module Serializable
  class Version

    def initialize(version_string)
      version_string = version_string.gsub('_','.')
      @levels = version_string.split('.')

      @levels.each_with_index do |number, index|
        @levels[index] = number.to_i
      end
    end

    def major
      get_level(0)
    end

    def minor
      get_level(1)
    end

    def build
      get_level(2)
    end

    def revision
      get_level(3)
    end

    def <(rhs)
      (self <=> rhs) < 0
    end

    def >(rhs)
      (self <=> rhs) > 0
    end

    def ==(rhs)
      (self <=> rhs) == 0
    end

    def <=>(rhs)
      max_levels = @levels.size - 1
      max_levels = rhs.levels.size - 1 if rhs.levels.size > max_levels

      (0..max_levels).each do |level|
        lhs_level = @levels[level] || 0
        rhs_level = rhs.levels[level] || 0

        if lhs_level == rhs_level
          next
        else
          return lhs_level <=> rhs_level
        end
      end
      0 # Ended on an equality
    end

    def to_s(seperator = '.')
      @levels.join(seperator)
    end

    def to_s_underscored
      to_s('_')
    end

    protected

    def levels
      @levels
    end

    private

    def get_level(level)
      if @levels.size > level
        @levels[level]
      else
        0
      end
    end

  end
end