Add projection and read models

Author: marlena-b

ecommerce/ordering/lib/ordering.rb

@@ -22,6 +22,7 @@
 require_relative "ordering/service"
 require_relative "ordering/order"
 require_relative "ordering/refund"
+require_relative "ordering/projections"
 
 module Ordering
   class Configuration

ecommerce/ordering/lib/ordering/projections.rb

@@ -0,0 +1,11 @@
+module Ordering
+  class Projections
+    def self.product_quantity_available_to_refund(order_id, product_id)
+      RubyEventStore::Projection
+        .from_stream("Ordering::Order$#{order_id}")
+        .init(-> { { available: 0 } })
+        .when(ItemAddedToBasket, -> (state, event) { state[:available] += 1 if event.data.fetch(:product_id) == product_id })
+        .when(ItemRemovedFromBasket, -> (state, event) { state[:available] -= 1 if event.data.fetch(:product_id) == product_id })
+    end
+  end
+end

ecommerce/ordering/lib/ordering/refund.rb

@@ -2,6 +2,7 @@ module Ordering
   class Refund
     include AggregateRoot
 
+    ExceedsOrderQuantityError = Class.new(StandardError)
     ProductNotFoundError = Class.new(StandardError)
 
     def initialize(id)
@@ -13,7 +14,8 @@ def create_draft(order_id)
       apply DraftRefundCreated.new(data: { refund_id: @id, order_id: order_id })
     end
 
-    def add_item(product_id)
+    def add_item(product_id, available_quantity_to_refund)
+      raise ExceedsOrderQuantityError unless enough_items?(available_quantity_to_refund, product_id)
       apply ItemAddedToRefund.new(data: { refund_id: @id, order_id: @order_id, product_id: product_id })
     end
 
@@ -33,6 +35,12 @@ def remove_item(product_id)
     on ItemRemovedFromRefund do |event|
       @refund_items.decrease_quantity(event.data[:product_id])
     end
+
+    private
+
+    def enough_items?(available_quantity_to_refund, product_id)
+      @refund_items.quantity(product_id) < available_quantity_to_refund
+    end
   end
 
   class ItemsList
@@ -48,7 +56,7 @@ def increase_quantity(product_id)
 
     def decrease_quantity(product_id)
       refund_items[product_id] -= 1
-      refund_items.delete(product_id) if refund_items.fetch(product_id).equal?(0)
+      refund_items.delete(product_id) if quantity(product_id).equal?(0)
     end
 
     def quantity(product_id)

ecommerce/ordering/lib/ordering/service.rb

@@ -88,13 +88,26 @@ def call(command)
   class OnAddItemToRefund
     def initialize(event_store)
       @repository = Infra::AggregateRootRepository.new(event_store)
+      @event_store = event_store
     end
 
     def call(command)
       @repository.with_aggregate(Refund, command.aggregate_id) do |refund|
-        refund.add_item(command.product_id)
+        refund.add_item(
+          command.product_id,
+          available_quantity_to_refund(command.order_id, command.product_id)
+        )
       end
     end
+
+    private
+
+    def available_quantity_to_refund(order_id, product_id)
+      Projections
+        .product_quantity_available_to_refund(order_id, product_id)
+        .run(@event_store)
+        .fetch(:available)
+    end
   end
 
   class OnRemoveItemFromRefund

ecommerce/ordering/test/add_item_to_refund_test.rb

@@ -11,6 +11,7 @@ def test_add_item_to_refund
       stream = "Ordering::Refund$#{aggregate_id}"
 
       arrange(
+        AddItemToBasket.new(order_id: order_id, product_id: product_id),
         CreateDraftRefund.new(
           refund_id: aggregate_id,
           order_id: order_id
@@ -37,5 +38,25 @@ def test_add_item_to_refund
         )
       end
     end
+
+    def test_add_item_raises_exceeds_order_quantity_error
+      aggregate_id = SecureRandom.uuid
+      order_id = SecureRandom.uuid
+      product_id = SecureRandom.uuid
+
+      arrange(
+        AddItemToBasket.new(order_id: order_id, product_id: product_id),
+        CreateDraftRefund.new(refund_id: aggregate_id, order_id: order_id),
+        AddItemToRefund.new(
+          refund_id: aggregate_id,
+          order_id: order_id,
+          product_id: product_id
+        )
+      )
+
+      assert_raises(Ordering::Refund::ExceedsOrderQuantityError) do
+        act(AddItemToRefund.new(refund_id: aggregate_id, order_id: order_id, product_id: product_id))
+      end
+    end
   end
 end

ecommerce/ordering/test/projections_test.rb

@@ -0,0 +1,26 @@
+require_relative "test_helper"
+
+module Ordering
+  class ProjectionsTest < Test
+    cover "Ordering::Projections"
+
+    def test_product_quantity_available_to_refund
+      order_id = SecureRandom.uuid
+      product_id = SecureRandom.uuid
+      another_product_id = SecureRandom.uuid
+      stream_name = "Ordering::Order$#{order_id}"
+      projection = Projections.product_quantity_available_to_refund(order_id, product_id)
+
+      event_store = RubyEventStore::Client.new(repository: RubyEventStore::InMemoryRepository.new)
+
+      event_store.publish(ItemAddedToBasket.new(data: { order_id: order_id, product_id: product_id }), stream_name: stream_name)
+      event_store.publish(ItemAddedToBasket.new(data: { order_id: order_id, product_id: product_id }), stream_name: stream_name)
+      event_store.publish(ItemRemovedFromBasket.new(data: { order_id: order_id, product_id: product_id }), stream_name: stream_name)
+      event_store.publish(ItemAddedToBasket.new(data: { order_id: order_id, product_id: another_product_id }), stream_name: stream_name)
+
+      available_quantity_to_refund = projection.run(event_store)
+
+      assert_equal({ available: 1 }, available_quantity_to_refund)
+    end
+  end
+end

ecommerce/ordering/test/refund_items_list_test.rb

@@ -0,0 +1,48 @@
+require_relative "test_helper"
+
+module Ordering
+  class RefundItemsListTest < Test
+
+    def test_initialize
+      list = ItemsList.new
+
+      assert_equal 0, list.refund_items.size
+    end
+
+    def test_increase_item_quantity
+      product_one_id = SecureRandom.uuid
+      product_two_id = SecureRandom.uuid
+      list = ItemsList.new
+
+      list.increase_quantity(product_one_id)
+
+      assert_equal 1, list.refund_items.size
+      assert_equal 1, list.quantity(product_one_id)
+
+      list.increase_quantity(product_two_id)
+
+      assert_equal 2, list.refund_items.size
+      assert_equal 1, list.quantity(product_two_id)
+    end
+
+    def test_decrease_item_quantity
+      product_id = SecureRandom.uuid
+      list = ItemsList.new
+
+      list.increase_quantity(product_id)
+      list.increase_quantity(product_id)
+
+      assert_equal 1, list.refund_items.size
+      assert_equal 2, list.quantity(product_id)
+
+      list.decrease_quantity(product_id)
+
+      assert_equal 1, list.refund_items.size
+      assert_equal 1, list.quantity(product_id)
+
+      list.decrease_quantity(product_id)
+
+      assert_equal 0, list.refund_items.size
+    end
+  end
+end

ecommerce/ordering/test/remove_item_from_refund_test.rb

@@ -11,6 +11,7 @@ def test_removing_items_from_refund
       stream = "Ordering::Refund$#{aggregate_id}"
 
       arrange(
+        AddItemToBasket.new(order_id: order_id, product_id: product_id),
         CreateDraftRefund.new(
           refund_id: aggregate_id,
           order_id: order_id
@@ -43,15 +44,26 @@ def test_removing_items_from_refund
       end
     end
 
-    def test_can_remove_only_added_items
+    def test_cant_remove_item_with_0_quantity
       order_id = SecureRandom.uuid
       aggregate_id = SecureRandom.uuid
       product_id = SecureRandom.uuid
 
       arrange(
+        AddItemToBasket.new(order_id: order_id, product_id: product_id),
         CreateDraftRefund.new(
           refund_id: aggregate_id,
           order_id: order_id
+        ),
+        AddItemToRefund.new(
+          refund_id: aggregate_id,
+          order_id: order_id,
+          product_id: product_id
+        ),
+        RemoveItemFromRefund.new(
+          refund_id: aggregate_id,
+          order_id: order_id,
+          product_id: product_id
         )
       )
 

rails_application/app/controllers/refunds_controller.rb

@@ -1,8 +1,8 @@
 class RefundsController < ApplicationController
   def edit
     @refund = Refunds::Refund.find_by_uid!(params[:id])
-    @order = Orders::Order.find_by_uid(@refund.order_uid)
-    @order_lines = @order.order_lines
+    @order = Orders::Order.find_by_uid!(@refund.order_uid)
+    @refund_items = build_refund_items_list(@order.order_lines, @refund.refund_items)
   end
 
   def create
@@ -14,10 +14,18 @@ def create
 
   def add_item
     add_item_to_refund
+    redirect_to edit_order_refund_path(params[:id], order_id: params[:order_id])
+  rescue Ordering::Refund::ExceedsOrderQuantityError
+    flash[:alert] = "You cannot add more of this product to the refund than is in the original order."
+    redirect_to edit_order_refund_path(params[:id], order_id: params[:order_id])
   end
 
   def remove_item
     remove_item_from_refund
+    redirect_to edit_order_refund_path(params[:id], order_id: params[:order_id])
+  rescue Ordering::Refund::ProductNotFoundError
+    flash[:alert] = "This product is not added to the refund."
+    redirect_to edit_order_refund_path(params[:id], order_id: params[:order_id])
   end
 
   private
@@ -45,4 +53,19 @@ def remove_item_from_refund_cmd
   def remove_item_from_refund
     command_bus.(remove_item_from_refund_cmd)
   end
+
+  def build_refund_items_list(order_lines, refund_items)
+    order_lines.map { |order_line| build_refund_item(order_line, refund_items) }
+  end
+
+  def build_refund_item(order_line, refund_items)
+    refund_item = refund_items.find { |item| item.product_uid == order_line.product_id } || initialize_refund_item(order_line)
+
+    refund_item.order_line = order_line
+    refund_item
+  end
+
+  def initialize_refund_item(order_line)
+    Refunds::RefundItem.new(product_uid: order_line.product_id, quantity: 0, price: order_line.price)
+  end
 end

rails_application/app/read_models/refunds/add_item_to_refund.rb

@@ -1,40 +1,21 @@
 module Refunds
   class AddItemToRefund
     def call(event)
-      refund_id = event.data.fetch(:refund_id)
-      Refund.find_or_create_by!(uid: refund_id)
-      product_id = event.data.fetch(:product_id)
-      item =
-        find(refund_id, product_id) ||
-          create(refund_id, product_id)
-      item.quantity += 1
-      item.save!
-    end
-
-    private
+      refund = Refund.find_by!(uid: event.data.fetch(:refund_id))
+      product = Orders::Product.find_by!(uid: event.data.fetch(:product_id))
 
-    def event_store
-      Rails.configuration.event_store
-    end
+      item = refund.refund_items.find_or_create_by(product_uid: product.uid) do |item|
+        item.price = product.price
+        item.quantity = 0
+      end
 
-    def find(refund_id, product_id)
-      Refund
-        .find_by_uid(refund_id)
-        .refund_items
-        .where(product_uid: product_id)
-        .first
-    end
+      refund.total_value += item.price
+      item.quantity += 1
 
-    def create(refund_id, product_id)
-      product = Orders::Product.find_by_uid(product_id)
-      Refund
-        .find_by(uid: refund_id)
-        .refund_items
-        .create(
-          product_uid: product_id,
-          price: product.price,
-          quantity: 0
-        )
+      ActiveRecord::Base.transaction do
+        refund.save!
+        item.save!
+      end
     end
   end
 end