miden-node-utils 0.16.0-rc.2

use std::net::{IpAddr, SocketAddr};
use std::task::{Context as TaskContext, Poll};

use tower::{Layer, Service};
use tower_governor::GovernorError;
use tower_governor::key_extractor::{KeyExtractor, SmartIpKeyExtractor};

/// The originating client IP, resolved by [`ResolveClientIpLayer`] and stored in a request's
/// extensions.
///
/// gRPC handlers can read this via `ClientIp::from_extensions(request.extensions())` to obtain the
/// load-balancer-aware client address without re-implementing IP extraction.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct ClientIp(pub IpAddr);

impl ClientIp {
    /// Returns the client IP resolved into `extensions` by [`ResolveClientIpLayer`], or `None` if
    /// it could not be determined.
    pub fn from_extensions(extensions: &http::Extensions) -> Option<IpAddr> {
        extensions.get::<Self>().map(|ip| ip.0)
    }
}

/// A [`tower::Layer`] that resolves the originating client IP and stores it in the request's
/// extensions as [`ClientIp`].
///
/// IP resolution reuses [`GrpcIpExtractor`], so clients behind a load balancer or reverse proxy are
/// identified by their forwarded IP (via `X-Forwarded-For` / `X-Real-Ip` / `Forwarded` headers),
/// falling back to the peer address. Resolving once at the transport layer lets handlers read the
/// result instead of re-deriving it.
#[derive(Debug, Clone, Copy, Default)]
pub struct ResolveClientIpLayer;

impl<S> Layer<S> for ResolveClientIpLayer {
    type Service = ResolveClientIp<S>;

    fn layer(&self, inner: S) -> Self::Service {
        ResolveClientIp { inner }
    }
}

/// The service produced by [`ResolveClientIpLayer`].
#[derive(Debug, Clone, Copy)]
pub struct ResolveClientIp<S> {
    inner: S,
}

impl<S, B> Service<http::Request<B>> for ResolveClientIp<S>
where
    S: Service<http::Request<B>>,
{
    type Response = S::Response;
    type Error = S::Error;
    type Future = S::Future;

    fn poll_ready(&mut self, cx: &mut TaskContext<'_>) -> Poll<Result<(), Self::Error>> {
        self.inner.poll_ready(cx)
    }

    fn call(&mut self, mut request: http::Request<B>) -> Self::Future {
        if let Ok(ip) = GrpcIpExtractor::default().extract(&request) {
            request.extensions_mut().insert(ClientIp(ip));
        }
        self.inner.call(request)
    }
}

/// Wraps [`SmartIpKeyExtractor`] by providing a fallback to the client IP address provided by the
/// gRPC transport.
///
/// [`SmartIpKeyExtractor`]'s own fallback of checking the peer IP directly fails because we are in
/// a gRPC transport and not the typical `SocketAddr` as it expects.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct GrpcIpExtractor(SmartIpKeyExtractor);

impl Default for GrpcIpExtractor {
    fn default() -> Self {
        Self(SmartIpKeyExtractor)
    }
}

impl GrpcIpExtractor {
    #[expect(clippy::result_large_err, reason = "this is a third party error type")]
    fn extract_tonic_address<T>(
        request: &http::Request<T>,
    ) -> Result<<Self as KeyExtractor>::Key, GovernorError> {
        request
            .extensions()
            .get::<tonic::transport::server::TcpConnectInfo>()
            .and_then(tonic::transport::server::TcpConnectInfo::remote_addr)
            .as_ref()
            .map(SocketAddr::ip)
            .ok_or(GovernorError::UnableToExtractKey)
    }
}

impl KeyExtractor for GrpcIpExtractor {
    type Key = IpAddr;

    #[expect(clippy::result_large_err, reason = "error type is dictated by tower-governor")]
    fn extract<T>(
        &self,
        request: &http::Request<T>,
    ) -> Result<Self::Key, tower_governor::GovernorError> {
        self.0.extract(request).or_else(|_| Self::extract_tonic_address(request))
    }
}