fix stripe payment flow

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

@@ -80,5 +80,15 @@ public class CartController {
     public ResponseEntity<CheckoutResponse> checkout(@Valid @RequestBody CheckoutRequest request) {
         Long userId = AuthenticationHelper.getAuthenticatedUserId();
 
-        return ResponseEntity.ok(cartService.checkout(userId, request.getStoreId(), request.getPaymentMethodId()));}
+        return ResponseEntity.ok(cartService.checkout(userId, request.getStoreId()));
+    }
+
+    @PostMapping("/checkout/complete")
+    @PreAuthorize("isAuthenticated()")
+    public ResponseEntity<Void> completeCheckout(@RequestParam String paymentIntentId) {
+        Long userId = AuthenticationHelper.getAuthenticatedUserId();
+        cartService.completeCheckout(userId, paymentIntentId);
+
+        return ResponseEntity.noContent().build();
+    }
 }

backend/src/main/java/com/petshop/backend/dto/cart/CheckoutRequest.java

@@ -1,6 +1,5 @@
 package com.petshop.backend.dto.cart;
 
-import jakarta.validation.constraints.NotBlank;
 import jakarta.validation.constraints.NotNull;
 
 public class CheckoutRequest {
@@ -8,17 +7,6 @@ public class CheckoutRequest {
     @NotNull
     private Long storeId;
 
-    @NotBlank
-    private String paymentMethodId;
-
     public Long getStoreId() { return storeId; }
     public void setStoreId(Long storeId) { this.storeId = storeId; }
-
-    public String getPaymentMethodId() {
-        return paymentMethodId;
-    }
-
-    public void setPaymentMethodId(String paymentMethodId) {
-        this.paymentMethodId = paymentMethodId;
-    }
 }

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

@@ -190,7 +190,7 @@ public class CartService {
     }
 
     @Transactional
-    public CheckoutResponse checkout(Long userId, Long storeId, String paymentMethodId) {
+    public CheckoutResponse checkout(Long userId, Long storeId) {
         Cart cart = cartRepository
                 .findActiveCartByUserAndStore(userId, storeId, "ACTIVE")
                 .orElseThrow(() -> new BusinessException("No active cart found"));
@@ -213,21 +213,12 @@ public class CartService {
             PaymentIntentCreateParams params = PaymentIntentCreateParams.builder()
                     .setAmount(amountInCents)
                     .setCurrency("usd")
-                    .setPaymentMethod(paymentMethodId)
-                    .setConfirm(true)
-                    .setReturnUrl("http://localhost:3000/cart/confirmation")
                     .putMetadata("cartId", String.valueOf(cart.getCartId()))
                     .putMetadata("userId", String.valueOf(userId))
                     .build();
 
             PaymentIntent intent = PaymentIntent.create(params);
 
-            if ("succeeded".equals(intent.getStatus())
-                    || "requires_action".equals(intent.getStatus())) {
-                cart.setCartStatus("CHECKED_OUT");
-                cartRepository.save(cart);
-            }
-
             return new CheckoutResponse(
                     cart.getCartId(),
                     intent.getClientSecret(),
@@ -235,13 +226,38 @@ public class CartService {
                     intent.getStatus()
             );
 
-        } 
-        
+        }
+
         catch (StripeException e) {
             throw new BusinessException("Payment processing failed: " + e.getMessage());
         }
     }
 
+    @Transactional
+    public void completeCheckout(Long userId, String paymentIntentId) {
+        try {
+            PaymentIntent intent = PaymentIntent.retrieve(paymentIntentId);
+
+            if (!"succeeded".equals(intent.getStatus())) {
+                throw new BusinessException("Payment has not been completed");
+            }
+
+            Long cartId = Long.parseLong(intent.getMetadata().get("cartId"));
+            Cart cart = cartRepository.findById(cartId)
+                    .orElseThrow(() -> new BusinessException("Cart not found"));
+
+            if (!cart.getUser().getUserId().equals(userId)) {
+                throw new BusinessException("Unauthorized");
+            }
+
+            cart.setCartStatus("CHECKED_OUT");
+            cartRepository.save(cart);
+
+        } catch (StripeException e) {
+            throw new BusinessException("Payment verification failed: " + e.getMessage());
+        }
+    }
+
     private void recalculate(Cart cart) {
         List<CartItem> items = cartItemRepository.findByCartCartId(cart.getCartId());