Make Request::BestChainBlockHash redirect to the ReadStateService

zebra-state/src/request.rs

@@ -599,6 +599,14 @@ pub enum Request {
     /// Returns [`Response::BestChainNextMedianTimePast`] when successful.
     BestChainNextMedianTimePast,
 
+    /// Looks up a block hash by height in the current best chain.
+    ///
+    /// Returns
+    ///
+    /// * [`Response::BlockHash(Some(hash))`](Response::BlockHash) if the block is in the best chain;
+    /// * [`Response::BlockHash(None)`](Response::BlockHash) otherwise.
+    BestChainBlockHash(block::Height),
+
     #[cfg(feature = "getblocktemplate-rpcs")]
     /// Performs contextual validation of the given block, but does not commit it to the state.
     ///
@@ -625,6 +633,7 @@ impl Request {
                 "best_chain_tip_nullifiers_anchors"
             }
             Request::BestChainNextMedianTimePast => "best_chain_next_median_time_past",
+            Request::BestChainBlockHash(_) => "best_chain_block_hash",
             #[cfg(feature = "getblocktemplate-rpcs")]
             Request::CheckBlockProposalValidity(_) => "check_block_proposal_validity",
         }
@@ -910,6 +919,7 @@ impl TryFrom<Request> for ReadRequest {
             Request::Tip => Ok(ReadRequest::Tip),
             Request::Depth(hash) => Ok(ReadRequest::Depth(hash)),
             Request::BestChainNextMedianTimePast => Ok(ReadRequest::BestChainNextMedianTimePast),
+            Request::BestChainBlockHash(hash) => Ok(ReadRequest::BestChainBlockHash(hash)),
 
             Request::Block(hash_or_height) => Ok(ReadRequest::Block(hash_or_height)),
             Request::Transaction(tx_hash) => Ok(ReadRequest::Transaction(tx_hash)),
@@ -933,14 +943,14 @@ impl TryFrom<Request> for ReadRequest {
                 Err("ReadService does not write blocks")
             }
 
+            Request::AwaitUtxo(_) => Err("ReadService does not track pending UTXOs. \
+                     Manually convert the request to ReadRequest::AnyChainUtxo, \
+                     and handle pending UTXOs"),
+
             #[cfg(feature = "getblocktemplate-rpcs")]
             Request::CheckBlockProposalValidity(prepared) => {
                 Ok(ReadRequest::CheckBlockProposalValidity(prepared))
             }
-
-            Request::AwaitUtxo(_) => Err("ReadService does not track pending UTXOs. \
-                     Manually convert the request to ReadRequest::AnyChainUtxo, \
-                     and handle pending UTXOs"),
         }
     }
 }

zebra-state/src/response.rs

@@ -65,15 +65,19 @@ pub enum Response {
     /// Contains the median-time-past for the *next* block on the best chain.
     BestChainNextMedianTimePast(DateTime32),
 
+    /// Response to [`Request::BestChainBlockHash`](Request::BestChainBlockHash) with the
+    /// specified block hash.
+    BlockHash(Option<block::Hash>),
+
     #[cfg(feature = "getblocktemplate-rpcs")]
-    /// Response to [`Request::CheckBlockProposalValidity`](crate::Request::CheckBlockProposalValidity)
+    /// Response to [`Request::CheckBlockProposalValidity`](Request::CheckBlockProposalValidity)
     ValidBlockProposal,
 }
 
 #[derive(Clone, Debug, PartialEq, Eq)]
 /// A response to a read-only
 /// [`ReadStateService`](crate::service::ReadStateService)'s
-/// [`ReadRequest`](crate::ReadRequest).
+/// [`ReadRequest`](ReadRequest).
 pub enum ReadResponse {
     /// Response to [`ReadRequest::Tip`] with the current best chain tip.
     Tip(Option<(block::Height, block::Hash)>),
@@ -137,21 +141,21 @@ pub enum ReadResponse {
     /// Contains the median-time-past for the *next* block on the best chain.
     BestChainNextMedianTimePast(DateTime32),
 
-    /// Response to [`ReadRequest::BestChainBlockHash`](crate::ReadRequest::BestChainBlockHash) with the
+    /// Response to [`ReadRequest::BestChainBlockHash`](ReadRequest::BestChainBlockHash) with the
     /// specified block hash.
     BlockHash(Option<block::Hash>),
 
     #[cfg(feature = "getblocktemplate-rpcs")]
-    /// Response to [`ReadRequest::ChainInfo`](crate::ReadRequest::ChainInfo) with the state
+    /// Response to [`ReadRequest::ChainInfo`](ReadRequest::ChainInfo) with the state
     /// information needed by the `getblocktemplate` RPC method.
     ChainInfo(GetBlockTemplateChainInfo),
 
     #[cfg(feature = "getblocktemplate-rpcs")]
-    /// Response to [`ReadRequest::SolutionRate`](crate::ReadRequest::SolutionRate)
+    /// Response to [`ReadRequest::SolutionRate`](ReadRequest::SolutionRate)
     SolutionRate(Option<u128>),
 
     #[cfg(feature = "getblocktemplate-rpcs")]
-    /// Response to [`ReadRequest::CheckBlockProposalValidity`](crate::ReadRequest::CheckBlockProposalValidity)
+    /// Response to [`ReadRequest::CheckBlockProposalValidity`](ReadRequest::CheckBlockProposalValidity)
     ValidBlockProposal,
 }
 
@@ -204,6 +208,7 @@ impl TryFrom<ReadResponse> for Response {
             ReadResponse::Tip(height_and_hash) => Ok(Response::Tip(height_and_hash)),
             ReadResponse::Depth(depth) => Ok(Response::Depth(depth)),
             ReadResponse::BestChainNextMedianTimePast(median_time_past) => Ok(Response::BestChainNextMedianTimePast(median_time_past)),
+            ReadResponse::BlockHash(hash) => Ok(Response::BlockHash(hash)),
 
             ReadResponse::Block(block) => Ok(Response::Block(block)),
             ReadResponse::Transaction(tx_and_height) => {
@@ -230,10 +235,6 @@ impl TryFrom<ReadResponse> for Response {
                 Err("there is no corresponding Response for this ReadResponse")
             }
 
-            ReadResponse::BlockHash(_) => {
-                Err("there is no corresponding Response for this ReadResponse")
-            }
-
             #[cfg(feature = "getblocktemplate-rpcs")]
             ReadResponse::ValidBlockProposal => Ok(Response::ValidBlockProposal),
 

zebra-state/src/service.rs

@@ -1032,6 +1032,7 @@ impl Service<Request> for StateService {
             Request::Tip
             | Request::Depth(_)
             | Request::BestChainNextMedianTimePast
+            | Request::BestChainBlockHash(_)
             | Request::BlockLocator
             | Request::Transaction(_)
             | Request::UnspentBestChainUtxo(_)