feat: implement automatic margin pricing and margin reverse engineering in sync

backend/test_group_binding_create_sync.py

@@ -387,3 +387,49 @@ def test_create_binding_does_not_notify_when_website_rate_unchanged(monkeypatch,
 
     assert result.target_group_id == "target"
     assert db_session.query(NotificationLog).count() == 0
+
+
+def test_sync_binding_auto_percent_writeback(monkeypatch, db_session):
+    website, upstream = seed_rows(db_session)
+    binding = WebsiteGroupBinding(
+        website_id=website.id,
+        target_group_id="target",
+        target_group_name="Target group",
+        source_groups_json=json.dumps([{
+            "upstream_id": upstream.id,
+            "upstream_name": "Upstream",
+            "group_id": "source",
+            "group_name": "Source",
+        }], ensure_ascii=False),
+        percent="0.00",
+        algorithm="priority_weighted_plus_percent",
+        enabled=True,
+    )
+    db_session.add(binding)
+    db_session.commit()
+    db_session.refresh(binding)
+
+    class FakeClient:
+        def __init__(self, **kwargs):
+            pass
+        def __enter__(self):
+            return self
+        def __exit__(self, *args):
+            pass
+        def get_groups(self, endpoint):
+            return [{"id": "target", "name": "Target group", "rate_multiplier": "2.0"}]
+        def update_group_rate(self, endpoint, group_id, rate):
+            pass
+
+    monkeypatch.setattr(websites_router, "Sub2ApiWebsiteClient", FakeClient)
+    monkeypatch.setattr("app.services.website_sync.Sub2ApiWebsiteClient", FakeClient)
+
+    from app.services.website_sync import sync_binding
+    sync_binding(db_session, binding, write=True)
+
+    db_session.refresh(binding)
+    assert binding.percent == "50.00"
+
+    log = db_session.query(WebsiteSyncLog).filter(WebsiteSyncLog.binding_id == binding.id).one()
+    assert log.percent == "50.00"
+    assert log.new_rate == "3.00"