Initial commit

netbox_services/engine/context.py

@@ -0,0 +1,52 @@
+"""Resolution context — carries service and parent references during tree walk."""
+
+
+class Context:
+    """Evaluation frame for the resolver.
+
+    Top-level context has ``service`` set and ``parent_object`` as None.
+    Each selected/allocated object pushes a child context so children
+    can reference ``parent`` and traverse its relations.
+    """
+
+    def __init__(self, service, parent_object=None):
+        self.service = service
+        self.parent_object = parent_object
+
+    def child(self, obj):
+        return Context(
+            service=self.service,
+            parent_object=obj,
+        )
+
+    @property
+    def parent(self):
+        return self.parent_object
+
+    def resolve_path(self, path):
+        """Resolve a dotted reference like ``parent.site.management_prefix``.
+
+        Supported roots:
+          - ``service``  → the Service instance
+          - ``parent``   → the parent object (or None at service scope)
+        Returns None if any segment is None or missing.
+        """
+        parts = path.split(".")
+        root = parts[0]
+
+        if root == "service":
+            obj = self.service
+        elif root == "parent":
+            obj = self.parent_object
+        else:
+            raise KeyError(f"Unknown context root: {root!r}")
+
+        for part in parts[1:]:
+            if obj is None:
+                return None
+            if isinstance(obj, dict):
+                obj = obj.get(part)
+            else:
+                obj = getattr(obj, part, None)
+
+        return obj