class FormattedDateDiff

class FormattedDateDiff implements RenderableInterface, CacheableDependencyInterface {
    use UnchangingCacheableDependencyTrait;
    
    /**
     * The actual formatted time difference.
     *
     * @var string
     */
    protected $string;
    
    /**
     * The maximum time in seconds that this string may be cached.
     *
     * Let's say the time difference is 1 day 1 hour. In this case, we can cache
     * it until now + 1 hour, so maxAge is 3600 seconds.
     *
     * @var int
     */
    protected $maxAge;
    
    /**
     * Creates a new FormattedDateDiff instance.
     *
     * @param string $string
     *   The formatted time difference.
     * @param int $max_age
     *   The maximum time in seconds that this string may be cached.
     */
    public function __construct($string, $max_age) {
        $this->string = $string;
        $this->maxAge = $max_age;
    }
    
    /**
     * @return string
     */
    public function getString() {
        return $this->string;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getCacheMaxAge() {
        return $this->maxAge;
    }
    
    /**
     * {@inheritdoc}
     */
    public function toRenderable() {
        return [
            '#markup' => $this->string,
            '#cache' => [
                'max-age' => $this->maxAge,
            ],
        ];
    }

}