Add CheckStockService#update_line_items

Update line item if any related variant has run out of stock or has had
stock reduced

app/services/orders/check_stock_service.rb

@@ -4,12 +4,24 @@ module Orders
   class CheckStockService
     attr_reader :order
 
-    def initialize(order: )
+    def initialize(order:)
       @order = order
     end
 
     def sufficient_stock?
       @sufficient_stock ||= order.insufficient_stock_lines.blank?
     end
+
+    def update_line_items
+      return [] if sufficient_stock?
+
+      variants = []
+      order.insufficient_stock_lines.each do |line_item|
+        order.contents.update_item(line_item, { quantity: line_item.variant.on_hand })
+        variants.push line_item.variant
+      end
+
+      variants
+    end
   end
 end

spec/services/orders/check_stock_service_spec.rb

@@ -21,4 +21,85 @@ RSpec.describe Orders::CheckStockService do
       end
     end
   end
+
+  describe "#update_line_items" do
+    context "with no variant out of stock" do
+      it "returns an empty array" do
+        expect(subject.update_line_items).to be_empty
+      end
+    end
+
+    context "with no variant with reduced stock" do
+      it "returns an empty array" do
+        expect(subject.update_line_items).to be_empty
+      end
+    end
+
+    context "with a variant out of stock" do
+      let(:variant) { order.line_items.first.variant }
+
+      before do
+        variant.update!(on_demand: false, on_hand: 0)
+      end
+
+      it "removes the machting line item" do
+        subject.update_line_items
+
+        expect(order.line_items.reload.select { |li| li.variant == variant }).to be_empty
+      end
+
+      it "returns an array including the out of stock variant" do
+        expect(subject.update_line_items).to eq([variant])
+      end
+    end
+
+    context "with a variant with reduced stock" do
+      let(:line_item) { order.line_items.last }
+      let(:variant) { line_item.variant }
+
+      before do
+        order.contents.add(variant, 2)
+        variant.update!(on_demand: false, on_hand: 1)
+      end
+
+      it "updates the machting line item quantity" do
+        subject.update_line_items
+
+        expect(line_item.reload.quantity).to be(1)
+      end
+
+      it "returns an array including the reduced stock variant" do
+        expect(subject.update_line_items).to eq([variant])
+      end
+    end
+
+    context "with a variant with reduced stock and a variant out of stock" do
+      let(:line_item_out_of_stock) { order.line_items.last }
+      let(:variant_out_of_stock) { line_item_out_of_stock.variant }
+      let(:line_item_reduced_stock) { order.line_items.first }
+      let(:variant_reduced_stock) { line_item_reduced_stock.variant }
+
+      before do
+        variant_out_of_stock.update!(on_demand: false, on_hand: 0)
+        order.contents.add(variant_reduced_stock, 3)
+        variant_reduced_stock.update!(on_demand: false, on_hand: 2)
+      end
+
+      it "removes the line item matching the out of stock variant" do
+        subject.update_line_items
+
+        expect(order.line_items).not_to include(line_item_out_of_stock)
+      end
+
+      it "updates the line item quantity matching the reduced stock variant" do
+        subject.update_line_items
+
+        expect(line_item_reduced_stock.reload.quantity).to eq(2)
+      end
+
+      it "returns an array including the out of stock variant and thereduced stock variant" do
+        expect(subject.update_line_items).to include(variant_out_of_stock, variant_reduced_stock)
+      end
+    end
+  end
 end