<?php
/**
* Appending the wp-block-heading to before rendering the stored `core/heading` block contents.
*
* @package WordPress
*/

/**
* Adds a wp-block-heading class to the heading block content.
*
* For example, the following block content:
* <h2 class="align-left">Hello World</h2>
*
* Would be transformed to:
* <h2 class="align-left wp-block-heading">Hello World</h2>
*
* @since 6.2.0
*
* @param array $attributes Attributes of the block being rendered.
* @param string $content Content of the block being rendered.
*
* @return string The content of the block being rendered.
*/
function block_core_heading_render( $attributes, $content ) {
if ( ! $content ) {
return $content;
}

$p = new WP_HTML_Tag_Processor( $content );

$header_tags = array( 'H1', 'H2', 'H3', 'H4', 'H5', 'H6' );
while ( $p->next_tag() ) {
if ( in_array( $p->get_tag(), $header_tags, true ) ) {
$p->add_class( 'wp-block-heading' );
break;
}
}

return $p->get_updated_html();
}

/**
* Registers the `core/heading` block on server.
*
* @since 6.2.0
*/
function register_block_core_heading() {
register_block_type_from_metadata(
__DIR__ . '/heading',
array(
'render_callback' => 'block_core_heading_render',
)
);
}

add_action( 'init', 'register_block_core_heading' );