Restyle Sale Badge With Percentage Off

<?php
if ( ! class_exists( 'WooCommerce' ) ) {
    return;
}

/**
 * To hide the sale badge entirely instead of restyling it, replace the
 * filter below with:
 *   add_filter( 'woocommerce_sale_flash', '__return_false' );
 */
add_filter( 'woocommerce_sale_flash', 'scseed_percentage_sale_badge', 10, 3 );
function scseed_percentage_sale_badge( $html, $post, $product ) {
    if ( $product->is_type( 'variable' ) ) {
        return $html; // keep default for variable products
    }

    $regular = (float) $product->get_regular_price();
    $sale    = (float) $product->get_sale_price();

    if ( $regular > 0 && $sale >= 0 && $sale < $regular ) {
        $pct = round( ( ( $regular - $sale ) / $regular ) * 100 );
        return '<span class="onsale">-' . esc_html( $pct ) . '%</span>';
    }

    return $html;
}