Add the model matching engine and make capabilities a flags enum

app/Tests/Models/ModelFactsTests.cs

@@ -0,0 +1,101 @@
+using AIStudio.Models;
+
+namespace AIStudio.Tests.Models;
+
+/// <summary>
+/// Checks the three types which have to be able to say "nobody knows".
+/// </summary>
+/// <remarks>
+/// They are tested together because they are tested for the same thing. Each of them is a value
+/// type sitting inside a model profile, so each of them has a default value somebody will read
+/// before anything was written into it, and that default has to mean unknown rather than zero. The
+/// day one of them answers "a context window of zero tokens" instead, a feature built on top of it
+/// will quietly do the wrong thing.
+/// </remarks>
+[TestFixture]
+public sealed class ModelFactsTests
+{
+    [Test]
+    public void AContextWindowNobodyWroteDownIsUnknown()
+    {
+        ContextWindow untouched = default;
+
+        Assert.Multiple(() =>
+        {
+            Assert.That(untouched.IsKnown, Is.False);
+            Assert.That(untouched, Is.EqualTo(ContextWindow.UNKNOWN));
+        });
+    }
+
+    [Test]
+    public void AContextWindowStatesWhatItShipsWithAndWhatItCanBeRaisedTo()
+    {
+        var window = ContextWindow.Of(128_000, 1_000_000);
+
+        Assert.Multiple(() =>
+        {
+            Assert.That(window.IsKnown, Is.True);
+            Assert.That(window.DefaultTokens, Is.EqualTo(128_000));
+            Assert.That(window.RaisableToTokens, Is.EqualTo(1_000_000));
+        });
+    }
+
+    [Test]
+    public void AContextWindowWhichCannotBeRaisedSaysSoWithNothingRatherThanWithItsOwnSize()
+    {
+        var window = ContextWindow.Of(32_768);
+
+        Assert.That(window.RaisableToTokens, Is.Null);
+    }
+
+    [Test]
+    public void AContextWindowOfNoTokensCannotBeStated() => Assert.Throws<ArgumentOutOfRangeException>(() => ContextWindow.Of(0));
+
+    [Test]
+    public void AContextWindowCannotBeRaisedToLessThanItAlreadyIs() => Assert.Throws<ArgumentOutOfRangeException>(() => ContextWindow.Of(128_000, 32_768));
+
+    [Test]
+    public void ATokenizerNobodyWroteDownIsTheBuiltInOne()
+    {
+        TokenizerRef untouched = default;
+
+        Assert.Multiple(() =>
+        {
+            Assert.That(untouched.IsKnown, Is.False);
+            Assert.That(untouched.Kind, Is.EqualTo(TokenizerKind.UNKNOWN));
+        });
+    }
+
+    [Test]
+    public void ATokenizerWithoutANameIsNotKnownEvenWhenItsKindIs()
+    {
+        var nameless = new TokenizerRef(TokenizerKind.HUGGING_FACE, string.Empty);
+
+        Assert.That(nameless.IsKnown, Is.False);
+    }
+
+    [Test]
+    public void ImageLimitsNobodyWroteDownAreUnknown()
+    {
+        ImageLimits untouched = default;
+
+        Assert.Multiple(() =>
+        {
+            Assert.That(untouched.IsKnown, Is.False);
+            Assert.That(untouched.MaxPerMessage, Is.Null);
+            Assert.That(untouched.MaxPerRequest, Is.Null);
+        });
+    }
+
+    [Test]
+    public void ImageLimitsTellNoImagesApartFromNobodyHavingSaid()
+    {
+        var noImages = new ImageLimits(MaxPerMessage: 0, MaxPerRequest: null);
+
+        Assert.Multiple(() =>
+        {
+            Assert.That(noImages.IsKnown, Is.True, "Zero images is a statement an operator can make.");
+            Assert.That(noImages.MaxPerMessage, Is.EqualTo(0));
+        });
+    }
+}