multi: add endpoints for best mainchain and sidechain hashes (#42)

* multi: add endpoints for best mainchain and sidechain hashes

* human-readable serialization for block hashes

* dev: fmt code

* fixups

---------

Co-authored-by: Ash Manning <[email protected]>

app/rpc_server.rs

@@ -98,6 +98,29 @@ impl RpcServer for RpcServerImpl {
         Ok(Some(block))
     }
 
+    async fn get_best_sidechain_block_hash(
+        &self,
+    ) -> RpcResult<Option<thunder::types::BlockHash>> {
+        self.app.node.try_get_tip().map_err(custom_err)
+    }
+
+    async fn get_best_mainchain_block_hash(
+        &self,
+    ) -> RpcResult<Option<bitcoin::BlockHash>> {
+        let Some(sidechain_hash) =
+            self.app.node.try_get_tip().map_err(custom_err)?
+        else {
+            // No sidechain tip, so no best mainchain block hash.
+            return Ok(None);
+        };
+        let block_hash = self
+            .app
+            .node
+            .get_best_main_verification(sidechain_hash)
+            .map_err(custom_err)?;
+        Ok(Some(block_hash))
+    }
+
     async fn get_bmm_inclusions(
         &self,
         block_hash: thunder::types::BlockHash,

cli/lib.rs

@@ -27,6 +27,10 @@ pub enum Command {
     FormatDepositAddress { address: Address },
     /// Generate a mnemonic seed phrase
     GenerateMnemonic,
+    /// Get the best mainchain block hash
+    GetBestMainchainBlockHash,
+    /// Get the best sidechain block hash
+    GetBestSidechainBlockHash,
     /// Get the block with specified block hash, if it exists
     GetBlock {
         block_hash: thunder::types::BlockHash,
@@ -137,6 +141,14 @@ where
             let block = rpc_client.get_block(block_hash).await?;
             serde_json::to_string_pretty(&block)?
         }
+        Command::GetBestMainchainBlockHash => {
+            let block_hash = rpc_client.get_best_mainchain_block_hash().await?;
+            serde_json::to_string_pretty(&block_hash)?
+        }
+        Command::GetBestSidechainBlockHash => {
+            let block_hash = rpc_client.get_best_sidechain_block_hash().await?;
+            serde_json::to_string_pretty(&block_hash)?
+        }
         Command::GetBmmInclusions { block_hash } => {
             let bmm_inclusions =
                 rpc_client.get_bmm_inclusions(block_hash).await?;

lib/node/mod.rs

@@ -318,6 +318,12 @@ where
         Ok(utxos)
     }
 
+    pub fn try_get_tip(&self) -> Result<Option<BlockHash>, Error> {
+        let rotxn = self.env.read_txn().map_err(EnvError::from)?;
+        let tip = self.state.try_get_tip(&rotxn).map_err(DbError::from)?;
+        Ok(tip)
+    }
+
     pub fn get_tip_accumulator(&self) -> Result<Accumulator, Error> {
         let rotxn = self.env.read_txn().map_err(EnvError::from)?;
         Ok(self.state.get_accumulator(&rotxn)?)
@@ -398,6 +404,15 @@ where
         Ok(self.archive.get_body(&rotxn, block_hash)?)
     }
 
+    pub fn get_best_main_verification(
+        &self,
+        hash: BlockHash,
+    ) -> Result<bitcoin::BlockHash, Error> {
+        let rotxn = self.env.read_txn().map_err(EnvError::from)?;
+        let hash = self.archive.get_best_main_verification(&rotxn, hash)?;
+        Ok(hash)
+    }
+
     pub fn get_bmm_inclusions(
         &self,
         block_hash: BlockHash,

lib/types/hashes.rs

@@ -24,7 +24,7 @@ pub type Hash = [u8; BLAKE3_LENGTH];
     PartialOrd,
     Serialize,
 )]
-pub struct BlockHash(pub Hash);
+pub struct BlockHash(#[serde(with = "serde_hexstr_human_readable")] pub Hash);
 
 impl From<Hash> for BlockHash {
     fn from(other: Hash) -> Self {

rpc-api/lib.rs

@@ -32,7 +32,9 @@ pub trait Rpc {
     #[method(name = "connect_peer")]
     async fn connect_peer(
         &self,
-        #[open_api_method_arg(schema(PartialSchema = "schema::SocketAddr"))]
+        #[open_api_method_arg(schema(
+            PartialSchema = "thunder_schema::SocketAddr"
+        ))]
         addr: SocketAddr,
     ) -> RpcResult<()>;
 
@@ -74,6 +76,24 @@ pub trait Rpc {
         block_hash: thunder::types::BlockHash,
     ) -> RpcResult<Vec<bitcoin::BlockHash>>;
 
+    /// Get the best mainchain block hash known by Thunder
+    #[open_api_method(output_schema(
+        PartialSchema = "schema::Optional<thunder_schema::BitcoinBlockHash>"
+    ))]
+    #[method(name = "get_best_mainchain_block_hash")]
+    async fn get_best_mainchain_block_hash(
+        &self,
+    ) -> RpcResult<Option<bitcoin::BlockHash>>;
+
+    /// Get the best sidechain block hash known by Thunder
+    #[open_api_method(output_schema(
+        PartialSchema = "schema::Optional<thunder::types::BlockHash>"
+    ))]
+    #[method(name = "get_best_sidechain_block_hash")]
+    async fn get_best_sidechain_block_hash(
+        &self,
+    ) -> RpcResult<Option<thunder::types::BlockHash>>;
+
     /// Get a new address
     #[method(name = "get_new_address")]
     async fn get_new_address(&self) -> RpcResult<Address>;

rpc-api/schema.rs

@@ -1,5 +1,7 @@
 //! Schemas for OpenAPI
 
+use std::marker::PhantomData;
+
 use utoipa::{
     openapi::{self, RefOr, Schema},
     PartialSchema, ToSchema,
@@ -29,11 +31,20 @@ impl PartialSchema for OpenApi {
     }
 }
 
-pub struct SocketAddr;
-
-impl PartialSchema for SocketAddr {
-    fn schema() -> RefOr<Schema> {
-        let obj = utoipa::openapi::Object::with_type(openapi::Type::String);
-        RefOr::T(Schema::Object(obj))
+/// Optional `T`
+pub struct Optional<T>(PhantomData<T>);
+
+impl<T> PartialSchema for Optional<T>
+where
+    T: PartialSchema,
+{
+    fn schema() -> openapi::RefOr<openapi::schema::Schema> {
+        openapi::schema::OneOf::builder()
+            .item(
+                openapi::schema::Object::builder()
+                    .schema_type(openapi::schema::Type::Null),
+            )
+            .item(T::schema())
+            .into()
     }
 }