TotalOrderValue - handle setting discounts

I'm copying the algorithm from the Offer class to later remove the original one.

Author: andrzejkrzywda

rails_application/app/processes/processes/total_order_value.rb

@@ -4,14 +4,15 @@ class TotalOrderValue
 
     subscribes_to(
       Pricing::PriceItemAdded,
-      Pricing::PriceItemRemoved
+      Pricing::PriceItemRemoved,
+      Pricing::PercentageDiscountSet
     )
 
     private
 
     def act
-      @total_value = state.lines.sum { |line| line.fetch(:price) }
-      publish_total_order_value
+      value = state.lines.sum { |line| line.fetch(:price) } - state.discount_amount
+      publish_total_order_value(value)
     end
 
     def apply(event)
@@ -24,16 +25,18 @@ def apply(event)
       when Pricing::PriceItemRemoved
         lines = state.lines.reject { |line| line.fetch(:product_id) == event.data.fetch(:product_id) }
         state.with(lines:)
+      when Pricing::PercentageDiscountSet
+        state.with(discount_amount: event.data.fetch(:amount))
       else
         state
       end
     end
 
     private
 
-    def publish_total_order_value
+    def publish_total_order_value(value)
       event_store.publish(
-        TotalOrderValueUpdated.new(data: { total_value: @total_value, order_id: @order_id }),
+        TotalOrderValueUpdated.new(data: { total_value: value, order_id: @order_id }),
         stream_name: "Processes::TotalOrderValue$#{@order_id}"
       )
     end
@@ -43,9 +46,9 @@ def fetch_id(event)
     end
   end
 
-  Offer = Data.define(:lines) do
-    def initialize(lines: [])
-      super(lines: lines.freeze)
+  Offer = Data.define(:lines, :discount_amount) do
+    def initialize(lines: [], discount_amount: 0)
+      super(lines: lines.freeze, discount_amount:)
     end
   end
 

rails_application/test/processes/total_order_value_test.rb

@@ -68,6 +68,7 @@ def test_total_order_value_calculation_for_2_items_of_different_products
         process.call(event_2)
       end
     end
+
     def test_total_order_value_calculation_for_2_items_of_different_products_and_1_item_removed
       process = TotalOrderValue.new(event_store, command_bus)
       product_id_1 = SecureRandom.uuid
@@ -99,6 +100,30 @@ def test_total_order_value_calculation_for_2_items_of_different_products_and_1_i
       end
     end
 
+    def test_with_discount
+      process = TotalOrderValue.new(event_store, command_bus)
+      product_id = SecureRandom.uuid
+      event_1 = price_item_added(product_id)
+      event_2 = Pricing::PercentageDiscountSet.new(data: {
+        order_id: order_id,
+        type: "test_discount",
+        amount: 10
+      })
+      event_store.append(event_1)
+      event_store.append(event_2)
+      process.call(event_1)
+      assert_events_contain(
+        "Processes::TotalOrderValue$#{event_2.data[:order_id]}",
+        Processes::TotalOrderValueUpdated.new(
+          data: {
+            total_value: 90,
+            order_id: order_id
+          }
+        )) do
+        process.call(event_2)
+      end
+    end
+
 
 
     private