From f6664b2477f4c8a2fa882760ddaeaf34439f2754 Mon Sep 17 00:00:00 2001
From: Oliver Walters <oliver.henry.walters@gmail.com>
Date: Mon, 4 Apr 2022 22:50:13 +1000
Subject: [PATCH] Add annotated fields to BomItem API:

- total-stock / allocated_to_build_orders / allocated_to_sales_orders
---
 InvenTree/part/api.py         |  3 +-
 InvenTree/part/serializers.py | 63 +++++++++++++++++++++++++++++++++++
 2 files changed, 65 insertions(+), 1 deletion(-)

diff --git a/InvenTree/part/api.py b/InvenTree/part/api.py
index f7bb81520d..911e5453a5 100644
--- a/InvenTree/part/api.py
+++ b/InvenTree/part/api.py
@@ -1601,9 +1601,10 @@ class BomList(generics.ListCreateAPIView):
 
     def get_queryset(self, *args, **kwargs):
 
-        queryset = BomItem.objects.all()
+        queryset = super().get_queryset(*args, **kwargs)
 
         queryset = self.get_serializer_class().setup_eager_loading(queryset)
+        queryset = self.get_serializer_class().annotate_queryset(queryset)
 
         return queryset
 
diff --git a/InvenTree/part/serializers.py b/InvenTree/part/serializers.py
index c352c59eab..09bb4799a0 100644
--- a/InvenTree/part/serializers.py
+++ b/InvenTree/part/serializers.py
@@ -577,6 +577,11 @@ class BomItemSerializer(InvenTreeModelSerializer):
 
     purchase_price_range = serializers.SerializerMethodField()
 
+    # Annotated fields
+    total_stock = serializers.FloatField(read_only=True)
+    allocated_to_sales_orders = serializers.FloatField(read_only=True)
+    allocated_to_build_orders = serializers.FloatField(read_only=True)
+
     def __init__(self, *args, **kwargs):
         # part_detail and sub_part_detail serializers are only included if requested.
         # This saves a bunch of database requests
@@ -613,6 +618,59 @@ class BomItemSerializer(InvenTreeModelSerializer):
         queryset = queryset.prefetch_related('sub_part__supplier_parts__pricebreaks')
         return queryset
 
+    @staticmethod
+    def annotate_queryset(queryset):
+        """
+        Annotate the BomItem queryset with extra information:
+
+        Annotations:
+            available_stock: The amount of stock available for the sub_part Part object
+        """
+
+        """
+        Construct an "available stock" quantity:
+        
+        available_stock = total_stock - build_order_allocations - sales_order_allocations
+        """
+
+        # Calculate "total stock" for the referenced sub_part
+        # Calculate the "build_order_allocations" for the sub_part
+        queryset = queryset.annotate(
+            total_stock=Coalesce(
+                SubquerySum('sub_part__stock_items__quantity', filter=StockItem.IN_STOCK_FILTER),
+                Decimal(0),
+                output_field=models.DecimalField(),
+            ),
+            allocated_to_sales_orders=Coalesce(
+                SubquerySum(
+                    'sub_part__stock_items__sales_order_allocations__quantity',
+                    filter=Q(
+                        line__order__status__in=SalesOrderStatus.OPEN,
+                        shipment__shipment_date=None,
+                    )
+                ),
+                Decimal(0),
+                output_field=models.DecimalField(),
+            ),
+            allocated_to_build_orders=Coalesce(
+                SubquerySum(
+                    'sub_part__stock_items__allocations__quantity',
+                    filter=Q(
+                        build__status__in=BuildStatus.ACTIVE_CODES,
+                    ),
+                ),
+                Decimal(0),
+                output_field=models.DecimalField(),
+            )
+            # build_order_allocations=Coalesce(
+            #     SubquerySum('sub_part__stock_items__allocations__quantity'), 
+            # )
+        )
+
+        # queryset = querty
+
+        return queryset
+
     def get_purchase_price_range(self, obj):
         """ Return purchase price range """
 
@@ -682,6 +740,11 @@ class BomItemSerializer(InvenTreeModelSerializer):
             'substitutes',
             'price_range',
             'validated',
+
+            'total_stock',
+            'allocated_to_sales_orders',
+            'allocated_to_build_orders',
+
         ]