class TwigEnvironment

class TwigEnvironment extends \Twig_Environment {
    
    /**
     * Key name of the Twig cache prefix metadata key-value pair in State.
     */
    const CACHE_PREFIX_METADATA_KEY = 'twig_extension_hash_prefix';
    
    /**
     * The state service.
     *
     * @var \Drupal\Core\State\StateInterface
     */
    protected $state;
    
    /**
     * Static cache of template classes.
     *
     * @var array
     */
    protected $templateClasses;
    
    /**
     * The template cache filename prefix.
     *
     * @var string
     */
    protected $twigCachePrefix = '';
    
    /**
     * Constructs a TwigEnvironment object and stores cache and storage
     * internally.
     *
     * @param string $root
     *   The app root.
     * @param \Drupal\Core\Cache\CacheBackendInterface $cache
     *   The cache bin.
     * @param string $twig_extension_hash
     *   The Twig extension hash.
     * @param \Drupal\Core\State\StateInterface $state
     *   The state service.
     * @param \Twig_LoaderInterface $loader
     *   The Twig loader or loader chain.
     * @param array $options
     *   The options for the Twig environment.
     */
    public function __construct($root, CacheBackendInterface $cache, $twig_extension_hash, StateInterface $state, \Twig_LoaderInterface $loader = NULL, array $options = []) {
        $this->state = $state;
        // Ensure that twig.engine is loaded, given that it is needed to render a
        // template because functions like TwigExtension::escapeFilter() are called.
        // @todo remove in Drupal 9.0.0 https://www.drupal.org/node/3011393.
        require_once $root . '/core/themes/engines/twig/twig.engine';
        $this->templateClasses = [];
        $options += [
            // @todo Ensure garbage collection of expired files.
'cache' => TRUE,
            'debug' => FALSE,
            'auto_reload' => NULL,
        ];
        // Ensure autoescaping is always on.
        $options['autoescape'] = 'html';
        if ($options['cache'] === TRUE) {
            $current = $state->get(static::CACHE_PREFIX_METADATA_KEY, [
                'twig_extension_hash' => '',
            ]);
            if ($current['twig_extension_hash'] !== $twig_extension_hash || empty($current['twig_cache_prefix'])) {
                $current = [
                    'twig_extension_hash' => $twig_extension_hash,
                    // Generate a new prefix which invalidates any existing cached files.
'twig_cache_prefix' => uniqid(),
                ];
                $state->set(static::CACHE_PREFIX_METADATA_KEY, $current);
            }
            $this->twigCachePrefix = $current['twig_cache_prefix'];
            $options['cache'] = new TwigPhpStorageCache($cache, $this->twigCachePrefix);
        }
        $this->setLoader($loader);
        parent::__construct($this->getLoader(), $options);
        $policy = new TwigSandboxPolicy();
        $sandbox = new \Twig_Extension_Sandbox($policy, TRUE);
        $this->addExtension($sandbox);
    }
    
    /**
     * Invalidates all compiled Twig templates.
     *
     * @see \drupal_flush_all_caches
     */
    public function invalidate() {
        PhpStorageFactory::get('twig')->deleteAll();
        $this->templateClasses = [];
        $this->state
            ->delete(static::CACHE_PREFIX_METADATA_KEY);
    }
    
    /**
     * Get the cache prefixed used by \Drupal\Core\Template\TwigPhpStorageCache
     *
     * @return string
     *   The file cache prefix, or empty string if the cache is disabled.
     */
    public function getTwigCachePrefix() {
        return $this->twigCachePrefix;
    }
    
    /**
     * Gets the template class associated with the given string.
     *
     * @param string $name
     *   The name for which to calculate the template class name.
     * @param int $index
     *   The index if it is an embedded template.
     *
     * @return string
     *   The template class name.
     */
    public function getTemplateClass($name, $index = NULL) {
        // We override this method to add caching because it gets called multiple
        // times when the same template is used more than once. For example, a page
        // rendering 50 nodes without any node template overrides will use the same
        // node.html.twig for the output of each node and the same compiled class.
        $cache_index = $name . (NULL === $index ? '' : '_' . $index);
        if (!isset($this->templateClasses[$cache_index])) {
            $this->templateClasses[$cache_index] = parent::getTemplateClass($name, $index);
        }
        return $this->templateClasses[$cache_index];
    }
    
    /**
     * Renders a twig string directly.
     *
     * Warning: You should use the render element 'inline_template' together with
     * the #template attribute instead of this method directly.
     * On top of that you have to ensure that the template string is not dynamic
     * but just an ordinary static php string, because there may be installations
     * using read-only PHPStorage that want to generate all possible twig
     * templates as part of a build step. So it is important that an automated
     * script can find the templates and extract them. This is only possible if
     * the template is a regular string.
     *
     * @param string $template_string
     *   The template string to render with placeholders.
     * @param array $context
     *   An array of parameters to pass to the template.
     *
     * @return \Drupal\Component\Render\MarkupInterface|string
     *   The rendered inline template as a Markup object.
     *
     * @see \Drupal\Core\Template\Loader\StringLoader::exists()
     */
    public function renderInline($template_string, array $context = []) {
        // Prefix all inline templates with a special comment.
        $template_string = '{# inline_template_start #}' . $template_string;
        return Markup::create($this->createTemplate($template_string)
            ->render($context));
    }

}