Add Application Callback for Subscription Handling

src/app/EventLoggingTypes.h

@@ -152,10 +152,10 @@ struct EventLoadOutContext
     EventNumber mStartingEventNumber = 0;
     Timestamp mPreviousTime;
     Timestamp mCurrentTime;
-    EventNumber mCurrentEventNumber                      = 0;
-    size_t mEventCount                                   = 0;
-    ObjectList<EventPathParams> * mpInterestedEventPaths = nullptr;
-    bool mFirst                                          = true;
+    EventNumber mCurrentEventNumber                            = 0;
+    size_t mEventCount                                         = 0;
+    const ObjectList<EventPathParams> * mpInterestedEventPaths = nullptr;
+    bool mFirst                                                = true;
     Access::SubjectDescriptor mSubjectDescriptor;
 };
 } // namespace app

src/app/EventManagement.cpp

@@ -733,7 +733,7 @@ CHIP_ERROR EventManagement::CopyEventsSince(const TLVReader & aReader, size_t aD
     return err;
 }
 
-CHIP_ERROR EventManagement::FetchEventsSince(TLVWriter & aWriter, ObjectList<EventPathParams> * apEventPathList,
+CHIP_ERROR EventManagement::FetchEventsSince(TLVWriter & aWriter, const ObjectList<EventPathParams> * apEventPathList,
                                              EventNumber & aEventMin, size_t & aEventCount,
                                              const Access::SubjectDescriptor & aSubjectDescriptor)
 {

src/app/EventManagement.h

@@ -340,7 +340,7 @@ class EventManagement
      *                                       available.
      *
      */
-    CHIP_ERROR FetchEventsSince(chip::TLV::TLVWriter & aWriter, ObjectList<EventPathParams> * apEventPathList,
+    CHIP_ERROR FetchEventsSince(chip::TLV::TLVWriter & aWriter, const ObjectList<EventPathParams> * apEventPathList,
                                 EventNumber & aEventMin, size_t & aEventCount,
                                 const Access::SubjectDescriptor & aSubjectDescriptor);
 

src/app/InteractionModelEngine.h

@@ -68,7 +68,9 @@ namespace app {
  * handlers
  *
  */
-class InteractionModelEngine : public Messaging::ExchangeDelegate, public CommandHandler::Callback, public ReadHandler::Callback
+class InteractionModelEngine : public Messaging::ExchangeDelegate,
+                               public CommandHandler::Callback,
+                               public ReadHandler::ManagementCallback
 {
 public:
     /**
@@ -157,6 +159,15 @@ class InteractionModelEngine : public Messaging::ExchangeDelegate, public Comman
     CommandHandlerInterface * FindCommandHandler(EndpointId endpointId, ClusterId clusterId);
     void UnregisterCommandHandlers(EndpointId endpointId);
 
+    /*
+     * Register an application callback to be notified of notable events when handling reads/subscribes.
+     */
+    void RegisterReadHandlerAppCallback(ReadHandler::ApplicationCallback * mpApplicationCallback)
+    {
+        mpReadHandlerApplicationCallback = mpApplicationCallback;
+    }
+    void UnregisterReadHandlerAppCallback() { mpReadHandlerApplicationCallback = nullptr; }
+
     /**
      * Called when a timed interaction has failed (i.e. the exchange it was
      * happening on has closed while the exchange delegate was the timed
@@ -252,6 +263,8 @@ class InteractionModelEngine : public Messaging::ExchangeDelegate, public Comman
     void OnDone(CommandHandler & apCommandObj) override;
     void OnDone(ReadHandler & apReadObj) override;
 
+    ReadHandler::ApplicationCallback * GetAppCallback() override { return mpReadHandlerApplicationCallback; }
+
     /**
      * Called when Interaction Model receives a Command Request message.  Errors processing
      * the Command Request are handled entirely within this function. The caller pre-sets status to failure and the callee is
@@ -325,6 +338,8 @@ class InteractionModelEngine : public Messaging::ExchangeDelegate, public Comman
     ObjectPool<ObjectList<DataVersionFilter>, CHIP_IM_SERVER_MAX_NUM_PATH_GROUPS> mDataVersionFilterPool;
     ReadClient * mpActiveReadClientList = nullptr;
 
+    ReadHandler::ApplicationCallback * mpReadHandlerApplicationCallback = nullptr;
+
 #if CONFIG_IM_BUILD_FOR_UNIT_TEST
     int mReadHandlerCapacityOverride = -1;
 #endif