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

src/ScadaLink.SiteRuntime/Scripts/TriggerExpressionGlobals.cs

@@ -0,0 +1,74 @@
+namespace ScadaLink.SiteRuntime.Scripts;
+
+/// <summary>
+/// Read-only globals a trigger expression is compiled against. Exposes only
+/// attribute reads, backed by an in-memory snapshot — no I/O, no actor Ask,
+/// no side-effecting APIs. A missing attribute key reads as <c>null</c> and
+/// never throws.
+///
+/// Canonical attribute keys are dotted (e.g. "TempSensor.Reading"); the prefix
+/// logic here mirrors <see cref="AttributeAccessor.Resolve"/>.
+/// </summary>
+public sealed class TriggerExpressionGlobals
+{
+    private readonly IReadOnlyDictionary<string, object?> _snapshot;
+
+    public TriggerExpressionGlobals(IReadOnlyDictionary<string, object?> snapshot)
+        => _snapshot = snapshot;
+
+    /// <summary>Attributes in the expression's own scope (root prefix).</summary>
+    public ReadOnlyAttributes Attributes => new(_snapshot, "");
+
+    /// <summary>Indexed access to child compositions' attributes.</summary>
+    public ReadOnlyChildren Children => new(_snapshot);
+
+    /// <summary>
+    /// Parent composition (null at root). Set by the caller for derived/composed
+    /// scopes; the runtime actors evaluate at root scope, so this stays null.
+    /// </summary>
+    public ReadOnlyComposition? Parent { get; init; }
+
+    /// <summary>
+    /// Read-only attribute view anchored at a canonical-name prefix. Indexing
+    /// resolves to the canonical key ("" → key, "TempSensor" → "TempSensor.key").
+    /// </summary>
+    public sealed class ReadOnlyAttributes
+    {
+        private readonly IReadOnlyDictionary<string, object?> _s;
+        private readonly string _prefix;
+
+        public ReadOnlyAttributes(IReadOnlyDictionary<string, object?> s, string prefix)
+        {
+            _s = s;
+            _prefix = prefix;
+        }
+
+        public object? this[string key] =>
+            _s.TryGetValue(_prefix.Length == 0 ? key : _prefix + "." + key, out var v) ? v : null;
+    }
+
+    /// <summary>A read-only view of one composition at a canonical-name path.</summary>
+    public sealed class ReadOnlyComposition
+    {
+        private readonly IReadOnlyDictionary<string, object?> _s;
+        private readonly string _path;
+
+        public ReadOnlyComposition(IReadOnlyDictionary<string, object?> s, string path)
+        {
+            _s = s;
+            _path = path;
+        }
+
+        public ReadOnlyAttributes Attributes => new(_s, _path);
+    }
+
+    /// <summary>Dictionary-style accessor for child compositions.</summary>
+    public sealed class ReadOnlyChildren
+    {
+        private readonly IReadOnlyDictionary<string, object?> _s;
+
+        public ReadOnlyChildren(IReadOnlyDictionary<string, object?> s) => _s = s;
+
+        public ReadOnlyComposition this[string compositionName] => new(_s, compositionName);
+    }
+}