some apis of pos

apps/warehouse/services/services.py

@@ -0,0 +1,25 @@
+from apps.warehouse.models import InventoryEntry, InventoryQuotaSaleTransaction
+from apps.herd.services.services import rancher_quota_weight
+from django.db.models import Sum
+
+
+def get_total_sold(inventory_entry, rancher):
+    """
+    """
+    return (
+            InventoryQuotaSaleTransaction.objects.filter(
+                inventory_entry=inventory_entry,
+                rancher=rancher
+            ).aggregate(total=Sum('weight'))['total'] or 0
+    )
+
+
+def can_buy_from_inventory(rancher, inventory_entry: InventoryEntry):
+    """
+    """
+    quota_weight = rancher_quota_weight(rancher, inventory_entry)  # {total, by_type}
+    total_allowed = quota_weight['total']
+
+    total_sold = get_total_sold(inventory_entry, rancher)
+
+    return total_sold < total_allowed