support multiple tax rates per invoice (#9)

* support multiple tax rates per invoice

* take into account line_item.quantity

lib/secretariat.rb

@@ -23,3 +23,4 @@
 require_relative 'secretariat/trade_party'
 require_relative 'secretariat/line_item'
 require_relative 'secretariat/validator'
+require_relative 'secretariat/tax'

lib/secretariat/invoice.rb

@@ -61,6 +61,16 @@ def tax_category_code(version: 2)
       TAX_CATEGORY_CODES[tax_category] || 'S'
     end
 
+    def taxes
+      taxes = {}
+      line_items.each do |line_item|
+        taxes[line_item.tax_percent] = Tax.new(tax_percent: BigDecimal(line_item.tax_percent)) if taxes[line_item.tax_percent].nil?
+        taxes[line_item.tax_percent].tax_amount += BigDecimal(line_item.tax_amount)
+        taxes[line_item.tax_percent].base_amount += BigDecimal(line_item.net_amount) * line_item.quantity
+      end
+      taxes.values
+    end
+
     def payment_code
       PAYMENT_CODES[payment_type] || '1'
     end
@@ -69,12 +79,24 @@ def valid?
       @errors = []
       tax = BigDecimal(tax_amount)
       basis = BigDecimal(basis_amount)
-      calc_tax = basis * BigDecimal(tax_percent) / BigDecimal(100)
-      calc_tax = calc_tax.round(2, :down)
-      if tax != calc_tax
-        @errors << "Tax amount and calculated tax amount deviate: #{tax} / #{calc_tax}"
+      summed_tax_amount = taxes.sum(&:tax_amount)
+      if tax != summed_tax_amount
+        @errors << "Tax amount and summed tax amounts deviate: #{tax_amount} / #{summed_tax_amount}"
+        return false
+      end
+      summed_tax_base_amount = taxes.sum(&:base_amount)
+      if basis != summed_tax_base_amount
+        @errors << "Base amount and summed tax base amount deviate: #{basis} / #{summed_tax_base_amount}"
         return false
       end
+      taxes.each do |tax|
+        calc_tax = tax.base_amount * BigDecimal(tax.tax_percent) / BigDecimal(100)
+        calc_tax = calc_tax.round(2, :down)
+        if tax.tax_amount != calc_tax
+          @errors << "Tax amount and calculated tax amount deviate for rate #{tax.tax_percent}: #{tax.tax_amount} / #{calc_tax}"
+          return false
+        end
+      end
       grand_total = BigDecimal(grand_total_amount)
       calc_grand_total = basis + tax
       if grand_total != calc_grand_total
@@ -200,18 +222,19 @@ def to_xml(version: 1, validate: true)
                   end
                 end
               end
-              xml['ram'].ApplicableTradeTax do
+              taxes.each do |tax|
+                xml['ram'].ApplicableTradeTax do
+                  Helpers.currency_element(xml, 'ram', 'CalculatedAmount', tax.tax_amount, currency_code, add_currency: version == 1)
+                  xml['ram'].TypeCode 'VAT'
+                  if tax_reason_text && tax_reason_text != ''
+                    xml['ram'].ExemptionReason tax_reason_text
+                  end
+                  Helpers.currency_element(xml, 'ram', 'BasisAmount', tax.base_amount, currency_code, add_currency: version == 1)
+                  xml['ram'].CategoryCode tax_category_code(version: version)
 
-                Helpers.currency_element(xml, 'ram', 'CalculatedAmount', tax_amount, currency_code, add_currency: version == 1)
-                xml['ram'].TypeCode 'VAT'
-                if tax_reason_text && tax_reason_text != ''
-                  xml['ram'].ExemptionReason tax_reason_text
+                  percent = by_version(version, 'ApplicablePercent', 'RateApplicablePercent')
+                  xml['ram'].send(percent, Helpers.format(tax.tax_percent))
                 end
-                Helpers.currency_element(xml, 'ram', 'BasisAmount', basis_amount, currency_code, add_currency: version == 1)
-                xml['ram'].CategoryCode tax_category_code(version: version)
-
-                percent = by_version(version, 'ApplicablePercent', 'RateApplicablePercent')
-                xml['ram'].send(percent, Helpers.format(tax_percent))
               end
               if version == 2 && service_period_start && service_period_end
                 xml['ram'].BillingSpecifiedPeriod do

lib/secretariat/tax.rb

@@ -0,0 +1,34 @@
+=begin
+Copyright Jan Krutisch
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+
+=end
+
+require 'bigdecimal'
+
+module Secretariat
+  Tax = Struct.new('Tax',
+    :tax_percent,
+    :tax_amount,
+    :base_amount,
+    keyword_init: true
+  ) do
+
+    def initialize(*)
+      super
+      self.tax_amount = 0
+      self.base_amount = 0
+    end
+  end
+end

test/invoice_test.rb

@@ -46,7 +46,6 @@ def make_eu_invoice
         payment_type: :CREDITCARD,
         payment_text: 'Kreditkarte',
         tax_category: :REVERSECHARGE,
-        tax_percent: 0,
         tax_amount: '0',
         basis_amount: '29',
         grand_total_amount: 29,
@@ -103,7 +102,6 @@ def make_de_invoice
         payment_iban: 'DE02120300000000202051',
         payment_terms_text: "Zahlbar innerhalb von 14 Tagen ohne Abzug",
         tax_category: :STANDARDRATE,
-        tax_percent: '19',
         tax_amount: '3.80',
         basis_amount: '20',
         grand_total_amount: '23.80',
@@ -113,6 +111,73 @@ def make_de_invoice
       )
     end
 
+    def make_de_invoice_with_multiple_tax_rates
+      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: 1,
+        unit: :PIECE,
+        gross_amount: '23.80',
+        net_amount: '20',
+        charge_amount: '20',
+        tax_category: :STANDARDRATE,
+        tax_percent: '19',
+        tax_amount: "3.80",
+        origin_country_code: 'DE',
+        currency_code: 'EUR'
+      )
+      line_item2 = LineItem.new(
+        name: 'Cup of Coffee',
+        quantity: 2,
+        unit: :PIECE,
+        gross_amount: '2.14',
+        net_amount: '2',
+        charge_amount: '4',
+        tax_category: :STANDARDRATE,
+        tax_percent: '7',
+        tax_amount: "0.28",
+        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, line_item2],
+        currency_code: 'USD',
+        payment_type: :CREDITCARD,
+        payment_text: 'Kreditkarte',
+        payment_iban: 'DE02120300000000202051',
+        payment_terms_text: "Zahlbar innerhalb von 14 Tagen ohne Abzug",
+        tax_category: :STANDARDRATE,
+        tax_amount: '4.08',
+        basis_amount: '24',
+        grand_total_amount: '28.08',
+        due_amount: 0,
+        paid_amount: '28.08',
+        payment_due_date: Date.today + 14
+      )
+    end
+
     def test_simple_eu_invoice_v2
       begin
         xml = make_eu_invoice.to_xml(version: 2)
@@ -204,5 +269,44 @@ def test_simple_de_invoice_against_schematron
       end
       assert_equal [], errors
     end
+
+    def test_de_multiple_taxes_invoice_v1
+      xml = make_de_invoice_with_multiple_tax_rates.to_xml(version: 1)
+      v = Validator.new(xml, version: 1)
+      errors = v.validate_against_schema
+      if !errors.empty?
+        puts xml
+        errors.each do |error|
+          puts error
+        end
+      end
+      assert_equal [], errors
+    end
+
+    def test_de_multiple_taxes_invoice_v2
+      xml = make_de_invoice_with_multiple_tax_rates.to_xml(version: 2)
+      v = Validator.new(xml, version: 2)
+      errors = v.validate_against_schema
+      if !errors.empty?
+        puts xml
+        errors.each do |error|
+          puts error
+        end
+      end
+      assert_equal [], errors
+    end
+
+    def test_de_multiple_taxes_invoice_against_schematron
+      xml = make_de_invoice_with_multiple_tax_rates.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
   end
 end