fix(affiliate): persist referral code through SPA checkout and process after save

includes/Api/CheckoutController.php

@@ -329,6 +329,11 @@ class CheckoutController
             return ['error' => $order->get_error_message()];
         }
 
+        if (!empty($payload['referral_code'])) {
+            $order->update_meta_data('_woonoow_referral_code', $payload['referral_code']);
+            $_COOKIE['woonoow_ref'] = $payload['referral_code'];
+        }
+
         // Track if user was logged in during this request (for frontend page reload)
         $user_logged_in = false;
 
@@ -516,6 +521,11 @@ class CheckoutController
 
         $order->save();
 
+        // wc_create_order() fires woocommerce_new_order before SPA checkout line
+        // items exist. Fire the processed hook after saving so integrations that
+        // calculate from order items, like affiliate tracking, see a complete order.
+        do_action('woocommerce_checkout_order_processed', $order->get_id(), $payload, $order);
+
         if (!headers_sent()) {
             header('Server-Timing: app;dur=' . round((microtime(true) - $__t0) * 1000, 1));
         }
@@ -842,6 +852,7 @@ class CheckoutController
             'shipping_title'  => isset($json['shipping_title']) ? sanitize_text_field($json['shipping_title']) : null,
             'custom_fields'   => $custom_fields,
             'customer_note'   => isset($json['customer_note']) ? sanitize_textarea_field($json['customer_note']) : '',
+            'referral_code'   => isset($json['referral_code']) ? sanitize_text_field($json['referral_code']) : '',
         ];
     }