Copy existing OrderUpdater implementation

In subsequent commits we'll ensure that this can update orders in
memory, without persisting changes using manipulative DB queries.

core/app/models/spree/in_memory_order_updater.rb

@@ -0,0 +1,242 @@
+# frozen_string_literal: true
+
+module Spree
+  class InMemoryOrderUpdater
+    attr_reader :order
+    delegate :payments, :line_items, :adjustments, :all_adjustments, :shipments, :quantity, to: :order
+
+    def initialize(order)
+      @order = order
+    end
+
+    # This is a multi-purpose method for processing logic related to changes in the Order.
+    # It is meant to be called from various observers so that the Order is aware of changes
+    # that affect totals and other values stored in the Order.
+    #
+    # This method should never do anything to the Order that results in a save call on the
+    # object with callbacks (otherwise you will end up in an infinite recursion as the
+    # associations try to save and then in turn try to call +update!+ again.)
+    def recalculate
+      order.transaction do
+        update_item_count
+        update_shipment_amounts
+        update_totals
+        if order.completed?
+          update_payment_state
+          update_shipments
+          update_shipment_state
+        end
+        Spree::Bus.publish :order_recalculated, order: order
+        persist_totals
+      end
+    end
+    alias_method :update, :recalculate
+    deprecate update: :recalculate, deprecator: Spree.deprecator
+
+    # Updates the +shipment_state+ attribute according to the following logic:
+    #
+    # shipped   when all Shipments are in the "shipped" state
+    # partial   when at least one Shipment has a state of "shipped" and there is another Shipment with a state other than "shipped"
+    #           or there are InventoryUnits associated with the order that have a state of "sold" but are not associated with a Shipment.
+    # ready     when all Shipments are in the "ready" state
+    # backorder when there is backordered inventory associated with an order
+    # pending   when all Shipments are in the "pending" state
+    #
+    # The +shipment_state+ value helps with reporting, etc. since it provides a quick and easy way to locate Orders needing attention.
+    def update_shipment_state
+      log_state_change('shipment') do
+        order.shipment_state = determine_shipment_state
+      end
+
+      order.shipment_state
+    end
+
+    # Updates the +payment_state+ attribute according to the following logic:
+    #
+    # paid          when +payment_total+ is equal to +total+
+    # balance_due   when +payment_total+ is less than +total+
+    # credit_owed   when +payment_total+ is greater than +total+
+    # failed        when most recent payment is in the failed state
+    # void          when the order has been canceled and the payment total is 0
+    #
+    # The +payment_state+ value helps with reporting, etc. since it provides a quick and easy way to locate Orders needing attention.
+    def update_payment_state
+      log_state_change('payment') do
+        order.payment_state = determine_payment_state
+      end
+
+      order.payment_state
+    end
+
+    private
+
+    def determine_payment_state
+      if payments.present? && payments.valid.empty? && order.outstanding_balance != 0
+        'failed'
+      elsif order.state == 'canceled' && order.payment_total.zero?
+        'void'
+      elsif order.outstanding_balance > 0
+        'balance_due'
+      elsif order.outstanding_balance < 0
+        'credit_owed'
+      else
+        # outstanding_balance == 0
+        'paid'
+      end
+    end
+
+    def determine_shipment_state
+      if order.backordered?
+        'backorder'
+      else
+        # get all the shipment states for this order
+        shipment_states = shipments.states
+        if shipment_states.size > 1
+          # multiple shiment states means it's most likely partially shipped
+          'partial'
+        else
+          # will return nil if no shipments are found
+          shipment_states.first
+        end
+      end
+    end
+
+    # This will update and select the best promotion adjustment, update tax
+    # adjustments, update cancellation adjustments, and then update the total
+    # fields (promo_total, included_tax_total, additional_tax_total, and
+    # adjustment_total) on the item.
+    # @return [void]
+    def recalculate_adjustments
+      # 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/
+      update_promotions
+      update_taxes
+      update_item_totals
+    end
+
+    # Updates the following Order total values:
+    #
+    # +payment_total+      The total value of all finalized Payments (NOTE: non-finalized Payments are excluded)
+    # +item_total+         The total value of all LineItems
+    # +adjustment_total+   The total value of all adjustments (promotions, credits, etc.)
+    # +promo_total+        The total value of all promotion adjustments
+    # +total+              The so-called "order total."  This is equivalent to +item_total+ plus +adjustment_total+.
+    def update_totals
+      update_payment_total
+      update_item_total
+      update_shipment_total
+      update_adjustment_total
+    end
+
+    def update_shipment_amounts
+      shipments.each(&:update_amounts)
+    end
+
+    # give each of the shipments a chance to update themselves
+    def update_shipments
+      shipments.each(&:update_state)
+    end
+
+    def update_payment_total
+      order.payment_total = payments.completed.includes(:refunds).sum { |payment| payment.amount - payment.refunds.sum(:amount) }
+    end
+
+    def update_shipment_total
+      order.shipment_total = shipments.to_a.sum(&:cost)
+      update_order_total
+    end
+
+    def update_order_total
+      order.total = order.item_total + order.shipment_total + order.adjustment_total
+    end
+
+    def update_adjustment_total
+      recalculate_adjustments
+
+      all_items = line_items + shipments
+      order_tax_adjustments = adjustments.select(&:tax?)
+
+      order.adjustment_total = all_items.sum(&:adjustment_total) + adjustments.sum(&:amount)
+      order.included_tax_total = all_items.sum(&:included_tax_total) + order_tax_adjustments.select(&:included?).sum(&:amount)
+      order.additional_tax_total = all_items.sum(&:additional_tax_total) + order_tax_adjustments.reject(&:included?).sum(&:amount)
+
+      update_order_total
+    end
+
+    def update_item_count
+      order.item_count = line_items.to_a.sum(&:quantity)
+    end
+
+    def update_item_total
+      order.item_total = line_items.to_a.sum(&:amount)
+      update_order_total
+    end
+
+    def persist_totals
+      order.save!
+    end
+
+    def log_state_change(name)
+      state = "#{name}_state"
+      old_state = order.public_send(state)
+      yield
+      new_state = order.public_send(state)
+      if old_state != new_state
+        order.state_changes.new(
+          previous_state: old_state,
+          next_state:     new_state,
+          name:           name,
+          user_id:        order.user_id
+        )
+      end
+    end
+
+    def update_promotions
+      Spree::Config.promotions.order_adjuster_class.new(order).call
+    end
+
+    def update_taxes
+      Spree::Config.tax_adjuster_class.new(order).adjust!
+
+      [*line_items, *shipments].each do |item|
+        tax_adjustments = item.adjustments.select(&:tax?)
+        # 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.
+        item.included_tax_total   = tax_adjustments.select(&:included?).sum(&:amount)
+        item.additional_tax_total = tax_adjustments.reject(&:included?).sum(&:amount)
+      end
+    end
+
+    def update_cancellations
+    end
+    deprecate :update_cancellations, deprecator: Spree.deprecator
+
+    def update_item_totals
+      [*line_items, *shipments].each do |item|
+        # The cancellation_total isn't persisted anywhere but is included in
+        # the adjustment_total
+        item.adjustment_total = item.adjustments.
+          reject(&:included?).
+          sum(&:amount)
+
+        if item.changed?
+          item.update_columns(
+            promo_total:          item.promo_total,
+            included_tax_total:   item.included_tax_total,
+            additional_tax_total: item.additional_tax_total,
+            adjustment_total:     item.adjustment_total,
+            updated_at:           Time.current,
+          )
+        end
+      end
+    end
+  end
+end