From 80ddb7239a40e23fb174e021e7892fe62b267c36 Mon Sep 17 00:00:00 2001
From: Jeb Bearer <jeb@espressosys.com>
Date: Thu, 2 May 2024 16:01:56 -0400
Subject: [PATCH] Expose synced merklized state height

This is really useful to have for debugging
---
 api/state.toml         | 13 ++++++++++---
 src/merklized_state.rs |  6 +++++-
 2 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/api/state.toml b/api/state.toml
index 8fb1fae3a..9528dcd41 100644
--- a/api/state.toml
+++ b/api/state.toml
@@ -14,7 +14,7 @@
 FORMAT_VERSION = "0.1.0"
 NAME = "hotshot-state"
 DESCRIPTION = """
-Query snapshot of merklized state. 
+Query snapshot of merklized state.
 
 The state API provides an interface for serving queries against arbitrarily old snapshots of the state. This allows a full Merkle tree to be reconstructed from storage. However, if any parent state is missing then the partial snapshot can not be queried.
 """
@@ -27,7 +27,7 @@ PATH = ["/:height/:key", "commit/:commit/:key"]
 DOC = """
 The endpoint offers two methods to query: by block height or by the tree's commitment.
 
-GET /:height/:key 
+GET /:height/:key
 Retrieves the Merkle Path for the membership proof of a leaf based on the block height and entry index.
 Parameters:
 :height : The block height of the snapshot.
@@ -41,4 +41,11 @@ Parameters:
 :key : The index of the entry in the Merkle tree.
 """
 
- 
\ No newline at end of file
+[route.get_height]
+PATH = ["/block-height"]
+DOC = """
+The latest block height for which the merklized state is available.
+
+Note that this may be less than the block height indicated by other APIs, such as `status` or
+`node`, since the merklized state storage is updated asynchronously.
+"""
diff --git a/src/merklized_state.rs b/src/merklized_state.rs
index 5c6359fed..5e0df4961 100644
--- a/src/merklized_state.rs
+++ b/src/merklized_state.rs
@@ -89,7 +89,8 @@ pub fn define_api<
 ) -> Result<Api<State, Error, Ver>, ApiError>
 where
     State: 'static + Send + Sync + ReadState,
-    <State as ReadState>::State: Send + Sync + MerklizedStateDataSource<Types, M, ARITY>,
+    <State as ReadState>::State:
+        Send + Sync + MerklizedStateDataSource<Types, M, ARITY> + MerklizedStateHeightPersistence,
     Types: NodeType,
     for<'a> <M::Commit as TryFrom<&'a TaggedBase64>>::Error: Display,
 {
@@ -118,6 +119,9 @@ where
                 state.get_path(snapshot, key).await.context(QuerySnafu)
             }
             .boxed()
+        })?
+        .get("get_height", move |_, state| {
+            async move { state.get_last_state_height().await.context(QuerySnafu) }.boxed()
         })?;
 
     Ok(api)