Apply coupon to order

ecommerce/pricing/lib/pricing.rb

@@ -86,6 +86,10 @@ def call(event_store, command_bus)
         RemoveFreeProductFromOrder,
         RemoveFreeProductFromOrderHandler.new(event_store)
       )
+      command_bus.register(
+        UseCoupon,
+        UseCouponHandler.new(event_store)
+      )
       event_store.subscribe(CalculateOrderTotalValue, to: [
         PriceItemAdded,
         PriceItemRemoved,

ecommerce/pricing/lib/pricing/commands.rb

@@ -80,4 +80,12 @@ class RemoveFreeProductFromOrder < Infra::Command
 
     alias aggregate_id order_id
   end
+
+  class UseCoupon < Infra::Command
+    attribute :order_id, Infra::Types::UUID
+    attribute :coupon_id, Infra::Types::UUID
+    attribute :discount, Infra::Types::CouponDiscount
+
+    alias aggregate_id order_id
+  end
 end

ecommerce/pricing/lib/pricing/events.rb

@@ -65,4 +65,10 @@ class FreeProductRemovedFromOrder < Infra::Event
     attribute :order_id, Infra::Types::UUID
     attribute :product_id, Infra::Types::UUID
   end
+
+  class CouponUsed < Infra::Event
+    attribute :order_id, Infra::Types::UUID
+    attribute :coupon_id, Infra::Types::UUID
+    attribute :discount, Infra::Types::CouponDiscount
+  end
 end

ecommerce/pricing/lib/pricing/offer.rb

@@ -111,6 +111,16 @@ def calculate_sub_amounts(pricing_catalog, time_promotions_discount)
       end
     end
 
+    def use_coupon(coupon_id, discount)
+      apply CouponUsed.new(
+        data: {
+          order_id: @id,
+          coupon_id: coupon_id,
+          discount: discount
+        }
+      )
+    end
+
     private
 
     on PriceItemAdded do |event|
@@ -151,6 +161,9 @@ def calculate_total_sub_discounts(pricing_catalog, time_promotions_discount)
       @list.sub_discounts(pricing_catalog, time_promotions_discount, @discount)
     end
 
+    on CouponUsed do |event|
+    end
+
     class List
 
       def initialize

ecommerce/pricing/lib/pricing/services.rb

@@ -180,4 +180,16 @@ def call(command)
       end
     end
   end
+
+  class UseCouponHandler
+    def initialize(event_store)
+      @repository = Infra::AggregateRootRepository.new(event_store)
+    end
+
+    def call(command)
+      @repository.with_aggregate(Offer, command.aggregate_id) do |order|
+        order.use_coupon(command.coupon_id, command.discount)
+      end
+    end
+  end
 end

ecommerce/pricing/test/coupons_test.rb

@@ -34,7 +34,7 @@ def test_100_is_ok
     end
 
     def test_0_01_is_ok
-      register_coupon(@uid, fake_name, @code, 0.01)
+      register_coupon(@uid, fake_name, @code, "0.01")
     end
   end
 end

ecommerce/pricing/test/use_coupon_test.rb

@@ -0,0 +1,38 @@
+require_relative "test_helper"
+
+module Pricing
+  class UseCouponTest < Test
+    cover "Pricing*"
+
+    def test_coupon_is_used
+      product_1_id = SecureRandom.uuid
+      set_price(product_1_id, 20)
+      coupon_id = SecureRandom.uuid
+      register_coupon(coupon_id, "Coupon", "coupon10", 10)
+      order_id = SecureRandom.uuid
+      add_item(order_id, product_1_id)
+
+      assert_events_contain(
+        stream_name(order_id),
+        CouponUsed.new(
+          data: {
+            order_id: order_id,
+            coupon_id: coupon_id,
+            discount: 10
+          }
+        )
+      ) do
+        run_command(
+          Pricing::UseCoupon.new(order_id: order_id, coupon_id: coupon_id, discount: 10)
+        )
+      end
+    end
+
+    private
+
+    def stream_name(id)
+      "Pricing::Offer$#{id}"
+    end
+
+  end
+end

ecommerce/processes/lib/processes.rb

@@ -28,6 +28,7 @@ class << self
     def call(event_store, command_bus)
       self.class.event_store = event_store
       self.class.command_bus = command_bus
+      enable_coupon_discount_process(event_store, command_bus)
       notify_payments_about_order_total_value(event_store, command_bus)
       enable_shipment_sync(event_store, command_bus)
       determine_vat_rates_on_order_placed(event_store, command_bus)
@@ -150,5 +151,11 @@ def register_order_on_order_placed(event_store, command_bus)
         to: [Ordering::OrderPlaced]
       )
     end
+
+    def enable_coupon_discount_process(event_store, command_bus)
+      Infra::Process.new(event_store, command_bus)
+                    .call(Pricing::CouponUsed, [:order_id, :discount],
+                          Pricing::SetPercentageDiscount, [:order_id, :amount])
+    end
   end
 end

infra/lib/infra/types.rb

@@ -16,7 +16,7 @@ module Types
     Price = Types::Coercible::Decimal.constrained(gt: 0)
     Value = Types::Coercible::Decimal
     PercentageDiscount = Types::Coercible::Decimal.constrained(gt: 0, lteq: 100)
-    CouponDiscount = Types::Coercible::Float.constrained(gt: 0, lteq: 100)
+    CouponDiscount = Types::Coercible::Decimal.constrained(gt: 0, lteq: 100)
     UUIDQuantityHash = Types::Hash.map(UUID, Quantity)
 
     class VatRate < Dry::Struct

rails_application/app/controllers/client/orders_controller.rb

@@ -59,5 +59,25 @@ def remove_item
       )
     end
 
+    def use_coupon
+      coupon = Coupons::Coupon.find_by!("lower(code) = ?", params[:coupon_code].downcase)
+      ActiveRecord::Base.transaction do
+        command_bus.(use_coupon_cmd(params[:id], coupon.uid, coupon.discount))
+      end
+      flash[:notice] = "Coupon applied!"
+      redirect_to edit_client_order_path(params[:id])
+    rescue ActiveRecord::RecordNotFound
+      flash[:alert] = "Coupon not found!"
+      redirect_to edit_client_order_path(params[:id])
+    rescue Pricing::NotPossibleToAssignDiscountTwice
+      flash[:alert] = "Coupon already used!"
+      redirect_to edit_client_order_path(params[:id])
+    end
+
+    private
+
+    def use_coupon_cmd(order_id, coupon_id, discount)
+      Pricing::UseCoupon.new(order_id: order_id, coupon_id: coupon_id, discount: discount)
+    end
   end
 end

rails_application/app/read_models/client_orders/edit_order.rb

@@ -12,6 +12,7 @@ def build(order_id, order_lines, products, attributes = {})
       super(attributes)
       div do
         products_table(order_id, products, order_lines)
+        coupon_form(order_id)
         submit_form(order_id)
       end
     end
@@ -67,6 +68,19 @@ def remove_item_button(order_id, product_id)
       button_to "Remove", remove_item_client_order_path(id: order_id, product_id: product_id), class: "hover:underline text-blue-500"
     end
 
+    def coupon_form(order_id)
+      form(action: use_coupon_client_order_path(id: order_id), method: :post, class: "inline-flex gap-4 mt-8") do
+        input(
+          id: "coupon_code",
+          type: :text,
+          name: :coupon_code,
+          class: "focus:ring-blue-500 focus:border-blue-500 block shadow-sm sm:text-sm border-gray-300 rounded-md",
+          "data-turbo-permanent": true
+        )
+        input(type: :submit, value: "Use Coupon", class: "px-4 py-2 border rounded-md shadow-sm text-sm font-medium border-gray-300 text-gray-700 bg-white hover:bg-gray-50")
+      end
+    end
+
     def submit_form(order_id)
       form(id: "form", action: client_orders_path, method: :post) do
         input(type: :hidden, name: :order_id, value: order_id)

rails_application/app/read_models/orders/update_discount.rb

@@ -1,7 +1,7 @@
 module Orders
   class UpdateDiscount
     def call(event)
-      order = Order.find_by_uid(event.data.fetch(:order_id))
+      order = Order.find_or_create_by(uid: event.data.fetch(:order_id))
       if is_newest_value?(event, order)
         order.percentage_discount = event.data.fetch(:amount)
         order.discount_updated_at = event.metadata.fetch(:timestamp)
@@ -28,4 +28,3 @@ def broadcaster
     end
   end
 end
-

rails_application/config/routes.rb

@@ -42,6 +42,7 @@
     member do
       post :add_item
       post :remove_item
+      post :use_coupon
     end
   end
 

rails_application/test/integration/client_orders_test.rb

@@ -203,6 +203,56 @@ def test_current_time_promotion_is_applied
     assert_select "tr td", "$2.00"
   end
 
+  def test_using_coupon_applies_discount
+    customer_id = register_customer("Customer Shop")
+    product_id = register_product("Fearless Refactoring", 4, 10)
+    register_coupon("Coupon", "coupon10", 10)
+
+    login(customer_id)
+    visit_client_orders
+
+    order_id = SecureRandom.uuid
+    as_client_add_item_to_basket_for_order(product_id, order_id)
+    as_client_use_coupon(order_id, "COUPON10")
+
+    assert_select "#notice", "Coupon applied!"
+
+    as_client_submit_order_for_customer(order_id)
+
+    assert_select "tr td", "$3.60"
+  end
+
+  def test_using_coupon_with_wrong_code
+    customer_id = register_customer("Customer Shop")
+    product_id = register_product("Fearless Refactoring", 4, 10)
+    register_coupon("Coupon", "coupon10", 10)
+
+    login(customer_id)
+    visit_client_orders
+
+    order_id = SecureRandom.uuid
+    as_client_add_item_to_basket_for_order(product_id, order_id)
+    as_client_use_coupon(order_id, "WRONGCODE")
+
+    assert_select "#alert", "Coupon not found!"
+  end
+
+  def test_using_coupon_twice
+    customer_id = register_customer("Customer Shop")
+    product_id = register_product("Fearless Refactoring", 4, 10)
+    register_coupon("Coupon", "coupon10", 10)
+
+    login(customer_id)
+    visit_client_orders
+
+    order_id = SecureRandom.uuid
+    as_client_add_item_to_basket_for_order(product_id, order_id)
+    as_client_use_coupon(order_id, "COUPON10")
+    as_client_use_coupon(order_id, "COUPON10")
+
+    assert_select "#alert", "Coupon already used!"
+  end
+
   private
 
   def submit_order_for_customer(customer_id, order_id)
@@ -223,6 +273,11 @@ def as_client_add_item_to_basket_for_order(async_remote_id, order_id)
     post "/client_orders/#{order_id}/add_item?product_id=#{async_remote_id}"
   end
 
+  def as_client_use_coupon(order_id, code)
+    post "/client_orders/#{order_id}/use_coupon", params: { coupon_code: code }
+    follow_redirect!
+  end
+
   def cancel_order(order_id)
     post "/orders/#{order_id}/cancel"
   end

rails_application/test/test_helper.rb

@@ -71,6 +71,10 @@ def register_product(name, price, vat_rate_code)
     product_id
   end
 
+  def register_coupon(name, code, discount)
+    post "/coupons", params: { coupon_id: SecureRandom.uuid, name: name, code: code, discount: discount }
+  end
+
   def add_available_vat_rate(rate, code = rate.to_s)
     post "/available_vat_rates", params: { code: code, rate: rate }
   end