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+# Order Calculation - WooCommerce Native Implementation
+
+## ✅ BACKEND COMPLETE
+
+### New Endpoints:
+
+1. **POST `/woonoow/v1/shipping/calculate`**
+   - Input: `{ items: [], shipping: {} }`
+   - Output: `{ methods: [{ id, method_id, instance_id, label, cost, taxes, meta_data }] }`
+   - Returns live rates from UPS, FedEx, etc.
+   - Returns service-level options (UPS Ground, UPS Express)
+
+2. **POST `/woonoow/v1/orders/preview`**
+   - Input: `{ items: [], billing: {}, shipping: {}, shipping_method: '', coupons: [] }`
+   - Output: `{ subtotal, shipping_total, total_tax, total, ... }`
+   - Calculates taxes correctly
+   - Applies coupons
+   - Uses WooCommerce cart engine
+
+---
+
+## 🔄 FRONTEND TODO
+
+### 1. Update OrderForm.tsx
+
+#### A. Add Shipping Rate Calculation Query
+
+```tsx
+// Query shipping rates when address changes
+const { data: shippingRates, refetch: refetchShipping } = useQuery({
+  queryKey: ['shipping-rates', items, shippingData],
+  queryFn: async () => {
+    if (!hasPhysicalProduct || !shippingData.country) return null;
+    return api.post('/shipping/calculate', {
+      items: items.map(i => ({ product_id: i.product_id, qty: i.qty })),
+      shipping: shippingData,
+    });
+  },
+  enabled: hasPhysicalProduct && !!shippingData.country,
+});
+```
+
+#### B. Add Order Preview Query
+
+```tsx
+// Query order preview for totals
+const { data: orderPreview } = useQuery({
+  queryKey: ['order-preview', items, bCountry, shippingData, shippingMethod, validatedCoupons],
+  queryFn: async () => {
+    if (items.length === 0) return null;
+    return api.post('/orders/preview', {
+      items: items.map(i => ({ product_id: i.product_id, qty: i.qty })),
+      billing: { country: bCountry, state: bState, postcode: bPost, city: bCity },
+      shipping: shipDiff ? shippingData : undefined,
+      shipping_method: shippingMethod,
+      coupons: validatedCoupons.map(c => c.code),
+    });
+  },
+  enabled: items.length > 0,
+});
+```
+
+#### C. Update Shipping Method Dropdown
+
+**Current:**
+```tsx
+<Select value={shippingMethod} onValueChange={setShippingMethod}>
+  {shippings.map(s => (
+    <SelectItem value={s.id}>{s.title} - {s.cost}</SelectItem>
+  ))}
+</Select>
+```
+
+**New:**
+```tsx
+<Select value={shippingMethod} onValueChange={setShippingMethod}>
+  {shippingRates?.methods?.map(rate => (
+    <SelectItem value={rate.id}>
+      {rate.label} - {money(rate.cost)}
+    </SelectItem>
+  ))}
+</Select>
+```
+
+#### D. Update Order Summary Display
+
+**Add tax breakdown:**
+```tsx
+<div className="space-y-2">
+  <div className="flex justify-between">
+    <span>Items</span>
+    <span>{items.length}</span>
+  </div>
+  <div className="flex justify-between">
+    <span>Subtotal</span>
+    <span>{money(orderPreview?.subtotal || 0)}</span>
+  </div>
+  {orderPreview?.shipping_total > 0 && (
+    <div className="flex justify-between">
+      <span>Shipping</span>
+      <span>{money(orderPreview.shipping_total)}</span>
+    </div>
+  )}
+  {orderPreview?.total_tax > 0 && (
+    <div className="flex justify-between">
+      <span>Tax</span>
+      <span>{money(orderPreview.total_tax)}</span>
+    </div>
+  )}
+  {orderPreview?.discount_total > 0 && (
+    <div className="flex justify-between text-green-600">
+      <span>Discount</span>
+      <span>-{money(orderPreview.discount_total)}</span>
+    </div>
+  )}
+  <div className="flex justify-between font-bold text-lg border-t pt-2">
+    <span>Total</span>
+    <span>{money(orderPreview?.total || 0)}</span>
+  </div>
+</div>
+```
+
+#### E. Trigger Recalculation
+
+```tsx
+// Refetch shipping when address changes
+useEffect(() => {
+  if (hasPhysicalProduct && shippingData.country) {
+    refetchShipping();
+  }
+}, [shippingData.country, shippingData.postcode, shippingData.state]);
+```
+
+---
+
+## 📋 Implementation Steps
+
+1. ✅ Backend endpoints created
+2. ⏳ Add shipping rate calculation query
+3. ⏳ Add order preview query
+4. ⏳ Update shipping method dropdown to show services
+5. ⏳ Update order summary to show tax
+6. ⏳ Add loading states
+7. ⏳ Test with UPS Live Rates
+8. ⏳ Test tax calculation
+
+---
+
+## 🎯 Expected Result
+
+### Before:
+- Shipping: "UPS Live Rates - RM0.00"
+- Total: RM97,000 (no tax)
+
+### After:
+- Shipping dropdown shows:
+  - UPS Ground - RM15,000
+  - UPS Express - RM25,000
+  - UPS Next Day Air - RM35,000
+- Order summary shows:
+  - Subtotal: RM97,000
+  - Shipping: RM15,000
+  - Tax (11%): RM12,320
+  - **Total: RM124,320**
+
+---
+
+## 🔧 Testing Checklist
+
+- [ ] Select UPS Live Rates → Shows service options
+- [ ] Select UPS Ground → Updates total
+- [ ] Change address → Recalculates rates
+- [ ] Add item → Recalculates totals
+- [ ] Apply coupon → Updates discount and total
+- [ ] Tax shows 11% of subtotal + shipping
+- [ ] Digital products → No shipping, no shipping tax
+- [ ] Physical products → Shipping + tax calculated
+
+---
+
+## ⚠️ Important Notes
+
+1. **Don't reinvent calculation** - Use WooCommerce cart engine
+2. **Clean up cart** - Always `WC()->cart->empty_cart()` after calculation
+3. **Session handling** - Use `WC()->session` for chosen shipping method
+4. **Tax context** - Set both billing and shipping addresses for accurate tax
+5. **Live rates** - May take 1-2 seconds to calculate, show loading state