func NewClient()

in lib/backend/s3backend/client.go [89:149]
50 lines of code
11 McCabe index (conditional complexity)

func NewClient(
	config Config, userAuth UserAuthConfig, stats tally.Scope, opts ...Option) (*Client, error) {

	config.applyDefaults()
	if config.Username == "" {
		return nil, errors.New("invalid config: username required")
	}
	if config.Region == "" {
		return nil, errors.New("invalid config: region required")
	}
	if config.Bucket == "" {
		return nil, errors.New("invalid config: bucket required")
	}
	if !path.IsAbs(config.RootDirectory) {
		return nil, errors.New("invalid config: root_directory must be absolute path")
	}

	pather, err := namepath.New(config.RootDirectory, config.NamePath)
	if err != nil {
		return nil, fmt.Errorf("namepath: %s", err)
	}

	auth, ok := userAuth[config.Username]
	if !ok {
		return nil, errors.New("auth not configured for username")
	}
	creds := credentials.NewStaticCredentials(
		auth.S3.AccessKeyID, auth.S3.AccessSecretKey, auth.S3.SessionToken)

	awsConfig := aws.NewConfig().WithRegion(config.Region).WithCredentials(creds)

	if config.Endpoint != "" {
		awsConfig = awsConfig.WithEndpoint(config.Endpoint)
	}

	if config.DisableSSL {
		awsConfig = awsConfig.WithDisableSSL(config.DisableSSL)
	}

	if config.S3ForcePathStyle {
		awsConfig = awsConfig.WithS3ForcePathStyle(config.S3ForcePathStyle)
	}

	api := s3.New(session.New(), awsConfig)

	downloader := s3manager.NewDownloaderWithClient(api, func(d *s3manager.Downloader) {
		d.PartSize = config.DownloadPartSize
		d.Concurrency = config.DownloadConcurrency
	})

	uploader := s3manager.NewUploaderWithClient(api, func(u *s3manager.Uploader) {
		u.PartSize = config.UploadPartSize
		u.Concurrency = config.UploadConcurrency
	})

	client := &Client{config, pather, stats, join{api, downloader, uploader}}
	for _, opt := range opts {
		opt(client)
	}
	return client, nil
}