Twig Filter in Plugin/PHP?

Question

Is it possible to access twig filters in a plugin? I want to be able to preview how text will look in a textarea using Markdown for a discussion board, it'd be awesome to use ajax to send the content to the controller then return the filtered version for preview, something like:

public function actionPreviewContentAjax()
{
    $this->requireAjaxRequest();

    $content = craft()->request->getPost('textarea_content');

    // somehow apply twig's "| markdown" filter to $content

    $this->returnJson( $content );
}

Is twig accessible in this manner or am I out of my mind? :X

Answer 1

In one of your plugin services, you can render a template that handles the markdown filter and return the results as an HTML string. You can then send that HTML to wherever you want to preview.

In your controller:

public function actionPreviewContentAjax()
{
    $this->requireAjaxRequest();

    $content = craft()->request->getPost('textarea_content');

    $html = craft()->pluginName_serviceName->renderMarkdown($content);

    $return = array('html' => $html);

    $this->returnJson( $return );
}

In your service:

public function renderMarkdown($content)
{
    $rendered = craft()->templates->render('path/to/template', array('content' => $content));
    return $rendered;
}

All you would need is a small template that renders your content. If you have this template in your plugin folder, be sure to adjust the template path as described here.

Template:

{{content|markdown}}

If you need more help with the writing services, let me know!

Answer 2

This was the only SE question I could find on the topic of parsing Markdown in a plugin, and making a template to run the Markdown filter seems way too roundabout. I found a better solution:

If you're working in Craft 3, Yii/Craft already includes this Markdown parser, which you can use like:

$parser = new \cebe\markdown\Markdown();
$parsedContent = $parser->parse($content);