protected function prepareAttributes($attributes)
    {
        foreach($this->getAttributeConfig() as $attr => $config){

            // If the attribute is not defined in model or $attributes array
            // set the default value.
            if(!isset($this->attributes[$attr]) && !isset($attributes[$attr])){

                $attributes[$attr] = $config['default'];

            }

        }

        foreach($attributes as $key => $value){

            if(isset($this->config['attributes'][$key])){

                $attributes[$key] = $this->$key()->before_save($value);

            } elseif(isset($this->config['relationships'][$key])){

                unset($attributes[$key]);

                $relationship = $this->config['relationships'][$key];

                $this->translateShorthand($value);

                switch($relationship['type']){

                    case Relationship::HAS_PIVOT:

                        if($value instanceof Collection) $value = $value->all();

                        if($value instanceof EntityContract) $value = [$value];

                        $this->$key()->saveMany($value);

                        break;

                    case Relationship::HAS_MANY:

                        $this->$key()->saveMany((array)$value);

                        break;

                    case Relationship::BELONGS_TO:

                        $this->$key()->associate($value);

                        break;

                    case Relationship::HAS_ONE:

                        $this->$key()->save($value);

                        break;

                    default:

                        throw new \Exception(sprintf(
                            "Unknown relationship type \"%s\" on entity \"%s\"",
                            $relationship['type'],
                            $relationship['entity']
                        ));

                        break;
                }

            }

        }

        return $attributes;
    }