Restore original url from the url made from some url shortening services.

url_extractor.rb

require 'net/http'
require 'uri'

# Restore original url from the url made from some url shortening services.
#
# Currently tested:
# bit.ly(j.mp), ustre.am, tinyurl

class URLExtractor
  def self.expand_url(short_url)
    uri = URI.parse(short_url)
    return nil unless uri.scheme =~ /^https?$/
    resp = nil
    Net::HTTP.start(uri.host, uri.port) do |http|
      resp = http.head(uri.path)
    end
    return nil unless ['301', '302'].include? resp.code
    resp['location']
  end
end