WooCommerce Admin Create Order & Adding Shipping on Order Pay - php

Question

I am creating order in the admin. I added some functionality to the order pay page which is sent to the customer (form-pay.php). I added ability to remove items from the order as well as update your billing and shipping info (both for the order and account). I use ajax and calculate_totals() after an item is removed, which works.
However, I can't seem to figure out how to get shipping applied to the order. I need this to happen when the order is created in the admin and when someone removes an item on the frontend.
I tried just setting the shipping post meta but that isn't working.
function my_order_update_shipping($order_id, $items) {
$order = wc_get_order($order_id);
$order_subtotal = $order->get_subtotal();
if($order_subtotal > '17.99'){
update_post_meta($order_id, '_order_shipping', '0');
}else{
update_post_meta($order_id, '_order_shipping', '4');
}
}
add_action('woocommerce_before_save_order_items', 'my_order_update_shipping');
How can I achieve this? Or apply a shipping method in this way?

Answer 1

I finally figure this out. Works good but you need to click the "recalculate" button when adding/removing an item in the admin > create order. The below code applies 1 of 2 shipping methods based on a static subtotal amount.
$delivery_zones = WC_Shipping_Zones::get_zones();
foreach ((array) $delivery_zones as $key => $the_zone) {
$shipping_methods = $the_zone['shipping_methods'];
}
// Apply Correct Shipping Method
if ($order_subtotal > '17.99') {
$rate = $shipping_methods[2];
$item = new WC_Order_Item_Shipping();
$item->set_props(array('method_id' => $rate->id, 'total' => wc_format_decimal($rate->cost)));
$order->add_item($item);
} else {
$rate = $shipping_methods[1];
$item = new WC_Order_Item_Shipping();
$item->set_props(array('method_id' => $rate->id, 'total' => wc_format_decimal($rate->cost)));
$order->add_item($item);
}
$order->calculate_totals();
$order->save();