Improved the OpenAI provider (#548)

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

@@ -0,0 +1,62 @@
+using System.Text.Json;
+using System.Text.Json.Serialization;
+
+namespace AIStudio.Provider.OpenAI;
+
+/// <summary>
+/// Custom JSON converter for the annotation class to handle polymorphic deserialization.
+/// </summary>
+/// <remarks>
+/// We use this converter for chat completion API and responses API annotation deserialization.
+/// </remarks>
+public sealed class AnnotationConverter : JsonConverter<Annotation>
+{
+    public override Annotation? Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+    {
+        using var doc = JsonDocument.ParseValue(ref reader);
+        var root = doc.RootElement;
+        
+        if (!root.TryGetProperty("type", out var typeElement))
+            return null;
+        
+        var type = typeElement.GetString();
+        var rawText = root.GetRawText();
+        
+        Annotation? annotation;
+        switch (type)
+        {
+            case "url_citation":
+                
+                // Let's check the responses API data type first:
+                var responsesAnnotation = JsonSerializer.Deserialize<ResponsesAnnotatingUrlCitationData>(rawText, options);
+                
+                // If it fails, let's try the chat completion API data type:
+                if(responsesAnnotation is null || string.IsNullOrWhiteSpace(responsesAnnotation.Title) || string.IsNullOrWhiteSpace(responsesAnnotation.URL))
+                {
+                    // Try chat completion API data type:
+                    var chatCompletionAnnotation = JsonSerializer.Deserialize<ChatCompletionAnnotatingURL>(rawText, options);
+                    
+                    // If both fail, we return the unknown type:
+                    if(chatCompletionAnnotation is null)
+                        annotation = new AnnotatingUnknown(type);
+                    else
+                        annotation = chatCompletionAnnotation;
+                }
+                else
+                    annotation = responsesAnnotation;
+                
+                break;
+            
+            default:
+                annotation = new AnnotatingUnknown(type ?? "unknown");
+                break;
+        }
+
+        return annotation;
+    }
+
+    public override void Write(Utf8JsonWriter writer, Annotation value, JsonSerializerOptions options)
+    {
+        JsonSerializer.Serialize(writer, value, value.GetType(), options);
+    }
+}