Improved the OpenAI provider (#548)

app/MindWork AI Studio/Provider/OpenAI/ChatCompletionDeltaStreamLine.cs

@@ -0,0 +1,45 @@
+namespace AIStudio.Provider.OpenAI;
+
+/// <summary>
+/// Data model for a delta line in the chat completion response stream.
+/// </summary>
+/// <param name="Id">The id of the response.</param>
+/// <param name="Object">The object describing the response.</param>
+/// <param name="Created">The timestamp of the response.</param>
+/// <param name="Model">The model used for the response.</param>
+/// <param name="SystemFingerprint">The system fingerprint; together with the seed, this allows you to reproduce the response.</param>
+/// <param name="Choices">The choices made by the AI.</param>
+public record ChatCompletionDeltaStreamLine(string Id, string Object, uint Created, string Model, string SystemFingerprint, IList<ChatCompletionChoice> Choices) : IResponseStreamLine
+{
+    public ChatCompletionDeltaStreamLine() : this(string.Empty, string.Empty, 0, string.Empty, string.Empty, [])
+    {
+    }
+    
+    /// <inheritdoc />
+    public bool ContainsContent() => this.Choices.Count > 0;
+
+    /// <inheritdoc />
+    public ContentStreamChunk GetContent() => new(this.Choices[0].Delta.Content, []);
+
+    #region Implementation of IAnnotationStreamLine
+
+    //
+    // Please note that there are multiple options where LLM providers might stream sources:
+    //
+    // - As part of the delta content while streaming. That would be part of this class.
+    // - By using a dedicated stream event and data structure. That would be another class implementing IResponseStreamLine.
+    //
+    // Right now, OpenAI uses the latter approach, so we don't have any sources here. And
+    // because no other provider does it yet, we don't have any implementation here either.
+    //
+    // One example where sources are part of the delta content is the Perplexity provider.
+    //
+    
+    /// <inheritdoc />
+    public bool ContainsSources() => false;
+
+    /// <inheritdoc />
+    public IList<ISource> GetSources() => [];
+
+    #endregion
+}