Handy HTTP requests with Curb and Ruby

module ApiRequest
  USER_AGENTS = [
    'Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.6; en-US; rv:1.9.2.3) Gecko/20100401 Firefox/3.6.3',
    'Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; .NET CLR 2.0.50727)',
    'Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.3) Gecko/20100423 Ubuntu/10.04 (lucid) Firefox/3.6.3',
    'Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10_6_3; en-US) AppleWebKit/533.4 (KHTML, like Gecko) Chrome/5.0.375.70 Safari/533.4',
    'Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.2.2) Gecko/20100323 Namoroka/3.6.2',
    'Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.1.9) Gecko/20100401 Ubuntu/9.10 (karmic) Firefox/3.5.9'
  ]
 
  CONNECTION_TIMEOUT = 10
 
  @@interfaces = []
 
  # get random user-agent string for usage
  def random_agent
    USER_AGENTS[rand(USER_AGENTS.size-1)]
  end
 
  # get random IP/network interface specified in @@interfaces
  def random_interface
    size = @@interfaces.size
    size > 0 ? @@interfaces[rand(size-1)] : nil
  end
 
  # perform request, assign_to - specify network interface/ip
  def perform(url, assign_to=nil)
    puts url
    interface = assign_to.nil? ? self.random_interface : assign_to
    req = Curl::Easy.new(url)
    req.timeout = CONNECTION_TIMEOUT
    req.interface = interface unless interface.nil?
    req.headers['User-Agent'] = self.random_agent
    begin
      req.perform
      if req.response_code == 200
        return req.downloaded_bytes > 0 ? req.body_str : nil
      else
        nil
      end
    rescue Exception
      return nil
    end
  end
 
  # perform request by number of attempts
  def fetch(url, attempts=3)
    result = nil
    1.upto(attempts) do |a|
      result = self.perform(url)
      break unless result.nil?
    end
    return result
  end
end

class TestRequest
  include ApiRequest
 
  def foo
     body = self.fetch('http://google.com')
  end
end