[commissioner] log commissioner state changes (#4207)

src/core/meshcop/commissioner.cpp

@@ -89,6 +89,8 @@ void Commissioner::SetState(otCommissionerState aState)
 {
     VerifyOrExit(mState != aState);
 
+    otLogInfoMeshCoP("Commissioner State: %s -> %s", StateToString(mState), StateToString(aState));
+
     mState = aState;
 
     if (mStateCallback)
@@ -1125,6 +1127,36 @@ exit:
     return error;
 }
 
+// LCOV_EXCL_START
+
+#if (OPENTHREAD_CONFIG_LOG_LEVEL >= OT_LOG_LEVEL_INFO) && (OPENTHREAD_CONFIG_LOG_MLE == 1)
+
+const char *Commissioner::StateToString(otCommissionerState aState)
+{
+    const char *str = "Unknown";
+
+    switch (aState)
+    {
+    case OT_COMMISSIONER_STATE_DISABLED:
+        str = "disabled";
+        break;
+    case OT_COMMISSIONER_STATE_PETITION:
+        str = "petition";
+        break;
+    case OT_COMMISSIONER_STATE_ACTIVE:
+        str = "active";
+        break;
+    default:
+        break;
+    }
+
+    return str;
+}
+
+#endif // (OPENTHREAD_CONFIG_LOG_LEVEL >= OT_LOG_LEVEL_INFO) && (OPENTHREAD_CONFIG_LOG_MLE == 1)
+
+// LCOV_EXCL_STOP
+
 } // namespace MeshCoP
 } // namespace ot
 

src/core/meshcop/commissioner.hpp

@@ -323,6 +323,8 @@ private:
     void SetState(otCommissionerState aState);
     void SignalJoinerEvent(otCommissionerJoinerEvent aEvent, const Mac::ExtAddress &aJoinerId);
 
+    static const char *StateToString(otCommissionerState aState);
+
     struct Joiner
     {
         Mac::ExtAddress mEui64;