在WooCommerce中以编程方式按顺序退款1x

I'm trying to create a partial refund for an order programatically. It's important to calculate the tax as well, but so far nothing seems to work correctly and I can't figure why.

I want to press a button and the function "ceb_wc_refund_order" will be called with $order_id, quantity and the reason. $qty is usually 1. The problem is that the order contains always only ONE item, but for example 3 times. Now I want to refund only one of these items.

I know how to do that manually so basically what I want to achieve is the following, but programatically:

At the moment the code seems to create the refund successfully and also the quantity of the item is right. But the refund amount is the item price * quantity and also the tax is not refunded.

I know my code does not lead to my goal so far. I did not find much on the internet about this... Can you help me?

function ceb_wc_refund_order( $order_id, $qty, $refund_reason = '') {

$order  = wc_get_order( $order_id );
// If it's something else such as a WC_Order_Refund, we don't want that.
if( ! is_a( $order, 'WC_Order') ) {
    return new WP_Error( 'wc-order', __( 'Provided ID is not a WC Order', 'yourtextdomain' ) );
}

if( 'refunded' == $order->get_status() ) {
    return new WP_Error( 'wc-order', __( 'Order has been already refunded', 'yourtextdomain' ) );
}
// Get Items
$order_items = $order->get_items();
// Refund Amount
$refund_amount = 0;
// Prepare line items which we are refunding
$line_items = array();


if ( $order_items ) {
    foreach( $order_items as $item_id => $item ) {
        $item_meta = $order->get_item_meta($item_id);
        $tax_data = $item_meta['_line_tax'];
        $refund_tax = $tax_data;

        $refund_amount = wc_format_decimal($refund_amount) + wc_format_decimal($item_meta['_line_total'][0]);
        $line_items[$item_id] = array(
            'qty' => $qty,
            'refund_total' => wc_format_decimal($item_meta['_line_total'][0]),
            'refund_tax' => $refund_tax);
    }
}

// ...
$refund = wc_create_refund( array(
    'amount'         => $refund_amount,
    'reason'         => $refund_reason,
    'order_id'       => $order_id,
    'line_items'     => $line_items,
    'refund_payment' => false
));
return $refund;
}