[ICD] Report before idle mode (project-chip#28714)

* Added a check before going to idle mode to emit a report if it would avoid the device waking up earlier

* Added check to prevent looping when emiting a report before leaving active mode, Changed OnActiveModeAlmostDone to OnTransitionToIdle, added check to prevent wrap around when computing OnTransitionToIdle timeout

* Moved boolean set to true to proper place

* Set flag before calling observer method

* Added stub in observer test function

src/app/icd/ICDManager.cpp

@@ -67,6 +67,7 @@ void ICDManager::Shutdown()
     // cancel any running timer of the icd
     DeviceLayer::SystemLayer().CancelTimer(OnIdleModeDone, this);
     DeviceLayer::SystemLayer().CancelTimer(OnActiveModeDone, this);
+    DeviceLayer::SystemLayer().CancelTimer(OnTransitionToIdle, this);
     mICDMode          = ICDMode::SIT;
     mOperationalState = OperationalState::IdleMode;
     mStorage          = nullptr;
@@ -157,6 +158,9 @@ void ICDManager::UpdateOperationState(OperationalState state)
             mOperationalState           = OperationalState::ActiveMode;
             uint32_t activeModeInterval = IcdManagementServer::GetInstance().GetActiveModeInterval();
             DeviceLayer::SystemLayer().StartTimer(System::Clock::Timeout(activeModeInterval), OnActiveModeDone, this);
+            uint32_t activeModeJitterInterval =
+                (activeModeInterval >= ICD_ACTIVE_TIME_JITTER_MS) ? activeModeInterval - ICD_ACTIVE_TIME_JITTER_MS : 0;
+            DeviceLayer::SystemLayer().StartTimer(System::Clock::Timeout(activeModeJitterInterval), OnTransitionToIdle, this);
 
             CHIP_ERROR err = DeviceLayer::ConnectivityMgr().SetPollingInterval(GetFastPollingInterval());
             if (err != CHIP_NO_ERROR)
@@ -170,6 +174,13 @@ void ICDManager::UpdateOperationState(OperationalState state)
         {
             uint16_t activeModeThreshold = IcdManagementServer::GetInstance().GetActiveModeThreshold();
             DeviceLayer::SystemLayer().ExtendTimerTo(System::Clock::Timeout(activeModeThreshold), OnActiveModeDone, this);
+            uint16_t activeModeJitterThreshold =
+                (activeModeThreshold >= ICD_ACTIVE_TIME_JITTER_MS) ? activeModeThreshold - ICD_ACTIVE_TIME_JITTER_MS : 0;
+            if (!mTransitionToIdleCalled)
+            {
+                DeviceLayer::SystemLayer().ExtendTimerTo(System::Clock::Timeout(activeModeJitterThreshold), OnTransitionToIdle,
+                                                         this);
+            }
         }
     }
 }
@@ -195,6 +206,10 @@ void ICDManager::OnIdleModeDone(System::Layer * aLayer, void * appState)
 {
     ICDManager * pIcdManager = reinterpret_cast<ICDManager *>(appState);
     pIcdManager->UpdateOperationState(OperationalState::ActiveMode);
+
+    // We only reset this flag when idle mode is complete to avoid re-triggering the check when an event brings us back to active,
+    // which could cause a loop.
+    pIcdManager->mTransitionToIdleCalled = false;
 }
 
 void ICDManager::OnActiveModeDone(System::Layer * aLayer, void * appState)
@@ -207,5 +222,16 @@ void ICDManager::OnActiveModeDone(System::Layer * aLayer, void * appState)
         pIcdManager->UpdateOperationState(OperationalState::IdleMode);
     }
 }
+
+void ICDManager::OnTransitionToIdle(System::Layer * aLayer, void * appState)
+{
+    ICDManager * pIcdManager = reinterpret_cast<ICDManager *>(appState);
+
+    // OnTransitionToIdle will trigger a report message if reporting is needed, which should extend the active mode until the
+    // ack for the report is received.
+    pIcdManager->mTransitionToIdleCalled = true;
+    pIcdManager->mStateObserver->OnTransitionToIdle();
+}
+
 } // namespace app
 } // namespace chip

src/app/icd/ICDManager.h

@@ -75,6 +75,13 @@ class ICDManager
 
     static void OnIdleModeDone(System::Layer * aLayer, void * appState);
     static void OnActiveModeDone(System::Layer * aLayer, void * appState);
+    /**
+     * @brief Callback function called shortly before the device enters idle mode to allow checks to be made. This is currently only
+     * called once to prevent entering in a loop if some events re-trigger this check (for instance if a check for subscription
+     * before entering idle mode leads to emiting a report, we will re-enter UpdateOperationState and check again for subscription,
+     * etc.)
+     */
+    static void OnTransitionToIdle(System::Layer * aLayer, void * appState);
 
 private:
     // SIT ICDs should have a SlowPollingThreshold shorter than or equal to 15s (spec 9.16.1.5)
@@ -95,6 +102,7 @@ class ICDManager
     PersistentStorageDelegate * mStorage = nullptr;
     FabricTable * mFabricTable           = nullptr;
     ICDStateObserver * mStateObserver    = nullptr;
+    bool mTransitionToIdleCalled         = false;
 };
 
 } // namespace app

src/app/icd/ICDStateObserver.h

@@ -16,14 +16,23 @@
  */
 #pragma once
 
+#ifndef ICD_SLEEP_TIME_JITTER_MS
+#define ICD_SLEEP_TIME_JITTER_MS (CHIP_CONFIG_ICD_IDLE_MODE_INTERVAL * 0.75)
+#endif
+
+#ifndef ICD_ACTIVE_TIME_JITTER_MS
+#define ICD_ACTIVE_TIME_JITTER_MS 300
+#endif
+
 namespace chip {
 namespace app {
 
 class ICDStateObserver
 {
 public:
     virtual ~ICDStateObserver() {}
-    virtual void OnEnterActiveMode() = 0;
+    virtual void OnEnterActiveMode()  = 0;
+    virtual void OnTransitionToIdle() = 0;
 };
 
 } // namespace app

src/app/reporting/ReportSchedulerImpl.cpp

@@ -37,6 +37,8 @@ ReportSchedulerImpl::ReportSchedulerImpl(TimerDelegate * aTimerDelegate) : Repor
     VerifyOrDie(nullptr != mTimerDelegate);
 }
 
+void ReportSchedulerImpl::OnTransitionToIdle() {}
+
 /// @brief Method that triggers a report emission on each ReadHandler that is not blocked on its min interval.
 ///        Each read handler that is not blocked is immediately marked dirty so that it will report as soon as possible.
 void ReportSchedulerImpl::OnEnterActiveMode()

src/app/reporting/ReportSchedulerImpl.h

@@ -34,6 +34,7 @@ class ReportSchedulerImpl : public ReportScheduler
 
     // ICDStateObserver
     void OnEnterActiveMode() override;
+    void OnTransitionToIdle() override;
 
     // ReadHandlerObserver
     void OnSubscriptionEstablished(ReadHandler * aReadHandler) final;

src/app/reporting/SynchronizedReportSchedulerImpl.cpp

@@ -44,6 +44,19 @@ void SynchronizedReportSchedulerImpl::OnReadHandlerDestroyed(ReadHandler * aRead
     }
 }
 
+void SynchronizedReportSchedulerImpl::OnTransitionToIdle()
+{
+    Timestamp now               = mTimerDelegate->GetCurrentMonotonicTimestamp();
+    uint32_t targetIdleInterval = static_cast<uint32_t>(ICD_SLEEP_TIME_JITTER_MS);
+    VerifyOrReturn(now >= mTestNextReportTimestamp);
+    if (((mTestNextReportTimestamp - now) < Seconds16(targetIdleInterval)) && (now > mNextMinTimestamp))
+    {
+        // If the next report is due in less than the idle mode interval and we are past the min interval, we can just send it now
+        CancelReport();
+        TimerFired();
+    }
+}
+
 CHIP_ERROR SynchronizedReportSchedulerImpl::ScheduleReport(Timeout timeout, ReadHandlerNode * node, const Timestamp & now)
 {
     // Cancel Report if it is currently scheduled

src/app/reporting/SynchronizedReportSchedulerImpl.h

@@ -38,6 +38,8 @@ class SynchronizedReportSchedulerImpl : public ReportSchedulerImpl, public Timer
     SynchronizedReportSchedulerImpl(TimerDelegate * aTimerDelegate) : ReportSchedulerImpl(aTimerDelegate) {}
     ~SynchronizedReportSchedulerImpl() override { UnregisterAllHandlers(); }
 
+    void OnTransitionToIdle() override;
+
     bool IsReportScheduled();
 
     void TimerFired() override;

src/app/tests/TestICDManager.cpp

@@ -37,6 +37,7 @@ class TestICDStateObserver : public app::ICDStateObserver
 {
 public:
     void OnEnterActiveMode() {}
+    void OnTransitionToIdle() {}
 };
 
 TestICDStateObserver mICDStateObserver;