Let tool results restrict a chat to self-hosted providers

app/Tests/Chat/ChatThreadDataSecurityTests.cs

@@ -0,0 +1,52 @@
+using AIStudio.Chat;
+using AIStudio.Settings.DataModel;
+
+namespace AIStudio.Tests.Chat;
+
+/// <summary>
+/// Checks how the data a chat has seen tightens the providers which may continue it.
+/// </summary>
+/// <remarks>
+/// A chat which once held data for self-hosted providers only must never be sent to any other
+/// provider again, whatever it brings in afterwards. The RAG process and Semantic Search both go
+/// through the same rule, so every combination of what a chat holds and what arrives is checked.
+/// </remarks>
+[TestFixture]
+public sealed class ChatThreadDataSecurityTests
+{
+    [TestCase(DataSourceSecurity.NOT_SPECIFIED, DataSourceSecurity.SELF_HOSTED, DataSourceSecurity.SELF_HOSTED)]
+    [TestCase(DataSourceSecurity.ALLOW_ANY, DataSourceSecurity.SELF_HOSTED, DataSourceSecurity.SELF_HOSTED)]
+    [TestCase(DataSourceSecurity.SELF_HOSTED, DataSourceSecurity.SELF_HOSTED, DataSourceSecurity.SELF_HOSTED)]
+    public void DataForSelfHostedProvidersOnlyRestrictsTheChat(DataSourceSecurity held, DataSourceSecurity arriving, DataSourceSecurity expected)
+    {
+        Assert.That(Tightened(held, arriving), Is.EqualTo(expected));
+    }
+
+    [TestCase(DataSourceSecurity.SELF_HOSTED, DataSourceSecurity.ALLOW_ANY)]
+    [TestCase(DataSourceSecurity.SELF_HOSTED, DataSourceSecurity.NOT_SPECIFIED)]
+    public void ARestrictionStays(DataSourceSecurity held, DataSourceSecurity arriving)
+    {
+        Assert.That(Tightened(held, arriving), Is.EqualTo(DataSourceSecurity.SELF_HOSTED), "The restricted data was seen by this chat. What arrives later cannot undo that.");
+    }
+
+    [TestCase(DataSourceSecurity.NOT_SPECIFIED)]
+    [TestCase(DataSourceSecurity.ALLOW_ANY)]
+    public void DataForAnyProviderMarksTheChat(DataSourceSecurity held)
+    {
+        Assert.That(Tightened(held, DataSourceSecurity.ALLOW_ANY), Is.EqualTo(DataSourceSecurity.ALLOW_ANY));
+    }
+
+    [TestCase(DataSourceSecurity.NOT_SPECIFIED)]
+    [TestCase(DataSourceSecurity.ALLOW_ANY)]
+    public void ResultsWhichDemandNothingChangeNothing(DataSourceSecurity held)
+    {
+        Assert.That(Tightened(held, DataSourceSecurity.NOT_SPECIFIED), Is.EqualTo(held), "A web search, say, says nothing about data sources and must leave the chat as it was.");
+    }
+
+    private static DataSourceSecurity Tightened(DataSourceSecurity held, DataSourceSecurity arriving)
+    {
+        var thread = new ChatThread { DataSecurity = held };
+        thread.RequireDataSecurity(arriving);
+        return thread.DataSecurity;
+    }
+}