Display percentage of savings on sale badge - WooCommerce

add_filter('woocommerce_sale_flash', 'tr245_woo_savings_on_sales_flash');

function tr245_woo_savings_on_sales_flash()
{
global $post, $product;
	if ( ! $product->is_in_stock() ) return;
	$sale_price = get_post_meta( $product->id, '_price', true);
	$regular_price = get_post_meta( $product->id, '_regular_price', true);
	if (empty($regular_price)){ //then this is a variable product
		$available_variations = $product->get_available_variations();
		$variation_id=$available_variations[0]['variation_id'];
		$variation= new WC_Product_Variation( $variation_id );
		$regular_price = $variation ->regular_price;
		$sale_price = $variation ->sale_price;
	}
	$savings = ceil(( ($regular_price - $sale_price) / $regular_price ) * 100);
	$sale_flash = '<span class="onsale"> - ' . $savings . '%</span>';
	return $sale_flash;
}