Refresh products cache when inventory items are changed

app/models/inventory_item.rb

@@ -1,3 +1,5 @@
+require 'open_food_network/products_cache'
+
 class InventoryItem < ActiveRecord::Base
   attr_accessible :enterprise, :enterprise_id, :variant, :variant_id, :visible
 
@@ -11,4 +13,13 @@ class InventoryItem < ActiveRecord::Base
 
   scope :visible, where(visible: true)
   scope :hidden, where(visible: false)
+
+  after_save :refresh_products_cache
+
+
+  private
+
+  def refresh_products_cache
+    OpenFoodNetwork::ProductsCache.inventory_item_changed self
+  end
 end

lib/open_food_network/products_cache.rb

@@ -95,6 +95,13 @@ module OpenFoodNetwork
     end
 
 
+    def self.inventory_item_changed(inventory_item)
+      exchanges_featuring_variants(inventory_item.variant, distributor: inventory_item.enterprise).each do |exchange|
+        refresh_cache exchange.receiver, exchange.order_cycle
+      end
+    end
+
+
     private
 
     def self.exchanges_featuring_variants(variants, distributor: nil)

spec/lib/open_food_network/products_cache_spec.rb

@@ -386,6 +386,25 @@ module OpenFoodNetwork
       end
     end
 
+    describe "when an inventory item is changed" do
+      let!(:d) { create(:distributor_enterprise) }
+      let!(:v) { create(:variant) }
+      let!(:oc1) { create(:open_order_cycle, distributors: [d], variants: [v]) }
+      let(:oc2) { create(:open_order_cycle, distributors: [d], variants: []) }
+      let!(:ii) { create(:inventory_item, enterprise: d, variant: v) }
+
+      it "updates each distribution for that enterprise+variant" do
+        expect(ProductsCache).to receive(:refresh_cache).with(d, oc1)
+        ProductsCache.inventory_item_changed ii
+      end
+
+      it "doesn't update distributions that don't feature the variant" do
+        oc2
+        expect(ProductsCache).to receive(:refresh_cache).with(d, oc2).never
+        ProductsCache.inventory_item_changed ii
+      end
+    end
+
     describe "refreshing the cache" do
       let(:distributor) { double(:distributor) }
       let(:order_cycle) { double(:order_cycle) }

spec/models/inventory_item_spec.rb

@@ -0,0 +1,16 @@
+require 'spec_helper'
+require 'open_food_network/products_cache'
+
+describe InventoryItem do
+  describe "caching" do
+    let(:ii) { create(:inventory_item) }
+
+    it "refreshes the products cache on save" do
+      expect(OpenFoodNetwork::ProductsCache).to receive(:inventory_item_changed).with(ii)
+      ii.visible = false
+      ii.save
+    end
+
+    # Inventory items are not destroyed
+  end
+end