Добавлена локальная загрузка снапшота

Makefile

@@ -41,10 +41,6 @@ test-coverage:
 	go test -v -coverprofile=coverage.out ./...
 	go tool cover -html=coverage.out -o coverage.html
 
-# Run linter
-lint:
-	golangci-lint run
-
 # Run all checks (tests + linter)
 check: test lint
 

grpc/snapshot.pb.go

@@ -1,7 +1,7 @@
 // Code generated by protoc-gen-go. DO NOT EDIT.
 // versions:
-// 	protoc-gen-go v1.36.6
+// 	protoc-gen-go v1.36.8
-// 	protoc        v4.25.3
+// 	protoc        v6.32.0
 // source: snapshot.proto
 
 package grpc
@@ -500,6 +500,112 @@ func (x *DownloadSnapshotDiffRequest) GetOffset() int64 {
 	return 0
 }
 
+// Запрос на получение информации о дифе
+type GetDiffInfoRequest struct {
+	state         protoimpl.MessageState `protogen:"open.v1"`
+	SnapshotId    string                 `protobuf:"bytes,1,opt,name=snapshot_id,json=snapshotId,proto3" json:"snapshot_id,omitempty"`
+	LocalParentId string                 `protobuf:"bytes,2,opt,name=local_parent_id,json=localParentId,proto3" json:"local_parent_id,omitempty"`
+	unknownFields protoimpl.UnknownFields
+	sizeCache     protoimpl.SizeCache
+}
+
+func (x *GetDiffInfoRequest) Reset() {
+	*x = GetDiffInfoRequest{}
+	mi := &file_snapshot_proto_msgTypes[9]
+	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+	ms.StoreMessageInfo(mi)
+}
+
+func (x *GetDiffInfoRequest) String() string {
+	return protoimpl.X.MessageStringOf(x)
+}
+
+func (*GetDiffInfoRequest) ProtoMessage() {}
+
+func (x *GetDiffInfoRequest) ProtoReflect() protoreflect.Message {
+	mi := &file_snapshot_proto_msgTypes[9]
+	if x != nil {
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		if ms.LoadMessageInfo() == nil {
+			ms.StoreMessageInfo(mi)
+		}
+		return ms
+	}
+	return mi.MessageOf(x)
+}
+
+// Deprecated: Use GetDiffInfoRequest.ProtoReflect.Descriptor instead.
+func (*GetDiffInfoRequest) Descriptor() ([]byte, []int) {
+	return file_snapshot_proto_rawDescGZIP(), []int{9}
+}
+
+func (x *GetDiffInfoRequest) GetSnapshotId() string {
+	if x != nil {
+		return x.SnapshotId
+	}
+	return ""
+}
+
+func (x *GetDiffInfoRequest) GetLocalParentId() string {
+	if x != nil {
+		return x.LocalParentId
+	}
+	return ""
+}
+
+// Информация о дифе
+type DiffInfo struct {
+	state         protoimpl.MessageState `protogen:"open.v1"`
+	Sha256Hash    string                 `protobuf:"bytes,1,opt,name=sha256_hash,json=sha256Hash,proto3" json:"sha256_hash,omitempty"`
+	SizeBytes     int64                  `protobuf:"varint,2,opt,name=size_bytes,json=sizeBytes,proto3" json:"size_bytes,omitempty"`
+	unknownFields protoimpl.UnknownFields
+	sizeCache     protoimpl.SizeCache
+}
+
+func (x *DiffInfo) Reset() {
+	*x = DiffInfo{}
+	mi := &file_snapshot_proto_msgTypes[10]
+	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+	ms.StoreMessageInfo(mi)
+}
+
+func (x *DiffInfo) String() string {
+	return protoimpl.X.MessageStringOf(x)
+}
+
+func (*DiffInfo) ProtoMessage() {}
+
+func (x *DiffInfo) ProtoReflect() protoreflect.Message {
+	mi := &file_snapshot_proto_msgTypes[10]
+	if x != nil {
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		if ms.LoadMessageInfo() == nil {
+			ms.StoreMessageInfo(mi)
+		}
+		return ms
+	}
+	return mi.MessageOf(x)
+}
+
+// Deprecated: Use DiffInfo.ProtoReflect.Descriptor instead.
+func (*DiffInfo) Descriptor() ([]byte, []int) {
+	return file_snapshot_proto_rawDescGZIP(), []int{10}
+}
+
+func (x *DiffInfo) GetSha256Hash() string {
+	if x != nil {
+		return x.Sha256Hash
+	}
+	return ""
+}
+
+func (x *DiffInfo) GetSizeBytes() int64 {
+	if x != nil {
+		return x.SizeBytes
+	}
+	return 0
+}
+
 var File_snapshot_proto protoreflect.FileDescriptor
 
 const file_snapshot_proto_rawDesc = "" +
@@ -538,12 +644,22 @@ const file_snapshot_proto_rawDesc = "" +
 	"\vsnapshot_id\x18\x01 \x01(\tR\n" +
 	"snapshotId\x12&\n" +
 	"\x0flocal_parent_id\x18\x02 \x01(\tR\rlocalParentId\x12\x16\n" +
-	"\x06offset\x18\x03 \x01(\x03R\x06offset2\xf1\x03\n" +
+	"\x06offset\x18\x03 \x01(\x03R\x06offset\"]\n" +
+	"\x12GetDiffInfoRequest\x12\x1f\n" +
+	"\vsnapshot_id\x18\x01 \x01(\tR\n" +
+	"snapshotId\x12&\n" +
+	"\x0flocal_parent_id\x18\x02 \x01(\tR\rlocalParentId\"J\n" +
+	"\bDiffInfo\x12\x1f\n" +
+	"\vsha256_hash\x18\x01 \x01(\tR\n" +
+	"sha256Hash\x12\x1d\n" +
+	"\n" +
+	"size_bytes\x18\x02 \x01(\x03R\tsizeBytes2\xb8\x04\n" +
 	"\x0fSnapshotService\x12k\n" +
 	"\rListSnapshots\x12 .agate.grpc.ListSnapshotsRequest\x1a!.agate.grpc.ListSnapshotsResponse\"\x15\x82\xd3\xe4\x93\x02\x0f\x12\r/v1/snapshots\x12}\n" +
 	"\x12GetSnapshotDetails\x12%.agate.grpc.GetSnapshotDetailsRequest\x1a\x1b.agate.grpc.SnapshotDetails\"#\x82\xd3\xe4\x93\x02\x1d\x12\x1b/v1/snapshots/{snapshot_id}\x12\x8a\x01\n" +
 	"\fDownloadFile\x12\x1f.agate.grpc.DownloadFileRequest\x1a .agate.grpc.DownloadFileResponse\"5\x82\xd3\xe4\x93\x02/\x12-/v1/snapshots/{snapshot_id}/files/{file_path}0\x01\x12e\n" +
-	"\x14DownloadSnapshotDiff\x12'.agate.grpc.DownloadSnapshotDiffRequest\x1a .agate.grpc.DownloadFileResponse\"\x000\x01B\"Z gitea.unprism.ru/KRBL/Agate/grpcb\x06proto3"
+	"\x14DownloadSnapshotDiff\x12'.agate.grpc.DownloadSnapshotDiffRequest\x1a .agate.grpc.DownloadFileResponse\"\x000\x01\x12E\n" +
+	"\vGetDiffInfo\x12\x1e.agate.grpc.GetDiffInfoRequest\x1a\x14.agate.grpc.DiffInfo\"\x00B\"Z gitea.unprism.ru/KRBL/Agate/grpcb\x06proto3"
 
 var (
 	file_snapshot_proto_rawDescOnce sync.Once
@@ -557,7 +673,7 @@ func file_snapshot_proto_rawDescGZIP() []byte {
 	return file_snapshot_proto_rawDescData
 }
 
-var file_snapshot_proto_msgTypes = make([]protoimpl.MessageInfo, 9)
+var file_snapshot_proto_msgTypes = make([]protoimpl.MessageInfo, 11)
 var file_snapshot_proto_goTypes = []any{
 	(*FileInfo)(nil),                    // 0: agate.grpc.FileInfo
 	(*SnapshotInfo)(nil),                // 1: agate.grpc.SnapshotInfo
@@ -568,26 +684,30 @@ var file_snapshot_proto_goTypes = []any{
 	(*DownloadFileRequest)(nil),         // 6: agate.grpc.DownloadFileRequest
 	(*DownloadFileResponse)(nil),        // 7: agate.grpc.DownloadFileResponse
 	(*DownloadSnapshotDiffRequest)(nil), // 8: agate.grpc.DownloadSnapshotDiffRequest
-	(*timestamppb.Timestamp)(nil),       // 9: google.protobuf.Timestamp
+	(*GetDiffInfoRequest)(nil),          // 9: agate.grpc.GetDiffInfoRequest
+	(*DiffInfo)(nil),                    // 10: agate.grpc.DiffInfo
+	(*timestamppb.Timestamp)(nil),       // 11: google.protobuf.Timestamp
 }
 var file_snapshot_proto_depIdxs = []int32{
-	9, // 0: agate.grpc.SnapshotInfo.creation_time:type_name -> google.protobuf.Timestamp
+	11, // 0: agate.grpc.SnapshotInfo.creation_time:type_name -> google.protobuf.Timestamp
-	1, // 1: agate.grpc.SnapshotDetails.info:type_name -> agate.grpc.SnapshotInfo
+	1,  // 1: agate.grpc.SnapshotDetails.info:type_name -> agate.grpc.SnapshotInfo
-	0, // 2: agate.grpc.SnapshotDetails.files:type_name -> agate.grpc.FileInfo
+	0,  // 2: agate.grpc.SnapshotDetails.files:type_name -> agate.grpc.FileInfo
-	1, // 3: agate.grpc.ListSnapshotsResponse.snapshots:type_name -> agate.grpc.SnapshotInfo
+	1,  // 3: agate.grpc.ListSnapshotsResponse.snapshots:type_name -> agate.grpc.SnapshotInfo
-	3, // 4: agate.grpc.SnapshotService.ListSnapshots:input_type -> agate.grpc.ListSnapshotsRequest
+	3,  // 4: agate.grpc.SnapshotService.ListSnapshots:input_type -> agate.grpc.ListSnapshotsRequest
-	5, // 5: agate.grpc.SnapshotService.GetSnapshotDetails:input_type -> agate.grpc.GetSnapshotDetailsRequest
+	5,  // 5: agate.grpc.SnapshotService.GetSnapshotDetails:input_type -> agate.grpc.GetSnapshotDetailsRequest
-	6, // 6: agate.grpc.SnapshotService.DownloadFile:input_type -> agate.grpc.DownloadFileRequest
+	6,  // 6: agate.grpc.SnapshotService.DownloadFile:input_type -> agate.grpc.DownloadFileRequest
-	8, // 7: agate.grpc.SnapshotService.DownloadSnapshotDiff:input_type -> agate.grpc.DownloadSnapshotDiffRequest
+	8,  // 7: agate.grpc.SnapshotService.DownloadSnapshotDiff:input_type -> agate.grpc.DownloadSnapshotDiffRequest
-	4, // 8: agate.grpc.SnapshotService.ListSnapshots:output_type -> agate.grpc.ListSnapshotsResponse
+	9,  // 8: agate.grpc.SnapshotService.GetDiffInfo:input_type -> agate.grpc.GetDiffInfoRequest
-	2, // 9: agate.grpc.SnapshotService.GetSnapshotDetails:output_type -> agate.grpc.SnapshotDetails
+	4,  // 9: agate.grpc.SnapshotService.ListSnapshots:output_type -> agate.grpc.ListSnapshotsResponse
-	7, // 10: agate.grpc.SnapshotService.DownloadFile:output_type -> agate.grpc.DownloadFileResponse
+	2,  // 10: agate.grpc.SnapshotService.GetSnapshotDetails:output_type -> agate.grpc.SnapshotDetails
-	7, // 11: agate.grpc.SnapshotService.DownloadSnapshotDiff:output_type -> agate.grpc.DownloadFileResponse
+	7,  // 11: agate.grpc.SnapshotService.DownloadFile:output_type -> agate.grpc.DownloadFileResponse
-	8, // [8:12] is the sub-list for method output_type
+	7,  // 12: agate.grpc.SnapshotService.DownloadSnapshotDiff:output_type -> agate.grpc.DownloadFileResponse
-	4, // [4:8] is the sub-list for method input_type
+	10, // 13: agate.grpc.SnapshotService.GetDiffInfo:output_type -> agate.grpc.DiffInfo
-	4, // [4:4] is the sub-list for extension type_name
+	9,  // [9:14] is the sub-list for method output_type
-	4, // [4:4] is the sub-list for extension extendee
+	4,  // [4:9] is the sub-list for method input_type
-	0, // [0:4] is the sub-list for field type_name
+	4,  // [4:4] is the sub-list for extension type_name
+	4,  // [4:4] is the sub-list for extension extendee
+	0,  // [0:4] is the sub-list for field type_name
 }
 
 func init() { file_snapshot_proto_init() }
@@ -601,7 +721,7 @@ func file_snapshot_proto_init() {
 			GoPackagePath: reflect.TypeOf(x{}).PkgPath(),
 			RawDescriptor: unsafe.Slice(unsafe.StringData(file_snapshot_proto_rawDesc), len(file_snapshot_proto_rawDesc)),
 			NumEnums:      0,
-			NumMessages:   9,
+			NumMessages:   11,
 			NumExtensions: 0,
 			NumServices:   1,
 		},

grpc/snapshot.pb.gw.go

@@ -40,7 +40,9 @@ func request_SnapshotService_ListSnapshots_0(ctx context.Context, marshaler runt
 		protoReq ListSnapshotsRequest
 		metadata runtime.ServerMetadata
 	)
-	io.Copy(io.Discard, req.Body)
+	if req.Body != nil {
+		_, _ = io.Copy(io.Discard, req.Body)
+	}
 	msg, err := client.ListSnapshots(ctx, &protoReq, grpc.Header(&metadata.HeaderMD), grpc.Trailer(&metadata.TrailerMD))
 	return msg, metadata, err
 }
@@ -60,7 +62,9 @@ func request_SnapshotService_GetSnapshotDetails_0(ctx context.Context, marshaler
 		metadata runtime.ServerMetadata
 		err      error
 	)
-	io.Copy(io.Discard, req.Body)
+	if req.Body != nil {
+		_, _ = io.Copy(io.Discard, req.Body)
+	}
 	val, ok := pathParams["snapshot_id"]
 	if !ok {
 		return nil, metadata, status.Errorf(codes.InvalidArgument, "missing parameter %s", "snapshot_id")
@@ -97,7 +101,9 @@ func request_SnapshotService_DownloadFile_0(ctx context.Context, marshaler runti
 		metadata runtime.ServerMetadata
 		err      error
 	)
-	io.Copy(io.Discard, req.Body)
+	if req.Body != nil {
+		_, _ = io.Copy(io.Discard, req.Body)
+	}
 	val, ok := pathParams["snapshot_id"]
 	if !ok {
 		return nil, metadata, status.Errorf(codes.InvalidArgument, "missing parameter %s", "snapshot_id")

grpc/snapshot.proto

@@ -32,6 +32,9 @@ service SnapshotService {
 
   // Скачать архив, содержащий только разницу между двумя снапшотами
   rpc DownloadSnapshotDiff(DownloadSnapshotDiffRequest) returns (stream DownloadFileResponse) {}
+
+  // Получить информацию о дифе (хеш и размер)
+  rpc GetDiffInfo(GetDiffInfoRequest) returns (DiffInfo) {}
 }
 
 // Метаданные файла внутри снапшота
@@ -86,3 +89,15 @@ message DownloadSnapshotDiffRequest {
   string local_parent_id = 2; // ID снапшота, который уже есть у клиента
   int64 offset = 3;           // Смещение в байтах для докачки
 }
+
+// Запрос на получение информации о дифе
+message GetDiffInfoRequest {
+  string snapshot_id = 1;
+  string local_parent_id = 2;
+}
+
+// Информация о дифе
+message DiffInfo {
+  string sha256_hash = 1;
+  int64 size_bytes = 2;
+}

grpc/snapshot_grpc.pb.go

@@ -1,7 +1,7 @@
 // Code generated by protoc-gen-go-grpc. DO NOT EDIT.
 // versions:
 // - protoc-gen-go-grpc v1.5.1
-// - protoc             v4.25.3
+// - protoc             v6.32.0
 // source: snapshot.proto
 
 package grpc
@@ -23,6 +23,7 @@ const (
 	SnapshotService_GetSnapshotDetails_FullMethodName   = "/agate.grpc.SnapshotService/GetSnapshotDetails"
 	SnapshotService_DownloadFile_FullMethodName         = "/agate.grpc.SnapshotService/DownloadFile"
 	SnapshotService_DownloadSnapshotDiff_FullMethodName = "/agate.grpc.SnapshotService/DownloadSnapshotDiff"
+	SnapshotService_GetDiffInfo_FullMethodName          = "/agate.grpc.SnapshotService/GetDiffInfo"
 )
 
 // SnapshotServiceClient is the client API for SnapshotService service.
@@ -39,6 +40,8 @@ type SnapshotServiceClient interface {
 	DownloadFile(ctx context.Context, in *DownloadFileRequest, opts ...grpc.CallOption) (grpc.ServerStreamingClient[DownloadFileResponse], error)
 	// Скачать архив, содержащий только разницу между двумя снапшотами
 	DownloadSnapshotDiff(ctx context.Context, in *DownloadSnapshotDiffRequest, opts ...grpc.CallOption) (grpc.ServerStreamingClient[DownloadFileResponse], error)
+	// Получить информацию о дифе (хеш и размер)
+	GetDiffInfo(ctx context.Context, in *GetDiffInfoRequest, opts ...grpc.CallOption) (*DiffInfo, error)
 }
 
 type snapshotServiceClient struct {
@@ -107,6 +110,16 @@ func (c *snapshotServiceClient) DownloadSnapshotDiff(ctx context.Context, in *Do
 // This type alias is provided for backwards compatibility with existing code that references the prior non-generic stream type by name.
 type SnapshotService_DownloadSnapshotDiffClient = grpc.ServerStreamingClient[DownloadFileResponse]
 
+func (c *snapshotServiceClient) GetDiffInfo(ctx context.Context, in *GetDiffInfoRequest, opts ...grpc.CallOption) (*DiffInfo, error) {
+	cOpts := append([]grpc.CallOption{grpc.StaticMethod()}, opts...)
+	out := new(DiffInfo)
+	err := c.cc.Invoke(ctx, SnapshotService_GetDiffInfo_FullMethodName, in, out, cOpts...)
+	if err != nil {
+		return nil, err
+	}
+	return out, nil
+}
+
 // SnapshotServiceServer is the server API for SnapshotService service.
 // All implementations must embed UnimplementedSnapshotServiceServer
 // for forward compatibility.
@@ -121,6 +134,8 @@ type SnapshotServiceServer interface {
 	DownloadFile(*DownloadFileRequest, grpc.ServerStreamingServer[DownloadFileResponse]) error
 	// Скачать архив, содержащий только разницу между двумя снапшотами
 	DownloadSnapshotDiff(*DownloadSnapshotDiffRequest, grpc.ServerStreamingServer[DownloadFileResponse]) error
+	// Получить информацию о дифе (хеш и размер)
+	GetDiffInfo(context.Context, *GetDiffInfoRequest) (*DiffInfo, error)
 	mustEmbedUnimplementedSnapshotServiceServer()
 }
 
@@ -143,6 +158,9 @@ func (UnimplementedSnapshotServiceServer) DownloadFile(*DownloadFileRequest, grp
 func (UnimplementedSnapshotServiceServer) DownloadSnapshotDiff(*DownloadSnapshotDiffRequest, grpc.ServerStreamingServer[DownloadFileResponse]) error {
 	return status.Errorf(codes.Unimplemented, "method DownloadSnapshotDiff not implemented")
 }
+func (UnimplementedSnapshotServiceServer) GetDiffInfo(context.Context, *GetDiffInfoRequest) (*DiffInfo, error) {
+	return nil, status.Errorf(codes.Unimplemented, "method GetDiffInfo not implemented")
+}
 func (UnimplementedSnapshotServiceServer) mustEmbedUnimplementedSnapshotServiceServer() {}
 func (UnimplementedSnapshotServiceServer) testEmbeddedByValue()                         {}
 
@@ -222,6 +240,24 @@ func _SnapshotService_DownloadSnapshotDiff_Handler(srv interface{}, stream grpc.
 // This type alias is provided for backwards compatibility with existing code that references the prior non-generic stream type by name.
 type SnapshotService_DownloadSnapshotDiffServer = grpc.ServerStreamingServer[DownloadFileResponse]
 
+func _SnapshotService_GetDiffInfo_Handler(srv interface{}, ctx context.Context, dec func(interface{}) error, interceptor grpc.UnaryServerInterceptor) (interface{}, error) {
+	in := new(GetDiffInfoRequest)
+	if err := dec(in); err != nil {
+		return nil, err
+	}
+	if interceptor == nil {
+		return srv.(SnapshotServiceServer).GetDiffInfo(ctx, in)
+	}
+	info := &grpc.UnaryServerInfo{
+		Server:     srv,
+		FullMethod: SnapshotService_GetDiffInfo_FullMethodName,
+	}
+	handler := func(ctx context.Context, req interface{}) (interface{}, error) {
+		return srv.(SnapshotServiceServer).GetDiffInfo(ctx, req.(*GetDiffInfoRequest))
+	}
+	return interceptor(ctx, in, info, handler)
+}
+
 // SnapshotService_ServiceDesc is the grpc.ServiceDesc for SnapshotService service.
 // It's only intended for direct use with grpc.RegisterService,
 // and not to be introspected or modified (even as a copy)
@@ -237,6 +273,10 @@ var SnapshotService_ServiceDesc = grpc.ServiceDesc{
 			MethodName: "GetSnapshotDetails",
 			Handler:    _SnapshotService_GetSnapshotDetails_Handler,
 		},
+		{
+			MethodName: "GetDiffInfo",
+			Handler:    _SnapshotService_GetDiffInfo_Handler,
+		},
 	},
 	Streams: []grpc.StreamDesc{
 		{

interfaces/snapshot.go

@@ -38,6 +38,9 @@ type SnapshotManager interface {
 	// It returns an io.ReadCloser for the archive stream and an error.
 	// The caller is responsible for closing the reader, which will also handle cleanup of temporary resources.
 	StreamSnapshotDiff(ctx context.Context, snapshotID, parentID string, offset int64) (io.ReadCloser, error)
+
+	// GetSnapshotDiffInfo calculates the hash and size of a differential archive between two snapshots.
+	GetSnapshotDiffInfo(ctx context.Context, snapshotID, parentID string) (*store.DiffInfo, error)
 }
 
 // SnapshotServer defines the interface for a server that can share snapshots

manager.go

@@ -403,6 +403,37 @@ func (data *SnapshotManagerData) UpdateSnapshotMetadata(ctx context.Context, sna
 	return nil
 }
 
+func (data *SnapshotManagerData) GetSnapshotDiffInfo(ctx context.Context, snapshotID, parentID string) (*store.DiffInfo, error) {
+	tempArchivePath, tempStagingDir, err := data.createDiffArchive(ctx, snapshotID, parentID)
+	if err != nil {
+		return nil, fmt.Errorf("failed to create diff archive for info: %w", err)
+	}
+
+	if tempArchivePath == "" {
+		return &store.DiffInfo{SHA256: "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855", Size: 0}, nil // sha256 of empty string
+	}
+
+	defer os.Remove(tempArchivePath)
+	if tempStagingDir != "" {
+		defer os.RemoveAll(tempStagingDir)
+	}
+
+	hash, err := hash.CalculateFileHash(tempArchivePath)
+	if err != nil {
+		return nil, fmt.Errorf("failed to calculate hash for diff archive: %w", err)
+	}
+
+	stat, err := os.Stat(tempArchivePath)
+	if err != nil {
+		return nil, fmt.Errorf("failed to get size of diff archive: %w", err)
+	}
+
+	return &store.DiffInfo{
+		SHA256: hash,
+		Size:   stat.Size(),
+	}, nil
+}
+
 // diffArchiveReader is a wrapper around an *os.File that handles cleanup of temporary files.
 type diffArchiveReader struct {
 	*os.File
@@ -418,10 +449,10 @@ func (r *diffArchiveReader) Close() error {
 	return err
 }
 
-func (data *SnapshotManagerData) StreamSnapshotDiff(ctx context.Context, snapshotID, parentID string, offset int64) (io.ReadCloser, error) {
+func (data *SnapshotManagerData) createDiffArchive(ctx context.Context, snapshotID, parentID string) (string, string, error) {
 	targetSnap, err := data.metadataStore.GetSnapshotMetadata(ctx, snapshotID)
 	if err != nil {
-		return nil, fmt.Errorf("failed to get target snapshot metadata: %w", err)
+		return "", "", fmt.Errorf("failed to get target snapshot metadata: %w", err)
 	}
 
 	parentFiles := make(map[string]string)
@@ -449,38 +480,38 @@ func (data *SnapshotManagerData) StreamSnapshotDiff(ctx context.Context, snapsho
 	}
 
 	if len(filesToInclude) == 0 {
-		return io.NopCloser(bytes.NewReader(nil)), nil
+		return "", "", nil
 	}
 
 	tempStagingDir, err := os.MkdirTemp(data.blobStore.GetBaseDir(), "diff-staging-*")
 	if err != nil {
-		return nil, fmt.Errorf("failed to create temp staging directory: %w", err)
+		return "", "", fmt.Errorf("failed to create temp staging directory: %w", err)
 	}
 
 	targetBlobPath, err := data.blobStore.GetBlobPath(ctx, snapshotID)
 	if err != nil {
 		os.RemoveAll(tempStagingDir)
-		return nil, err
+		return "", "", err
 	}
 
 	for _, filePath := range filesToInclude {
 		destPath := filepath.Join(tempStagingDir, filePath)
 		if err := os.MkdirAll(filepath.Dir(destPath), 0755); err != nil {
 			os.RemoveAll(tempStagingDir)
-			return nil, fmt.Errorf("failed to create dir for diff file: %w", err)
+			return "", "", fmt.Errorf("failed to create dir for diff file: %w", err)
 		}
 
 		fileWriter, err := os.Create(destPath)
 		if err != nil {
 			os.RemoveAll(tempStagingDir)
-			return nil, err
+			return "", "", err
 		}
 
 		err = archive.ExtractFileFromArchive(targetBlobPath, filePath, fileWriter)
 		fileWriter.Close()
 		if err != nil {
 			os.RemoveAll(tempStagingDir)
-			return nil, fmt.Errorf("failed to extract file %s for diff: %w", filePath, err)
+			return "", "", fmt.Errorf("failed to extract file %s for diff: %w", filePath, err)
 		}
 	}
 
@@ -488,12 +519,27 @@ func (data *SnapshotManagerData) StreamSnapshotDiff(ctx context.Context, snapsho
 	if err := archive.CreateArchive(tempStagingDir, tempArchivePath); err != nil {
 		os.RemoveAll(tempStagingDir)
 		os.Remove(tempArchivePath)
-		return nil, fmt.Errorf("failed to create diff archive: %w", err)
+		return "", "", fmt.Errorf("failed to create diff archive: %w", err)
+	}
+
+	return tempArchivePath, tempStagingDir, nil
+}
+
+func (data *SnapshotManagerData) StreamSnapshotDiff(ctx context.Context, snapshotID, parentID string, offset int64) (io.ReadCloser, error) {
+	tempArchivePath, tempStagingDir, err := data.createDiffArchive(ctx, snapshotID, parentID)
+	if err != nil {
+		return nil, fmt.Errorf("failed to create diff archive for streaming: %w", err)
+	}
+
+	if tempArchivePath == "" {
+		return io.NopCloser(bytes.NewReader(nil)), nil
 	}
 
 	archiveFile, err := os.Open(tempArchivePath)
 	if err != nil {
-		os.RemoveAll(tempStagingDir)
+		if tempStagingDir != "" {
+			os.RemoveAll(tempStagingDir)
+		}
 		os.Remove(tempArchivePath)
 		return nil, err
 	}
@@ -501,7 +547,9 @@ func (data *SnapshotManagerData) StreamSnapshotDiff(ctx context.Context, snapsho
 	if offset > 0 {
 		if _, err := archiveFile.Seek(offset, io.SeekStart); err != nil {
 			archiveFile.Close()
-			os.RemoveAll(tempStagingDir)
+			if tempStagingDir != "" {
+				os.RemoveAll(tempStagingDir)
+			}
 			os.Remove(tempArchivePath)
 			return nil, fmt.Errorf("failed to seek in diff archive: %w", err)
 		}

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{

store/store.go

@@ -6,6 +6,12 @@ import (
 	"time"
 )
 
+// DiffInfo represents metadata about a differential archive.
+type DiffInfo struct {
+	SHA256 string
+	Size   int64
+}
+
 // FileInfo represents metadata and attributes of a file or directory.
 type FileInfo struct {
 	Path   string // Path represents the relative or absolute location of the file or directory in the filesystem.