First attempt at ripping out agnostic code into ifcopenshell.api namespace. See #1399.

src/ifcopenshell-python/ifcopenshell/api/geometry/remove_representation.py

@@ -0,0 +1,43 @@
+import ifcopenshell.util.element
+
+
+class Usecase:
+    def __init__(self, file, settings=None):
+        self.file = file
+        self.settings = {"representation": None}
+        for key, value in settings.items():
+            self.settings[key] = value
+
+    def execute(self):
+        if self.settings["representation"].RepresentationType == "MappedRepresentation":
+            return self.remove_mapped_representation_portion_only()
+        return self.remove_entire_representation_tree()
+
+    def remove_mapped_representation_portion_only(self):
+        dummy_context = self.file.create_entity("IfcRepresentationContext")
+        dummy_representation_map = self.file.createIfcRepresentationMap()
+        self.settings["representation"].ContextOfItems = dummy_context
+        for item in self.settings["representation"].Items:
+            item.MappingSource = dummy_representation_map
+        ifcopenshell.util.element.remove_deep(self.file, self.settings["representation"])
+
+    def remove_entire_representation_tree(self):
+        dummy_context = self.file.create_entity("IfcRepresentationContext")
+        for subelement in self.file.traverse(self.settings["representation"]):
+            if subelement.is_a("IfcRepresentationItem") and subelement.StyledByItem:
+                [self.file.remove(s) for s in subelement.StyledByItem]
+            elif subelement.is_a("IfcRepresentation"):
+                subelement.ContextOfItems = dummy_context
+                self.purge_representation_inverses(subelement)
+        self.purge_representation_inverses(self.settings["representation"])
+        ifcopenshell.util.element.remove_deep(self.file, self.settings["representation"])
+
+    def purge_representation_inverses(self, element):
+        for inverse in self.file.get_inverse(element):
+            if inverse.is_a("IfcPresentationLayerAssignment"):
+                assigned_items = set(inverse.AssignedItems)
+                if len(assigned_items) == 1:
+                    self.file.remove(inverse)
+                else:
+                    assigned_items.remove(element)
+                    inverse.AssignedItems = list(assigned_items)