[Server] Add support for SupportsFilteredRetain (#2913)

* Work In Progress

* Working Implementation of SupportsFilteredRetain

* Potential solution

Contains test debug messages that should be cleaned up

* Update comments showing discussion required

* Address Comments

* Use the NodeId from the ConditionState for the ConditionId.

Existing case was not guaranteed to be correct.

Author: Archie-Miller

Libraries/Opc.Ua.Server/Subscription/MonitoredItem.cs

@@ -1042,7 +1042,7 @@ public virtual void QueueEvent(IFilterTarget instance, bool bypassFilter)
                 // apply filter.
                 if (!bypassFilter)
                 {
-                    if (!filter.WhereClause.Evaluate(context, instance))
+                    if ( !CanSendFilteredAlarm( context, filter, instance ) )
                     {
                         return;
                     }
@@ -1079,6 +1079,78 @@ public virtual void QueueEvent(EventFieldList fields)
             }
         }
 
+        /// <summary>
+        /// Determines whether an event can be sent with SupportsFilteredRetain in consideration.
+        /// </summary>
+        /// <returns></returns>
+        protected bool CanSendFilteredAlarm(FilterContext context, EventFilter filter, IFilterTarget instance)
+        {
+            bool passedFilter = filter.WhereClause.Evaluate(context, instance);
+
+            ConditionState alarmCondition = null;
+            NodeId conditionId = null;
+            InstanceStateSnapshot instanceStateSnapshot = instance as InstanceStateSnapshot;
+            if (instanceStateSnapshot != null)
+            {
+                alarmCondition = instanceStateSnapshot.Handle as ConditionState;
+
+                if (alarmCondition != null &&
+                    alarmCondition.SupportsFilteredRetain != null &&
+                    alarmCondition.SupportsFilteredRetain.Value &&
+                    filter.SelectClauses != null)
+                {
+                    conditionId = alarmCondition.NodeId;
+                }
+            }
+
+            bool canSend = passedFilter;
+
+            // ConditionId is valid only if FilteredRetain is set for the alarm condition
+            if (conditionId != null && alarmCondition != null)
+            {
+                HashSet<string> conditionIds = GetFilteredRetainConditionIds();
+
+                string key = conditionId.ToString();
+
+                bool saved = conditionIds.Contains(key);
+
+                if ( saved )
+                {
+                    conditionIds.Remove(key);
+                }
+
+                if ( passedFilter )
+                {
+                    // Archie - December 17 2024
+                    // Requires discussion with Part 9 Editor
+                    // if (alarmCondition.Retain.Value)
+                    {
+                        conditionIds.Add(key);
+                    }
+                }
+                else
+                {
+                    if ( saved )
+                    {
+                        canSend = true;
+                    }
+                }
+            }
+
+            return canSend;
+        }
+
+        private HashSet<string> GetFilteredRetainConditionIds()
+        {
+            if (m_filteredRetainConditionIds == null)
+            {
+                m_filteredRetainConditionIds = new HashSet<string>();
+            }
+
+            return m_filteredRetainConditionIds;
+        }
+
+
         /// <summary>
         /// Whether the item has notifications that are ready to publish.
         /// </summary>
@@ -1873,6 +1945,9 @@ private void QueueOverflowHandler()
         private IAggregateCalculator m_calculator;
         private bool m_triggered;
         private bool m_resendData;
+        private HashSet<string> m_filteredRetainConditionIds = null;
+
+
         #endregion
     }
 }

Stack/Opc.Ua.Core/Stack/State/ConditionState.cs

@@ -49,6 +49,29 @@ protected override void OnAfterCreate(ISystemContext context, NodeState node)
         }
         #endregion
 
+        #region Public Properties
+
+        /// <remarks />
+        public PropertyState<bool> SupportsFilteredRetain
+        {
+            get
+            {
+                return m_supportsFilteredRetain;
+            }
+
+            set
+            {
+                if (!Object.ReferenceEquals(m_supportsFilteredRetain, value))
+                {
+                    ChangeMasks |= NodeStateChangeMasks.Children;
+                }
+
+                m_supportsFilteredRetain = value;
+            }
+        }
+
+        #endregion
+
         #region Public Methods
         /// <summary>
         /// Gets or sets a value indicating whether the condition will automatically report an event when a method call completes.
@@ -762,6 +785,7 @@ protected bool IsBranch()
         /// 
         /// </summary>
         protected Dictionary<string, ConditionState> m_branches = null;
+        private PropertyState<bool> m_supportsFilteredRetain = null;
 
         #endregion
     }