module IceCube
  module Validations::YearlyInterval
    def interval(interval)
      @interval = normalized_interval(interval)
      replace_validations_for(:interval, [Validation.new(@interval)])
      clobber_base_validations(:year)
      self
    end

    class Validation
      attr_reader :interval

      def initialize(interval)
        @interval = interval
      end

      def type
        :year
      end

      def dst_adjust?
        true
      end

      def validate(step_time, start_time)
        years = step_time.year - start_time.year
        offset = (years % interval).nonzero?
        interval - offset if offset
      end

      def build_s(builder)
        builder.base = IceCube::I18n.t("ice_cube.each_year", count: interval)
      end

      def build_hash(builder)
        builder[:interval] = interval
      end

      def build_ical(builder)
        builder["FREQ"] << "YEARLY"
        unless interval == 1
          builder["INTERVAL"] << interval
        end
      end
    end
  end
end
