rpc(funding): rpc service scaffolding for nullifier queries

crates/core/component/funding/Cargo.toml

@@ -20,7 +20,8 @@ component = [
     "penumbra-sdk-shielded-pool/component",
     "penumbra-sdk-stake/component",
     "metrics",
-    "futures"
+    "futures",
+    "tonic",
 ]
 default = ["component"]
 parallel = [
@@ -62,6 +63,7 @@ penumbra-sdk-txhash = {workspace = true, default-features = false}
 serde = {workspace = true, features = ["derive"]}
 tendermint = {workspace = true}
 tracing = {workspace = true}
+tonic = {workspace = true, optional = true}
 
 [dev-dependencies]
 proptest = {workspace = true}

crates/core/component/funding/src/component.rs

@@ -1,4 +1,5 @@
 pub mod metrics;
+pub mod rpc;
 mod state_key;
 pub mod view;
 use ::metrics::{gauge, histogram};

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

@@ -0,0 +1,55 @@
+use cnidarium::Storage;
+use penumbra_sdk_proto::core::component::funding::v1::{
+    self as pb, funding_service_server::FundingService,
+};
+use penumbra_sdk_sct::Nullifier;
+
+use super::liquidity_tournament::nullifier::NullifierRead;
+
+pub struct Server {
+    storage: Storage,
+}
+
+impl Server {
+    pub fn new(storage: Storage) -> Self {
+        Self { storage }
+    }
+}
+
+#[tonic::async_trait]
+impl FundingService for Server {
+    async fn lqt_current_epoch_voted(
+        &self,
+        request: tonic::Request<pb::LqtCurrentEpochVotedRequest>,
+    ) -> Result<tonic::Response<pb::LqtCurrentEpochVotedResponse>, tonic::Status> {
+        // Retrieve latest state snapshot.
+        let state = self.storage.latest_snapshot();
+
+        let req_nullifier = request.into_inner();
+        let nullifier_proto = req_nullifier
+            .nullifier
+            .ok_or_else(|| tonic::Status::invalid_argument("missing nullifier"))?;
+
+        // Proto to domain type conversion.
+        let nullifier: Nullifier = nullifier_proto
+            .try_into()
+            .map_err(|e| tonic::Status::invalid_argument(format!("invalid nullifier: {e}")))?;
+
+        // Perform a state nullifier lookup.
+        let maybe_tx_id = state.get_lqt_spent_nullifier(nullifier).await;
+
+        if let Some(tx_id) = maybe_tx_id {
+            // Nullifier was spent and user has already voted.
+            Ok(tonic::Response::new(pb::LqtCurrentEpochVotedResponse {
+                tx_id: Some(tx_id.into()),
+                already_voted: true,
+            }))
+        } else {
+            // Nullifier was not spent and user has not voted yet.
+            Ok(tonic::Response::new(pb::LqtCurrentEpochVotedResponse {
+                tx_id: None,
+                already_voted: false,
+            }))
+        }
+    }
+}