Points now subtract from costs

backend/src/main/java/com/petshop/backend/controller/CartController.java

@@ -75,6 +75,16 @@ public class CartController {
         return ResponseEntity.ok(cartService.applyCoupon(userId, storeId, request.getCouponCode()));
     }
 
+    @PostMapping("/apply-points")
+    @PreAuthorize("isAuthenticated()")
+    public ResponseEntity<CartResponse> applyPoints(
+            @RequestParam Long storeId,
+            @RequestParam Boolean useLoyaltyPoints) {
+        Long userId = AuthenticationHelper.getAuthenticatedUserId();
+
+        return ResponseEntity.ok(cartService.applyPoints(userId, storeId, useLoyaltyPoints));
+    }
+
     @DeleteMapping("/coupon")
     @PreAuthorize("isAuthenticated()")
     public ResponseEntity<CartResponse> removeCoupon(@RequestParam Long storeId) {

backend/src/main/java/com/petshop/backend/service/CartService.java

@@ -257,6 +257,34 @@ public class CartService {
                 .setScale(0, RoundingMode.HALF_UP)
                 .longValue();
 
+        // Free checkout: total is $0.00, or points are applied and the remaining
+        // amount is below Stripe's $0.50 minimum (cannot be charged via card)
+        if (amountInCents == 0 || (amountInCents < 50 && Boolean.TRUE.equals(cart.getPointsApplied()))) {
+            SaleRequest saleRequest = new SaleRequest();
+            saleRequest.setStoreId(cart.getStore().getStoreId());
+            saleRequest.setCustomerId(cart.getUser().getId());
+            saleRequest.setCartId(cart.getCartId());
+            saleRequest.setCouponId(cart.getCoupon() != null ? cart.getCoupon().getCouponId() : null);
+            saleRequest.setPaymentMethod("Points");
+            saleRequest.setChannel("WEBSITE");
+            saleRequest.setItems(items.stream()
+                    .map(item -> {
+                        SaleItemRequest sir = new SaleItemRequest();
+                        sir.setProdId(item.getProduct().getProdId());
+                        sir.setQuantity(item.getQuantity());
+                        return sir;
+                    })
+                    .toList());
+
+            saleService.createSale(saleRequest);
+
+            cart.setCartStatus("CHECKED_OUT");
+            cart.setCheckoutPending(false);
+            cartRepository.save(cart);
+
+            return new CheckoutResponse(cart.getCartId(), null, BigDecimal.ZERO, "succeeded");
+        }
+
         if (amountInCents < 50) {
             throw new BusinessException("Order total is too low to process payment");
         }
@@ -489,10 +517,12 @@ public class CartService {
             return BigDecimal.ZERO;
         }
 
-        BigDecimal maxRedeemable = remainingAmount.setScale(0, RoundingMode.DOWN);
+        BigDecimal maxDiscount = BigDecimal.valueOf(wholeDollars);
-        return BigDecimal.valueOf(wholeDollars)
+        // If points can fully cover the remaining amount, discount the entire total to $0.00
-                .min(maxRedeemable)
+        if (maxDiscount.compareTo(remainingAmount) >= 0) {
-                .setScale(2, RoundingMode.HALF_UP);
+            return remainingAmount.setScale(2, RoundingMode.HALF_UP);
+        }
+        return maxDiscount.setScale(2, RoundingMode.HALF_UP);
     }
 
     private CartResponse toResponse(Cart cart) {

web/app/cart/page.js

@@ -87,6 +87,7 @@ export default function CartPage() {
     removeItem,
     clearCart,
     applyCoupon,
+    applyPoints,
     removeCoupon,
     checkout,
     cancelCheckout,
@@ -98,6 +99,10 @@ export default function CartPage() {
   const [couponSuccess, setCouponSuccess] = useState(null);
   const [couponLoading, setCouponLoading] = useState(false);
 
+  const [pointsLoading, setPointsLoading] = useState(false);
+  const [pointsError, setPointsError] = useState(null);
+  const [optimisticPointsApplied, setOptimisticPointsApplied] = useState(null);
+
   const [checkoutLoading, setCheckoutLoading] = useState(false);
   const [checkoutError, setCheckoutError] = useState(null);
   const [clientSecret, setClientSecret] = useState(null);
@@ -118,6 +123,8 @@ export default function CartPage() {
       cart.items.forEach((i) => (map[i.cartItemId] = i.quantity));
       setLocalQuantities(map);
     }
+    // Sync optimistic state back to server truth whenever cart updates
+    setOptimisticPointsApplied(null);
   }, [cart]);
 
   // If the cart arrives already locked (e.g. user closed the page mid-checkout)
@@ -184,6 +191,20 @@ export default function CartPage() {
     }
   }
 
+  async function handleTogglePoints(checked) {
+    setOptimisticPointsApplied(checked);
+    setPointsLoading(true);
+    setPointsError(null);
+    try {
+      await applyPoints(checked);
+    } catch (err) {
+      setOptimisticPointsApplied(null);
+      setPointsError(err.message || "Failed to apply loyalty points.");
+    } finally {
+      setPointsLoading(false);
+    }
+  }
+
   async function handleRemoveCoupon() {
     setCouponLoading(true);
     setCouponError(null);
@@ -213,6 +234,7 @@ export default function CartPage() {
       } 
       
       else if (result?.status === "succeeded") {
+        refreshUser().catch(() => {});
         setConfirmed(true);
       }
     } 
@@ -341,7 +363,7 @@ export default function CartPage() {
             {parseFloat(cart.discountAmount ?? 0) > 0 && (
               <div className="cart-summary-row cart-summary-discount">
                 <span>
-                  Discount
+                  Coupon discount
                   {cart.couponCode && ` (${cart.couponCode}`}
                   {(() => {
                     const t = cart.couponDiscountType?.toUpperCase();
@@ -356,15 +378,21 @@ export default function CartPage() {
                 <span>−${parseFloat(cart.discountAmount).toFixed(2)}</span>
               </div>
             )}
+            {parseFloat(cart.pointsDiscountAmount ?? 0) > 0 && (
+              <div className="cart-summary-row cart-summary-discount">
+                <span>Loyalty discount ({Math.round(parseFloat(cart.pointsDiscountAmount) * 20)} pts)</span>
+                <span>−${parseFloat(cart.pointsDiscountAmount).toFixed(2)}</span>
+              </div>
+            )}
             <div className="cart-summary-row cart-summary-total">
               <span>Total</span>
               <div className="cart-total-prices">
-                {parseFloat(cart.discountAmount ?? 0) > 0 && (
+                {(parseFloat(cart.discountAmount ?? 0) > 0 || parseFloat(cart.pointsDiscountAmount ?? 0) > 0) && (
                   <span className="cart-total-original">
                     ${parseFloat(cart.subtotalAmount ?? 0).toFixed(2)}
                   </span>
                 )}
-                <span className={parseFloat(cart.discountAmount ?? 0) > 0 ? "cart-total-discounted" : ""}>
+                <span className={(parseFloat(cart.discountAmount ?? 0) > 0 || parseFloat(cart.pointsDiscountAmount ?? 0) > 0) ? "cart-total-discounted" : ""}>
                   ${parseFloat(cart.totalAmount ?? 0).toFixed(2)}
                 </span>
               </div>
@@ -382,6 +410,36 @@ export default function CartPage() {
               </div>
             )}
 
+            {user?.role === "CUSTOMER" && (
+              <div className="cart-points-section">
+                <div className="cart-points-balance-row">
+                  <span>Your points balance:</span>
+                  <strong>{cart.availableLoyaltyPoints ?? 0} pts</strong>
+                </div>
+                {(cart.availableLoyaltyPoints ?? 0) < 20 ? (
+                  <p className="cart-points-msg">You need at least 20 points to redeem $1.</p>
+                ) : (
+                  <label className="cart-points-label">
+                    <input
+                      type="checkbox"
+                      className="cart-points-checkbox"
+                      checked={optimisticPointsApplied !== null ? optimisticPointsApplied : !!cart.pointsApplied}
+                      disabled={pointsLoading}
+                      onChange={(e) => handleTogglePoints(e.target.checked)}
+                    />
+                    Use loyalty points for this purchase
+                  </label>
+                )}
+                {pointsError && <p className="cart-points-msg" style={{ color: "#dc2626" }}>{pointsError}</p>}
+                {(optimisticPointsApplied ?? !!cart.pointsApplied) && parseFloat(cart.pointsDiscountAmount ?? 0) > 0 && (
+                  <div className="cart-points-applied-detail">
+                    <span>Applying {Math.round(parseFloat(cart.pointsDiscountAmount) * 20)} pts:</span>
+                    <span>${parseFloat(cart.pointsDiscountAmount).toFixed(2)} off</span>
+                  </div>
+                )}
+              </div>
+            )}
+
             <div className="cart-coupon-section">
               {cart.couponCode && (
                 <div className="cart-coupon-applied">

web/app/globals.css

@@ -2417,6 +2417,71 @@ body {
   text-align: center;
 }
 
+.cart-points-section {
+  display: flex;
+  flex-direction: column;
+  gap: 0.5rem;
+  margin-top: 0.75rem;
+  padding-top: 0.75rem;
+  border-top: 1px solid #e5e7eb;
+}
+
+.cart-points-balance-row {
+  display: flex;
+  justify-content: space-between;
+  align-items: center;
+  font-size: 0.9rem;
+  color: #374151;
+}
+
+.cart-points-balance-row strong {
+  color: #7c3aed;
+  font-weight: 700;
+}
+
+.cart-points-label {
+  display: flex;
+  align-items: center;
+  gap: 0.5rem;
+  font-size: 0.9rem;
+  color: #374151;
+  cursor: pointer;
+  user-select: none;
+}
+
+.cart-points-label:has(.cart-points-checkbox:disabled) {
+  cursor: not-allowed;
+  opacity: 0.6;
+}
+
+.cart-points-checkbox {
+  width: 1rem;
+  height: 1rem;
+  accent-color: #7c3aed;
+  cursor: pointer;
+  flex-shrink: 0;
+}
+
+.cart-points-msg {
+  font-size: 0.82rem;
+  color: #6b7280;
+  margin: 0;
+  font-style: italic;
+}
+
+.cart-points-applied-detail {
+  display: flex;
+  justify-content: space-between;
+  align-items: center;
+  background: #f5f3ff;
+  border: 1px solid #ddd6fe;
+  border-radius: 6px;
+  padding: 0.4rem 0.7rem;
+  font-size: 0.85rem;
+  color: #5b21b6;
+  font-weight: 500;
+}
+
 .cart-coupon-section {
   display: flex;
   flex-direction: column;

web/context/CartContext.js

@@ -10,6 +10,7 @@ import {
   apiClearCart,
   apiApplyCoupon,
   apiRemoveCoupon,
+  apiApplyPoints,
   apiCheckout,
   apiCancelCheckout,
 } from "@/lib/cartApi";
@@ -125,6 +126,17 @@ export function CartProvider({ children }) {
     [token, selectedStoreId]
   );
 
+  const applyPoints = useCallback(
+    async (useLoyaltyPoints) => {
+      if (!token || !selectedStoreId) throw new Error("Select a store first");
+      const updated = await apiApplyPoints(token, selectedStoreId, useLoyaltyPoints);
+      setCart(updated);
+
+      return updated;
+    },
+    [token, selectedStoreId]
+  );
+
   const removeCoupon = useCallback(
     async () => {
       if (!token || !selectedStoreId) throw new Error("Select a store first");
@@ -171,6 +183,7 @@ export function CartProvider({ children }) {
         removeItem,
         clearCart,
         applyCoupon,
+        applyPoints,
         removeCoupon,
         checkout,
         cancelCheckout,

web/lib/cartApi.js

@@ -73,6 +73,15 @@ export async function apiApplyCoupon(token, storeId, couponCode) {
   return handleResponse(res);
 }
 
+export async function apiApplyPoints(token, storeId, useLoyaltyPoints) {
+  const res = await fetch(`${BASE}/apply-points?storeId=${storeId}&useLoyaltyPoints=${useLoyaltyPoints}`, {
+    method: "POST",
+    headers: authHeaders(token),
+  });
+
+  return handleResponse(res);
+}
+
 export async function apiRemoveCoupon(token, storeId) {
   const res = await fetch(`${BASE}/coupon?storeId=${storeId}`, {
     method: "DELETE",