email.rb

=begin
<span class="next">
<a href="/group/douban_radio/discussion?start=525">后页></a>
</span>
http://www.douban.com/group/douban_radio/discussion?start=0
=end
require 'open-uri'
require 'hpricot'
module Douban
  #PER_PAGE = 25
  HOST     = "http://www.douban.com/"

  class Topic
    attr_reader :topic_url
    attr_reader :total_pages
    attr_reader :emails

    def initialize(url)
      @topic_url   = url
      @total_pages = Hpricot.parse(open(topic_url + "?start=0").read).search("div.paginator/a/*").last.to_s.to_i
      @emails       = []
    end

    def emails
      (0..total_pages).each do |i|
        @emails + open(topic_url + "?start=#{100*i}").read.scan(/\A[a-z0-9.]+@[a-z0-9.]{2,10}\Z/mi)
      end
    end
  end

  class Group
    attr_reader :group_url
    attr_reader :total_pages
    attr_reader :topic_urls

    def initialize(url)
      @group_url   = url
      @total_pages =  Hpricot.parse(open(File.join(group_url, "discussion?start=0")).read).search("div.paginator/a/*").last.to_s.to_i
      @topic_urls  = []
    end
    
    def topics
      (0..total_pages).each do |i|
        @topic_urls + Hpricot.parse(open(File.join(group_url, "discussion?start=#{25*i}")).read).search("div.article//tr/td[1]/a").map{|a| a["href"]}
      end
      self
    end
  end
end

url = "http://www.douban.com/group/douban_radio/"
client = Douban::Group.new(url)
puts client.total_pages
p client.topics.topic_urls