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modules/account_stock_shipment_cost_weight/account.py

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+# This file is part of Tryton.  The COPYRIGHT file at the top level of
+# this repository contains the full copyright notices and license terms.
+from decimal import Decimal
+
+from trytond.pool import PoolMeta
+
+
+class ShipmentCost(metaclass=PoolMeta):
+    __name__ = 'account.shipment_cost'
+
+    @classmethod
+    def __setup__(cls):
+        super().__setup__()
+        cls.allocation_method.selection.append(('weight', "By Weight"))
+
+    def allocate_cost_by_weight(self):
+        self.factors = self._get_factors('weight')
+        self._allocate_cost(self.factors)
+
+    def unallocate_cost_by_weight(self):
+        factors = self.factors or self._get_factors('weight')
+        self._allocate_cost(factors, sign=-1)
+
+    def _get_weight_factors(self):
+        "Return the factor for each shipment based on weight"
+        shipments = self.all_shipments
+        sum_weight = sum(Decimal(s.weight or 0) for s in shipments)
+        length = Decimal(len(shipments))
+        factors = {}
+        for shipment in shipments:
+            if not sum_weight:
+                factors[str(shipment)] = 1 / length
+            else:
+                factors[str(shipment)] = (
+                    Decimal(shipment.weight or 0) / sum_weight)
+        return factors