<?php
/**
 * Server-side rendering of the `core/button` block.
 *
 * @package WordPress
 */

/**
 * Renders the `core/button` block on the server,
 *
 * @since 6.6.0
 *
 * @param array  $attributes The block attributes.
 * @param string $content    The block content.
 *
 * @return string The block content.
 */
function render_block_core_button( $attributes, $content ) {
    $p = new WP_HTML_Tag_Processor( $content );

    /*
     * The button block can render an `<a>` or `<button>` and also has a
     * `<div>` wrapper. Find the a or button tag.
     */
    $tag = null;
    while ( $p->next_tag() ) {
        $tag = $p->get_tag();
        if ( 'A' === $tag || 'BUTTON' === $tag ) {
            break;
        }
    }

    /*
     * If this happens, the likelihood is there's no block content,
     * or the block has been modified by a plugin.
     */
    if ( null === $tag ) {
        return $content;
    }

    // If the next token is the closing tag, the button is empty.
    $is_empty = true;
    while ( $p->next_token() && $tag !== $p->get_token_name() && $is_empty ) {
        if ( '#comment' !== $p->get_token_type() ) {
            /**
             * Anything else implies this is not empty.
             * This might include any text content (including a space),
             * inline images or other HTML.
             */
            $is_empty = false;
        }
    }

    /*
     * When there's no text, render nothing for the block.
     * See https://github.com/WordPress/gutenberg/issues/17221 for the
     * reasoning behind this.
     */
    if ( $is_empty ) {
        return '';
    }

    return $content;
}

/**
 * Registers the `core/button` block on server.
 *
 * @since 6.6.0
 */
function register_block_core_button() {
    register_block_type_from_metadata(
        __DIR__ . '/button',
        array(
            'render_callback' => 'render_block_core_button',
        )
    );
}
add_action( 'init', 'register_block_core_button' );