Oprava dane pri zlave pre Superfaktura plugin

superfaktura-discount-fix.php

/**
 *  Oprava dane pri zlave pre Superfaktura plugin - min. verzia 1.8.21
 *
 *  Opravuje chybu, ked dan zlavy vychadza nespravne, napr.
 *  ak je cena 9.90 + 2.50 doprava, tak potom 7% zlava spravi
 *  ze dan pri zlave je nespravne 19% kvoli nespravnemu
 *  prepoctu na strane Woocommerce
 *
 *  https://github.com/woocommerce/woocommerce/issues/23835
 *  https://github.com/woocommerce/woocommerce/issues/23827
 */

/**
 * @param array $discount_data
 * @param \WC_Order $order
 * @return mixed
 */
function sf_discount_tax_data_fix($discount_data, $order) {
    $discount_price = $order->get_total_discount(false);

    $cart_total = $order->get_total();
    $cart_tax = $order->get_total_tax();
    $cart_total_tax_excluded = $cart_total - $cart_tax;
    $discount_tax = round(($cart_total / $cart_total_tax_excluded)  * 100) - 100;

    $discount_data['unit_price']  = ($discount_price / (1 + $discount_tax / 100)) * -1;
    $discount_data['tax'] = $discount_tax;
    return $discount_data;
}
add_filter('sf_discount_data', 'sf_discount_tax_data_fix', 10, 2);