feat(vertexai): support meta's llama models

packages/genkit_google_genai/lib/src/api_client.dart

@@ -62,15 +62,24 @@ class GenerativeLanguageBaseClient {
 
   Future<Map<String, dynamic>> listPublisherModels({
     required String projectId,
+    String publisher = 'google',
   }) async {
     // Vertex AI endpoint for publisher models uses v1beta1 and does not have the 'projects/...' in the path
     // when using this specific endpoint, but it requires the google user project header (or just works with ADC).
     // The base URL for this is https://{location}-aiplatform.googleapis.com
-    // And path is /v1beta1/publishers/google/models
-    final url = 'v1beta1/publishers/google/models';
+    // And path is /v1beta1/publishers/{publisher}/models
+    final safePublisher = Uri.encodeComponent(publisher);
+    final url = 'v1beta1/publishers/$safePublisher/models';
     return await _call('GET', url, null, {'x-goog-user-project': projectId});
   }
 
+  Future<Map<String, dynamic>> chatCompletions(
+    Map<String, dynamic> request,
+  ) async {
+    final url = '${apiUrlPrefix}chat/completions';
+    return await _call('POST', url, request);
+  }
+
   Future<Map<String, dynamic>> predict(
     Map<String, dynamic> request, {
     required String model,
@@ -197,4 +206,11 @@ class GenerativeLanguageBaseClient {
       status: StatusCodes.INTERNAL,
     );
   }
+
+  Stream<Map<String, dynamic>> streamChatCompletions(
+    Map<String, dynamic> request,
+  ) async* {
+    final url = '${apiUrlPrefix}chat/completions';
+    yield* _callStream('POST', url, request);
+  }
 }

packages/genkit_vertexai/lib/genkit_vertexai.dart

@@ -16,6 +16,7 @@ import 'package:genkit/plugin.dart';
 import 'package:genkit_google_genai/genkit_google_genai.dart';
 import 'package:http/http.dart' as http;
 
+import 'src/meta_model.dart';
 import 'src/vertex_api_client.dart';
 
 export 'package:genkit_google_genai/genkit_google_genai.dart'
@@ -31,6 +32,7 @@ export 'package:genkit_google_genai/genkit_google_genai.dart'
         TextEmbedderOptions,
         ThinkingConfig,
         VoiceConfig;
+export 'src/meta_model.dart' show VertexAiMetaOptions;
 
 const VertexAiPluginHandle vertexAI = VertexAiPluginHandle();
 
@@ -53,6 +55,14 @@ class VertexAiPluginHandle {
     return modelRef('vertexai/$name', customOptions: GeminiOptions.$schema);
   }
 
+  ModelRef<VertexAiMetaOptions> meta(String name) {
+    final modelName = name.startsWith('meta/') ? name.substring(5) : name;
+    return modelRef(
+      'vertexai/$modelName',
+      customOptions: VertexAiMetaOptions.$schema,
+    );
+  }
+
   EmbedderRef<TextEmbedderOptions> textEmbedding(String name) {
     return embedderRef(
       'vertexai/$name',