Factor out a best_chain_tip_height() function (#5540)

zebra-rpc/src/methods.rs

@@ -360,7 +360,7 @@ where
         + Sync
         + 'static,
     State::Future: Send,
-    Tip: ChainTip + Send + Sync + 'static,
+    Tip: ChainTip + Clone + Send + Sync + 'static,
 {
     fn get_info(&self) -> Result<GetInfo> {
         let response = GetInfo {
@@ -869,18 +869,16 @@ where
         request: GetAddressTxIdsRequest,
     ) -> BoxFuture<Result<Vec<String>>> {
         let mut state = self.state.clone();
+        let latest_chain_tip = self.latest_chain_tip.clone();
+
         let start = Height(request.start);
         let end = Height(request.end);
 
-        let chain_height = self.latest_chain_tip.best_tip_height().ok_or(Error {
-            code: ErrorCode::ServerError(0),
-            message: "No blocks in state".to_string(),
-            data: None,
-        });
-
         async move {
+            let chain_height = best_chain_tip_height(&latest_chain_tip)?;
+
             // height range checks
-            check_height_range(start, end, chain_height?)?;
+            check_height_range(start, end, chain_height)?;
 
             let valid_addresses = AddressStrings {
                 addresses: request.addresses,
@@ -994,6 +992,19 @@ where
     }
 }
 
+/// Returns the best chain tip height of `latest_chain_tip`,
+/// or an RPC error if there are no blocks in the state.
+pub fn best_chain_tip_height<Tip>(latest_chain_tip: &Tip) -> Result<Height>
+where
+    Tip: ChainTip + Clone + Send + Sync + 'static,
+{
+    latest_chain_tip.best_tip_height().ok_or(Error {
+        code: ErrorCode::ServerError(0),
+        message: "No blocks in state".to_string(),
+        data: None,
+    })
+}
+
 /// Response to a `getinfo` RPC request.
 ///
 /// See the notes for the [`Rpc::get_info` method].

zebra-rpc/src/methods/get_block_template_rpcs.rs

@@ -18,6 +18,7 @@ use zebra_consensus::{BlockError, VerifyBlockError, VerifyChainError, VerifyChec
 use zebra_node_services::mempool;
 
 use crate::methods::{
+    best_chain_tip_height,
     get_block_template_rpcs::types::{
         default_roots::DefaultRoots, get_block_template::GetBlockTemplate, hex_data::HexData,
         submit_block, transaction::TransactionTemplate,
@@ -197,7 +198,7 @@ where
         + Sync
         + 'static,
     <State as Service<zebra_state::ReadRequest>>::Future: Send,
-    Tip: ChainTip + Send + Sync + 'static,
+    Tip: ChainTip + Clone + Send + Sync + 'static,
     ChainVerifier: Service<Arc<Block>, Response = block::Hash, Error = zebra_consensus::BoxError>
         + Clone
         + Send
@@ -206,27 +207,15 @@ where
     <ChainVerifier as Service<Arc<Block>>>::Future: Send,
 {
     fn get_block_count(&self) -> Result<u32> {
-        self.latest_chain_tip
-            .best_tip_height()
-            .map(|height| height.0)
-            .ok_or(Error {
-                code: ErrorCode::ServerError(0),
-                message: "No blocks in state".to_string(),
-                data: None,
-            })
+        best_chain_tip_height(&self.latest_chain_tip).map(|height| height.0)
     }
 
     fn get_block_hash(&self, index: i32) -> BoxFuture<Result<GetBlockHash>> {
         let mut state = self.state.clone();
-
-        let maybe_tip_height = self.latest_chain_tip.best_tip_height();
+        let latest_chain_tip = self.latest_chain_tip.clone();
 
         async move {
-            let tip_height = maybe_tip_height.ok_or(Error {
-                code: ErrorCode::ServerError(0),
-                message: "No blocks in state".to_string(),
-                data: None,
-            })?;
+            let tip_height = best_chain_tip_height(&latest_chain_tip)?;
 
             let height = get_height_from_int(index, tip_height)?;
 
@@ -256,9 +245,12 @@ where
 
     fn get_block_template(&self) -> BoxFuture<Result<GetBlockTemplate>> {
         let mempool = self.mempool.clone();
+        let latest_chain_tip = self.latest_chain_tip.clone();
 
         // Since this is a very large RPC, we use separate functions for each group of fields.
         async move {
+            let _tip_height = best_chain_tip_height(&latest_chain_tip)?;
+
             // TODO: put this in a separate get_mempool_transactions() function
             let request = mempool::Request::FullTransactions;
             let response = mempool.oneshot(request).await.map_err(|error| Error {