Make code work with one shipment per order (even if the DB still supports Spree's multi shipments per order model)

app/models/spree/order.rb

@@ -4,11 +4,9 @@
 require 'open_food_network/enterprise_fee_calculator'
 require 'open_food_network/feature_toggle'
 require 'open_food_network/tag_rule_applicator'
-require 'concerns/order_shipment'
 
 module Spree
   class Order < ActiveRecord::Base
-    prepend OrderShipment
     include Checkout
 
     checkout_flow do
@@ -226,7 +224,7 @@ def item_count
     end
 
     def backordered?
-      shipments.any?(&:backordered?)
+      shipment&.backordered? || false
     end
 
     # Returns the relevant zone (if any) to be used for taxation purposes.
@@ -438,10 +436,8 @@ def finalize!
 
       # update payment and shipment(s) states, and save
       updater.update_payment_state
-      shipments.each do |shipment|
-        shipment.update!(self)
-        shipment.finalize!
-      end
+      shipment&.update!(self)
+      shipment&.finalize!
 
       updater.update_shipment_state
       updater.before_save_hook
@@ -547,20 +543,52 @@ def state_changed(name)
       )
     end
 
+    # The Spree 2 db model we use supports multiple shipments per order,
+    #   in OFN we have only one shipment per order.
+    # A shipment is associated to a shipping_method through a selected shipping_rate.
+    def shipment
+      return if shipments.blank?
+
+      shipments.first
+    end
+
+    # The shipping method of the shipment in the order
+    def shipping_method
+      return if shipment.blank?
+
+      shipment.shipping_method
+    end
+
+    # Finds the shipment's shipping_rate for the given shipping_method_id and selects that shipping_rate.
+    # If the selection is successful, it persists it in the database by saving the shipment.
+    # If it fails, it does not clear the current shipping_method selection.
+    #
+    # @return [ShippingMethod] the selected shipping method, or nil if the given shipping_method_id is
+    #   empty or if it cannot find the given shipping_method_id in the order
+    def select_shipping_method(shipping_method_id)
+      return if shipping_method_id.blank? || shipment.blank?
+
+      shipment = shipments.first
+
+      shipping_rate = shipment.shipping_rates.find_by(shipping_method_id: shipping_method_id)
+      return unless shipping_rate
+
+      shipment.selected_shipping_rate_id = shipping_rate.id
+      shipment.shipping_method
+    end
+
     def shipped?
       %w(partial shipped).include?(shipment_state)
     end
 
     # Does this order have shipments that can be shipped?
     def ready_to_ship?
-      shipments.any?(&:can_ship?)
+      shipment&.can_ship? || false
     end
 
     # Ship all pending orders
     def ship
-      shipments.each do |s|
-        s.ship if s.can_ship?
-      end
+      shipment.ship if ready_to_ship?
     end
 
     def line_item_variants
@@ -582,12 +610,10 @@ def create_proposed_shipments
       adjustments.shipping.delete_all
       shipments.destroy_all
 
-      packages = OrderManagement::Stock::Coordinator.new(self).packages
-      packages.each do |package|
-        shipments << package.to_shipment
-      end
+      package = OrderManagement::Stock::Coordinator.new(self).package
+      shipments << package.to_shipment
 
-      shipments
+      shipments #
     end
 
     # Clean shipments and make order back to address state
@@ -596,7 +622,7 @@ def create_proposed_shipments
     # to delivery again so that proper updated shipments are created.
     # e.g. customer goes back from payment step and changes order items
     def ensure_updated_shipments
-      return unless shipments.any?
+      return if shipment.blank?
 
       shipments.destroy_all
       update_columns(
@@ -606,7 +632,7 @@ def ensure_updated_shipments
     end
 
     def refresh_shipment_rates
-      shipments.map(&:refresh_rates)
+      shipment.refresh_rates
     end
 
     # Check that line_items in the current order are available from a newly selected distribution
@@ -625,12 +651,10 @@ def disallow_guest_order
 
     # After changing line items of a completed order
     def update_shipping_fees!
-      shipments.each do |shipment|
-        next if shipment.shipped?
+      return if shipment.blank? || shipment.shipped?
 
-        update_adjustment! shipment.adjustment if shipment.adjustment
-        save_or_rescue_shipment(shipment)
-      end
+      update_adjustment!(shipment.adjustment) if shipment.adjustment
+      save_or_rescue_shipment(shipment)
     end
 
     def save_or_rescue_shipment(shipment)
@@ -788,20 +812,20 @@ def has_available_shipment
     end
 
     def ensure_available_shipping_rates
-      return unless shipments.empty? || shipments.any? { |shipment| shipment.shipping_rates.blank? }
+      return unless shipment.blank? || shipment.shipping_rates.blank?
 
       errors.add(:base, Spree.t(:items_cannot_be_shipped)) && (return false)
     end
 
     def after_cancel
-      shipments.each(&:cancel!)
+      shipment&.cancel!
 
       OrderMailer.cancel_email(id).deliver_later
       self.payment_state = 'credit_owed' unless shipped?
     end
 
     def after_resume
-      shipments.each(&:resume!)
+      shipment&.resume!
     end
 
     def use_billing?

engines/order_management/app/services/order_management/stock/coordinator.rb

@@ -9,35 +9,33 @@ def initialize(order)
         @order = order
       end
 
-      def packages
-        packages = build_packages
-        packages = prioritize_packages(packages)
-        estimate_packages(packages)
+      def package
+        package = build_package
+        package = prioritize_package(package)
+        estimate_package(package)
       end
 
       # Build package with default stock location
       # No need to check items are in the stock location,
       #   there is only one stock location so the items will be on that stock location.
       #
-      # Returns an array with a single Package for the default stock location
-      def build_packages
+      # Returns a single Package for the default stock location
+      def build_package
         packer = build_packer(order)
-        [packer.package]
+        packer.package
       end
 
       private
 
-      def prioritize_packages(packages)
-        prioritizer = OrderManagement::Stock::Prioritizer.new(order, packages)
-        prioritizer.prioritized_packages
+      def prioritize_package(package)
+        prioritizer = OrderManagement::Stock::Prioritizer.new(order, package)
+        prioritizer.prioritized_package
       end
 
-      def estimate_packages(packages)
+      def estimate_package(package)
         estimator = OrderManagement::Stock::Estimator.new(order)
-        packages.each do |package|
-          package.shipping_rates = estimator.shipping_rates(package)
-        end
-        packages
+        package.shipping_rates = estimator.shipping_rates(package)
+        package
       end
 
       def build_packer(order)

engines/order_management/app/services/order_management/stock/prioritizer.rb

@@ -3,42 +3,37 @@
 module OrderManagement
   module Stock
     class Prioritizer
-      attr_reader :packages, :order
+      attr_reader :package, :order
 
-      def initialize(order, packages, adjuster_class = OrderManagement::Stock::Adjuster)
+      def initialize(order, package, adjuster_class = OrderManagement::Stock::Adjuster)
         @order = order
-        @packages = packages
+        @package = package
         @adjuster_class = adjuster_class
       end
 
-      def prioritized_packages
-        adjust_packages
-        prune_packages
-        packages
+      def prioritized_package
+        adjust_package
+        return if package.blank?
+
+        package
       end
 
       private
 
-      def adjust_packages
+      def adjust_package
         order.line_items.each do |line_item|
           adjuster = @adjuster_class.new(line_item.variant, line_item.quantity, :on_hand)
 
-          visit_packages(adjuster)
+          visit_package(adjuster)
 
           adjuster.status = :backordered
-          visit_packages(adjuster)
-        end
-      end
-
-      def visit_packages(adjuster)
-        packages.each do |package|
-          item = package.find_item adjuster.variant, adjuster.status
-          adjuster.adjust(item) if item
+          visit_package(adjuster)
         end
       end
 
-      def prune_packages
-        packages.reject!(&:empty?)
+      def visit_package(adjuster)
+        item = package.find_item(adjuster.variant, adjuster.status)
+        adjuster.adjust(item) if item
       end
     end
   end

engines/order_management/spec/services/order_management/stock/coordinator_spec.rb

@@ -14,12 +14,12 @@ module Stock
 
       subject { Coordinator.new(order) }
 
-      context "packages" do
+      context "package" do
         it "builds, prioritizes and estimates" do
-          expect(subject).to receive(:build_packages).ordered
-          expect(subject).to receive(:prioritize_packages).ordered
-          expect(subject).to receive(:estimate_packages).ordered
-          subject.packages
+          expect(subject).to receive(:build_package).ordered
+          expect(subject).to receive(:prioritize_package).ordered
+          expect(subject).to receive(:estimate_package).ordered
+          subject.package
         end
       end
     end