text: #!/usr/bin/env python
  #
  # Copyright 2010 Facebook
  #
  # Licensed under the Apache License, Version 2.0 (the "License"); you may
  # not use this file except in compliance with the License. You may obtain
  # a copy of the License at
  #
  #     https://www.apache.org/licenses/LICENSE-2.0
  #
  # Unless required by applicable law or agreed to in writing, software
  # distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
  # WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
  # License for the specific language governing permissions and limitations
  # under the License.
  
  """A barebones Tornado application that uses Facebook for login.
  
  Assumes a database with a schema as specified in schema.sql. We store a
  local copy of basic user data so we don't need to make a round-trip to
  the Facebook API on every request once a user has logged in.
  """
  
  import facebook
  import tornado.database
  import tornado.httpserver
  import tornado.options
  import tornado.web
  
  from tornado.options import define, options
  
  define("port", default=8888, help="run on the given port", type=int)
  define("facebook_app_id", help="Facebook Application ID")
  define("facebook_app_secret", help="Facebook Application Secret")
  define("mysql_host", help="MySQL database host")
  define("mysql_database", help="MySQL database database")
  define("mysql_user", help="MySQL database user")
  define("mysql_password", help="MySQL database password")
  
  
  class BaseHandler(tornado.web.RequestHandler):
      """Implements authentication via the Facebook JavaScript SDK cookie."""
  
      def get_current_user(self):
          cookies = dict((n, self.cookies[n].value) for n in self.cookies.keys())
          cookie = facebook.get_user_from_cookie(
              cookies, options.facebook_app_id, options.facebook_app_secret
          )
          if not cookie:
              return None
          user = self.db.get("SELECT * FROM users WHERE id = %s", cookie["uid"])
          if not user:
              # TODO: Make this fetch async rather than blocking
              graph = facebook.GraphAPI(cookie["access_token"])
              profile = graph.get_object("me")
              self.db.execute(
                  "REPLACE INTO users (id, name, profile_url, access_token) "
                  "VALUES (%s,%s,%s,%s)",
                  profile["id"],
                  profile["name"],
                  profile["link"],
                  cookie["access_token"],
              )
              user = self.db.get("SELECT * FROM users WHERE id = %s", profile["id"])
          elif user.access_token != cookie["access_token"]:
              self.db.execute(
                  "UPDATE users SET access_token = %s WHERE id = %s",
                  cookie["access_token"],
                  user.id,
              )
          return user
  
      @property
      def db(self):
          if not hasattr(BaseHandler, "_db"):
              BaseHandler._db = tornado.database.Connection(
                  host=options.mysql_host,
                  database=options.mysql_database,
                  user=options.mysql_user,
                  password=options.mysql_password,
              )
          return BaseHandler._db
  
  
  class MainHandler(BaseHandler):
      def get(self):
          self.render("example.html", options=options)
  
  
  def main():
      tornado.options.parse_command_line()
      http_server = tornado.httpserver.HTTPServer(
          tornado.web.Application([(r"/", MainHandler)])
      )
      http_server.listen(options.port)
      tornado.ioloop.IOLoop.instance().start()
  
  
  if __name__ == "__main__":
      main()
  