From 0cdea88f4edca22954ad41f104af7544356e1b4c Mon Sep 17 00:00:00 2001
From: Gonza Montiel <gonzamontiel@users.noreply.github.com>
Date: Wed, 10 Jul 2024 11:10:49 +0200
Subject: [PATCH] Expose moon_getLatestSyncedBlock  RPC endpoint (#2858)

* Expose RPC endpoint
* add test
* apply review suggestions
---
 client/rpc/finality/src/lib.rs                | 19 +++++++++++++++++++
 moonbeam-types-bundle/index.ts                |  5 +++++
 .../dev/moonbase/test-moon/test-moon-rpc.ts   | 10 ++++++++++
 .../moonbase/interfaces/augment-api-rpc.ts    |  2 ++
 .../moonbase/interfaces/moon/definitions.ts   |  5 +++++
 5 files changed, 41 insertions(+)

diff --git a/client/rpc/finality/src/lib.rs b/client/rpc/finality/src/lib.rs
index 24e1e87f92..988d8d316c 100644
--- a/client/rpc/finality/src/lib.rs
+++ b/client/rpc/finality/src/lib.rs
@@ -14,10 +14,13 @@
 // You should have received a copy of the GNU General Public License
 // along with Moonbeam.  If not, see <http://www.gnu.org/licenses/>.
 use fc_rpc::frontier_backend_client::{self, is_canon};
+
+use jsonrpsee::types::error::ErrorObject;
 use jsonrpsee::{core::RpcResult, proc_macros::rpc};
 use sp_blockchain::HeaderBackend;
 use sp_core::H256;
 use sp_runtime::traits::Block;
+use std::ops::Deref;
 use std::{marker::PhantomData, sync::Arc};
 
 /// An RPC endpoint to check for finality of blocks and transactions in Moonbeam
@@ -33,6 +36,10 @@ pub trait MoonbeamFinalityApi {
 	/// Returns false if the transaction is not found
 	#[method(name = "moon_isTxFinalized")]
 	async fn is_tx_finalized(&self, tx_hash: H256) -> RpcResult<bool>;
+
+	/// Gets the latest block hash that is fully indexed in frontier's backend.
+	#[method(name = "moon_getLatestBlockHash")]
+	async fn get_latest_block_hash(&self) -> RpcResult<H256>;
 }
 
 pub struct MoonbeamFinality<B: Block, C> {
@@ -80,6 +87,18 @@ where
 			Ok(false)
 		}
 	}
+
+	async fn get_latest_block_hash(&self) -> RpcResult<H256> {
+		let res = self.backend.deref().latest_block_hash().await;
+		match res {
+			Ok(val) => Ok(val),
+			Err(e) => Err(ErrorObject::owned(
+				jsonrpsee::types::error::UNKNOWN_ERROR_CODE,
+				"No synced block",
+				Some(e),
+			)),
+		}
+	}
 }
 
 async fn is_block_finalized_inner<B: Block<Hash = H256>, C: HeaderBackend<B> + 'static>(
diff --git a/moonbeam-types-bundle/index.ts b/moonbeam-types-bundle/index.ts
index 3c3c47ab19..cccdf7a149 100644
--- a/moonbeam-types-bundle/index.ts
+++ b/moonbeam-types-bundle/index.ts
@@ -88,6 +88,11 @@ export const rpcDefinitions: Record<string, Record<string, DefinitionRpc | Defin
       params: [{ name: "txHash", type: "Hash" }],
       type: "bool",
     },
+    getLatestSyncedBlock: {
+      description: "Returns the latest synced block from frontier's backend",
+      params: [],
+      type: "u32",
+    },
   },
 };
 
diff --git a/test/suites/dev/moonbase/test-moon/test-moon-rpc.ts b/test/suites/dev/moonbase/test-moon/test-moon-rpc.ts
index c6c27247d2..cfd45d7ba8 100644
--- a/test/suites/dev/moonbase/test-moon/test-moon-rpc.ts
+++ b/test/suites/dev/moonbase/test-moon/test-moon-rpc.ts
@@ -155,5 +155,15 @@ describeSuite({
         expect(resp, "Transaction finalization status mismatch").toBe(true);
       },
     });
+
+    it({
+      id: "T11",
+      title: "should return latest synced block",
+      test: async function () {
+        const expected = await context.createBlock([], { finalize: true });
+        const resp = await customDevRpcRequest("moon_getLatestBlockHash", []);
+        expect(resp, "Latest block hash").toBe(expected.block.hash);
+      },
+    });
   },
 });
diff --git a/typescript-api/src/moonbase/interfaces/augment-api-rpc.ts b/typescript-api/src/moonbase/interfaces/augment-api-rpc.ts
index 244f545e21..797ead0556 100644
--- a/typescript-api/src/moonbase/interfaces/augment-api-rpc.ts
+++ b/typescript-api/src/moonbase/interfaces/augment-api-rpc.ts
@@ -618,6 +618,8 @@ declare module "@polkadot/rpc-core/types/jsonrpc" {
       isBlockFinalized: AugmentedRpc<(blockHash: Hash | string | Uint8Array) => Observable<bool>>;
       /** Returns whether an Ethereum transaction is finalized */
       isTxFinalized: AugmentedRpc<(txHash: Hash | string | Uint8Array) => Observable<bool>>;
+      /** Returns the latest synced block from Frontier's backend */
+      getLatestSyncedBlock: AugmentedRpc<() => Observable<u32>>;
     };
     net: {
       /** Returns true if client is actively listening for network connections. Otherwise false. */
diff --git a/typescript-api/src/moonbase/interfaces/moon/definitions.ts b/typescript-api/src/moonbase/interfaces/moon/definitions.ts
index d368c8f2b0..301a9c80d0 100644
--- a/typescript-api/src/moonbase/interfaces/moon/definitions.ts
+++ b/typescript-api/src/moonbase/interfaces/moon/definitions.ts
@@ -11,5 +11,10 @@ export default {
       params: [{ name: "txHash", type: "Hash" }],
       type: "bool",
     },
+    getLatestSyncedBlock: {
+      description: "Returns the latest synced block from Frontier's backend",
+      params: [],
+      type: "u32",
+    },
   },
 };