CommonMarkExtension

<?php

use League\CommonMark\Block\Element\AbstractBlock;
use League\CommonMark\Block\Element\Paragraph;
use League\CommonMark\Block\Renderer\BlockRendererInterface;
use League\CommonMark\CommonMarkConverter;
use League\CommonMark\ElementRendererInterface;
use League\CommonMark\Environment;
use Twig_Extension;

class CommonMarkExtension extends Twig_Extension implements BlockRendererInterface
{
    private $converter;

    public function getFilters()
    {
        return [
            new \Twig_SimpleFilter('markdown', [$this, 'markdown'], ['is_safe' => ['html']]),
        ];
    }

    public function markdown($value, $inline = false)
    {
        if (null === $this->converter) {
            $environment = Environment::createCommonMarkEnvironment();
            $environment->addBlockRenderer(Paragraph::class, $this);
            $this->converter = new CommonMarkConverter(['html_input' => 'strip'], $environment);
        }

        return $this->converter->convertToHtml($value);
    }

    public function render(AbstractBlock $block, ElementRendererInterface $htmlRenderer, $inTightList = false)
    {
        return $htmlRenderer->renderInlines($block->children());
    }
}