fix: handle OCPI version negotiation in push_object

push_object now accepts both a versions URL and a version details URL
as endpoints_url. When a versions list is returned (data is a list),
it automatically picks the best mutual version and fetches the details
URL to discover endpoints. This follows the proper OCPI spec flow:

1. GET /versions → list of supported versions with details URLs
2. Pick best mutual version
3. GET /{version}/details → list of endpoints
4. Push to the correct module endpoint

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: Alfonso Sastre

ocpi/core/push.py

@@ -16,6 +16,29 @@
 from ocpi.modules.versions.v_2_2_1.enums import InterfaceRole
 
 
+_VERSION_PREFERENCE = ["2.3.0", "2.2.1", "2.1.1"]
+
+
+def _pick_version_details_url(
+    versions_list: list[dict], requested: VersionNumber
+) -> str | None:
+    """Pick the best version details URL from an OCPI /versions response.
+
+    Tries the requested version first, then falls back to the highest
+    mutually supported version.
+    """
+    by_version = {v["version"]: v["url"] for v in versions_list if "version" in v}
+
+    if requested.value in by_version:
+        return by_version[requested.value]
+
+    for v in _VERSION_PREFERENCE:
+        if v in by_version:
+            return by_version[v]
+
+    return None
+
+
 def client_url(module_id: ModuleID, object_id: str, base_url: str) -> str:
     if module_id == ModuleID.cdrs:
         return base_url
@@ -106,7 +129,33 @@ async def push_object(
                 headers={"authorization": client_auth_token},
             )
             logger.info(f"Response status_code - `{response.status_code}`")
-            endpoints = response.json()["data"]["endpoints"]
+            response_data = response.json()["data"]
+
+            # If response is a versions list, negotiate version and
+            # fetch the details URL for the best mutual version.
+            if isinstance(response_data, list):
+                details_url = _pick_version_details_url(
+                    response_data, version
+                )
+                if not details_url:
+                    raise ValueError(
+                        f"No mutual OCPI version found. "
+                        f"Requested {version.value}, receiver supports: "
+                        f"{[v.get('version') for v in response_data]}"
+                    )
+                logger.info(
+                    f"Resolved version details URL: {details_url}"
+                )
+                response = await client.get(
+                    details_url,
+                    headers={"authorization": client_auth_token},
+                )
+                logger.info(
+                    f"Version details response: {response.status_code}"
+                )
+                response_data = response.json()["data"]
+
+            endpoints = response_data["endpoints"]
             logger.debug(f"Endpoints response data - `{endpoints}`")
 
         # get object data