Added Faker::Company.indian_gst_number fixed faker-ruby#2823

doc/default/company.md

@@ -84,4 +84,8 @@ Faker::Company.russian_tax_number #=> "0965855857"
 Faker::Company.russian_tax_number(region: '77') #=> "7717152803"
 Faker::Company.russian_tax_number(type: :individual) #=> "488935903348"
 Faker::Company.russian_tax_number(region: '77', type: :individual) #=> "779124694601"
+
+# Get a random formatted Indian tax number (GST)
+Faker::Company.indian_gst_number #=> "15VQPNZ2126J2ZU"
+Faker::Company.indian_gst_number(state_code: "22") #=> "22ZVWEY6632K0ZN"
 ```

lib/faker/default/company.rb

@@ -464,6 +464,35 @@ def sic_code
         fetch('company.sic_code')
       end
 
+      ##
+      # Get a random Indian Goods and Services Tax (GST) number.
+      # For more on Indian tax number here:
+      # https://simple.wikipedia.org/wiki/GSTIN
+      # @params state code [String] Any state code.
+      #
+      # @return [String]
+      # @example
+      #   Faker::Company.indian_gst_number #=> "15VQPNZ2126J2ZU"
+      #   Faker::Company.indian_gst_number(state_code: "22") #=> "22ZVWEY6632K0ZN"
+      #
+      # @faker.version 3.2.1
+      def indian_gst_number(state_code: nil)
+        state_code_list = %w[01 02 03 04 05 06 07 08 09 10 11 12 13 14 97]
+        state_code = state_code_list.sample(random: Faker::Config.random) if state_code.nil?
+        taxpayer_number = Array.new(3) { ('A'..'Z').to_a.sample(random: Faker::Config.random) } + Array.new(1) {
+                                                                                                    %w[A B C F G H L J P T
+                                                                                                       K].to_a.sample(random: Faker::Config.random)
+                                                                                                  } + Array.new(1) {
+                                                                                                        ('A'..'Z').to_a.sample(random: Faker::Config.random)
+                                                                                                      } + Array.new(4) {
+                                                                                                            rand(10)
+                                                                                                          } + [('A'..'Z').to_a.sample(random: Faker::Config.random)]
+        taxpayer_number = taxpayer_number.join
+        registration_number = rand(10).to_s
+        checksum = calculate_gst_checksum(state_code, taxpayer_number, registration_number)
+        "#{state_code}#{taxpayer_number}#{registration_number}Z#{checksum}"
+      end
+
       private
 
       # Mod11 functionality from https://github.com/badmanski/mod11/blob/master/lib/mod11.rb
@@ -605,6 +634,19 @@ def spanish_b_algorithm(value)
 
         result.to_s[0].to_i + result.to_s[1].to_i
       end
+
+      def calculate_gst_checksum(state_code, taxpayer_number, registration_number)
+        gst_base = "#{state_code}#{taxpayer_number}#{registration_number}"
+        chars = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ'.chars
+        values = gst_base.upcase.chars
+        sum = values.map.with_index do |char, index|
+          product = chars.index(char) * (index.odd? ? 2 : 1)
+          (product / chars.length).floor + (product % chars.length)
+        end.reduce(:+)
+
+        checksum = (chars.length - (sum % chars.length)) % chars.length
+        chars[checksum]
+      end
     end
   end
 end

test/faker/default/test_faker_company.rb

@@ -250,6 +250,15 @@ def test_spanish_b_algorithm
     assert_equal(3, @tester.send(:spanish_b_algorithm, 6))
   end
 
+  def text_indian_gst_number
+    assert_match(/^([0-2][0-9]|[3][0-7])[A-Z]{3}[ABCFGHLJPTK][A-Z]\d{4}[A-Z][A-Z0-9][Z][A-Z0-9]$/i, @tester.indian_gst_number)
+  end
+
+  def test_indian_gst_number_with_state_code
+    assert_match(/^(22)[A-Z]{3}[ABCFGHLJPTK][A-Z]\d{4}[A-Z][A-Z0-9][Z][A-Z0-9]$/i, @tester.indian_gst_number(state_code: '22'))
+    assert_match(/^(01)[A-Z]{3}[ABCFGHLJPTK][A-Z]\d{4}[A-Z][A-Z0-9][Z][A-Z0-9]$/i, @tester.indian_gst_number(state_code: '01'))
+  end
+
   private
 
   def czech_o_n_checksum(org_no)