Add DiscountRate to line items (#121)

lib/xero_gateway/line_item.rb

@@ -3,73 +3,75 @@
 module XeroGateway
   class LineItem
     include Money
-    
+
     TAX_TYPE = Account::TAX_TYPE unless defined?(TAX_TYPE)
 
     # Any errors that occurred when the #valid? method called.
     attr_reader :errors
 
     # All accessible fields
-    attr_accessor :line_item_id, :description, :quantity, :unit_amount, :item_code, :tax_type, :tax_amount, :account_code, :tracking
-        
+    attr_accessor :line_item_id, :description, :quantity, :unit_amount, :discount_rate, :item_code, :tax_type, :tax_amount, :account_code, :tracking
+
     def initialize(params = {})
       @errors ||= []
       @tracking ||= []
       @quantity = 1
       @unit_amount = BigDecimal.new('0')
-      
+
       params.each do |k,v|
         self.send("#{k}=", v)
       end
     end
-    
+
     # Validate the LineItem record according to what will be valid by the gateway.
     #
-    # Usage: 
+    # Usage:
     #  line_item.valid?     # Returns true/false
-    #  
+    #
     #  Additionally sets line_item.errors array to an array of field/error.
     def valid?
       @errors = []
-      
+
       if !line_item_id.nil? && line_item_id !~ GUID_REGEX
         @errors << ['line_item_id', 'must be blank or a valid Xero GUID']
       end
-      
+
       unless description
         @errors << ['description', "can't be blank"]
       end
-            
+
       if tax_type && !TAX_TYPE[tax_type]
         @errors << ['tax_type', "must be one of #{TAX_TYPE.keys.join('/')}"]
       end
-      
+
       @errors.size == 0
     end
-    
+
     def has_tracking?
       return false if tracking.nil?
-      
+
       if tracking.is_a?(Array)
         return tracking.any?
       else
         return tracking.is_a?(TrackingCategory)
       end
     end
-    
+
     # Deprecated (but API for setter remains).
     #
     # As line_amount must equal quantity * unit_amount for the API call to pass, this is now
     # automatically calculated in the line_amount method.
     def line_amount=(value)
     end
-    
+
     # Calculate the line_amount as quantity * unit_amount as this value must be correct
     # for the API call to succeed.
     def line_amount
-      quantity * unit_amount
+      total = quantity * unit_amount
+      total = total * (1 - (discount_rate / BigDecimal.new(100))) if discount_rate
+      total
     end
-    
+
     def to_xml(b = Builder::XmlMarkup.new)
       b.LineItem {
         b.Description description
@@ -79,6 +81,7 @@ def to_xml(b = Builder::XmlMarkup.new)
         b.TaxType tax_type if tax_type
         b.TaxAmount tax_amount if tax_amount
         b.LineAmount line_amount if line_amount
+        b.DiscountRate discount_rate if discount_rate
         b.AccountCode account_code if account_code
         if has_tracking?
           b.Tracking {
@@ -92,7 +95,7 @@ def to_xml(b = Builder::XmlMarkup.new)
         end
       }
     end
-    
+
     def self.from_xml(line_item_element)
       line_item = LineItem.new
       line_item_element.children.each do |element|
@@ -105,6 +108,7 @@ def self.from_xml(line_item_element)
           when "TaxType" then line_item.tax_type = element.text
           when "TaxAmount" then line_item.tax_amount = BigDecimal.new(element.text)
           when "LineAmount" then line_item.line_amount = BigDecimal.new(element.text)
+          when "DiscountRate" then line_item.discount_rate = BigDecimal.new(element.text)
           when "AccountCode" then line_item.account_code = element.text
           when "Tracking" then
             element.children.each do | tracking_element |
@@ -113,13 +117,13 @@ def self.from_xml(line_item_element)
         end
       end
       line_item
-    end    
+    end
 
     def ==(other)
-      [:description, :quantity, :unit_amount, :tax_type, :tax_amount, :line_amount, :account_code, :item_code].each do |field|
+      [:description, :quantity, :unit_amount, :tax_type, :tax_amount, :line_amount, :discount_rate, :account_code, :item_code].each do |field|
         return false if send(field) != other.send(field)
       end
       return true
     end
-  end  
+  end
 end

test/unit/invoice_test.rb

@@ -68,6 +68,18 @@ class InvoiceTest < Test::Unit::TestCase
       parsed_invoice = XeroGateway::Invoice.from_xml(invoice_element)
       assert_equal 'http://example.com?with=params&and=more', parsed_invoice.url
     end
+
+    should "work with line_item discount rates" do
+      invoice = create_test_invoice
+      invoice.line_items.first.discount_rate = 27
+      invoice_as_xml = invoice.to_xml
+
+      invoice_element = REXML::XPath.first(REXML::Document.new(invoice_as_xml), "/Invoice")
+      result_invoice = XeroGateway::Invoice.from_xml(invoice_element)
+
+      assert_equal(invoice, result_invoice)
+      assert_equal 27, result_invoice.line_items.first.discount_rate
+    end
   end
 
   # Tests the sub_total calculation and that setting it manually doesn't modify the data.
@@ -154,6 +166,26 @@ def test_line_amount_calculation
     assert_equal(quantity * line_item.unit_amount, line_item.line_amount)
   end
 
+  def test_line_amount_discount_calculation
+    invoice = create_test_invoice
+    line_item = invoice.line_items.first
+    line_item.discount_rate = 12.5
+
+    # Make sure that everything adds up to begin with.
+    expected_amount = line_item.quantity * line_item.unit_amount * 0.875
+    assert_equal(expected_amount, line_item.line_amount)
+
+    # Change the line_amount and check that it doesn't modify anything.
+    line_item.line_amount = expected_amount * 10
+    assert_equal(expected_amount, line_item.line_amount)
+
+    # Change the quantity and check that the line_amount has been updated.
+    quantity = line_item.quantity + 2
+    line_item.quantity = quantity
+    assert_not_equal(expected_amount, line_item.line_amount)
+    assert_equal(quantity * line_item.unit_amount * 0.875, line_item.line_amount)
+  end
+
   # Ensure that the totalling methods don't raise exceptions, even when
   # invoice.line_items is empty.
   def test_totalling_methods_when_line_items_empty
@@ -286,7 +318,7 @@ def test_instantiate_invoice_with_default_line_amount_types
   def test_optional_params
     eur_code = "EUR"
     eur_rate = 1.80
-    
+
     invoice = create_test_invoice(:url => 'http://example.com', :branding_theme_id => 'a94a78db-5cc6-4e26-a52b-045237e56e6e', :currency_code => eur_code, :currency_rate => eur_rate)
     assert_equal 'http://example.com', invoice.url
     assert_equal 'a94a78db-5cc6-4e26-a52b-045237e56e6e', invoice.branding_theme_id