migrate_cookies_to_redis_store.rb

require 'rack/session/abstract/id'
require 'redis-actionpack'

module ActionDispatch
  module Session
    module MigrateCookiesStore
      # Ultimately loads session data from the database, after first checking
      # for session data in the cookie and persisting it to the database if we
      # find any.
      def load_session(request)
        # migrate_session_data will return the extracted session id if there
        # was one; otherwise, we fetch the session id from the request object.
        session_id = migrate_session_data(request) || current_session_id(request)
        session_id, session = find_session(request, session_id)
        [session_id, session || {}]
      end

      private

      # If we already have existing session data in the cookie, this helper
      # method will clear the cookie, write that session data to the database,
      # and return the session id it extracted from the cookie.
      #
      # If the cookie does not contain any existing session data, do nothing
      # and return nothing.
      def migrate_session_data(request)
        stale_session_check! do
          session_data = unpacked_cookie_data(request)
          if session_data.is_a?(Hash) && !session_data.empty?
            session_id = Rack::Session::SessionId.new(session_data["session_id"])
            request.set_header("action_dispatch.request.unsigned_session_cookie", {})
            write_session(request, session_id, session_data.except("session_id"), request.session_options)
            return session_id
          end
        end
      end

      def unpacked_cookie_data(request)
        stale_session_check! do
          if data = get_cookie(request) && data.is_a?(Hash)
            data.stringify_keys!
          end
          data || {}
        end
      end

      def get_cookie(request)
        cookie_jar(request)[@key]
      end

      def cookie_jar(request)
        request.cookie_jar.signed_or_encrypted
      end
    end

    class MigrateCookiesToRedisStore < RedisStore
      include MigrateCookiesStore
    end
  end
end