version

0.7.7

[yanns]

A possibility is to handle this on the layer level: https://docs.rs/axum/latest/axum/response/index.html#returning-different-response-types

I don't know if you have many layers, and if it's a valid approach for you.

[yanns]

You could have something like:

async fn user_handler(...) -> Response {
  if accept_json(req) {
    user_json_handler(...)
  } else {
    user_html_handler(...)
  }
}

async fn user_html_handler(...) -> Response {
...
}

async fn user_json_handler(...) -> Response {
...
}

and have only the route /user using user_handler.
But I guess you don't like the boilerplate code.

[Grafcube]

I should have mentioned this in my original post, the html routes are being generated by leptos so I have no way to manually call it (that I know of). I only have the handler that needs to be behind the accept header.

[yanns]

Thanks for the clarification. I don't have more knowledge how you could get it.
Maybe someone else can help here.

[jplatte]

Can you update your question with some actual code snippets, indicating what is generated (unchangeable) then? And leave a comment on this thread once it's updated, as editing generally doesn't generate notifications.

[Grafcube]

I've edited my original post.

[mladedav]

This seems like another case similar to #1654

What you can do now is nesting the router under a prefix and then use middleware around the Router to rewrite the URL by prepending the same prefix based on your headers.

[Grafcube]

This worked for me, thanks!

let app = Router::new()
    .leptos_routes_with_context(
        &uiconf.leptos_options,
        routes,
        {
            let state = instance_metadata.clone();
            move || provide_context(state.clone())
        },
        App,
    )
    .with_state(uiconf.leptos_options.clone())
    .nest("/apub", apub_router)

let apub_middleware = axum::middleware::map_request(apub_middleware);
let app = apub_middleware.layer(app);
let app = ServiceExt::<Request>::into_make_service(app);

async fn apub_middleware<B>(mut request: Request<B>) -> Request<B> {
    if let Some(accept) = request.headers().get(ACCEPT) {
        if let Ok(accept) = accept.to_str() {
            if accept == FEDERATION_CONTENT_TYPE {
                let path = request.uri().path();
                if !path.starts_with("/apub") {
                    let new_path = Uri::builder()
                        .path_and_query(format!("/apub{}", path))
                        .build()
                        .unwrap();
                    *request.uri_mut() = new_path;
                }
            }
        }
    }
    request
}