Test whether or not a user has Gravatar

gravatar.rb

require "net/http"

class GravatarGenerator
  URL_FORMAT = "http://www.gravatar.com/avatar/%s"
  LAST_MODIFIED_TEST_STRING = "Wed, 11 Jan 1984 08:00:00 GMT"

  def self.test(email)
    url = URI(URL_FORMAT % generate(email))

    Net::HTTP.start(url.host, url.port) do |http|
      http.head(url.path)["Last-Modified"] != LAST_MODIFIED_TEST_STRING
    end
  end

  def self.generate(string)
    Digest::MD5.hexdigest(string.strip.downcase)
  end
end