sct(component): Add anchor_by_height rpc method (#4250)

## Describe your changes
This PR adds a `anchor_by_height` method to the
[`SctQueryService`](https://github.com/penumbra-zone/penumbra/tree/main/crates/core/component/sct/src/component/rpc.rs).

## Issue ticket number and link
Closes #4153

## Checklist before requesting a review

- [x] If this code contains consensus-breaking changes, I have added the
"consensus-breaking" label. Otherwise, I declare my belief that there
are not consensus-breaking changes, for the following reason:

> This is an added rpc method for consumer convenience. It prevents
consumers from being forced to perform raw KV queries against the chain
state.

crates/core/component/sct/src/component/rpc.rs

@@ -1,10 +1,13 @@
 use cnidarium::Storage;
 use penumbra_proto::core::component::sct::v1::query_service_server::QueryService;
-use penumbra_proto::core::component::sct::v1::{EpochByHeightRequest, EpochByHeightResponse};
+use penumbra_proto::core::component::sct::v1::{
+    AnchorByHeightRequest, AnchorByHeightResponse, EpochByHeightRequest, EpochByHeightResponse,
+};
 use tonic::Status;
 use tracing::instrument;
 
 use super::clock::EpochRead;
+use super::tree::SctRead;
 
 // TODO: Hide this and only expose a Router?
 pub struct Server {
@@ -35,4 +38,21 @@ impl QueryService for Server {
             epoch: Some(epoch.into()),
         }))
     }
+
+    #[instrument(skip(self, request))]
+    async fn anchor_by_height(
+        &self,
+        request: tonic::Request<AnchorByHeightRequest>,
+    ) -> Result<tonic::Response<AnchorByHeightResponse>, Status> {
+        let state = self.storage.latest_snapshot();
+
+        let height = request.get_ref().height;
+        let anchor = state.get_anchor_by_height(height).await.map_err(|e| {
+            tonic::Status::unknown(format!("could not get anchor for height {height}: {e}"))
+        })?;
+
+        Ok(tonic::Response::new(AnchorByHeightResponse {
+            anchor: anchor.map(Into::into),
+        }))
+    }
 }

crates/proto/src/gen/penumbra.core.component.sct.v1.rs

@@ -299,6 +299,34 @@ impl ::prost::Name for EpochByHeightResponse {
         ::prost::alloc::format!("penumbra.core.component.sct.v1.{}", Self::NAME)
     }
 }
+#[allow(clippy::derive_partial_eq_without_eq)]
+#[derive(Clone, PartialEq, ::prost::Message)]
+pub struct AnchorByHeightRequest {
+    #[prost(uint64, tag = "1")]
+    pub height: u64,
+}
+impl ::prost::Name for AnchorByHeightRequest {
+    const NAME: &'static str = "AnchorByHeightRequest";
+    const PACKAGE: &'static str = "penumbra.core.component.sct.v1";
+    fn full_name() -> ::prost::alloc::string::String {
+        ::prost::alloc::format!("penumbra.core.component.sct.v1.{}", Self::NAME)
+    }
+}
+#[allow(clippy::derive_partial_eq_without_eq)]
+#[derive(Clone, PartialEq, ::prost::Message)]
+pub struct AnchorByHeightResponse {
+    #[prost(message, optional, tag = "1")]
+    pub anchor: ::core::option::Option<
+        super::super::super::super::crypto::tct::v1::MerkleRoot,
+    >,
+}
+impl ::prost::Name for AnchorByHeightResponse {
+    const NAME: &'static str = "AnchorByHeightResponse";
+    const PACKAGE: &'static str = "penumbra.core.component.sct.v1";
+    fn full_name() -> ::prost::alloc::string::String {
+        ::prost::alloc::format!("penumbra.core.component.sct.v1.{}", Self::NAME)
+    }
+}
 /// Generated client implementations.
 #[cfg(feature = "rpc")]
 pub mod query_service_client {
@@ -386,6 +414,36 @@ pub mod query_service_client {
             self.inner = self.inner.max_encoding_message_size(limit);
             self
         }
+        pub async fn anchor_by_height(
+            &mut self,
+            request: impl tonic::IntoRequest<super::AnchorByHeightRequest>,
+        ) -> std::result::Result<
+            tonic::Response<super::AnchorByHeightResponse>,
+            tonic::Status,
+        > {
+            self.inner
+                .ready()
+                .await
+                .map_err(|e| {
+                    tonic::Status::new(
+                        tonic::Code::Unknown,
+                        format!("Service was not ready: {}", e.into()),
+                    )
+                })?;
+            let codec = tonic::codec::ProstCodec::default();
+            let path = http::uri::PathAndQuery::from_static(
+                "/penumbra.core.component.sct.v1.QueryService/AnchorByHeight",
+            );
+            let mut req = request.into_request();
+            req.extensions_mut()
+                .insert(
+                    GrpcMethod::new(
+                        "penumbra.core.component.sct.v1.QueryService",
+                        "AnchorByHeight",
+                    ),
+                );
+            self.inner.unary(req, path, codec).await
+        }
         pub async fn epoch_by_height(
             &mut self,
             request: impl tonic::IntoRequest<super::EpochByHeightRequest>,
@@ -426,6 +484,13 @@ pub mod query_service_server {
     /// Generated trait containing gRPC methods that should be implemented for use with QueryServiceServer.
     #[async_trait]
     pub trait QueryService: Send + Sync + 'static {
+        async fn anchor_by_height(
+            &self,
+            request: tonic::Request<super::AnchorByHeightRequest>,
+        ) -> std::result::Result<
+            tonic::Response<super::AnchorByHeightResponse>,
+            tonic::Status,
+        >;
         async fn epoch_by_height(
             &self,
             request: tonic::Request<super::EpochByHeightRequest>,
@@ -514,6 +579,52 @@ pub mod query_service_server {
         fn call(&mut self, req: http::Request<B>) -> Self::Future {
             let inner = self.inner.clone();
             match req.uri().path() {
+                "/penumbra.core.component.sct.v1.QueryService/AnchorByHeight" => {
+                    #[allow(non_camel_case_types)]
+                    struct AnchorByHeightSvc<T: QueryService>(pub Arc<T>);
+                    impl<
+                        T: QueryService,
+                    > tonic::server::UnaryService<super::AnchorByHeightRequest>
+                    for AnchorByHeightSvc<T> {
+                        type Response = super::AnchorByHeightResponse;
+                        type Future = BoxFuture<
+                            tonic::Response<Self::Response>,
+                            tonic::Status,
+                        >;
+                        fn call(
+                            &mut self,
+                            request: tonic::Request<super::AnchorByHeightRequest>,
+                        ) -> Self::Future {
+                            let inner = Arc::clone(&self.0);
+                            let fut = async move {
+                                <T as QueryService>::anchor_by_height(&inner, request).await
+                            };
+                            Box::pin(fut)
+                        }
+                    }
+                    let accept_compression_encodings = self.accept_compression_encodings;
+                    let send_compression_encodings = self.send_compression_encodings;
+                    let max_decoding_message_size = self.max_decoding_message_size;
+                    let max_encoding_message_size = self.max_encoding_message_size;
+                    let inner = self.inner.clone();
+                    let fut = async move {
+                        let inner = inner.0;
+                        let method = AnchorByHeightSvc(inner);
+                        let codec = tonic::codec::ProstCodec::default();
+                        let mut grpc = tonic::server::Grpc::new(codec)
+                            .apply_compression_config(
+                                accept_compression_encodings,
+                                send_compression_encodings,
+                            )
+                            .apply_max_message_size_config(
+                                max_decoding_message_size,
+                                max_encoding_message_size,
+                            );
+                        let res = grpc.unary(method, req).await;
+                        Ok(res)
+                    };
+                    Box::pin(fut)
+                }
                 "/penumbra.core.component.sct.v1.QueryService/EpochByHeight" => {
                     #[allow(non_camel_case_types)]
                     struct EpochByHeightSvc<T: QueryService>(pub Arc<T>);

crates/proto/src/gen/penumbra.core.component.sct.v1.serde.rs

@@ -1,3 +1,196 @@
+impl serde::Serialize for AnchorByHeightRequest {
+    #[allow(deprecated)]
+    fn serialize<S>(&self, serializer: S) -> std::result::Result<S::Ok, S::Error>
+    where
+        S: serde::Serializer,
+    {
+        use serde::ser::SerializeStruct;
+        let mut len = 0;
+        if self.height != 0 {
+            len += 1;
+        }
+        let mut struct_ser = serializer.serialize_struct("penumbra.core.component.sct.v1.AnchorByHeightRequest", len)?;
+        if self.height != 0 {
+            #[allow(clippy::needless_borrow)]
+            struct_ser.serialize_field("height", ToString::to_string(&self.height).as_str())?;
+        }
+        struct_ser.end()
+    }
+}
+impl<'de> serde::Deserialize<'de> for AnchorByHeightRequest {
+    #[allow(deprecated)]
+    fn deserialize<D>(deserializer: D) -> std::result::Result<Self, D::Error>
+    where
+        D: serde::Deserializer<'de>,
+    {
+        const FIELDS: &[&str] = &[
+            "height",
+        ];
+
+        #[allow(clippy::enum_variant_names)]
+        enum GeneratedField {
+            Height,
+            __SkipField__,
+        }
+        impl<'de> serde::Deserialize<'de> for GeneratedField {
+            fn deserialize<D>(deserializer: D) -> std::result::Result<GeneratedField, D::Error>
+            where
+                D: serde::Deserializer<'de>,
+            {
+                struct GeneratedVisitor;
+
+                impl<'de> serde::de::Visitor<'de> for GeneratedVisitor {
+                    type Value = GeneratedField;
+
+                    fn expecting(&self, formatter: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+                        write!(formatter, "expected one of: {:?}", &FIELDS)
+                    }
+
+                    #[allow(unused_variables)]
+                    fn visit_str<E>(self, value: &str) -> std::result::Result<GeneratedField, E>
+                    where
+                        E: serde::de::Error,
+                    {
+                        match value {
+                            "height" => Ok(GeneratedField::Height),
+                            _ => Ok(GeneratedField::__SkipField__),
+                        }
+                    }
+                }
+                deserializer.deserialize_identifier(GeneratedVisitor)
+            }
+        }
+        struct GeneratedVisitor;
+        impl<'de> serde::de::Visitor<'de> for GeneratedVisitor {
+            type Value = AnchorByHeightRequest;
+
+            fn expecting(&self, formatter: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+                formatter.write_str("struct penumbra.core.component.sct.v1.AnchorByHeightRequest")
+            }
+
+            fn visit_map<V>(self, mut map_: V) -> std::result::Result<AnchorByHeightRequest, V::Error>
+                where
+                    V: serde::de::MapAccess<'de>,
+            {
+                let mut height__ = None;
+                while let Some(k) = map_.next_key()? {
+                    match k {
+                        GeneratedField::Height => {
+                            if height__.is_some() {
+                                return Err(serde::de::Error::duplicate_field("height"));
+                            }
+                            height__ = 
+                                Some(map_.next_value::<::pbjson::private::NumberDeserialize<_>>()?.0)
+                            ;
+                        }
+                        GeneratedField::__SkipField__ => {
+                            let _ = map_.next_value::<serde::de::IgnoredAny>()?;
+                        }
+                    }
+                }
+                Ok(AnchorByHeightRequest {
+                    height: height__.unwrap_or_default(),
+                })
+            }
+        }
+        deserializer.deserialize_struct("penumbra.core.component.sct.v1.AnchorByHeightRequest", FIELDS, GeneratedVisitor)
+    }
+}
+impl serde::Serialize for AnchorByHeightResponse {
+    #[allow(deprecated)]
+    fn serialize<S>(&self, serializer: S) -> std::result::Result<S::Ok, S::Error>
+    where
+        S: serde::Serializer,
+    {
+        use serde::ser::SerializeStruct;
+        let mut len = 0;
+        if self.anchor.is_some() {
+            len += 1;
+        }
+        let mut struct_ser = serializer.serialize_struct("penumbra.core.component.sct.v1.AnchorByHeightResponse", len)?;
+        if let Some(v) = self.anchor.as_ref() {
+            struct_ser.serialize_field("anchor", v)?;
+        }
+        struct_ser.end()
+    }
+}
+impl<'de> serde::Deserialize<'de> for AnchorByHeightResponse {
+    #[allow(deprecated)]
+    fn deserialize<D>(deserializer: D) -> std::result::Result<Self, D::Error>
+    where
+        D: serde::Deserializer<'de>,
+    {
+        const FIELDS: &[&str] = &[
+            "anchor",
+        ];
+
+        #[allow(clippy::enum_variant_names)]
+        enum GeneratedField {
+            Anchor,
+            __SkipField__,
+        }
+        impl<'de> serde::Deserialize<'de> for GeneratedField {
+            fn deserialize<D>(deserializer: D) -> std::result::Result<GeneratedField, D::Error>
+            where
+                D: serde::Deserializer<'de>,
+            {
+                struct GeneratedVisitor;
+
+                impl<'de> serde::de::Visitor<'de> for GeneratedVisitor {
+                    type Value = GeneratedField;
+
+                    fn expecting(&self, formatter: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+                        write!(formatter, "expected one of: {:?}", &FIELDS)
+                    }
+
+                    #[allow(unused_variables)]
+                    fn visit_str<E>(self, value: &str) -> std::result::Result<GeneratedField, E>
+                    where
+                        E: serde::de::Error,
+                    {
+                        match value {
+                            "anchor" => Ok(GeneratedField::Anchor),
+                            _ => Ok(GeneratedField::__SkipField__),
+                        }
+                    }
+                }
+                deserializer.deserialize_identifier(GeneratedVisitor)
+            }
+        }
+        struct GeneratedVisitor;
+        impl<'de> serde::de::Visitor<'de> for GeneratedVisitor {
+            type Value = AnchorByHeightResponse;
+
+            fn expecting(&self, formatter: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+                formatter.write_str("struct penumbra.core.component.sct.v1.AnchorByHeightResponse")
+            }
+
+            fn visit_map<V>(self, mut map_: V) -> std::result::Result<AnchorByHeightResponse, V::Error>
+                where
+                    V: serde::de::MapAccess<'de>,
+            {
+                let mut anchor__ = None;
+                while let Some(k) = map_.next_key()? {
+                    match k {
+                        GeneratedField::Anchor => {
+                            if anchor__.is_some() {
+                                return Err(serde::de::Error::duplicate_field("anchor"));
+                            }
+                            anchor__ = map_.next_value()?;
+                        }
+                        GeneratedField::__SkipField__ => {
+                            let _ = map_.next_value::<serde::de::IgnoredAny>()?;
+                        }
+                    }
+                }
+                Ok(AnchorByHeightResponse {
+                    anchor: anchor__,
+                })
+            }
+        }
+        deserializer.deserialize_struct("penumbra.core.component.sct.v1.AnchorByHeightResponse", FIELDS, GeneratedVisitor)
+    }
+}
 impl serde::Serialize for CommitmentSource {
     #[allow(deprecated)]
     fn serialize<S>(&self, serializer: S) -> std::result::Result<S::Ok, S::Error>

proto/penumbra/penumbra/core/component/sct/v1/sct.proto

@@ -109,7 +109,16 @@ message EpochByHeightResponse {
   Epoch epoch = 1;
 }
 
+message AnchorByHeightRequest {
+  uint64 height = 1;
+}
+
+message AnchorByHeightResponse {
+  crypto.tct.v1.MerkleRoot anchor = 1;
+}
+
 // Query operations for the SCT component.
 service QueryService {
+  rpc AnchorByHeight(AnchorByHeightRequest) returns (AnchorByHeightResponse);
   rpc EpochByHeight(EpochByHeightRequest) returns (EpochByHeightResponse);
 }