Extract compute_tax from EnterpriseFeeApplicator to Spree::TaxRate model

app/models/spree/tax_rate_decorator.rb

@@ -1,20 +1,61 @@
-Spree::TaxRate.class_eval do
-  class << self
-    def match_with_sales_tax_registration(order)
-      return [] if order.distributor && !order.distributor.charges_sales_tax
-      match_without_sales_tax_registration(order)
+module Spree
+  TaxRate.class_eval do
+    class << self
+      def match_with_sales_tax_registration(order)
+        return [] if order.distributor && !order.distributor.charges_sales_tax
+        match_without_sales_tax_registration(order)
+      end
+      alias_method_chain :match, :sales_tax_registration
     end
-    alias_method_chain :match, :sales_tax_registration
-  end
 
 
-  def adjust_with_included_tax(order)
-    adjust_without_included_tax(order)
+    def adjust_with_included_tax(order)
+      adjust_without_included_tax(order)
 
-    order.reload
-    (order.adjustments.tax + order.price_adjustments).each do |a|
-      a.set_absolute_included_tax! a.amount
+      order.reload
+      (order.adjustments.tax + order.price_adjustments).each do |a|
+        a.set_absolute_included_tax! a.amount
+      end
+    end
+    alias_method_chain :adjust, :included_tax
+
+
+    # Manually apply a TaxRate to a particular amount. TaxRates normally compute against
+    # LineItems or Orders, so we mock out a line item here to fit the interface
+    # that our calculator (usually DefaultTax) expects.
+    def compute_tax(amount)
+      product = OpenStruct.new tax_category: tax_category
+      line_item = LineItem.new quantity: 1
+      line_item.define_singleton_method(:product) { product }
+      line_item.define_singleton_method(:price) { amount }
+
+      # Tax on adjustments (represented by the included_tax field) is always inclusive of
+      # tax. However, there's nothing to stop an admin from setting one up with a tax rate
+      # that's marked as not inclusive of tax, and that would result in the DefaultTax
+      # calculator generating a slightly incorrect value. Therefore, we treat the tax
+      # rate as inclusive of tax for the calculations below, regardless of its original
+      # setting.
+      with_tax_included_in_price do
+        calculator.compute line_item
+      end
+    end
+
+
+    private
+
+    def with_tax_included_in_price
+      old_included_in_price = self.included_in_price
+
+      self.included_in_price = true
+      calculator.calculable.included_in_price = true
+
+      result = yield
+
+      # TODO: ensure
+      self.included_in_price = old_included_in_price
+      calculator.calculable.included_in_price = old_included_in_price
+
+      result
     end
   end
-  alias_method_chain :adjust, :included_tax
 end

lib/open_food_network/enterprise_fee_applicator.rb

@@ -35,43 +35,8 @@ module OpenFoodNetwork
       tax_rates = enterprise_fee.tax_category ? enterprise_fee.tax_category.tax_rates.match(order) : []
 
       tax_rates.sum do |rate|
-        compute_tax rate, adjustment.amount
+        rate.compute_tax adjustment.amount
       end
     end
-
-    # Apply a TaxRate to a particular amount. TaxRates normally compute against
-    # LineItems or Orders, so we mock out a line item here to fit the interface
-    # that our calculator (usually DefaultTax) expects.
-    def compute_tax(tax_rate, amount)
-      product = OpenStruct.new tax_category: tax_rate.tax_category
-      line_item = Spree::LineItem.new quantity: 1
-      line_item.define_singleton_method(:product) { product }
-      line_item.define_singleton_method(:price) { amount }
-
-      # The enterprise fee adjustments for which we're calculating tax are always inclusive of
-      # tax. However, there's nothing to stop an admin from setting one up with a tax rate
-      # that's marked as not inclusive of tax, and that would result in the DefaultTax
-      # calculator generating a slightly incorrect value. Therefore, we treat the tax
-      # rate as inclusive of tax for the calculations below, regardless of its original
-      # setting.
-      with_tax_included_in_price(tax_rate) do
-        tax_rate.calculator.compute line_item
-      end
-    end
-
-    def with_tax_included_in_price(tax_rate)
-      old_included_in_price = tax_rate.included_in_price
-
-      tax_rate.included_in_price = true
-      tax_rate.calculator.calculable.included_in_price = true
-
-      result = yield
-
-      tax_rate.included_in_price = old_included_in_price
-      tax_rate.calculator.calculable.included_in_price = old_included_in_price
-
-      result
-    end
   end
 end
-

spec/lib/open_food_network/enterprise_fee_applicator_spec.rb

@@ -65,33 +65,4 @@ module OpenFoodNetwork
       efa.send(:order_adjustment_label).should == "Whole order - packing fee by distributor Ballantyne"
     end
   end
-
-  describe "ensuring that tax rate is marked as tax included_in_price" do
-    let(:efa) { EnterpriseFeeApplicator.new nil, nil, nil }
-    let(:tax_rate) { create(:tax_rate, included_in_price: false, calculator: Spree::Calculator::DefaultTax.new) }
-
-    it "sets included_in_price to true" do
-      efa.send(:with_tax_included_in_price, tax_rate) do
-        tax_rate.included_in_price.should be_true
-      end
-    end
-
-    it "sets the included_in_price value accessible to the calculator to true" do
-      efa.send(:with_tax_included_in_price, tax_rate) do
-        tax_rate.calculator.calculable.included_in_price.should be_true
-      end
-    end
-
-    it "passes through the return value of the block" do
-      efa.send(:with_tax_included_in_price, tax_rate) do
-        'asdf'
-      end.should == 'asdf'
-    end
-
-    it "restores both values to their original afterwards" do
-      efa.send(:with_tax_included_in_price, tax_rate) {}
-      tax_rate.included_in_price.should be_false
-      tax_rate.calculator.calculable.included_in_price.should be_false
-    end
-  end
 end

spec/models/spree/tax_rate_spec.rb

@@ -29,5 +29,33 @@ module Spree
         end
       end
     end
+
+    describe "ensuring that tax rate is marked as tax included_in_price" do
+      let(:tax_rate) { create(:tax_rate, included_in_price: false, calculator: Spree::Calculator::DefaultTax.new) }
+
+      it "sets included_in_price to true" do
+        tax_rate.send(:with_tax_included_in_price) do
+          tax_rate.included_in_price.should be_true
+        end
+      end
+
+      it "sets the included_in_price value accessible to the calculator to true" do
+        tax_rate.send(:with_tax_included_in_price) do
+          tax_rate.calculator.calculable.included_in_price.should be_true
+        end
+      end
+
+      it "passes through the return value of the block" do
+        tax_rate.send(:with_tax_included_in_price) do
+          'asdf'
+        end.should == 'asdf'
+      end
+
+      it "restores both values to their original afterwards" do
+        tax_rate.send(:with_tax_included_in_price) {}
+        tax_rate.included_in_price.should be_false
+        tax_rate.calculator.calculable.included_in_price.should be_false
+      end
+    end
   end
 end