subreddits.rb

require 'rubygems'
require 'hpricot'
require 'open-uri'
require 'builder'

def get_subreddits(uri = 'http://www.reddit.com/reddits/')
  reddits = []
  
  while uri
    page = download_page(uri)
    reddits += find_reddits_on(page)
    uri = get_next(page)
  end
  
  reddits
end

def download_page(uri)
  Hpricot(open(uri))
end

def get_next(page)
  a = page.search("//p[@class='nextprev']/a").last
  if a and a.inner_html == 'next'
    a.attributes['href']
  else
    false
  end
end

def find_reddits_on(page)
  subreddits = []
  for div in page.search("div.subreddit")
    subreddits << [div.search('.title').inner_html, div.search('.title').first.attributes['href'], div.search('.description').inner_html, div.search('.score').inner_html.split[0]]
  end
  return subreddits
end

def output_subreddits(subreddits)
  # TODO doctype
  xml = Builder::XmlMarkup.new(:target => STDOUT, :indent => 2)
  xml.instruct!  
  xml.subreddits do 
    subreddits.each do | subreddit |
      xml.reddit{ xml.title(subreddit[0]); 
                  xml.href(subreddit[1]); 
                  xml.description(subreddit[2]);
                  xml.score(subreddit[3]);}
    end
  end
end

output_subreddits get_subreddits