Check if facebook user has uploaded a profile picture or uses the default in ruby

snippet.rb

require 'net/http'
# idea: default profile photos has the Content-Type image/gif
# read this: http://stackoverflow.com/questions/5555199  
def default_facebook_photo?(facebook_uid)
  resp = fetch("https://graph.facebook.com/#{facebook_uid}/picture")
  resp['content-type'] == 'image/gif'
end

# http head request which follows redirects
def fetch(uri, limit = 10)
  raise ArgumentError, 'HTTP redirect too deep' if limit == 0

  url = URI.parse(uri)
  req = Net::HTTP::Head.new(url.path)
  response = Net::HTTP.start(url.host, url.port) { |http| http.request(req) }
  case response
  when Net::HTTPSuccess     then response
  when Net::HTTPRedirection then fetch(response['location'], limit - 1)
  else
    response.error!
  end
end


# usage example, if you use omniauth-facebook (https://github.com/mkdynamic/omniauth-facebook)
default_facebook_photo?(omniauth['uid']) # just pass the uid, you got from the omniauth hash