killbill-aplcache

diff --git a/subscription/src/main/java/org/killbill/billing/subscription/api/user/DefaultSubscriptionBaseApiService.java b/subscription/src/main/java/org/killbill/billing/subscription/api/user/DefaultSubscriptionBaseApiService.java
index cffcd6b..28f23e0 100644
--- a/subscription/src/main/java/org/killbill/billing/subscription/api/user/DefaultSubscriptionBaseApiService.java
+++ b/subscription/src/main/java/org/killbill/billing/subscription/api/user/DefaultSubscriptionBaseApiService.java
@@ -385,6 +385,18 @@ public class DefaultSubscriptionBaseApiService implements SubscriptionBaseApiSer
         return planChangeResult;
     }
 
+    private int countExistingAddOnsWithSamePlanName(final List<SubscriptionBase> subscriptionsForBundle, final String planName) {
+        int countExistingAddOns = 0;
+        for (SubscriptionBase subscription : subscriptionsForBundle) {
+            if (subscription.getCurrentPlan().getName().equalsIgnoreCase(planName)
+                && subscription.getLastActiveProduct().getCategory() != null
+                && ProductCategory.ADD_ON.equals(subscription.getLastActiveProduct().getCategory())) {
+                countExistingAddOns++;
+            }
+        }
+        return countExistingAddOns;
+    }
+
     private void doChangePlan(final DefaultSubscriptionBase subscription,
                               final PlanSpecifier spec,
                               final List<PlanPhasePriceOverride> overrides,
@@ -394,6 +406,16 @@ public class DefaultSubscriptionBaseApiService implements SubscriptionBaseApiSer
         final PlanPhasePriceOverridesWithCallContext overridesWithContext = new DefaultPlanPhasePriceOverridesWithCallContext(overrides, context);
         final Plan newPlan = catalogService.getFullCatalog(true, true, internalCallContext).createOrFindPlan(spec, overridesWithContext, effectiveDate, subscription.getStartDate());
 
+        if (ProductCategory.ADD_ON.toString().equalsIgnoreCase(newPlan.getProduct().getCategory().toString())) {
+            if (newPlan.getPlansAllowedInBundle() != -1
+                && newPlan.getPlansAllowedInBundle() > 0
+                && countExistingAddOnsWithSamePlanName(dao.getSubscriptions(subscription.getBundleId(), null, internalCallContext), newPlan.getName())
+                   >= newPlan.getPlansAllowedInBundle()) {
+                // the plan can be changed to the new value, because it has reached its limit by bundle
+                throw new SubscriptionBaseApiException(ErrorCode.SUB_CHANGE_AO_MAX_PLAN_ALLOWED_BY_BUNDLE, newPlan.getName());
+            }
+        }
+
         if (newPlan.getProduct().getCategory() != subscription.getCategory()) {
             throw new SubscriptionBaseApiException(ErrorCode.SUB_CHANGE_INVALID, subscription.getId());
         }