app_dart/lib/src/service/access_token_provider.dart

// Copyright 2019 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

import 'package:googleapis_auth/auth_io.dart';
import 'package:http/http.dart' as http;

import 'config.dart';

/// Function signature for a [TaskService] provider.
typedef AccessTokenServiceProvider = AccessTokenService Function(Config config);

/// A provider for Oauth2 tokens from Service Account JSON.
class AccessTokenService {
  /// Creates a new Access Token provider.
  const AccessTokenService(this.config);

  /// The Cocoon configuration.
  final Config config;

  /// Creates and returns a [AccessTokenService] using a [Config] object.
  static AccessTokenService defaultProvider(Config config) {
    return AccessTokenService(config);
  }

  /// Returns an OAuth 2.0 access token for the device lab service account.
  Future<AccessToken> createAccessToken() async {
    final http.Client httpClient = http.Client();
    try {
      final AccessCredentials credentials = await obtainAccessCredentialsViaMetadataServer(httpClient);
      return credentials.accessToken;
    } finally {
      httpClient.close();
    }
  }
}