Extendable adjustable updater

core/app/models/spree/adjustable_updater.rb

@@ -0,0 +1,72 @@
+module Spree
+  class AdjustableUpdater
+    attr_reader :adjustable
+
+    def self.update(adjustable)
+      return adjustable unless adjustable.persisted?
+
+      adjustableUpdater = Spree::AdjustableUpdater.new(adjustable)
+
+      # Promotion adjustments must be applied first, then tax adjustments.
+      # This fits the criteria for VAT tax as outlined here:
+      # http://www.hmrc.gov.uk/vat/managing/charging/discounts-etc.htm#1
+      #
+      # It also fits the criteria for sales tax as outlined here:
+      # http://www.boe.ca.gov/formspubs/pub113/
+
+      # Rails.application.config.spree.adjustments_updater.pre_tax_updaters.each { |adjusterKlass| adjusterKlass.new(adjustableUpdate).update }
+      Spree::AdjustmentsUpdater::Promotion.new(adjustableUpdater).update
+
+      # We want to select the best promotion for the order, but the remainder
+      # of the calculations here are done in the OrderUpdater instead.
+      return if Spree::Order === adjustable
+
+      # Rails.application.config.spree.adjustments_updater.tax_updater.new(adjustableUpdater).update
+      # Rails.application.config.spree.adjustments_updater.post_tax_updaters.each { |adjusterKlass| adjusterKlass.new(adjustableUpdate).update }
+      Spree::AdjustmentsUpdater::Tax.new(adjustableUpdater).update
+      Spree::AdjustmentsUpdater::Cancellation.new(adjustableUpdater).update
+
+      adjustableUpdater.persist if adjustable.changed?
+
+      adjustableUpdater.adjustable
+    end
+
+    # @param adjustable [Order, LineItem, Shipment] the item whose adjustments should be updated
+    def initialize(adjustable)
+      @adjustable = adjustable
+      @attributes_to_persist = {adjustment_total: 0}
+    end
+
+    def set_attribute(attribute, value, include_in_adjustment_total = true)
+      # Setting totals for the order here would be incorrect. Order's
+      # totals are the sum of the adjustments on all child models, as well as
+      # its own.
+      return if Spree::Order === adjustable
+
+      adjustable.send("#{attribute}=", value)
+      @attributes_to_persist[attribute] = value
+
+      add_to_adjustment_total(value) if include_in_adjustment_total
+    end
+
+    def add_to_adjustment_total(value)
+      adjustable.adjustment_total += value
+      @attributes_to_persist[:adjustment_total] += value
+    end
+
+    def adjustments
+      # This is done intentionally to avoid loading the association. If the
+      # association is loaded, the records may become stale due to code
+      # elsewhere in Spree. When that is remedied, this should be changed to
+      # just item.adjustments
+      @adjustments ||= adjustable.adjustments.all.to_a
+    end
+
+    def persist
+      attributes = @attributes_to_persist
+      attributes[:updated_at] = Time.current
+
+      adjustable.update_columns(attributes)
+    end
+  end
+end

core/app/models/spree/adjustment.rb

@@ -183,7 +183,7 @@ def currency
 
     def update_adjustable_adjustment_total
       # Cause adjustable's total to be recalculated
-      ItemAdjustments.new(adjustable).update
+      AdjustableUpdater.update(adjustable)
     end
 
     def require_promotion_code?

core/app/models/spree/adjustments_updater/cancellation.rb

@@ -0,0 +1,22 @@
+module Spree
+  module AdjustmentsUpdater
+    class Cancellation
+
+      def initialize(adjustableUpdater)
+        @adjustableUpdater = adjustableUpdater
+      end
+
+      def update
+        item_cancellation_total = adjustments.select(&:cancellation?).map(&:update!).compact.sum
+
+        @adjustableUpdater.add_to_adjustment_total(item_cancellation_total)
+      end
+
+      private
+
+      def adjustments
+        @adjustableUpdater.adjustments
+      end
+    end
+  end
+end

core/app/models/spree/adjustments_updater/promotion.rb

@@ -0,0 +1,25 @@
+module Spree
+  module AdjustmentsUpdater
+    class Promotion
+
+      def initialize(adjustableUpdater)
+        @adjustableUpdater = adjustableUpdater
+      end
+
+      def update
+        promotion_adjustments = adjustments.select(&:promotion?)
+        promotion_adjustments.each(&:update!)
+
+        promo_total = Spree::Config.promotion_chooser_class.new(promotion_adjustments).update
+
+        @adjustableUpdater.set_attribute(:promo_total, promo_total)
+      end
+
+      private
+
+      def adjustments
+        @adjustments ||= @adjustableUpdater.adjustments
+      end
+    end
+  end
+end

core/app/models/spree/adjustments_updater/tax.rb

@@ -0,0 +1,33 @@
+# Tax adjustments come in not one but *two* exciting flavours:
+# Included & additional
+
+# Included tax adjustments are those which are included in the price.
+# These ones should not affect the eventual total price.
+#
+# Additional tax adjustments are the opposite, affecting the final total.
+module Spree
+  module AdjustmentsUpdater
+    class Tax
+
+      def initialize(adjustableUpdater)
+        @adjustableUpdater = adjustableUpdater
+      end
+
+      def update
+        tax = adjustments.select(&:tax?)
+
+        included_tax_total = tax.select(&:included?).map(&:update!).compact.sum
+        additional_tax_total = tax.reject(&:included?).map(&:update!).compact.sum
+
+        @adjustableUpdater.set_attribute(:included_tax_total, included_tax_total, false)
+        @adjustableUpdater.set_attribute(:additional_tax_total, additional_tax_total)
+      end
+
+      private
+
+      def adjustments
+        @adjustments ||= @adjustableUpdater.adjustments
+      end
+    end
+  end
+end

core/app/models/spree/line_item.rb

@@ -170,7 +170,7 @@ def update_adjustments
       end
 
       def recalculate_adjustments
-        Spree::ItemAdjustments.new(self).update
+        Spree::AdjustableUpdater.update(self)
       end
 
       def update_tax_charge

core/app/models/spree/order.rb

@@ -504,7 +504,7 @@ def create_proposed_shipments
 
     def apply_free_shipping_promotions
       Spree::PromotionHandler::FreeShipping.new(self).activate
-      shipments.each { |shipment| ItemAdjustments.new(shipment).update }
+      shipments.each { |shipment| AdjustableUpdater.update(shipment) }
       updater.update_shipment_total
       persist_totals
     end

core/app/models/spree/order_contents.rb

@@ -62,7 +62,7 @@ def after_add_or_remove(line_item, options = {})
         shipment = options[:shipment]
         shipment.present? ? shipment.update_amounts : order.ensure_updated_shipments
         PromotionHandler::Cart.new(order, line_item).activate
-        ItemAdjustments.new(line_item).update
+        AdjustableUpdater.update(line_item)
         reload_totals
         line_item
       end

core/app/models/spree/order_updater.rb

@@ -31,7 +31,7 @@ def run_hooks
     end
 
     def recalculate_adjustments
-      all_adjustments.includes(:adjustable).map(&:adjustable).uniq.each { |adjustable| Spree::ItemAdjustments.new(adjustable).update }
+      all_adjustments.includes(:adjustable).map(&:adjustable).uniq.each { |adjustable| Spree::AdjustableUpdater.update(adjustable) }
     end
 
     # Updates the following Order total values:

core/app/models/spree/shipment.rb

@@ -392,7 +392,7 @@ def manifest_unstock(item)
       end
 
       def recalculate_adjustments
-        Spree::ItemAdjustments.new(self).update
+        Spree::AdjustableUpdater.update(self)
       end
 
       def set_cost_zero_when_nil