add safe home assistant error handling

app/core/__init__.py

@@ -0,0 +1 @@
+"""Core application helpers."""

app/core/exception_handlers.py

@@ -0,0 +1,23 @@
+from __future__ import annotations
+
+from fastapi import FastAPI, Request, status
+from fastapi.responses import JSONResponse
+
+from app.ha.exceptions import HaAuthError, HaClientError, HaHttpError, HaTimeoutError
+
+
+def register_exception_handlers(app: FastAPI) -> None:
+    @app.exception_handler(HaClientError)
+    async def handle_ha_client_error(_: Request, exc: HaClientError) -> JSONResponse:
+        return JSONResponse(
+            status_code=_status_code_for_ha_error(exc),
+            content={"detail": exc.public_detail},
+        )
+
+
+def _status_code_for_ha_error(exc: HaClientError) -> int:
+    if isinstance(exc, HaTimeoutError):
+        return status.HTTP_504_GATEWAY_TIMEOUT
+    if isinstance(exc, (HaAuthError, HaHttpError)):
+        return status.HTTP_502_BAD_GATEWAY
+    return status.HTTP_502_BAD_GATEWAY