Tokoo- Display percentage of discount instead of sale badge in Single Product page

functions.php

add_action( 'init', 'tk_child_display_discount_percentage_in_single_product_page' );

function tk_child_display_discount_percentage_in_single_product_page() {
  remove_action( 'woocommerce_before_single_product_summary', 'woocommerce_show_product_sale_flash',          10 );
  add_action( 'woocommerce_before_single_product_summary',	'tokoo_get_sale_flash',					21  );
}

function tokoo_get_sale_flash() {

    global $product;

    if ( $product->is_on_sale() ) {

        if ( ! $product->is_type( 'variable' ) ) {

            $max_percentage = ( ( $product->get_regular_price() - $product->get_sale_price() ) / $product->get_regular_price() ) * 100;

        } else {

            $max_percentage = 0;

            foreach ( $product->get_children() as $child_id ) {
                $variation = wc_get_product( $child_id );
                $price = $variation->get_regular_price();
                $sale = $variation->get_sale_price();
                if ( $price != 0 && ! empty( $sale ) ) {
                    $percentage = ( $price - $sale ) / $price * 100;
                }
                if ( $percentage > $max_percentage ) {
                    $max_percentage = $percentage;
                }
            }

        }

        echo "<div class='onsale'>-" . round($max_percentage) . "%</div>";

    }

}

style.css

.single-product .single-product-inner .onsale {
    position: absolute;
    top: 0;
    left: 15px;
    z-index: 1;
}