Refactor JSON attribute parsing in rest (#97526)

* Refactor JSON attribute parsing in rest

* Early return

homeassistant/components/rest/util.py

@@ -0,0 +1,40 @@
+"""Helpers for RESTful API."""
+
+import logging
+from typing import Any
+
+from jsonpath import jsonpath
+
+from homeassistant.util.json import json_loads
+
+_LOGGER = logging.getLogger(__name__)
+
+
+def parse_json_attributes(
+    value: str | None, json_attrs: list[str], json_attrs_path: str | None
+) -> dict[str, Any]:
+    """Parse JSON attributes."""
+    if not value:
+        _LOGGER.warning("Empty reply found when expecting JSON data")
+        return {}
+
+    try:
+        json_dict = json_loads(value)
+        if json_attrs_path is not None:
+            json_dict = jsonpath(json_dict, json_attrs_path)
+        # jsonpath will always store the result in json_dict[0]
+        # so the next line happens to work exactly as needed to
+        # find the result
+        if isinstance(json_dict, list):
+            json_dict = json_dict[0]
+        if isinstance(json_dict, dict):
+            return {k: json_dict[k] for k in json_attrs if k in json_dict}
+
+        _LOGGER.warning(
+            "JSON result was not a dictionary or list with 0th element a dictionary"
+        )
+    except ValueError:
+        _LOGGER.warning("REST result could not be parsed as JSON")
+        _LOGGER.debug("Erroneous JSON: %s", value)
+
+    return {}