Merged OrderItemInvoicingProcess into InvoiceGeneration process

Removed InvoiceItemCalculated event.
Removed the choreography with VAT determination via commands and events. Instead now, we access to the VatRateCatalog - not perfect either. Next time we work in this area, it would be nice to just subscribe in process for VAT events. Or have a read model for the process.
Many tests had to be updated to set proper vat rate.

Author: andrzejkrzywda

ecommerce/taxes/lib/taxes.rb

@@ -9,7 +9,6 @@ module Taxes
   class Configuration
     def call(event_store, command_bus)
       command_bus.register(SetVatRate, SetVatRateHandler.new(event_store))
-      command_bus.register(DetermineVatRate, DetermineVatRateHandler.new(event_store))
       command_bus.register(AddAvailableVatRate, AddAvailableVatRateHandler.new(event_store))
       command_bus.register(RemoveAvailableVatRate, RemoveAvailableVatRateHandler.new(event_store))
     end

ecommerce/taxes/lib/taxes/commands.rb

@@ -4,11 +4,6 @@ class SetVatRate < Infra::Command
     attribute :vat_rate_code, Infra::Types::String
   end
 
-  class DetermineVatRate < Infra::Command
-    attribute :product_id, Infra::Types::UUID
-    attribute :order_id, Infra::Types::UUID
-  end
-
   class AddAvailableVatRate < Infra::Command
     attribute :available_vat_rate_id, Infra::Types::UUID
     attribute :vat_rate, Infra::Types::VatRate

ecommerce/taxes/lib/taxes/events.rb

@@ -4,12 +4,6 @@ class VatRateSet < Infra::Event
     attribute :vat_rate, Infra::Types::VatRate
   end
 
-  class VatRateDetermined < Infra::Event
-    attribute :order_id, Infra::Types::UUID
-    attribute :product_id, Infra::Types::UUID
-    attribute :vat_rate, Infra::Types::VatRate
-  end
-
   class AvailableVatRateAdded < Infra::Event
     attribute :available_vat_rate_id, Infra::Types::UUID
     attribute :vat_rate, Infra::Types::VatRate

ecommerce/taxes/lib/taxes/services.rb

@@ -17,30 +17,6 @@ def call(cmd)
     end
   end
 
-  class DetermineVatRateHandler
-    def initialize(event_store)
-      @catalog = VatRateCatalog.new(event_store)
-      @event_store = event_store
-    end
-
-    def call(cmd)
-      order_id = cmd.order_id
-      product_id = cmd.product_id
-      vat_rate = catalog.vat_rate_for(product_id)
-      return unless vat_rate
-      event = VatRateDetermined.new(data: { order_id: order_id, product_id: product_id, vat_rate: vat_rate })
-      event_store.publish(event, stream_name: stream_name(order_id))
-    end
-
-    private
-
-    attr_reader :catalog, :event_store
-
-    def stream_name(order_id)
-      "Taxes::Order$#{order_id}"
-    end
-  end
-
   class AddAvailableVatRateHandler
     include Infra::Retry
 

rails_application/.mutant.yml

@@ -45,7 +45,6 @@ matcher:
     - Processes::Test*
     - Processes::ReleasePaymentProcess*
     - Processes::MoneySplitter*
-    - Processes::OrderItemInvoicingProcess#fetch_id
     - Processes::SyncShipmentFromPricing*
     - Processes::SyncInventoryFromOrdering*
     - Processes::NotifyPaymentsAboutOrderValue*

rails_application/app/processes/processes/configuration.rb

@@ -16,7 +16,6 @@ def call(event_store, command_bus)
 
       enable_release_payment_process(event_store, command_bus)
       enable_shipment_process(event_store, command_bus)
-      enable_order_item_invoicing_process(event_store, command_bus)
       enable_reservation_process(event_store, command_bus)
       enable_welcome_message_process(event_store, command_bus)
       enable_total_order_value_process(event_store, command_bus)
@@ -60,17 +59,6 @@ def enable_release_payment_process(event_store, command_bus)
       )
     end
 
-    def enable_order_item_invoicing_process(event_store, command_bus)
-      event_store.subscribe(
-        OrderItemInvoicingProcess.new(event_store, command_bus),
-        to: [
-          Processes::InvoiceItemValueCalculated,
-          Taxes::VatRateDetermined
-        ]
-      )
-    end
-
-
     def enable_product_name_sync(event_store, command_bus)
       Infra::Process.new(event_store, command_bus)
                     .call(ProductCatalog::ProductNamed, [:product_id, :name],

rails_application/app/processes/processes/invoice_generation.rb

@@ -2,6 +2,11 @@ module Processes
   class InvoiceGeneration
     include Infra::ProcessManager.with_state { Invoice }
 
+    def initialize(event_store, command_bus)
+      super(event_store, command_bus)
+      @vat_rate_catalog = Taxes::VatRateCatalog.new(event_store)
+    end
+
     subscribes_to(
       Pricing::PriceItemAdded,
       Pricing::PriceItemRemoved,
@@ -13,7 +18,6 @@ class InvoiceGeneration
 
     def act
       calculate_sub_amounts
-      determine_vat_rates if state.placed?
     end
 
     private
@@ -37,37 +41,36 @@ def apply(event)
         apply_percentage_discount_removed(event)
       when Fulfillment::OrderRegistered
         apply_order_registered
-      else
-        state
       end
     end
 
     def calculate_sub_amounts
+      return unless state.placed?
+      
       sub_amounts_total = state.sub_amounts_total
-
       sub_amounts_total.each_pair do |product_id, h|
-        publish_invoice_item_value_calculated(
+        create_invoice_items_for_product(
           product_id: product_id,
           quantity: h.fetch(:quantity),
-          amount: h.fetch(:base_amount),
           discounted_amount: h.fetch(:amount)
         )
       end
     end
 
-    def publish_invoice_item_value_calculated(product_id:, quantity:, amount:, discounted_amount:)
-      event_store.publish(
-        InvoiceItemValueCalculated.new(
-          data: {
-            order_id: @order_id,
+    def create_invoice_items_for_product(product_id:, quantity:, discounted_amount:)
+      vat_rate = @vat_rate_catalog.vat_rate_for(product_id)
+      unit_prices = MoneySplitter.new(discounted_amount, quantity).call
+      unit_prices.tally.each do |unit_price, quantity|
+        command_bus.call(
+          Invoicing::AddInvoiceItem.new(
+            invoice_id: @order_id,
             product_id: product_id,
+            vat_rate: vat_rate,
             quantity: quantity,
-            amount: amount,
-            discounted_amount: discounted_amount
-          }
-        ),
-        stream_name: "Processes::InvoiceGeneration$#{@order_id}"
-      )
+            unit_price: unit_price
+          )
+        )
+      end
     end
 
     def apply_price_item_added(event)
@@ -125,13 +128,6 @@ def apply_discounts_to_existing_lines(new_state)
       new_state.with(lines: updated_lines)
     end
 
-    def determine_vat_rates
-      state.sub_amounts_total.each_key do |product_id|
-        command = Taxes::DetermineVatRate.new(order_id: @order_id, product_id: product_id)
-        command_bus.call(command)
-      end
-    end
-
     def apply_order_registered
       state.with(order_placed: true)
     end
@@ -174,4 +170,30 @@ def placed?
     end
   end
 
+  class MoneySplitter
+    def initialize(amount, quantity)
+      @amount = amount
+      @weights = Array.new(quantity, 1)
+    end
+
+    def call
+      distributed_amounts = []
+      total_weight = @weights.sum.to_d
+      @weights.each do |weight|
+        if total_weight.eql?(0)
+          distributed_amounts << 0
+          next
+        end
+
+        p = weight / total_weight
+        distributed_amount = (p * @amount).round(2)
+        distributed_amounts << distributed_amount
+        total_weight -= weight
+        @amount -= distributed_amount
+      end
+
+      distributed_amounts
+    end
+  end
+
 end

rails_application/app/processes/processes/invoice_item_value_calculated.rb

@@ -38,9 +38,11 @@ def test_order_confirmed
     private
 
     def create_product(product_id, name, price)
+      vat_rate = Infra::Types::VatRate.new(rate: 20, code: "20")
       run_command(ProductCatalog::RegisterProduct.new(product_id: product_id))
       run_command(ProductCatalog::NameProduct.new(product_id: product_id, name: name))
       run_command(Pricing::SetPrice.new(product_id: product_id, price: price))
+      Rails.configuration.event_store.publish(Taxes::VatRateSet.new(data: { product_id: product_id, vat_rate: vat_rate }))
     end
   end
 end