feat(triggers): runtime expression trigger evaluation for scripts and alarms

src/ScadaLink.SiteRuntime/Actors/AlarmActor.cs

@@ -50,6 +50,12 @@ public class AlarmActor : ReceiveActor
     private readonly string? _onTriggerScriptName;
     private readonly Script<object?>? _onTriggerCompiledScript;
 
+    // Expression trigger: compiled expression + the attribute snapshot it
+    // evaluates against. The compiled expression is also held on the
+    // ExpressionEvalConfig; this field caches it for the hot path.
+    private readonly Script<object?>? _compiledTriggerExpression;
+    private readonly Dictionary<string, object?> _attributeSnapshot = new();
+
     // Rate of change tracking
     private readonly Queue<(DateTimeOffset Timestamp, double Value)> _rateOfChangeWindow = new();
     private readonly TimeSpan _rateOfChangeWindowDuration;
@@ -65,6 +71,7 @@ public class AlarmActor : ReceiveActor
         SharedScriptLibrary sharedScriptLibrary,
         SiteRuntimeOptions options,
         ILogger logger,
+        Script<object?>? compiledTriggerExpression = null,
         ISiteHealthCollector? healthCollector = null)
     {
         _alarmName = alarmName;
@@ -77,6 +84,7 @@ public class AlarmActor : ReceiveActor
         _priority = alarmConfig.PriorityLevel;
         _onTriggerScriptName = alarmConfig.OnTriggerScriptCanonicalName;
         _onTriggerCompiledScript = onTriggerCompiledScript;
+        _compiledTriggerExpression = compiledTriggerExpression;
 
         // Parse trigger type
         _triggerType = Enum.TryParse<AlarmTriggerType>(alarmConfig.TriggerType, true, out var tt)
@@ -126,9 +134,18 @@ public class AlarmActor : ReceiveActor
     /// </summary>
     private void HandleAttributeValueChanged(AttributeValueChanged changed)
     {
-        // Only evaluate if this change is for an attribute we're monitoring
-        if (!IsMonitoredAttribute(changed.AttributeName))
+        // Expression triggers evaluate against a snapshot of every attribute,
+        // not a single monitored attribute. Keep the snapshot current for every
+        // change before the IsMonitoredAttribute gate (which does not apply).
+        if (_triggerType == AlarmTriggerType.Expression)
+        {
+            _attributeSnapshot[changed.AttributeName] = changed.Value;
+        }
+        else if (!IsMonitoredAttribute(changed.AttributeName))
+        {
+            // Only evaluate if this change is for an attribute we're monitoring
             return;
+        }
 
         try
         {
@@ -143,6 +160,7 @@ public class AlarmActor : ReceiveActor
                 AlarmTriggerType.ValueMatch => EvaluateValueMatch(changed.Value),
                 AlarmTriggerType.RangeViolation => EvaluateRangeViolation(changed.Value),
                 AlarmTriggerType.RateOfChange => EvaluateRateOfChange(changed.Value, changed.Timestamp),
+                AlarmTriggerType.Expression => EvaluateExpression(),
                 _ => false
             };
 
@@ -337,6 +355,22 @@ public class AlarmActor : ReceiveActor
         }
     }
 
+    /// <summary>
+    /// Evaluates the compiled trigger expression against the current attribute
+    /// snapshot, returning the resulting bool. This bool feeds the existing
+    /// binary Normal↔Active state path — the alarm is active while true. A
+    /// throwing or non-bool expression is treated as false; the exception
+    /// propagates to the caller's catch, which logs it and continues.
+    /// </summary>
+    private bool EvaluateExpression()
+    {
+        if (_compiledTriggerExpression == null) return false;
+
+        var globals = new TriggerExpressionGlobals(_attributeSnapshot);
+        var state = _compiledTriggerExpression.RunAsync(globals).GetAwaiter().GetResult();
+        return state.ReturnValue is bool b && b;
+    }
+
     /// <summary>
     /// HiLo level evaluator: returns the most-severe matching band for the
     /// given value. Severity order checked from highest to lowest so that a
@@ -473,6 +507,14 @@ public class AlarmActor : ReceiveActor
                     HiMessage: TryReadString(root, "hiMessage"),
                     HiHiMessage: TryReadString(root, "hiHiMessage")),
 
+                // Expression triggers have no single monitored attribute; they
+                // evaluate the compiled expression (passed into the actor) over
+                // the full attribute snapshot. MonitoredAttributeName is unused.
+                AlarmTriggerType.Expression => new ExpressionEvalConfig(
+                    "",
+                    TryReadString(root, "expression") ?? "",
+                    _compiledTriggerExpression),
+
                 _ => new ValueMatchEvalConfig(attr, null)
             };
         }
@@ -535,6 +577,17 @@ internal record RateOfChangeEvalConfig(
     TimeSpan WindowDuration,
     RateOfChangeDirection Direction) : AlarmEvalConfig(MonitoredAttributeName);
 
+/// <summary>
+/// Expression evaluation config: a read-only boolean C# expression evaluated
+/// over the full attribute snapshot. Has no single monitored attribute
+/// (<see cref="AlarmEvalConfig.MonitoredAttributeName"/> is empty); the
+/// compiled expression is passed into the actor and cached here.
+/// </summary>
+internal record ExpressionEvalConfig(
+    string MonitoredAttributeName,
+    string Expression,
+    Script<object?>? CompiledExpression) : AlarmEvalConfig(MonitoredAttributeName);
+
 /// <summary>
 /// HiLo evaluation config: any subset of the four setpoints may be set; null
 /// means "don't evaluate that band". Per-setpoint priorities override the