<?php

/**
 * @copyright 2018 Vladimir Jimenez
 * @license   https://github.com/allejo/stakx/blob/master/LICENSE.md MIT
 */

namespace allejo\stakx\MarkupEngine;

/**
 * This interface defines the markup engines stakx will know how to parse as ContentItems and as regular text within
 * Twig by registering custom tags and filters.
 *
 * @since 0.2.0
 */
interface MarkupEngine
{
    const CONTAINER_TAG = 'stakx.markup_engine';

    /**
     * Get the custom tag and filter to register with our templating engine.
     *
     * For the Markdown engine, we'd be registering a tag called 'markdown' and a filter called 'markdown' to support
     * the following example.
     *
     * ```twig
     * {% markdown %}my content{% endmarkdown %}
     *
     * {{ 'my content' | markdown }}
     * ```
     *
     * @since 0.2.0
     *
     * @return null|string If null, then no tag or filter will be registered.
     */
    public function getTemplateTag();

    /**
     * List of file extensions this engine will be charged with parsing.
     *
     * @since 0.2.0
     *
     * @return string[]
     */
    public function getExtensions();

    /**
     * Parse a given string using this engine.
     *
     * @param string $content
     *
     * @since 0.2.0
     *
     * @return string
     */
    public function parse($content);
}

<?php

/**
 * @copyright 2018 Vladimir Jimenez
 * @license   https://github.com/allejo/stakx/blob/master/LICENSE.md MIT
 */

namespace allejo\stakx\MarkupEngine;

interface MarkupEngine
{
    const CONTAINER_TAG = 'stakx.markup_engine';

    /**
     * Get the custom tag and filter to register with our templating engine.
     *
     * For the Markdown engine, we'd be registering a tag called 'markdown' and a filter called 'markdown' to support
     * the following example.
     *
     * ```twig
     * {% markdown %}{% endmarkdown %}
     *
     * {{ 'my content' | markdown }}
     * ```
     *
     * @return null|string If null, then no tag or filter will be registered.
     */
    public function getTemplateTag();

    /**
     * List of extensions this engine will accept and parse.
     *
     * @return string[]
     */
    public function getExtensions();

    /**
     * Parse a given string using this engine.
     *
     * @param string $content
     *
     * @return string
     */
    public function parse($content);
}

--- 
+++ 
@@ -7,6 +7,12 @@
 
 namespace allejo\stakx\MarkupEngine;
 
+/**
+ * This interface defines the markup engines stakx will know how to parse as ContentItems and as regular text within
+ * Twig by registering custom tags and filters.
+ *
+ * @since 0.2.0
+ */
 interface MarkupEngine
 {
     const CONTAINER_TAG = 'stakx.markup_engine';
@@ -18,17 +24,21 @@
      * the following example.
      *
      * ```twig
-     * {% markdown %}{% endmarkdown %}
+     * {% markdown %}my content{% endmarkdown %}
      *
      * {{ 'my content' | markdown }}
      * ```
+     *
+     * @since 0.2.0
      *
      * @return null|string If null, then no tag or filter will be registered.
      */
     public function getTemplateTag();
 
     /**
-     * List of extensions this engine will accept and parse.
+     * List of file extensions this engine will be charged with parsing.
+     *
+     * @since 0.2.0
      *
      * @return string[]
      */
@@ -39,6 +49,8 @@
      *
      * @param string $content
      *
+     * @since 0.2.0
+     *
      * @return string
      */
     public function parse($content);
Update some documentation for the interface

[ci skip]