1 files changed, 88 insertions, 0 deletions
diff --git a/tvix/nar-bridge-go/pkg/importer/directory_upload.go b/tvix/nar-bridge-go/pkg/importer/directory_upload.go
new file mode 100644
index 000000000000..117f442fa54f
--- /dev/null
+++ b/tvix/nar-bridge-go/pkg/importer/directory_upload.go
@@ -0,0 +1,88 @@
+package importer
+
+import (
+	"bytes"
+	"context"
+	"encoding/base64"
+	"fmt"
+
+	castorev1pb "code.tvl.fyi/tvix/castore-go"
+	log "github.com/sirupsen/logrus"
+)
+
+// DirectoriesUploader opens a Put stream when it receives the first Put() call,
+// and then uses the opened stream for subsequent Put() calls.
+// When the uploading is finished, a call to Done() will close the stream and
+// return the root digest returned from the directoryServiceClient.
+type DirectoriesUploader struct {
+	ctx                       context.Context
+	directoryServiceClient    castorev1pb.DirectoryServiceClient
+	directoryServicePutStream castorev1pb.DirectoryService_PutClient
+	lastDirectoryDigest       []byte
+}
+
+func NewDirectoriesUploader(ctx context.Context, directoryServiceClient castorev1pb.DirectoryServiceClient) *DirectoriesUploader {
+	return &DirectoriesUploader{
+		ctx:                       ctx,
+		directoryServiceClient:    directoryServiceClient,
+		directoryServicePutStream: nil,
+	}
+}
+
+func (du *DirectoriesUploader) Put(directory *castorev1pb.Directory) ([]byte, error) {
+	directoryDigest, err := directory.Digest()
+	if err != nil {
+		return nil, fmt.Errorf("failed calculating directory digest: %w", err)
+	}
+
+	// Send the directory to the directory service
+	// If the stream hasn't been initialized yet, do it first
+	if du.directoryServicePutStream == nil {
+		directoryServicePutStream, err := du.directoryServiceClient.Put(du.ctx)
+		if err != nil {
+			return nil, fmt.Errorf("unable to initialize directory service put stream: %v", err)
+		}
+		du.directoryServicePutStream = directoryServicePutStream
+	}
+
+	// send the directory out
+	err = du.directoryServicePutStream.Send(directory)
+	if err != nil {
+		return nil, fmt.Errorf("error sending directory: %w", err)
+	}
+	log.WithField("digest", base64.StdEncoding.EncodeToString(directoryDigest)).Debug("uploaded directory")
+
+	// update lastDirectoryDigest
+	du.lastDirectoryDigest = directoryDigest
+
+	return directoryDigest, nil
+}
+
+// Done closes the stream and returns the response.
+// It returns null if closed for a second time.
+func (du *DirectoriesUploader) Done() (*castorev1pb.PutDirectoryResponse, error) {
+	// only close once, and only if we opened.
+	if du.directoryServicePutStream == nil {
+		return nil, nil
+	}
+
+	putDirectoryResponse, err := du.directoryServicePutStream.CloseAndRecv()
+	if err != nil {
+		return nil, fmt.Errorf("unable to close directory service put stream: %v", err)
+	}
+
+	// ensure the response contains the same digest as the one we have in lastDirectoryDigest.
+	// Otherwise, the backend came up with another digest than we, in which we return an error.
+	if !bytes.Equal(du.lastDirectoryDigest, putDirectoryResponse.RootDigest) {
+		return nil, fmt.Errorf(
+			"backend calculated different root digest as we, expected %s, actual %s",
+			base64.StdEncoding.EncodeToString(du.lastDirectoryDigest),
+			base64.StdEncoding.EncodeToString(putDirectoryResponse.RootDigest),
+		)
+	}
+
+	// clear directoryServicePutStream.
+	du.directoryServicePutStream = nil
+
+	return putDirectoryResponse, nil
+}