Implement task-based parametric cost item quantities

src/ifcopenshell-python/ifcopenshell/api/cost/assign_cost_item_quantity.py

@@ -0,0 +1,35 @@
+import ifcopenshell.api
+
+
+class Usecase:
+    def __init__(self, file, **settings):
+        self.file = file
+        self.settings = {"cost_item": None, "products": [], "prop_name": ""}
+        for key, value in settings.items():
+            self.settings[key] = value
+
+    def execute(self):
+        self.quantities = set(self.settings["cost_item"].CostQuantities or [])
+        for product in self.settings["products"]:
+            ifcopenshell.api.run(
+                "control.assign_control",
+                self.file,
+                related_object=product,
+                relating_control=self.settings["cost_item"],
+            )
+            self.add_quantity_from_related_object(product)
+        self.settings["cost_item"].CostQuantities = list(self.quantities)
+
+    def add_quantity_from_related_object(self, element):
+        if not element.is_a("IfcObject"):
+            return
+        for relationship in element.IsDefinedBy:
+            if relationship.is_a("IfcRelDefinesByProperties"):
+                self.add_quantity_from_qto(relationship.RelatingPropertyDefinition)
+
+    def add_quantity_from_qto(self, qto):
+        if not qto.is_a("IfcElementQuantity"):
+            return
+        for prop in qto.Quantities:
+            if prop.is_a("IfcPhysicalSimpleQuantity") and prop.Name.lower() == self.settings["prop_name"].lower():
+                self.quantities.add(prop)