Add CachedProductsRenderer - wraps ProductsRenderer using Rails cache

lib/open_food_network/cached_products_renderer.rb

@@ -0,0 +1,35 @@
+require 'open_food_network/products_renderer'
+
+# Wrapper for ProductsRenderer that caches the JSON output.
+# ProductsRenderer::NoProducts is represented in the cache as nil,
+# but re-raised to provide the same interface as ProductsRenderer.
+
+module OpenFoodNetwork
+  class CachedProductsRenderer
+    def initialize(distributor, order_cycle)
+      @distributor = distributor
+      @order_cycle = order_cycle
+    end
+
+    def products_json
+      products_json = Rails.cache.fetch("products-json-#{@distributor.id}-#{@order_cycle.id}") do
+        begin
+          uncached_products_json
+        rescue ProductsRenderer::NoProducts
+          nil
+        end
+      end
+
+      raise ProductsRenderer::NoProducts.new if products_json.nil?
+
+      products_json
+    end
+
+
+    private
+
+    def uncached_products_json
+      ProductsRenderer.new(@distributor, @order_cycle).products_json
+    end
+  end
+end