api: small touchups

src/lean_spec/subspecs/api/client.py

@@ -13,6 +13,7 @@
 import httpx
 
 from lean_spec.subspecs.chain.config import DEVNET_CONFIG
+from lean_spec.subspecs.containers import Slot
 from lean_spec.subspecs.ssz.hash import hash_tree_root
 
 if TYPE_CHECKING:
@@ -28,8 +29,6 @@
 class CheckpointSyncError(Exception):
     """Error during checkpoint sync."""
 
-    pass
-
 
 async def fetch_finalized_state(url: str, state_class: type[Any]) -> "State":
     """
@@ -52,9 +51,7 @@ async def fetch_finalized_state(url: str, state_class: type[Any]) -> "State":
 
     logger.info(f"Fetching finalized state from {full_url}")
 
-    headers = {
-        "Accept": "application/octet-stream",
-    }
+    headers = {"Accept": "application/octet-stream"}
 
     try:
         async with httpx.AsyncClient(timeout=DEFAULT_TIMEOUT) as client:
@@ -77,8 +74,6 @@ async def fetch_finalized_state(url: str, state_class: type[Any]) -> "State":
         raise CheckpointSyncError(
             f"HTTP error {exc.response.status_code}: {exc.response.text[:200]}"
         ) from exc
-    except CheckpointSyncError:
-        raise
     except Exception as e:
         raise CheckpointSyncError(f"Failed to fetch state: {e}") from e
 
@@ -96,9 +91,7 @@ async def verify_checkpoint_state(state: "State") -> bool:
         True if valid, False otherwise
     """
     try:
-        computed_root = hash_tree_root(state)
-
-        if int(state.slot) < 0:
+        if state.slot < Slot(0):
             logger.error("Invalid state: negative slot")
             return False
 
@@ -114,7 +107,8 @@ async def verify_checkpoint_state(state: "State") -> bool:
             )
             return False
 
-        root_preview = computed_root.hex()[:16]
+        state_root = hash_tree_root(state)
+        root_preview = state_root.hex()[:16]
         logger.info(f"Checkpoint state verified: slot={state.slot}, root={root_preview}...")
         return True
 

src/lean_spec/subspecs/api/server.py

@@ -13,7 +13,7 @@
 import asyncio
 import logging
 from collections.abc import Callable
-from dataclasses import dataclass
+from dataclasses import dataclass, field
 from typing import TYPE_CHECKING
 
 from aiohttp import web
@@ -24,6 +24,16 @@
 logger = logging.getLogger(__name__)
 
 
+def _no_store() -> Store | None:
+    """Default store getter that returns None."""
+    return None
+
+
+async def _handle_health(_request: web.Request) -> web.Response:
+    """Handle health check endpoint."""
+    return web.json_response({"status": "healthy", "service": "lean-spec-api"})
+
+
 @dataclass(frozen=True, slots=True)
 class ApiServerConfig:
     """Configuration for the API server."""
@@ -38,6 +48,7 @@ class ApiServerConfig:
     """Whether the API server is enabled."""
 
 
+@dataclass(slots=True)
 class ApiServer:
     """
     HTTP API server for checkpoint sync and node status.
@@ -49,36 +60,22 @@ class ApiServer:
     Uses aiohttp to handle HTTP protocol details efficiently.
     """
 
-    def __init__(
-        self,
-        config: ApiServerConfig,
-        store_getter: Callable[[], Store | None] = lambda: None,
-    ):
-        """
-        Initialize the API server.
+    config: ApiServerConfig
+    """Server configuration."""
 
-        Args:
-            config: Server configuration.
-            store_getter: Callable that returns the current Store instance.
-        """
-        self.config = config
-        self._store_getter = store_getter
-        self._runner: web.AppRunner | None = None
-        self._site: web.TCPSite | None = None
+    store_getter: Callable[[], Store | None] = _no_store
+    """Callable that returns the current Store instance."""
 
-    def set_store_getter(self, getter: Callable[[], Store | None]) -> None:
-        """
-        Set the store getter function.
+    _runner: web.AppRunner | None = field(default=None, init=False)
+    """The aiohttp application runner."""
 
-        Args:
-            getter: Callable that returns the current Store instance.
-        """
-        self._store_getter = getter
+    _site: web.TCPSite | None = field(default=None, init=False)
+    """The TCP site for the server."""
 
     @property
     def store(self) -> Store | None:
         """Get the current Store instance."""
-        return self._store_getter()
+        return self.store_getter()
 
     async def start(self) -> None:
         """Start the API server in the background."""
@@ -89,7 +86,7 @@ async def start(self) -> None:
         app = web.Application()
         app.add_routes(
             [
-                web.get("/health", self._handle_health),
+                web.get("/health", _handle_health),
                 web.get("/lean/states/finalized", self._handle_finalized_state),
             ]
         )
@@ -127,11 +124,7 @@ async def _async_stop(self) -> None:
             self._site = None
             logger.info("API server stopped")
 
-    async def _handle_health(self, request: web.Request) -> web.Response:
-        """Handle health check endpoint."""
-        return web.json_response({"status": "healthy", "service": "lean-spec-api"})
-
-    async def _handle_finalized_state(self, request: web.Request) -> web.Response:
+    async def _handle_finalized_state(self, _request: web.Request) -> web.Response:
         """
         Handle finalized checkpoint state endpoint.
 

src/lean_spec/subspecs/node/node.py

@@ -145,10 +145,11 @@ def from_genesis(cls, config: NodeConfig) -> Node:
         # Create API server if configured
         api_server: ApiServer | None = None
         if config.api_config is not None:
-            api_server = ApiServer(config=config.api_config)
-            # Set up store getter so API server can access current state
-            # We use a lambda that captures sync_service to get the live store
-            api_server.set_store_getter(lambda: sync_service.store)
+            # Store getter captures sync_service to get the live store
+            api_server = ApiServer(
+                config=config.api_config,
+                store_getter=lambda: sync_service.store,
+            )
 
         return cls(
             store=store,

tests/lean_spec/subspecs/api/test_server.py

@@ -56,9 +56,7 @@ def test_server_created_without_store(self) -> None:
     def test_store_getter_provides_access_to_store(self, store: Store) -> None:
         """Store getter callable provides access to the forkchoice store."""
         config = ApiServerConfig()
-        server = ApiServer(config=config)
-
-        server.set_store_getter(lambda: store)
+        server = ApiServer(config=config, store_getter=lambda: store)
 
         assert server.store is store