From b032d7fe48fa3e071d5b480e7c64aa07eb8e951c Mon Sep 17 00:00:00 2001
From: Joseph Doherty <dohejw01@gmail.com>
Date: Thu, 22 Oct 2026 08:37:20 -0400
Subject: [PATCH] fix(centralui): bound FlowDebugService script cache (review
 2026-10-21 07/M-2)

---
 .../Services/FlowDebugService.cs               | 11 +++++++++++
 .../Services/FlowDebugServiceTests.cs          | 18 ++++++++++++++++++
 2 files changed, 29 insertions(+)

diff --git a/src/ZB.MOM.WW.ScadaBridge.CentralUI/Services/FlowDebugService.cs b/src/ZB.MOM.WW.ScadaBridge.CentralUI/Services/FlowDebugService.cs
index 4c7c106c..f0c090c2 100644
--- a/src/ZB.MOM.WW.ScadaBridge.CentralUI/Services/FlowDebugService.cs
+++ b/src/ZB.MOM.WW.ScadaBridge.CentralUI/Services/FlowDebugService.cs
@@ -107,6 +107,13 @@ public sealed class FlowDebugService : IFlowDebugService
     /// </summary>
     private readonly Dictionary<int, InstanceScripts> _scriptCache = new();
 
+    /// <summary>
+    /// Ceiling on <see cref="_scriptCache"/> entries (review 2026-10-21 07/M-2). Only the most
+    /// recently selected instance is ever read back, so a small bound loses nothing; reaching it
+    /// drops the whole cache before the new entry goes in.
+    /// </summary>
+    internal const int ScriptCacheCapacity = 8;
+
     /// <summary>One instance's flattened scripts: the unique name the site keys on, the raw resolved scripts, and the picker projection.</summary>
     private sealed record InstanceScripts(
         string UniqueName,
@@ -484,6 +491,10 @@ public sealed class FlowDebugService : IFlowDebugService
             .ToList();
 
         var loaded = new InstanceScripts(instance.UniqueName, scripts, options);
+        if (_scriptCache.Count >= ScriptCacheCapacity && !_scriptCache.ContainsKey(instanceId))
+        {
+            _scriptCache.Clear();
+        }
         _scriptCache[instanceId] = loaded;
         return loaded;
     }
diff --git a/tests/ZB.MOM.WW.ScadaBridge.CentralUI.Tests/Services/FlowDebugServiceTests.cs b/tests/ZB.MOM.WW.ScadaBridge.CentralUI.Tests/Services/FlowDebugServiceTests.cs
index a194447e..4b940953 100644
--- a/tests/ZB.MOM.WW.ScadaBridge.CentralUI.Tests/Services/FlowDebugServiceTests.cs
+++ b/tests/ZB.MOM.WW.ScadaBridge.CentralUI.Tests/Services/FlowDebugServiceTests.cs
@@ -677,6 +677,24 @@ public sealed class FlowDebugServiceTests : IDisposable
         Assert.False(options.Single(o => o.CanonicalName == "Mod.Tick").IsWriteKind);
     }
 
+    /// <summary>Verifies the per-circuit script cache stays bounded however many instances are browsed (review 2026-10-21 07/M-2).</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
+    [Fact]
+    public async Task GetInstanceScripts_BrowsingManyInstances_KeepsCacheBounded()
+    {
+        var svc = CreateService(reply: null);
+        for (var id = 100; id < 100 + 3 * FlowDebugService.ScriptCacheCapacity; id++)
+        {
+            WireFlattened(id, "Sim" + id, new ResolvedScript { CanonicalName = "Manual", Code = "x", TriggerType = "Call" });
+            await svc.GetInstanceScriptsAsync(id);
+        }
+
+        var cache = (System.Collections.IDictionary)typeof(FlowDebugService)
+            .GetField("_scriptCache", System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.NonPublic)!
+            .GetValue(svc)!;
+        Assert.True(cache.Count <= FlowDebugService.ScriptCacheCapacity);
+    }
+
     /// <summary>Verifies that requesting scripts for an unknown instance yields an empty result.</summary>
     /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]