Add one model host per provider and the unwrapping walk

app/MindWork AI Studio/Models/Hosting/ModelHost.cs

@@ -0,0 +1,68 @@
+using AIStudio.Models.Matching;
+using AIStudio.Provider;
+
+namespace AIStudio.Models.Hosting;
+
+/// <summary>
+/// The ordinary host: it serves models under the names they are known by, through the ordinary API.
+/// </summary>
+/// <remarks>
+/// Most hosts differ from each other in one sentence, and this is what carries the rest. A host
+/// which wraps its names says how to unwrap one; a host which speaks an API the others do not says
+/// so; everything else is stated here once.
+///
+/// What a source means for a host: the page names where the behaviour is documented, so that a
+/// person can re-check it in a minute. The statements themselves were read off the app's own
+/// provider implementations and the model corpus, both of which are in this repository -- the
+/// pages are where somebody looks when they doubt them.
+/// </remarks>
+public abstract class ModelHost : IModelHost
+{
+    /// <summary>
+    /// The two capabilities which say through which API a model is reached.
+    /// </summary>
+    private const Capability THE_APIS = Capability.CHAT_COMPLETION_API | Capability.RESPONSES_API;
+
+    /// <inheritdoc />
+    public abstract LLMProviders Provider { get; }
+
+    /// <inheritdoc />
+    public abstract ModelSource Source { get; }
+
+    /// <inheritdoc />
+    /// <remarks>
+    /// Nothing is wrapped here: this host serves models under the names they are known by.
+    /// </remarks>
+    public virtual bool TryUnwrap(in ModelId id, out ModelId inner, out ModelVendor? declaredVendor)
+    {
+        inner = id;
+        declaredVendor = null;
+        return false;
+    }
+
+    /// <inheritdoc />
+    /// <remarks>
+    /// The Responses API is OpenAI's own, and the app speaks it in exactly one place, its OpenAI
+    /// provider. Wherever else a model is reached, it is reached through the ordinary chat
+    /// completion API -- whatever the model itself could do at its vendor.
+    /// </remarks>
+    public virtual ModelProfile ApplyTransport(in ModelProfile profile) => ThroughTheOrdinaryApi(profile);
+
+    /// <summary>
+    /// Puts a profile on the ordinary chat completion API.
+    /// </summary>
+    /// <remarks>
+    /// A profile which says nothing about APIs is left alone. An embedding model is reached through
+    /// neither of the two, and answering that it speaks the chat completion API would be a claim
+    /// nobody made.
+    /// </remarks>
+    /// <param name="profile">What the model can do.</param>
+    /// <returns>What it can do when reached through the ordinary API.</returns>
+    public static ModelProfile ThroughTheOrdinaryApi(in ModelProfile profile)
+    {
+        if (!profile.HasAny(THE_APIS))
+            return profile;
+
+        return profile with { Capabilities = (profile.Capabilities & ~Capability.RESPONSES_API) | Capability.CHAT_COMPLETION_API };
+    }
+}