Add stream_options property to get token usage.

lib/src/core/models/chat/stream/chat.dart

@@ -1,6 +1,6 @@
 import 'package:collection/collection.dart';
 
-import 'sub_models/choices/choices.dart';
+import 'sub_models/usage.dart';
 
 export 'sub_models/choices/choices.dart';
 export 'sub_models/usage.dart';
@@ -21,6 +21,9 @@ final class OpenAIStreamChatCompletionModel {
   /// This fingerprint represents the backend configuration that the model runs with.
   final String? systemFingerprint;
 
+  /// An optional field that will only be present when you set `streamOptions: {"include_usage": true}` in your request. When present, it contains a null value except for the last chunk which contains the token usage statistics for the entire request.
+  final OpenAIStreamChatCompletionUsageModel? usage;
+
   /// Wether the chat completion have at least one choice in [choices].
   bool get haveChoices => choices.isNotEmpty;
 
@@ -41,6 +44,7 @@ final class OpenAIStreamChatCompletionModel {
     required this.created,
     required this.choices,
     required this.systemFingerprint,
+    this.usage,
   });
 
   /// {@macro openai_stream_chat_completion}
@@ -55,6 +59,9 @@ final class OpenAIStreamChatCompletionModel {
           )
           .toList(),
       systemFingerprint: json['system_fingerprint'],
+      usage: json['usage'] != null
+          ? OpenAIStreamChatCompletionUsageModel.fromMap(json['usage'])
+          : null,
     );
   }
 

lib/src/instance/chat/chat.dart

@@ -180,6 +180,7 @@ interface class OpenAIChat implements OpenAIChatBase {
     int? seed,
     String? user,
     http.Client? client,
+    Map<String, dynamic>? streamOptions,
   }) {
     return OpenAINetworkingClient.postStream<OpenAIStreamChatCompletionModel>(
       to: BaseApiUrlBuilder.build(endpoint),
@@ -201,6 +202,7 @@ interface class OpenAIChat implements OpenAIChatBase {
         if (user != null) "user": user,
         if (seed != null) "seed": seed,
         if (responseFormat != null) "response_format": responseFormat,
+        if (streamOptions != null && streamOptions.isNotEmpty) "stream_options": streamOptions,
       },
       onSuccess: (Map<String, dynamic> response) {
         return OpenAIStreamChatCompletionModel.fromMap(response);

test/openai_test.dart

@@ -331,6 +331,9 @@ void main() async {
     test('create with a stream', () async {
       final chatStream = OpenAI.instance.chat.createStream(
         model: "gpt-3.5-turbo",
+        streamOptions: {
+          "include_usage": true,
+        },
         messages: [
           OpenAIChatCompletionChoiceMessageModel(
             content: [
@@ -352,6 +355,13 @@ void main() async {
               isA<List<OpenAIChatCompletionChoiceMessageContentItemModel>?>());
           expect(streamEvent.choices.first.delta.content?.first?.text,
               isA<String?>());
+          if (streamEvent.usage != null) {
+            final u = streamEvent.usage!;
+            expect(u, isA<OpenAIStreamChatCompletionUsageModel>());
+            expect(u.promptTokens, greaterThan(0));
+            expect(u.completionTokens, greaterThan(0));
+            expect(u.totalTokens, equals(u.promptTokens + u.completionTokens));
+          }
         },
         onDone: () {
           completer.complete(true);