Use DiscountCalculator and fix duplication

There's no reason for both the TaxCalculator and the API to have nearly
the same logic... so I unified that while was in there.

1 files changed, 9 insertions, 5 deletions

diff --git a/lib/super_good/solidus_taxjar/api.rb b/lib/super_good/solidus_taxjar/api.rb
index ffefd5f..2504216 100644
--- a/lib/super_good/solidus_taxjar/api.rb
+++ b/lib/super_good/solidus_taxjar/api.rb
@@ -26,10 +26,6 @@ module SuperGood
         )
       end
 
-      private
-
-      attr_reader :taxjar_client
-
       def order_params(order)
         tax_address = order.tax_address
 
@@ -47,12 +43,20 @@ module SuperGood
               id: line_item.id,
               quantity: line_item.quantity,
               unit_price: line_item.price,
-              discount: -line_item.promo_total,
+              discount: discount(line_item),
               product_tax_code: line_item.tax_category&.tax_code
             }
           end
         }
       end
+
+      private
+
+      attr_reader :taxjar_client
+
+      def discount(line_item)
+        ::SuperGood::SolidusTaxJar.discount_calculator.new(line_item).discount
+      end
     end
   end
 end