Updating cart totals after ajax request - woocommerce

Question

Here is my custom ajax request callback.
I use some data with wp_remote_post and getting json results about my own woocommerce payment gateway installments.
/**
* Check avaliblity for installments via WordPress Ajax
*
* #return void
*/
function check_installment() {
if ( isset($_REQUEST) ) {
$action = data_get($_REQUEST, 'action');
if($action == 'check_installment')
{
$cart_data = WC()->session->get('cart_totals');
$binNumber = data_get($_REQUEST, 'bin');
if(!$binNumber)
{
return;
}
$_initGateway = new Woo_Ipara_Gateway();
$_initGateway = $_initGateway->checkInstallment($binNumber);
$data = [
'cardFamilyName' => data_get($_initGateway, 'cardFamilyName'),
'supportedInstallments' => data_get($_initGateway, 'supportedInstallments')
];
echo json_encode(getInstallmentComissions(data_get($_initGateway, 'cardFamilyName')));
}
}
die();
}
add_action( 'wp_ajax_check_installment', 'check_installment');
add_action( 'wp_ajax_nopriv_check_installment', 'check_installment');
Right now, payment provider, have different comissions for spesific credit card. So it means, i want to change order total after this request, when user's selected installment value.
I also found some filter, about calculated total woocommerce_calculated_total, but how to trigger this, after ajax request and user, selected installment choice?
add_filter( 'woocommerce_calculated_total', 'custom_calculated_total', 10, 2 );
function custom_calculated_total( $total, $cart ){
// some magic.
}
Any helps ? Thanks.

Answer 1

First of all, filter method was wrong, what i wanted to try woocommerce_calculated_total.
It must be, woocommerce_checkout_order_processed
Other issue is, WC()->cart->add_fee( "text", $fee, false, '' ); not really work correctly.
You should use, new WC_Order_Item_Fee() class in your action directly.
Here is the some part of code in my case ;
add_action('woocommerce_checkout_order_processed', 'addFeesBeforePayment', 10, 3);
function addFeesBeforePayment( $order_id, $posted_data, $order ) {
// some logic about bin verification and remote fetch about installment comissions.
$cartTotal = WC()->cart->cart_contents_total;
$newCartTotal = $cartTotal + ( $cartTotal * $defaultComission / 100 );
$installmentFee = $cartTotal * ($defaultComission / 100 );
$item_fee = new WC_Order_Item_Fee();
$item_fee->set_name( 'Kredi Kartı Komisyonu ('.$defaultInstallment.' Taksit)' ); // Generic fee name
$item_fee->set_amount( $installmentFee ); // Fee amount
$item_fee->set_tax_class( '' ); // default for ''
$item_fee->set_tax_status( 'none' ); // or 'none'
$item_fee->set_total( $installmentFee ); // Fee amount
$order->add_item( $item_fee );
$order->calculate_totals();
$order->add_order_note( 'Bu sipariş için ödeme '. $defaultInstallment . ' taksit seçeneği seçilerek oluşturuldu. Toplam taksit komisyonu, sipariş tutarına ek olarak ' . $installmentFee. ' TL karşılığında eklendi.' );
}
Happy coding.