getting around BSON serialization issues

part_of_mongo_storage.rb

 def to_mongo(doc, with = {})
      prep_for_save(doc) if ["msgs","configurations"].include? doc["type"]
        #ruote functional tests suggest that messages will occasionally have 
        #an unserialized FlowExpressionId if they are representing an error.
        #Since we are no longer converting documents to JSON, this will cause
        #mongo db to reject the document, so we convert it. configurations need classes
        #converted to strings
      doc.merge(with).merge!("put_at" => Ruote.now_to_utc_s)
    end

    def prep_for_save(doc)
      if doc.is_a?(Hash)
        doc.keys.each do |key|
          val = doc[key]
          if key.nil?
            #this exists purely to survive ruotes functional tests
            #where errors are deliberately introduced. 
            doc.delete(key)
            doc[""] = val
          elsif val.respond_to?(:to_storage_id)
            doc[key] = val.to_storage_id
          elsif val.kind_of?(Class)
            doc[key] = val.name
          else
            prep_for_save(val)
          end
        end
      elsif doc.kind_of?(Array)
        doc.each_with_index do |child, idx|
          if child.kind_of?(Class)
            doc[idx] = child.name
          else
            prep_for_save(child)
          end
        end
      end
    end