domain.rb

require "valaptor/utilities/idn"

module Valaptor
  module Utilities
    class Domain
      def initialize
        Valaptor.use "simpleidn"
      end

      def errors(domain)
        result  = []
        ascii   = Idn.to_ascii(domain)
        labels  = ascii.split(".".freeze, -1)

        result << :trailing_dots if domain =~ /\.{2,}\z/ # SimpleIDN removes trailing dots, hence test on domain instead of ascii. A single trailing dot is valid.
        result << :domain_too_long if ascii.bytesize > 253
        result << :multiple_dots if labels.include?("".freeze)
        result << :label_too_long if labels.any? { |label| label.bytesize > 63 }
        result << :invalid_label unless labels.all? { |label| label =~ /\A[A-Za-z0-9](?:[A-Za-z0-9-]*[A-Za-z0-9]|[A-Za-z0-9]*)\z/ }

        result
      end

      def valid?(domain)
        errors(domain).empty?
      end
    end
  end
end