Добавлена локальная загрузка снапшота

remote/client.go

@@ -11,6 +11,7 @@ import (
 	"google.golang.org/grpc/credentials/insecure"
 
 	agateGrpc "gitea.unprism.ru/KRBL/Agate/grpc"
+	"gitea.unprism.ru/KRBL/Agate/hash"
 	"gitea.unprism.ru/KRBL/Agate/interfaces"
 	"gitea.unprism.ru/KRBL/Agate/store"
 )
@@ -89,8 +90,43 @@ func (c *Client) FetchSnapshotDetails(ctx context.Context, snapshotID string) (*
 	return snapshot, nil
 }
 
+// GetDiffInfo gets the hash and size of a differential archive.
+func (c *Client) GetDiffInfo(ctx context.Context, snapshotID, localParentID string) (*store.DiffInfo, error) {
+	req := &agateGrpc.GetDiffInfoRequest{
+		SnapshotId:    snapshotID,
+		LocalParentId: localParentID,
+	}
+
+	info, err := c.client.GetDiffInfo(ctx, req)
+	if err != nil {
+		return nil, fmt.Errorf("failed to get diff info: %w", err)
+	}
+
+	return &store.DiffInfo{
+		SHA256: info.Sha256Hash,
+		Size:   info.SizeBytes,
+	}, nil
+}
+
 // DownloadSnapshotDiff скачивает архив с разницей между снапшотами.
 func (c *Client) DownloadSnapshotDiff(ctx context.Context, snapshotID, localParentID, targetPath string) error {
+	// Check for local file and validate it
+	if fileInfo, err := os.Stat(targetPath); err == nil {
+		remoteDiffInfo, err := c.GetDiffInfo(ctx, snapshotID, localParentID)
+		if err != nil {
+			// Log the error but proceed with download
+			fmt.Printf("could not get remote diff info: %v. proceeding with download.", err)
+		} else {
+			if fileInfo.Size() == remoteDiffInfo.Size {
+				localHash, err := hash.CalculateFileHash(targetPath)
+				if err == nil && localHash == remoteDiffInfo.SHA256 {
+					fmt.Printf("local snapshot archive %s is valid, skipping download.", targetPath)
+					return nil // File is valid, skip download
+				}
+			}
+		}
+	}
+
 	var offset int64
 	fileInfo, err := os.Stat(targetPath)
 	if err == nil {

remote/server.go

@@ -158,6 +158,19 @@ func (s *Server) DownloadSnapshotDiff(req *agateGrpc.DownloadSnapshotDiffRequest
 	return nil
 }
 
+// GetDiffInfo реализует gRPC-метод GetDiffInfo.
+func (s *Server) GetDiffInfo(ctx context.Context, req *agateGrpc.GetDiffInfoRequest) (*agateGrpc.DiffInfo, error) {
+	diffInfo, err := s.manager.GetSnapshotDiffInfo(ctx, req.SnapshotId, req.LocalParentId)
+	if err != nil {
+		return nil, fmt.Errorf("failed to get diff info: %w", err)
+	}
+
+	return &agateGrpc.DiffInfo{
+		Sha256Hash: diffInfo.SHA256,
+		SizeBytes:  diffInfo.Size,
+	}, nil
+}
+
 // Вспомогательная функция для конвертации store.SnapshotInfo в grpc.SnapshotInfo
 func convertToGrpcSnapshotInfo(info store.SnapshotInfo) *agateGrpc.SnapshotInfo {
 	return &agateGrpc.SnapshotInfo{