google_cloud/example/example.dart

// Copyright (c) 2021, the Dart project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

import 'dart:convert';

import 'package:google_cloud/google_cloud.dart';
import 'package:googleapis/firestore/v1.dart';
import 'package:googleapis_auth/auth_io.dart';
import 'package:shelf/shelf.dart';

Future<void> main() async {
  final server = await _Server.create();

  try {
    await serveHandler(server.handler);
  } finally {
    server.close();
  }
}

class _Server {
  _Server._({
    required this.projectId,
    required this.client,
    required this.hosted,
  });

  static Future<_Server> create() async {
    String? projectId;
    bool hosted;

    try {
      projectId = await projectIdFromMetadataServer();
      hosted = true;
    } on BadConfigurationException {
      projectId = projectIdFromEnvironment();
      hosted = false;
    }

    if (projectId == null) {
      throw BadConfigurationException(
        '''
Could not contact GCP metadata server or find the project-id in one of these
environment variables:
  ${gcpProjectIdEnvironmentVariables.join('\n  ')}''',
      );
    }

    print('Current GCP project id: $projectId');

    final authClient = await clientViaApplicationDefaultCredentials(
      scopes: [FirestoreApi.datastoreScope],
    );

    return _Server._(projectId: projectId, client: authClient, hosted: hosted);
  }

  final String projectId;
  final AutoRefreshingAuthClient client;
  final bool hosted;

  late final FirestoreApi api = FirestoreApi(client);
  late final handler =
      createLoggingMiddleware(projectId: hosted ? projectId : null)
          .addMiddleware(_onlyGetRootMiddleware)
          .addHandler(_incrementHandler);

  Future<Response> _incrementHandler(Request request) async {
    final result = await api.projects.databases.documents.commit(
      _incrementRequest(projectId),
      'projects/$projectId/databases/(default)',
    );

    return Response.ok(
      JsonUtf8Encoder(' ').convert(result),
      headers: {'content-type': 'application/json'},
    );
  }

  void close() {
    client.close();
  }
}

/// For `GET` `request` objects to [handler], otherwise sends a 404.
Handler _onlyGetRootMiddleware(Handler handler) => (Request request) async {
      if (request.method == 'GET' && request.url.pathSegments.isEmpty) {
        return await handler(request);
      }

      throw BadRequestException(404, 'Not found');
    };

CommitRequest _incrementRequest(String projectId) => CommitRequest(
      writes: [
        Write(
          transform: DocumentTransform(
            document:
                'projects/$projectId/databases/(default)/documents/settings/count',
            fieldTransforms: [
              FieldTransform(
                fieldPath: 'count',
                increment: Value(integerValue: '1'),
              ),
            ],
          ),
        ),
      ],
    );