Add Faker::IDNumber.croatian_id method

doc/default/id_number.md

@@ -34,4 +34,9 @@ Faker::IDNumber.brazilian_id(formatted: true) #=> "49.305.402-9"
 # Generate a Chilean ID (Rut with 8 digits)
 # For more advanced cases, please refer to Faker::ChileRut
 Faker::IDNumber.chilean_id #=> "15620613-K"
+
+# Generate a Croatian ID number (OIB)
+# Keyword arguments: international
+Faker::IDNumber.croatian_id #=> "88467617508"
+Faker::IDNumber.croatian_id(international: true) #=> "HR88467617508"
 ```

lib/faker/default/id_number.rb

@@ -200,8 +200,42 @@ def chilean_id
         "#{digits}-#{verification_code}"
       end
 
+      ##
+      # Produces a random Croatian ID number (OIB).
+      #
+      # @param international [Boolean] Specifies whether to add international prefix.
+      # @return [String]
+      #
+      # @example
+      #   Faker::IDNumber.croatian_id #=> "88467617508"
+      #   Faker::IDNumber.croatian_id(international: true) #=> "HR88467617508"
+      #
+      # @faker.version next
+      def croatian_id(international: false)
+        prefix = international ? 'HR' : ''
+        digits = Faker::Number.number(digits: 10).to_s
+        checksum_digit = croatian_id_checksum_digit(digits)
+
+        "#{prefix}#{digits}#{checksum_digit}"
+      end
+
       private
 
+      def croatian_id_checksum_digit(digits)
+        control_sum = 10
+
+        digits.chars.map(&:to_i).each do |digit|
+          control_sum += digit
+          control_sum %= 10
+          control_sum = 10 if control_sum.zero?
+          control_sum *= 2
+          control_sum %= 11
+        end
+
+        control_sum = 11 - control_sum
+        control_sum % 10
+      end
+
       def chilean_verification_code(digits)
         # First digit is multiplied by 3, second by 2, and so on
         multiplication_rule = [3, 2, 7, 6, 5, 4, 3, 2]

test/faker/default/test_faker_id_number.rb

@@ -160,6 +160,22 @@ def test_chilean_verification_code_0
     assert_equal verification_code, 0
   end
 
+  def test_croatian_id
+    sample = @tester.croatian_id
+    assert_match(/^\d{11}$/, sample)
+  end
+
+  def test_croatian_id_international
+    sample = @tester.croatian_id(international: true)
+    assert_match(/^HR\d{11}$/, sample)
+  end
+
+  def test_croatian_id_checksum_digit
+    digits = '8764670153'
+    checksum_digit = Faker::IDNumber.send(:croatian_id_checksum_digit, digits)
+    assert_equal checksum_digit, 5
+  end
+
   private
 
   def south_african_id_number_to_date_of_birth_string(sample)