Adjust quantities of backorder before completion

app/jobs/complete_backorder_job.rb

@@ -3,12 +3,13 @@
 # After an order cycle closed, we need to finalise open draft orders placed
 # to replenish stock.
 class CompleteBackorderJob < ApplicationJob
-  def perform(user, order_id)
-    # TODO: review our stock levels and adjust quantities if we got surplus.
-    # This can happen when orders are cancelled and products restocked.
+  def perform(user, distributor, order_cycle, order_id)
     service = FdcBackorderer.new(user)
     order = service.find_order(order_id)
-    adjust_quantities(order)
+
+    variants = order_cycle.variants_distributed_by(distributor)
+    adjust_quantities(user, order, variants)
+
     service.complete_order(order)
   end
 
@@ -17,7 +18,20 @@ def perform(user, order_id)
   # Our local stock can increase when users cancel their orders.
   # But stock levels could also have been adjusted manually. So we review all
   # quantities before finalising the order.
-  def adjust_quantities(order)
-    # TODO
+  def adjust_quantities(user, order, variants)
+    broker = FdcOfferBroker.new(BackorderJob.load_catalog(user))
+
+    order.lines.each do |line|
+      wholesale_product_id = line.offer.offeredItem.semanticId
+      transformation = broker.wholesale_to_retail(wholesale_product_id)
+      linked_variant = variants.linked_to(transformation.retail_product_id)
+
+      # Note that a division of integers dismisses the remainder, like `floor`:
+      wholesale_items_contained_in_stock = linked_variant.on_hand / transformation.factor
+      line.quantity = line.quantity.to_i - wholesale_items_contained_in_stock
+
+      retail_stock_changes = wholesale_items_contained_in_stock * transformation.factor
+      linked_variant.on_hand -= retail_stock_changes
+    end
   end
 end

app/services/fdc_offer_broker.rb

@@ -2,7 +2,9 @@
 
 # Finds wholesale offers for retail products.
 class FdcOfferBroker
+  # TODO: Find a better way to provide this data.
   Solution = Struct.new(:product, :factor, :offer)
+  RetailSolution = Struct.new(:retail_product_id, :factor)
 
   def initialize(catalog)
     @catalog = catalog
@@ -14,13 +16,25 @@ def best_offer(product_id)
 
     contained_quantity = consumption_flow.quantity.value.to_i
     wholesale_product_id = production_flow.product
-    wholesale_product = catalog_item(wholesale_product_id )
+    wholesale_product = catalog_item(wholesale_product_id)
 
     offer = offer_of(wholesale_product)
 
     Solution.new(wholesale_product, contained_quantity, offer)
   end
 
+  def wholesale_to_retail(wholesale_product_id)
+    production_flow = flow_producing(wholesale_product_id)
+    consumption_flow = catalog_item(
+      production_flow.semanticId.sub("AsPlannedProductionFlow", "AsPlannedConsumptionFlow")
+    )
+    retail_product_id = consumption_flow.product
+
+    contained_quantity = consumption_flow.quantity.value.to_i
+
+    RetailSolution.new(retail_product_id, contained_quantity)
+  end
+
   def offer_of(product)
     product&.catalogItems&.first&.offers&.first&.tap do |offer|
       # Unfortunately, the imported catalog doesn't provide the reverse link:
@@ -32,4 +46,15 @@ def catalog_item(id)
     @catalog_by_id ||= @catalog.index_by(&:semanticId)
     @catalog_by_id[id]
   end
+
+  def flow_producing(wholesale_product_id)
+    @production_flows_by_product_id ||= production_flows.index_by(&:product)
+    @production_flows_by_product_id[wholesale_product_id]
+  end
+
+  def production_flows
+    @production_flows ||= @catalog.select do |i|
+      i.semanticType == "dfc-b:AsPlannedProductionFlow"
+    end
+  end
 end

spec/jobs/complete_backorder_job_spec.rb

@@ -5,26 +5,60 @@
 RSpec.describe CompleteBackorderJob do
   let(:user) { build(:testdfc_user) }
   let(:catalog) { BackorderJob.load_catalog(user) }
-  let(:product) {
+  let(:retail_product) {
     catalog.find { |item| item.semanticType == "dfc-b:SuppliedProduct" }
   }
+  let(:wholesale_product) {
+    flow = catalog.find { |item| item.semanticType == "dfc-b:AsPlannedProductionFlow" }
+    catalog.find { |item| item.semanticId == flow.product }
+  }
   let(:orderer) { FdcBackorderer.new(user) }
   let(:order) {
-    ofn_order = build(:order, distributor_id: 1)
-    ofn_order.order_cycle = build(:order_cycle)
     backorder = orderer.find_or_build_order(ofn_order)
-    offer = FdcOfferBroker.new(nil).offer_of(product)
+    broker = FdcOfferBroker.new(catalog)
+    offer = broker.best_offer(retail_product.semanticId).offer
     line = orderer.find_or_build_order_line(backorder, offer)
     line.quantity = 3
 
     orderer.send_order(backorder)
   }
+  let(:ofn_order) { create(:completed_order_with_totals) }
+  let(:distributor) { ofn_order.distributor }
+  let(:order_cycle) { ofn_order.order_cycle }
+  let(:variant) { ofn_order.variants[0] }
 
   describe "#perform" do
+    before do
+      variant.semantic_links << SemanticLink.new(
+        semantic_id: retail_product.semanticId
+      )
+
+      # We are assuming 12 cans in a slab.
+      # We got more stock than we need.
+      variant.on_hand = 13
+
+      ofn_order.order_cycle = create(
+        :simple_order_cycle,
+        distributors: [distributor],
+        variants: [variant],
+      )
+    end
+
     it "completes an order", vcr: true do
-      subject.perform(user, order.semanticId)
-      updated_order = orderer.find_order(order.semanticId)
-      expect(updated_order.orderStatus[:path]).to eq "Complete"
+      current_order = order
+
+      expect {
+        subject.perform(user, distributor, order_cycle, order.semanticId)
+        current_order = orderer.find_order(order.semanticId)
+      }.to change {
+        current_order.orderStatus[:path]
+      }.from("Held").to("Complete")
+        .and change {
+          current_order.lines[0].quantity.to_i
+        }.from(3).to(2)
+        .and change {
+          variant.on_hand
+        }.from(13).to(1)
     end
   end
 end