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

src/ScadaLink.SiteRuntime/Actors/ScriptActor.cs

@@ -1,10 +1,12 @@
 using Akka.Actor;
 using Microsoft.CodeAnalysis.Scripting;
+using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Logging;
 using ScadaLink.Commons.Messages.ScriptExecution;
 using ScadaLink.Commons.Messages.Streaming;
 using ScadaLink.Commons.Types.Flattening;
 using ScadaLink.HealthMonitoring;
+using ScadaLink.SiteEventLogging;
 using ScadaLink.SiteRuntime.Scripts;
 using System.Text.Json;
 
@@ -40,6 +42,12 @@ public class ScriptActor : ReceiveActor, IWithTimers
     private int _executionCounter;
     private readonly Commons.Types.Scripts.ScriptScope _scope;
 
+    // Expression trigger state: compiled expression, edge-tracking, and the
+    // attribute snapshot the expression evaluates against.
+    private readonly Script<object?>? _compiledTriggerExpression;
+    private bool _lastExpressionResult;
+    private readonly Dictionary<string, object?> _attributeSnapshot = new();
+
     public ITimerScheduler Timers { get; set; } = null!;
 
     public ScriptActor(
@@ -51,6 +59,7 @@ public class ScriptActor : ReceiveActor, IWithTimers
         SharedScriptLibrary sharedScriptLibrary,
         SiteRuntimeOptions options,
         ILogger logger,
+        Script<object?>? compiledTriggerExpression = null,
         ISiteHealthCollector? healthCollector = null,
         IServiceProvider? serviceProvider = null)
     {
@@ -65,6 +74,7 @@ public class ScriptActor : ReceiveActor, IWithTimers
         _serviceProvider = serviceProvider;
         _minTimeBetweenRuns = scriptConfig.MinTimeBetweenRuns;
         _scope = scriptConfig.Scope;
+        _compiledTriggerExpression = compiledTriggerExpression;
 
         // Parse trigger configuration
         _triggerConfig = ParseTriggerConfig(scriptConfig.TriggerType, scriptConfig.TriggerConfiguration);
@@ -143,10 +153,15 @@ public class ScriptActor : ReceiveActor, IWithTimers
     }
 
     /// <summary>
-    /// Handles attribute value changes — triggers script if configured for value-change or conditional.
+    /// Handles attribute value changes — triggers script if configured for
+    /// value-change, conditional, or expression. The attribute snapshot is
+    /// updated for every change before any trigger logic runs.
     /// </summary>
     private void HandleAttributeValueChanged(AttributeValueChanged changed)
     {
+        // Keep the snapshot current for every change, regardless of trigger type.
+        _attributeSnapshot[changed.AttributeName] = changed.Value;
+
         if (_triggerConfig is ValueChangeTriggerConfig valueTrigger)
         {
             if (valueTrigger.AttributeName == changed.AttributeName)
@@ -165,6 +180,55 @@ public class ScriptActor : ReceiveActor, IWithTimers
                 }
             }
         }
+        else if (_triggerConfig is ExpressionTriggerConfig)
+        {
+            EvaluateExpressionTrigger();
+        }
+    }
+
+    /// <summary>
+    /// Evaluates the compiled trigger expression against the current attribute
+    /// snapshot and runs the script edge-triggered — once per false→true
+    /// transition. A throwing or non-bool expression is treated as false and
+    /// logged as a script error; the actor never crashes.
+    /// </summary>
+    private void EvaluateExpressionTrigger()
+    {
+        if (_compiledTriggerExpression == null) return;
+
+        bool result;
+        try
+        {
+            var globals = new TriggerExpressionGlobals(_attributeSnapshot);
+            var state = _compiledTriggerExpression.RunAsync(globals).GetAwaiter().GetResult();
+            result = state.ReturnValue is bool b && b;
+        }
+        catch (Exception ex)
+        {
+            LogExpressionError(ex);
+            result = false;
+        }
+
+        if (result && !_lastExpressionResult)
+        {
+            TrySpawnExecution(null);
+        }
+
+        _lastExpressionResult = result;
+    }
+
+    /// <summary>
+    /// Records a trigger-expression evaluation failure to the site event log,
+    /// mirroring how ScriptExecutionActor reports script errors.
+    /// </summary>
+    private void LogExpressionError(Exception ex)
+    {
+        _healthCollector?.IncrementScriptError();
+        var errorMsg = $"Trigger expression for script '{_scriptName}' on instance '{_instanceName}' failed: {ex.Message}";
+        _logger.LogError(ex, "Trigger expression evaluation failed: {Script} on {Instance}", _scriptName, _instanceName);
+
+        _ = _serviceProvider?.GetService<ISiteEventLogger>()?.LogEventAsync(
+            "script", "Error", _instanceName, $"ScriptActor:{_scriptName}", errorMsg, ex.ToString());
     }
 
     /// <summary>
@@ -264,11 +328,26 @@ public class ScriptActor : ReceiveActor, IWithTimers
             "interval" => ParseIntervalTrigger(triggerConfigJson),
             "valuechange" => ParseValueChangeTrigger(triggerConfigJson),
             "conditional" => ParseConditionalTrigger(triggerConfigJson),
+            "expression" => ParseExpressionTrigger(triggerConfigJson),
             "call" => null, // No automatic trigger — invoked only via Instance.CallScript()
             _ => null
         };
     }
 
+    private static ExpressionTriggerConfig? ParseExpressionTrigger(string? json)
+    {
+        if (string.IsNullOrEmpty(json)) return null;
+        try
+        {
+            var doc = JsonDocument.Parse(json);
+            var expr = doc.RootElement.TryGetProperty("expression", out var e)
+                ? e.GetString()
+                : null;
+            return string.IsNullOrWhiteSpace(expr) ? null : new ExpressionTriggerConfig(expr);
+        }
+        catch { return null; }
+    }
+
     private static IntervalTriggerConfig? ParseIntervalTrigger(string? json)
     {
         if (string.IsNullOrEmpty(json)) return null;
@@ -323,4 +402,5 @@ public class ScriptActor : ReceiveActor, IWithTimers
 internal record IntervalTriggerConfig(TimeSpan Interval) : ScriptTriggerConfig;
 internal record ValueChangeTriggerConfig(string AttributeName) : ScriptTriggerConfig;
 internal record ConditionalTriggerConfig(string AttributeName, string Operator, double Threshold) : ScriptTriggerConfig;
+internal record ExpressionTriggerConfig(string Expression) : ScriptTriggerConfig;
 internal abstract record ScriptTriggerConfig;