Bring Spree::StockItem code from spree_core into the app

app/models/spree/stock_item.rb

@@ -0,0 +1,52 @@
+module Spree
+  class StockItem < ActiveRecord::Base
+    belongs_to :stock_location, class_name: 'Spree::StockLocation'
+    belongs_to :variant, class_name: 'Spree::Variant'
+    has_many :stock_movements, dependent: :destroy
+
+    validates_presence_of :stock_location, :variant
+    validates_uniqueness_of :variant_id, scope: :stock_location_id
+
+    attr_accessible :count_on_hand, :variant, :stock_location, :backorderable, :variant_id
+
+    delegate :weight, to: :variant
+
+    def backordered_inventory_units
+      Spree::InventoryUnit.backordered_for_stock_item(self)
+    end
+
+    def variant_name
+      variant.name
+    end
+
+    def adjust_count_on_hand(value)
+      self.with_lock do
+        self.count_on_hand = self.count_on_hand + value
+        process_backorders if in_stock?
+
+        self.save!
+      end
+    end
+
+    def in_stock?
+      self.count_on_hand > 0
+    end
+
+    # Tells whether it's available to be included in a shipment
+    def available?
+      self.in_stock? || self.backorderable?
+    end
+
+    private
+      def count_on_hand=(value)
+        write_attribute(:count_on_hand, value)
+      end
+
+      def process_backorders
+        backordered_inventory_units.each do |unit|
+          return unless in_stock?
+          unit.fill_backorder
+        end
+      end
+  end
+end

spec/models/spree/stock_item_spec.rb

@@ -0,0 +1,74 @@
+require 'spec_helper'
+
+describe Spree::StockItem do
+  let(:stock_location) { create(:stock_location_with_items) }
+
+  subject { stock_location.stock_items.order(:id).first }
+
+  it 'maintains the count on hand for a variant' do
+    subject.count_on_hand.should eq 10
+  end
+
+  it "can return the stock item's variant's name" do
+    subject.variant_name.should == subject.variant.name
+  end
+
+  context "available to be included in shipment" do
+    context "has stock" do
+      it { subject.should be_available }
+    end
+
+    context "backorderable" do
+      before { subject.backorderable = true }
+      it { subject.should be_available }
+    end
+
+    context "no stock and not backorderable" do
+      before do
+        subject.backorderable = false
+        subject.stub(count_on_hand: 0)
+      end
+
+      it { subject.should_not be_available }
+    end
+  end
+
+  context "adjust count_on_hand" do
+    let!(:current_on_hand) { subject.count_on_hand }
+
+    it 'is updated pessimistically' do
+      copy = Spree::StockItem.find(subject.id)
+
+      subject.adjust_count_on_hand(5)
+      subject.count_on_hand.should eq(current_on_hand + 5)
+
+      copy.count_on_hand.should eq(current_on_hand)
+      copy.adjust_count_on_hand(5)
+      copy.count_on_hand.should eq(current_on_hand + 10)
+    end
+
+    context "item out of stock (by two items)" do
+      let(:inventory_unit) { double('InventoryUnit') }
+      let(:inventory_unit_2) { double('InventoryUnit2') }
+
+      before { subject.adjust_count_on_hand(- (current_on_hand + 2)) }
+
+      it "doesn't process backorders" do
+        subject.should_not_receive(:backordered_inventory_units)
+        subject.adjust_count_on_hand(1)
+      end
+
+      context "adds new items" do
+        before { subject.stub(:backordered_inventory_units => [inventory_unit, inventory_unit_2]) }
+
+        it "fills existing backorders" do
+          inventory_unit.should_receive(:fill_backorder)
+          inventory_unit_2.should_receive(:fill_backorder)
+
+          subject.adjust_count_on_hand(3)
+          subject.count_on_hand.should == 1
+        end
+      end
+    end
+  end
+end