Find wholesale offer for retail variant

app/jobs/backorder_job.rb

@@ -36,23 +36,34 @@ class BackorderJob < ApplicationJob
     orderer = FdcBackorderer.new(user)
     backorder = orderer.find_or_build_order(order)
     broker = load_broker(order.distributor.owner)
+    ordered_quantities = {}
 
     linked_variants.each do |variant|
       needed_quantity = -1 * variant.on_hand
-      offer = broker.best_offer(variant.semantic_links[0].semantic_id)
+      solution = broker.best_offer(variant.semantic_links[0].semantic_id)
 
-      line = orderer.find_or_build_order_line(backorder, offer)
-      line.quantity = line.quantity.to_i + needed_quantity
+      # The number of wholesale packs we need to order to fulfill the
+      # needed quantity.
+      # For example, we order 2 packs of 12 cans if we need 15 cans.
+      wholesale_quantity = (needed_quantity.to_f / solution.factor).ceil
+
+      # The number of individual retail items we get with the wholesale order.
+      # For example, if we order 2 packs of 12 cans, we will get 24 cans
+      # and we'll account for that in our stock levels.
+      retail_quantity = wholesale_quantity * solution.factor
+
+      line = orderer.find_or_build_order_line(backorder, solution.offer)
+      line.quantity = line.quantity.to_i + wholesale_quantity
+
+      ordered_quantities[variant] = retail_quantity
     end
 
     placed_order = orderer.send_order(backorder)
 
     schedule_order_completion(user, order, placed_order) if orderer.new?(backorder)
 
-    # Once we have transformations and know the quantities in bulk products
-    # we will need to increase on_hand by the ordered quantity.
     linked_variants.each do |variant|
-      variant.on_hand = 0
+      variant.on_hand += ordered_quantities[variant]
     end
   end
 

app/services/fdc_offer_broker.rb

@@ -2,13 +2,23 @@
 
 # Finds wholesale offers for retail products.
 class FdcOfferBroker
+  Solution = Struct.new(:product, :factor, :offer)
+
   def initialize(catalog)
     @catalog = catalog
   end
 
   def best_offer(product_id)
-    product = @catalog.find { |item| item.semanticId == product_id }
-    offer_of(product)
+    consumption_flow = catalog_item("#{product_id}/AsPlannedConsumptionFlow")
+    production_flow = catalog_item("#{product_id}/AsPlannedProductionFlow")
+
+    contained_quantity = consumption_flow.quantity.value.to_i
+    wholesale_product_id = production_flow.product
+    wholesale_product = catalog_item(wholesale_product_id )
+
+    offer = offer_of(wholesale_product)
+
+    Solution.new(wholesale_product, contained_quantity, offer)
   end
 
   def offer_of(product)
@@ -17,4 +27,9 @@ class FdcOfferBroker
       offer.offeredItem = product
     end
   end
+
+  def catalog_item(id)
+    @catalog_by_id ||= @catalog.index_by(&:semanticId)
+    @catalog_by_id[id]
+  end
 end

spec/jobs/backorder_job_spec.rb

@@ -35,7 +35,8 @@ RSpec.describe BackorderJob do
         BackorderJob.check_stock(order)
       }.to enqueue_job CompleteBackorderJob
 
-      expect(variant.on_hand).to eq 0
+      # We ordered a case of 12 cans: -3 + 12 = 9
+      expect(variant.on_hand).to eq 9
 
       # Clean up after ourselves:
       perform_enqueued_jobs(only: CompleteBackorderJob)

spec/services/fdc_offer_broker_spec.rb

@@ -11,14 +11,14 @@ RSpec.describe FdcOfferBroker do
   }
 
   describe ".best_offer" do
-    it "finds a linked offer", vcr: true do
-      offer = subject.best_offer(product.semanticId)
+    it "finds a linked wholesale offer", vcr: true do
+      solution = subject.best_offer(product.semanticId)
 
-      # This is the URL structure on the FDC API:
-      expect(offer.semanticId).to eq "#{product.semanticId}/Offer"
-
-      # Well, if you ask the orders endpoint, you actually get different ids
-      # for the same offers...
+      # These values depend on the test data but are a good sanity check:
+      expect(product.name).to eq "Baked British Beans - Retail can, 400g (can)"
+      expect(solution.product.name).to eq "Baked British Beans - Case, 12 x 400g (can)"
+      expect(solution.factor).to eq 12
+      expect(solution.offer.offeredItem).to eq solution.product
     end
   end
 end