add an experimental gemini call to the backend

pkgs/dart_services/Dockerfile

@@ -1,6 +1,7 @@
 ARG PROJECT_ID
 ARG FLUTTER_CHANNEL
 ARG BUILD_SHA
+ARG GOOGLE_API_KEY
 
 FROM gcr.io/$PROJECT_ID/flutter:$FLUTTER_CHANNEL
 
@@ -16,6 +17,7 @@ RUN dart compile exe bin/server.dart -o bin/server
 RUN dart run grinder build-project-templates
 
 ENV BUILD_SHA=$BUILD_SHA
+ENV GOOGLE_API_KEY=$GOOGLE_API_KEY
 
 EXPOSE 8080
 CMD ["/app/bin/server"]

pkgs/dart_services/README.md

@@ -43,12 +43,6 @@ To rebuild the shelf router, run:
 dart run build_runner build --delete-conflicting-outputs
 ```
 
-And to update the shared code from dartpad_shared, run:
-
-```
-dart tool/grind.dart copy-shared-source
-```
-
 ### Modifying supported packages
 
 Package dependencies are pinned using the `pub_dependencies_<CHANNEL>.yaml`

pkgs/dart_services/analysis_options.yaml

@@ -17,3 +17,4 @@ linter:
   rules:
     - prefer_final_in_for_each
     - prefer_final_locals
+    - sort_pub_dependencies

pkgs/dart_services/lib/src/common_server.dart

@@ -10,6 +10,8 @@ import 'package:dartpad_shared/model.dart' as api;
 import 'package:logging/logging.dart';
 import 'package:shelf/shelf.dart';
 import 'package:shelf_router/shelf_router.dart';
+import 'package:google_generative_ai/google_generative_ai.dart' as google_ai;
+import 'package:http/http.dart' as http;
 
 import 'analysis.dart';
 import 'caching.dart';
@@ -200,6 +202,54 @@ class CommonServerApi {
     return ok(version().toJson());
   }
 
+  static String? googleApiKey = Platform.environment['GOOGLE_API_KEY'];
+  http.Client? geminiHttpClient;
+
+  @Route.post('$apiPrefix/_gemini')
+  Future<Response> gemini(Request request, String apiVersion) async {
+    if (apiVersion != api3) return unhandledVersion(apiVersion);
+
+    // Read the api key from env variables (populated on the server).
+    final apiKey = googleApiKey;
+    if (apiKey == null) {
+      return Response.internalServerError(
+          body: 'gemini key not configured on server');
+    }
+
+    // Only allow the call from known clients / endpoints.
+    const firebaseHostAddress = '199.36.158.100';
+    const localHostAddress = '127.0.0.1';
+
+    final clientAddress = request.shelfClientAddress ?? '';
+    if (clientAddress != firebaseHostAddress &&
+        clientAddress != localHostAddress) {
+      return Response.badRequest(
+          body: 'gemini calls only allowed from the DartPad frontend');
+    }
+
+    final sourceRequest =
+        api.SourceRequest.fromJson(await request.readAsJson());
+
+    geminiHttpClient ??= http.Client();
+
+    final model = google_ai.GenerativeModel(
+      model: 'models/gemini-1.5-flash-latest',
+      apiKey: apiKey,
+      httpClient: geminiHttpClient,
+    );
+
+    final result = await serialize(() async {
+      // call gemini
+      final result = await model.generateContent([
+        google_ai.Content.text(sourceRequest.source),
+      ]);
+
+      return api.GeminiResponse(response: result.text!);
+    });
+
+    return ok(result.toJson());
+  }
+
   Response ok(Map<String, dynamic> json) {
     return Response.ok(
       _jsonEncoder.convert(json),
@@ -327,3 +377,11 @@ String _formatMessage(
 
   return message;
 }
+
+extension on Request {
+  /// Return the IP address of the request client.
+  String? get shelfClientAddress =>
+      (context['shelf.io.connection_info'] as HttpConnectionInfo?)
+          ?.remoteAddress
+          .address;
+}

pkgs/dart_services/pubspec.yaml

@@ -12,6 +12,7 @@ dependencies:
   bazel_worker: ^1.1.1
   dartpad_shared: any
   encrypt: ^5.0.3
+  google_generative_ai: ^0.4.0  
   http: ^1.2.1
   json_annotation: any
   logging: ^1.2.0

pkgs/dartpad_shared/lib/model.dart

@@ -375,6 +375,23 @@ class VersionResponse {
   Map<String, dynamic> toJson() => _$VersionResponseToJson(this);
 }
 
+@JsonSerializable()
+class GeminiResponse {
+  final String response;
+
+  GeminiResponse({
+    required this.response,
+  });
+
+  factory GeminiResponse.fromJson(Map<String, dynamic> json) =>
+      _$GeminiResponseFromJson(json);
+
+  Map<String, dynamic> toJson() => _$GeminiResponseToJson(this);
+
+  @override
+  String toString() => 'GeminiResponse[response=$response]';
+}
+
 @JsonSerializable()
 class PackageInfo {
   final String name;

pkgs/dartpad_shared/lib/services.dart

@@ -40,6 +40,11 @@ class ServicesClient {
   Future<CompileDDCResponse> compileDDC(CompileRequest request) =>
       _requestPost('compileDDC', request.toJson(), CompileDDCResponse.fromJson);
 
+  /// Note: this API is experimental and could change or be removed at any time.
+  @experimental
+  Future<GeminiResponse> gemini(SourceRequest request) =>
+      _requestPost('_gemini', request.toJson(), GeminiResponse.fromJson);
+
   void dispose() => client.close();
 
   Future<T> _requestGet<T>(
@@ -92,3 +97,9 @@ class ApiRequestError implements Exception {
   @override
   String toString() => '$message: $body';
 }
+
+class _Experimental {
+  const _Experimental();
+}
+
+const _Experimental experimental = _Experimental();

pkgs/dartpad_ui/lib/model.dart

@@ -317,6 +317,10 @@ class AppServices {
     return await services.document(request);
   }
 
+  Future<GeminiResponse> gemini(SourceRequest request) async {
+    return await services.gemini(request);
+  }
+
   Future<CompileResponse> compile(CompileRequest request) async {
     try {
       appModel.compilingBusy.value = true;