module Egn
  class Parser

    def initialize(egn)
      return ArgumentError, 'invalid length (should == 10)' unless egn.length == 10

      @year, @month, @day = egn.scan(/.{1,2}/)
      @month = @month.to_i
      @day = @day.to_i

      case @month
      when (1..12)
        @year = "19#{@year}"
      when (21..32)
        @month -= 20
        @year = "18#{@year}"
      when (41..52)
        @month -= 40
        @year = "20#{@year}"
      end
      @year = @year.to_i

      raise ArgumentError, "invalid date" unless Date.valid_date? @year, @month, @day
    end

    def birth_date
      Date.parse("#{@year}-#{@month}-#{@day}")
    end

    def gender

    end

  end
end