module Faker
  class Invoice < Base
    flexible :invoice

    class << self
      # Generate random amount between values with 2 decimals
      def amount_between(from = 0, to = 0)
        Faker::Base.rand_in_range(from, to).round(2)
      end

      # International bank slip reference https://en.wikipedia.org/wiki/Creditor_Reference
      # ref is optional so that we can create unit tests
      def creditor_reference(ref = '')
        ref = reference if ref.empty?

        'RF' + iban_checksum('RF', ref) + ref
      end

      # Payment references have some rules in certain countries
      # ref is optional so that we can create unit tests
      def reference(ref = '')
        pattern = fetch('invoice.reference.pattern')

        ref = Base.regexify(/#{pattern}/) if ref.empty?

        # If reference contains reserved '#' characters we need to calculate check_digits as well
        check_digit_match = ref.match(/#+/)
        if check_digit_match
          # Get the method for selected language
          check_digit_method = fetch('invoice.reference.check_digit_method')

          # Calculate the check digit with matching method name
          # Trim all '#' from the reference before calculating that
          check_digit = send(check_digit_method, ref.tr('#', ''))

          # Make sure that our check digit is as long as all of the '###' we found
          check_digit = check_digit.to_s.rjust(check_digit_match[0].length, '0')

          # Replace all of the
          ref.sub!(check_digit_match[0], check_digit)
        end

        ref
      end

      private

      # Calculates the mandatory checksum in 3rd and 4th characters in IBAN format
      # source: https://en.wikipedia.org/wiki/International_Bank_Account_Number#Validating_the_IBAN
      def iban_checksum(country_code, account)
        # Converts letters to numbers according the iban rules, A=10..Z=35
        account_to_number = "#{account}#{country_code}00".upcase.chars.map do |d|
          d =~ /[A-Z]/ ? (d.ord - 55).to_s : d
        end.join.to_i

        # This is answer to (iban_to_num + checksum) % 97 == 1
        checksum = (1 - account_to_number) % 97

        # Use leftpad to make the size always to 2
        checksum.to_s.rjust(2, '0')
      end

      # 731 Method
      # Source: https://wiki.xmldation.com/support/fk/finnish_reference_number
      def method_731(base)
        weighted_sum = calculate_weighted_sum(base, [7, 3, 1])
        mod10_remainder(weighted_sum)
      end

      # Norsk Modulus 10 - KIDMOD10
      def kidmod10(base)
        weighted_sum = calculate_weighted_sum(base, [1, 2])
        mod10_remainder(weighted_sum)
      end

      # Calculates weigthed sum
      #
      # For example with 12345678, [1,2]
      # Ref.num. 1 2 3 4 5 6 7 8
      # Multipl. 1 2 1 2 1 2 1 2
      # Total 1+ 4+ 3+ 8+ 5+1+2+ 7+1+6 = 38
      def calculate_weighted_sum(base, weight_factors)
        base.to_s.reverse.each_char.with_index.map do |digit, index|
          digit.to_i * weight_factors.at(index % weight_factors.length)
        end.reduce(:+) # reduce(:+) = sum() but with better ruby version support
      end

      # MOD-10 - remainder
      def mod10_remainder(number)
        -number % 10
      end
    end
  end
end