<?php
/**
 * Plugin Name: WCAS Backorders Unlocker
 * Description: Forces the “Allow backorders” checkbox to be enabled on all WooCommerce product pages.
 * Version: 1.0
 * Author: Your Name
 */

// Bail if accessed directly
if ( ! defined( 'ABSPATH' ) ) {
    exit;
}

add_action( 'admin_footer', 'wcas_force_unlock_backorders' );
function wcas_force_unlock_backorders() {
    global $pagenow;

    // Only run on the product edit/new page
    if ( ( $pagenow === 'post.php' || $pagenow === 'post-new.php' ) ) {
        $screen = get_current_screen();
        if ( $screen && $screen->post_type === 'product' ) {
            ?>
            <script type="text/javascript">
            jQuery(function($){
                // Always uncheck “Internal stock” and unblock backorders
                function unlockBackordersField(){
                    $('#mewz_wcas_internal').prop('checked', false).off('change');
                    $('#mewz_wcas_backorders').prop('disabled', false);
                }

                // On load:
                unlockBackordersField();

                // Also whenever someone toggles “Internal stock,” force backorders back on:
                $(document).on('change', '#mewz_wcas_internal', unlockBackordersField);
            });
            </script>
            <?php
        }
    }
}