take into account line_items with negative quantity

lib/secretariat/invoice.rb

@@ -105,7 +105,7 @@ def valid?
         return false
       end
       line_item_sum = line_items.inject(BigDecimal(0)) do |m, item|
-        m + BigDecimal(item.charge_amount)
+        m + BigDecimal(item.quantity.negative? ? -item.charge_amount : item.charge_amount)
       end
       if line_item_sum != basis
         @errors << "Line items do not add up to basis amount #{line_item_sum} / #{basis}"

lib/secretariat/line_item.rb

@@ -49,7 +49,7 @@ def valid?
       gross_price = BigDecimal(gross_amount)
       charge_price = BigDecimal(charge_amount)
       tax = BigDecimal(tax_amount)
-      unit_price = net_price * BigDecimal(quantity)
+      unit_price = net_price * BigDecimal(quantity.abs)
 
       if charge_price != unit_price
         @errors << "charge price and gross price times quantity deviate: #{charge_price} / #{unit_price}"
@@ -66,6 +66,7 @@ def valid?
 
       calculated_tax = charge_price * BigDecimal(tax_percent) / BigDecimal(100)
       calculated_tax = calculated_tax.round(2)
+      calculated_tax = -calculated_tax if quantity.negative?
       if calculated_tax != tax
         @errors << "Tax and calculated tax deviate: #{tax} / #{calculated_tax}"
         return false
@@ -85,6 +86,17 @@ def tax_category_code(version: 2)
     end
 
     def to_xml(xml, line_item_index, version: 2, validate: true)
+      if net_amount&.zero?
+        self.tax_percent = 0
+      end
+      if net_amount&.negative?
+        # Zugferd doesn't allow negative amounts at the item level.
+        # Instead, a negative quantity is used.
+        self.quantity = -quantity
+        self.gross_amount = gross_amount&.abs
+        self.net_amount = net_amount&.abs
+        self.charge_amount = charge_amount&.abs
+      end
       if validate && !valid?
         pp errors
         raise ValidationError.new("LineItem #{line_item_index} is invalid", errors)
@@ -160,7 +172,7 @@ def to_xml(xml, line_item_index, version: 2, validate: true)
           end
           monetary_summation = by_version(version, 'SpecifiedTradeSettlementMonetarySummation', 'SpecifiedTradeSettlementLineMonetarySummation')
           xml['ram'].send(monetary_summation) do
-            Helpers.currency_element(xml, 'ram', 'LineTotalAmount', charge_amount, currency_code, add_currency: version == 1)
+            Helpers.currency_element(xml, 'ram', 'LineTotalAmount', (quantity.negative? ? -charge_amount  : charge_amount), currency_code, add_currency: version == 1)
           end
         end
 

test/invoice_test.rb

@@ -24,13 +24,13 @@ def make_eu_invoice
       line_item = LineItem.new(
         name: 'Depfu Starter Plan',
         quantity: 1,
-        gross_amount: '29',
-        net_amount: '29',
+        gross_amount: BigDecimal('29'),
+        net_amount: BigDecimal('29'),
         unit: :PIECE,
-        charge_amount: '29',
+        charge_amount: BigDecimal('29'),
         tax_category: :REVERSECHARGE,
         tax_percent: 0,
-        tax_amount: "0",
+        tax_amount: 0,
         origin_country_code: 'DE',
         currency_code: 'EUR'
       )
@@ -46,9 +46,9 @@ def make_eu_invoice
         payment_type: :CREDITCARD,
         payment_text: 'Kreditkarte',
         tax_category: :REVERSECHARGE,
-        tax_amount: '0',
-        basis_amount: '29',
-        grand_total_amount: 29,
+        tax_amount: 0,
+        basis_amount: BigDecimal('29'),
+        grand_total_amount: BigDecimal('29'),
         due_amount: 0,
         paid_amount: 29,
         payment_due_date: Date.today + 14
@@ -76,14 +76,14 @@ def make_de_invoice
         name: 'Depfu Starter Plan',
         quantity: 1,
         unit: :PIECE,
-        gross_amount: '29',
-        net_amount: '20',
-        charge_amount: '20',
-        discount_amount: '9',
+        gross_amount: BigDecimal('29'),
+        net_amount: BigDecimal('20'),
+        charge_amount: BigDecimal('20'),
+        discount_amount: BigDecimal('9'),
         discount_reason: 'Rabatt',
         tax_category: :STANDARDRATE,
         tax_percent: '19',
-        tax_amount: "3.80",
+        tax_amount: BigDecimal("3.80"),
         origin_country_code: 'DE',
         currency_code: 'EUR'
       )
@@ -103,11 +103,11 @@ def make_de_invoice
         payment_iban: 'DE02120300000000202051',
         payment_terms_text: "Zahlbar innerhalb von 14 Tagen ohne Abzug",
         tax_category: :STANDARDRATE,
-        tax_amount: '3.80',
-        basis_amount: '20',
-        grand_total_amount: '23.80',
+        tax_amount: BigDecimal('3.80'),
+        basis_amount: BigDecimal('20'),
+        grand_total_amount: BigDecimal('23.80'),
         due_amount: 0,
-        paid_amount: '23.80',
+        paid_amount: BigDecimal('23.80'),
         payment_due_date: Date.today + 14
       )
     end
@@ -133,38 +133,38 @@ def make_de_invoice_with_multiple_tax_rates
         name: 'Depfu Starter Plan',
         quantity: 2,
         unit: :PIECE,
-        gross_amount: '23.80',
-        net_amount: '20',
-        charge_amount: '40',
+        gross_amount: BigDecimal('23.80'),
+        net_amount: BigDecimal('20'),
+        charge_amount: BigDecimal('40'),
         tax_category: :STANDARDRATE,
         tax_percent: '19',
-        tax_amount: "7.60",
+        tax_amount: BigDecimal("7.60"),
         origin_country_code: 'DE',
         currency_code: 'EUR'
       )
       line_item2 = LineItem.new(
         name: 'Cup of Coffee',
         quantity: 1,
         unit: :PIECE,
-        gross_amount: '2.68',
-        net_amount: '2.50',
-        charge_amount: '2.50',
+        gross_amount: BigDecimal('2.68'),
+        net_amount: BigDecimal('2.50'),
+        charge_amount: BigDecimal('2.50'),
         tax_category: :STANDARDRATE,
         tax_percent: '7',
-        tax_amount: "0.18",
+        tax_amount: BigDecimal("0.18"),
         origin_country_code: 'DE',
         currency_code: 'EUR'
       )
       line_item3 = LineItem.new(
         name: 'Returnable Deposit',
         quantity: 1,
         unit: :PIECE,
-        gross_amount: '5',
-        net_amount: '5',
-        charge_amount: '5',
+        gross_amount: BigDecimal('5'),
+        net_amount: BigDecimal('5'),
+        charge_amount: BigDecimal('5'),
         tax_category: :ZEROTAXPRODUCTS,
         tax_percent: '0',
-        tax_amount: "0",
+        tax_amount: BigDecimal("0"),
         origin_country_code: 'DE',
         currency_code: 'EUR'
       )
@@ -183,11 +183,66 @@ def make_de_invoice_with_multiple_tax_rates
         payment_iban: 'DE02120300000000202051',
         payment_terms_text: "Zahlbar innerhalb von 14 Tagen ohne Abzug",
         tax_category: :STANDARDRATE,
-        tax_amount: '7.78',
-        basis_amount: '47.50',
-        grand_total_amount: '55.28',
+        tax_amount: BigDecimal('7.78'),
+        basis_amount: BigDecimal('47.50'),
+        grand_total_amount: BigDecimal('55.28'),
         due_amount: 0,
-        paid_amount: '55.28',
+        paid_amount: BigDecimal('55.28'),
+        payment_due_date: Date.today + 14
+      )
+    end
+
+    def make_negative_de_invoice
+      seller = TradeParty.new(
+        name: 'Depfu inc',
+        street1: 'Quickbornstr. 46',
+        city: 'Hamburg',
+        postal_code: '20253',
+        country_id: 'DE',
+        vat_id: 'DE304755032'
+      )
+      buyer = TradeParty.new(
+        name: 'Depfu inc',
+        street1: 'Quickbornstr. 46',
+        city: 'Hamburg',
+        postal_code: '20253',
+        country_id: 'DE',
+        vat_id: 'DE304755032'
+      )
+      line_item = LineItem.new(
+        name: 'Depfu Starter Plan',
+        quantity: 2,
+        unit: :PIECE,
+        gross_amount: BigDecimal('-100'),
+        net_amount: BigDecimal('-100'),
+        charge_amount: BigDecimal('-200'),
+        tax_category: :STANDARDRATE,
+        tax_percent: '19',
+        tax_amount: BigDecimal('-38'),
+        origin_country_code: 'DE',
+        currency_code: 'EUR'
+      )
+      Invoice.new(
+        id: '12345',
+        issue_date: Date.today,
+        service_period_start: Date.today,
+        service_period_end: Date.today + 30,
+        seller: seller,
+        buyer: buyer,
+        buyer_reference: "112233",
+        line_items: [line_item],
+        currency_code: 'USD',
+        payment_type: :CREDITCARD,
+        payment_text: 'Kreditkarte',
+        payment_reference: 'INV 123123123',
+        payment_iban: 'DE02120300000000202051',
+        payment_terms_text: "Wir zahlen die Gutschrift unmittelbar aus",
+        tax_category: :STANDARDRATE,
+        tax_amount: BigDecimal('-38'),
+        basis_amount: BigDecimal('-200'),
+        grand_total_amount: BigDecimal('-238'),
+        due_amount: BigDecimal('-238'),
+        paid_amount: 0,
         payment_due_date: Date.today + 14
       )
     end
@@ -334,5 +389,29 @@ def test_de_multiple_taxes_invoice_against_schematron_2
       end
       assert_equal [], errors
     end
+    def test_negative_de_invoice_against_schematron_1
+      xml = make_negative_de_invoice.to_xml(version: 1)
+      v = Validator.new(xml, version: 1)
+      errors = v.validate_against_schematron
+      if !errors.empty?
+        puts xml
+        errors.each do |error|
+          puts "#{error[:line]}: #{error[:message]}"
+        end
+      end
+      assert_equal [], errors
+    end
+    def test_negative_de_invoice_against_schematron_2
+      xml = make_negative_de_invoice.to_xml(version: 2)
+      v = Validator.new(xml, version: 2)
+      errors = v.validate_against_schematron
+      if !errors.empty?
+        puts xml
+        errors.each do |error|
+          puts "#{error[:line]}: #{error[:message]}"
+        end
+      end
+      assert_equal [], errors
+    end
   end
 end