module RangePpoiString

# File lib/range_ppoi_string.rb, line 35
def to_a
  self.split(",").flat_map { |s|
    a, b = s.split("-")
    b.nil? ? a : [*a..b]
  }
end

# File lib/range_ppoi_string.rb, line 10
def to_s
  unless self.all?(&HAVE_NEXT)
    raise NoNextError.new("No next method: #{self.reject(&HAVE_NEXT)}")
  end

  SortedSet[*self].each_with_object([[]]) { |o, res|
    res.push([]) if res.empty?

    if res.last.empty? || res.last.last.next == o
      res.last.push(o)
    else
      res.push([o])
    end
  }.map { |a|
    case a.size
    when 0, 1
      a[0]
    else
      "#{a[0]}-#{a[-1]}"
    end
  }.join(",")
end