Rewriter: deleting elements works

transformation/rewriter.py

@@ -0,0 +1,36 @@
+# Things you can do:
+#   - Create/delete objects, associations, attributes
+#   - Change attribute values
+#   - ? that's it?
+
+from uuid import UUID
+from services.bottom.V0 import Bottom
+
+def process_rule(state, lhs: UUID, rhs: UUID):
+    bottom = Bottom(state)
+
+    # : bottom.read_outgoing_elements(rhs, name)[0]
+    to_delete = { name for name in bottom.read_keys(lhs) if name not in bottom.read_keys(rhs) }
+    to_create = { name for name in bottom.read_keys(rhs) if name not in bottom.read_keys(lhs) }
+
+    print("to_delete:", to_delete)
+    print("to_create:", to_create)
+
+    return to_delete, to_create
+
+def rewrite(state, lhs: UUID, rhs: UUID, match_mapping: dict, model_to_transform: UUID) -> UUID:
+    bottom = Bottom(state)
+
+    to_delete, to_create = process_rule(state, lhs, rhs)
+
+    for pattern_name_to_delete in to_delete:
+        # For every name in `to_delete`, look up the name of the matched element in the host graph
+        model_element_name_to_delete = match_mapping[pattern_name_to_delete]
+        print('deleting', model_element_name_to_delete)
+        # Look up the matched element in the host graph
+        element_to_delete, = bottom.read_outgoing_elements(model_to_transform, model_element_name_to_delete)
+        # Delete
+        bottom.delete_element(element_to_delete)
+
+    for pattern_name_to_create in to_create:
+        pass