[#266] pkg/client: Export Client interface instead of structure

Make it easier to test API clients and mock specific methods.
Also add comments on exported methods.

Signed-off-by: Evgenii Stratonikov <evgeniy@nspcc.ru>

pkg/client/accounting.go

@@ -11,11 +11,19 @@ import (
 	"github.com/pkg/errors"
 )
 
-func (c Client) GetSelfBalance(ctx context.Context, opts ...CallOption) (*accounting.Decimal, error) {
+// Accounting contains methods related to balance querying.
+type Accounting interface {
+	// GetSelfBalance returns balance of the account deduced from client's key.
+	GetSelfBalance(context.Context, ...CallOption) (*accounting.Decimal, error)
+	// GetBalance returns balance of provided account.
+	GetBalance(context.Context, *owner.ID, ...CallOption) (*accounting.Decimal, error)
+}
+
+func (c clientImpl) GetSelfBalance(ctx context.Context, opts ...CallOption) (*accounting.Decimal, error) {
 	return c.GetBalance(ctx, nil, opts...)
 }
 
-func (c Client) GetBalance(ctx context.Context, owner *owner.ID, opts ...CallOption) (*accounting.Decimal, error) {
+func (c clientImpl) GetBalance(ctx context.Context, owner *owner.ID, opts ...CallOption) (*accounting.Decimal, error) {
 	// check remote node version
 	switch c.remoteNode.Version.Major() {
 	case 2:
@@ -25,7 +33,7 @@ func (c Client) GetBalance(ctx context.Context, owner *owner.ID, opts ...CallOpt
 	}
 }
 
-func (c Client) getBalanceV2(ctx context.Context, ownerID *owner.ID, opts ...CallOption) (*accounting.Decimal, error) {
+func (c clientImpl) getBalanceV2(ctx context.Context, ownerID *owner.ID, opts ...CallOption) (*accounting.Decimal, error) {
 	// apply all available options
 	callOptions := c.defaultCallOptions()
 

pkg/client/client.go

@@ -9,7 +9,16 @@ import (
 )
 
 type (
-	Client struct {
+	// Client represents NeoFS client.
+	Client interface {
+		Accounting
+		Container
+		Netmap
+		Object
+		Session
+	}
+
+	clientImpl struct {
 		key        *ecdsa.PrivateKey
 		remoteNode TransportInfo
 
@@ -35,7 +44,8 @@ const (
 
 var errUnsupportedProtocol = errors.New("unsupported transport protocol")
 
-func New(key *ecdsa.PrivateKey, opts ...Option) (*Client, error) {
+// New returns new client which uses key as default signing key.
+func New(key *ecdsa.PrivateKey, opts ...Option) (Client, error) {
 	clientOptions := defaultClientOptions()
 
 	for i := range opts {
@@ -43,7 +53,7 @@ func New(key *ecdsa.PrivateKey, opts ...Option) (*Client, error) {
 	}
 
 	// todo: make handshake to check latest version
-	return &Client{
+	return &clientImpl{
 		key: key,
 		remoteNode: TransportInfo{
 			Version:  pkg.SDKVersion(),

pkg/client/container.go

@@ -15,6 +15,28 @@ import (
 	"github.com/pkg/errors"
 )
 
+// Container contains methods related to container and ACL.
+type Container interface {
+	// PutContainer creates new container in the NeoFS network.
+	PutContainer(context.Context, *container.Container, ...CallOption) (*container.ID, error)
+	// GetContainer returns container by ID.
+	GetContainer(context.Context, *container.ID, ...CallOption) (*container.Container, error)
+	// ListContainers return container list with the provided owner.
+	ListContainers(context.Context, *owner.ID, ...CallOption) ([]*container.ID, error)
+	// ListSelfContainers is similar to ListContainers but uses client's key to deduce owner ID.
+	ListSelfContainers(context.Context, ...CallOption) ([]*container.ID, error)
+	// DeleteContainer removes container from NeoFS network.
+	DeleteContainer(context.Context, *container.ID, ...CallOption) error
+	// GetEACL returns extended ACL for a given container.
+	GetEACL(context.Context, *container.ID, ...CallOption) (*eacl.Table, error)
+	// GetEACLWithSignature is similar to GetEACL but returns signed ACL.
+	GetEACLWithSignature(context.Context, *container.ID, ...CallOption) (*EACLWithSignature, error)
+	// SetEACL sets extended ACL.
+	SetEACL(context.Context, *eacl.Table, ...CallOption) error
+	// AnnounceContainerUsedSpace announces amount of space which is taken by stored objects.
+	AnnounceContainerUsedSpace(context.Context, []container.UsedSpaceAnnouncement, ...CallOption) error
+}
+
 type delContainerSignWrapper struct {
 	body *v2container.DeleteRequestBody
 }
@@ -46,7 +68,7 @@ func (e EACLWithSignature) Signature() *pkg.Signature {
 	return e.sig
 }
 
-func (c Client) PutContainer(ctx context.Context, cnr *container.Container, opts ...CallOption) (*container.ID, error) {
+func (c clientImpl) PutContainer(ctx context.Context, cnr *container.Container, opts ...CallOption) (*container.ID, error) {
 	switch c.remoteNode.Version.Major() {
 	case 2:
 		return c.putContainerV2(ctx, cnr, opts...)
@@ -58,7 +80,7 @@ func (c Client) PutContainer(ctx context.Context, cnr *container.Container, opts
 // GetContainer receives container structure through NeoFS API call.
 //
 // Returns error if container structure is received but does not meet NeoFS API specification.
-func (c Client) GetContainer(ctx context.Context, id *container.ID, opts ...CallOption) (*container.Container, error) {
+func (c clientImpl) GetContainer(ctx context.Context, id *container.ID, opts ...CallOption) (*container.Container, error) {
 	switch c.remoteNode.Version.Major() {
 	case 2:
 		return c.getContainerV2(ctx, id, opts...)
@@ -71,7 +93,7 @@ func (c Client) GetContainer(ctx context.Context, id *container.ID, opts ...Call
 // which checks if the structure of the resulting container matches its identifier.
 //
 // Returns container.ErrIDMismatch if container does not match the identifier.
-func GetVerifiedContainerStructure(ctx context.Context, c *Client, id *container.ID, opts ...CallOption) (*container.Container, error) {
+func GetVerifiedContainerStructure(ctx context.Context, c Client, id *container.ID, opts ...CallOption) (*container.Container, error) {
 	cnr, err := c.GetContainer(ctx, id, opts...)
 	if err != nil {
 		return nil, err
@@ -84,7 +106,7 @@ func GetVerifiedContainerStructure(ctx context.Context, c *Client, id *container
 	return cnr, nil
 }
 
-func (c Client) ListContainers(ctx context.Context, owner *owner.ID, opts ...CallOption) ([]*container.ID, error) {
+func (c clientImpl) ListContainers(ctx context.Context, owner *owner.ID, opts ...CallOption) ([]*container.ID, error) {
 	switch c.remoteNode.Version.Major() {
 	case 2:
 		return c.listContainerV2(ctx, owner, opts...)
@@ -93,11 +115,11 @@ func (c Client) ListContainers(ctx context.Context, owner *owner.ID, opts ...Cal
 	}
 }
 
-func (c Client) ListSelfContainers(ctx context.Context, opts ...CallOption) ([]*container.ID, error) {
+func (c clientImpl) ListSelfContainers(ctx context.Context, opts ...CallOption) ([]*container.ID, error) {
 	return c.ListContainers(ctx, nil, opts...)
 }
 
-func (c Client) DeleteContainer(ctx context.Context, id *container.ID, opts ...CallOption) error {
+func (c clientImpl) DeleteContainer(ctx context.Context, id *container.ID, opts ...CallOption) error {
 	switch c.remoteNode.Version.Major() {
 	case 2:
 		return c.delContainerV2(ctx, id, opts...)
@@ -106,7 +128,7 @@ func (c Client) DeleteContainer(ctx context.Context, id *container.ID, opts ...C
 	}
 }
 
-func (c Client) GetEACL(ctx context.Context, id *container.ID, opts ...CallOption) (*eacl.Table, error) {
+func (c clientImpl) GetEACL(ctx context.Context, id *container.ID, opts ...CallOption) (*eacl.Table, error) {
 	v, err := c.getEACL(ctx, id, true, opts...)
 	if err != nil {
 		return nil, err
@@ -115,11 +137,11 @@ func (c Client) GetEACL(ctx context.Context, id *container.ID, opts ...CallOptio
 	return v.table, nil
 }
 
-func (c Client) GetEACLWithSignature(ctx context.Context, id *container.ID, opts ...CallOption) (*EACLWithSignature, error) {
+func (c clientImpl) GetEACLWithSignature(ctx context.Context, id *container.ID, opts ...CallOption) (*EACLWithSignature, error) {
 	return c.getEACL(ctx, id, false, opts...)
 }
 
-func (c Client) getEACL(ctx context.Context, id *container.ID, verify bool, opts ...CallOption) (*EACLWithSignature, error) {
+func (c clientImpl) getEACL(ctx context.Context, id *container.ID, verify bool, opts ...CallOption) (*EACLWithSignature, error) {
 	switch c.remoteNode.Version.Major() {
 	case 2:
 		resp, err := c.getEACLV2(ctx, id, verify, opts...)
@@ -136,7 +158,7 @@ func (c Client) getEACL(ctx context.Context, id *container.ID, verify bool, opts
 	}
 }
 
-func (c Client) SetEACL(ctx context.Context, eacl *eacl.Table, opts ...CallOption) error {
+func (c clientImpl) SetEACL(ctx context.Context, eacl *eacl.Table, opts ...CallOption) error {
 	switch c.remoteNode.Version.Major() {
 	case 2:
 		return c.setEACLV2(ctx, eacl, opts...)
@@ -147,7 +169,7 @@ func (c Client) SetEACL(ctx context.Context, eacl *eacl.Table, opts ...CallOptio
 
 // AnnounceContainerUsedSpace used by storage nodes to estimate their container
 // sizes during lifetime. Use it only in storage node applications.
-func (c Client) AnnounceContainerUsedSpace(
+func (c clientImpl) AnnounceContainerUsedSpace(
 	ctx context.Context,
 	announce []container.UsedSpaceAnnouncement,
 	opts ...CallOption) error {
@@ -159,7 +181,7 @@ func (c Client) AnnounceContainerUsedSpace(
 	}
 }
 
-func (c Client) putContainerV2(ctx context.Context, cnr *container.Container, opts ...CallOption) (*container.ID, error) {
+func (c clientImpl) putContainerV2(ctx context.Context, cnr *container.Container, opts ...CallOption) (*container.ID, error) {
 	// apply all available options
 	callOptions := c.defaultCallOptions()
 
@@ -231,7 +253,7 @@ func (c Client) putContainerV2(ctx context.Context, cnr *container.Container, op
 	}
 }
 
-func (c Client) getContainerV2(ctx context.Context, id *container.ID, opts ...CallOption) (*container.Container, error) {
+func (c clientImpl) getContainerV2(ctx context.Context, id *container.ID, opts ...CallOption) (*container.Container, error) {
 	// apply all available options
 	callOptions := c.defaultCallOptions()
 
@@ -274,7 +296,7 @@ func (c Client) getContainerV2(ctx context.Context, id *container.ID, opts ...Ca
 	}
 }
 
-func (c Client) listContainerV2(ctx context.Context, ownerID *owner.ID, opts ...CallOption) ([]*container.ID, error) {
+func (c clientImpl) listContainerV2(ctx context.Context, ownerID *owner.ID, opts ...CallOption) ([]*container.ID, error) {
 	// apply all available options
 	callOptions := c.defaultCallOptions()
 
@@ -332,7 +354,7 @@ func (c Client) listContainerV2(ctx context.Context, ownerID *owner.ID, opts ...
 	}
 }
 
-func (c Client) delContainerV2(ctx context.Context, id *container.ID, opts ...CallOption) error {
+func (c clientImpl) delContainerV2(ctx context.Context, id *container.ID, opts ...CallOption) error {
 	// apply all available options
 	callOptions := c.defaultCallOptions()
 
@@ -391,7 +413,7 @@ func (c Client) delContainerV2(ctx context.Context, id *container.ID, opts ...Ca
 	}
 }
 
-func (c Client) getEACLV2(ctx context.Context, id *container.ID, verify bool, opts ...CallOption) (*v2container.GetExtendedACLResponseBody, error) {
+func (c clientImpl) getEACLV2(ctx context.Context, id *container.ID, verify bool, opts ...CallOption) (*v2container.GetExtendedACLResponseBody, error) {
 	// apply all available options
 	callOptions := c.defaultCallOptions()
 
@@ -455,7 +477,7 @@ func (c Client) getEACLV2(ctx context.Context, id *container.ID, verify bool, op
 	}
 }
 
-func (c Client) setEACLV2(ctx context.Context, eacl *eacl.Table, opts ...CallOption) error {
+func (c clientImpl) setEACLV2(ctx context.Context, eacl *eacl.Table, opts ...CallOption) error {
 	// apply all available options
 	callOptions := c.defaultCallOptions()
 
@@ -511,7 +533,7 @@ func (c Client) setEACLV2(ctx context.Context, eacl *eacl.Table, opts ...CallOpt
 	}
 }
 
-func (c Client) announceContainerUsedSpaceV2(
+func (c clientImpl) announceContainerUsedSpaceV2(
 	ctx context.Context,
 	announce []container.UsedSpaceAnnouncement,
 	opts ...CallOption) error {

pkg/client/netmap.go

@@ -10,10 +10,22 @@ import (
 	"github.com/pkg/errors"
 )
 
+// Netmap contains methods related to netmap.
+type Netmap interface {
 	// EndpointInfo returns attributes, address and public key of the node, specified
 	// in client constructor via address or open connection. This can be used as a
 	// health check to see if node is alive and responses to requests.
-func (c Client) EndpointInfo(ctx context.Context, opts ...CallOption) (*netmap.NodeInfo, error) {
+	EndpointInfo(context.Context, ...CallOption) (*netmap.NodeInfo, error)
+	// Epoch returns the epoch number from the local state of the remote host.
+	Epoch(context.Context, ...CallOption) (uint64, error)
+	// NetworkInfo returns information about the NeoFS network of which the remote server is a part.
+	NetworkInfo(context.Context, ...CallOption) (*netmap.NetworkInfo, error)
+}
+
+// EndpointInfo returns attributes, address and public key of the node, specified
+// in client constructor via address or open connection. This can be used as a
+// health check to see if node is alive and responses to requests.
+func (c clientImpl) EndpointInfo(ctx context.Context, opts ...CallOption) (*netmap.NodeInfo, error) {
 	switch c.remoteNode.Version.Major() {
 	case 2:
 		resp, err := c.endpointInfoV2(ctx, opts...)
@@ -28,7 +40,7 @@ func (c Client) EndpointInfo(ctx context.Context, opts ...CallOption) (*netmap.N
 }
 
 // Epoch returns the epoch number from the local state of the remote host.
-func (c Client) Epoch(ctx context.Context, opts ...CallOption) (uint64, error) {
+func (c clientImpl) Epoch(ctx context.Context, opts ...CallOption) (uint64, error) {
 	switch c.remoteNode.Version.Major() {
 	case 2:
 		resp, err := c.endpointInfoV2(ctx, opts...)
@@ -42,7 +54,7 @@ func (c Client) Epoch(ctx context.Context, opts ...CallOption) (uint64, error) {
 	}
 }
 
-func (c Client) endpointInfoV2(ctx context.Context, opts ...CallOption) (*v2netmap.LocalNodeInfoResponse, error) {
+func (c clientImpl) endpointInfoV2(ctx context.Context, opts ...CallOption) (*v2netmap.LocalNodeInfoResponse, error) {
 	// apply all available options
 	callOptions := c.defaultCallOptions()
 
@@ -116,7 +128,7 @@ func v2NetmapClientFromOptions(opts *clientOptions) (cli *v2netmap.Client, err e
 }
 
 // NetworkInfo returns information about the NeoFS network of which the remote server is a part.
-func (c Client) NetworkInfo(ctx context.Context, opts ...CallOption) (*netmap.NetworkInfo, error) {
+func (c clientImpl) NetworkInfo(ctx context.Context, opts ...CallOption) (*netmap.NetworkInfo, error) {
 	switch c.remoteNode.Version.Major() {
 	case 2:
 		resp, err := c.networkInfoV2(ctx, opts...)
@@ -130,7 +142,7 @@ func (c Client) NetworkInfo(ctx context.Context, opts ...CallOption) (*netmap.Ne
 	}
 }
 
-func (c Client) networkInfoV2(ctx context.Context, opts ...CallOption) (*v2netmap.NetworkInfoResponse, error) {
+func (c clientImpl) networkInfoV2(ctx context.Context, opts ...CallOption) (*v2netmap.NetworkInfoResponse, error) {
 	// apply all available options
 	callOptions := c.defaultCallOptions()
 

pkg/client/object.go

@@ -19,6 +19,26 @@ import (
 	"github.com/pkg/errors"
 )
 
+// Object contains methods for working with objects.
+type Object interface {
+	// PutObject puts new object to NeoFS.
+	PutObject(context.Context, *PutObjectParams, ...CallOption) (*object.ID, error)
+	// DeleteObject deletes object to NeoFS.
+	DeleteObject(context.Context, *DeleteObjectParams, ...CallOption) error
+	// GetObject returns object stored in NeoFS.
+	GetObject(context.Context, *GetObjectParams, ...CallOption) (*object.Object, error)
+	// GetObjectHeader returns object header.
+	GetObjectHeader(context.Context, *ObjectHeaderParams, ...CallOption) (*object.Object, error)
+	// ObjectPayloadRangeData returns range of object payload.
+	ObjectPayloadRangeData(context.Context, *RangeDataParams, ...CallOption) ([]byte, error)
+	// ObjectPayloadRangeSHA256 returns sha-256 hashes of object sub-ranges from NeoFS.
+	ObjectPayloadRangeSHA256(context.Context, *RangeChecksumParams, ...CallOption) ([][sha256.Size]byte, error)
+	// ObjectPayloadRangeTZ returns homomorphic hashes of object sub-ranges from NeoFS.
+	ObjectPayloadRangeTZ(context.Context, *RangeChecksumParams, ...CallOption) ([][TZSize]byte, error)
+	// SearchObject searches for objects in NeoFS using provided parameters.
+	SearchObject(context.Context, *SearchObjectParams, ...CallOption) ([]*object.ID, error)
+}
+
 type PutObjectParams struct {
 	obj *object.Object
 
@@ -190,7 +210,7 @@ func (p *PutObjectParams) PayloadReader() io.Reader {
 	return nil
 }
 
-func (c *Client) PutObject(ctx context.Context, p *PutObjectParams, opts ...CallOption) (*object.ID, error) {
+func (c *clientImpl) PutObject(ctx context.Context, p *PutObjectParams, opts ...CallOption) (*object.ID, error) {
 	// check remote node version
 	switch c.remoteNode.Version.Major() {
 	case 2:
@@ -200,7 +220,7 @@ func (c *Client) PutObject(ctx context.Context, p *PutObjectParams, opts ...Call
 	}
 }
 
-func (c *Client) putObjectV2(ctx context.Context, p *PutObjectParams, opts ...CallOption) (*object.ID, error) {
+func (c *clientImpl) putObjectV2(ctx context.Context, p *PutObjectParams, opts ...CallOption) (*object.ID, error) {
 	// create V2 Object client
 	cli, err := v2ObjectClient(c.remoteNode.Protocol, c.opts)
 	if err != nil {
@@ -342,7 +362,7 @@ func (p *DeleteObjectParams) TombstoneAddressTarget() ObjectAddressWriter {
 // DeleteObject is a wrapper over Client.DeleteObject method
 // that provides the ability to receive tombstone address
 // without setting a target in the parameters.
-func DeleteObject(ctx context.Context, c *Client, p *DeleteObjectParams, opts ...CallOption) (*object.Address, error) {
+func DeleteObject(ctx context.Context, c Client, p *DeleteObjectParams, opts ...CallOption) (*object.Address, error) {
 	w := new(objectAddressWriter)
 
 	err := c.DeleteObject(ctx, p.WithTombstoneAddressTarget(w), opts...)
@@ -356,7 +376,7 @@ func DeleteObject(ctx context.Context, c *Client, p *DeleteObjectParams, opts ..
 // DeleteObject removes object by address.
 //
 // If target of tombstone address is not set, the address is ignored.
-func (c *Client) DeleteObject(ctx context.Context, p *DeleteObjectParams, opts ...CallOption) error {
+func (c *clientImpl) DeleteObject(ctx context.Context, p *DeleteObjectParams, opts ...CallOption) error {
 	// check remote node version
 	switch c.remoteNode.Version.Major() {
 	case 2:
@@ -378,7 +398,7 @@ func (c *Client) DeleteObject(ctx context.Context, p *DeleteObjectParams, opts .
 	}
 }
 
-func (c *Client) deleteObjectV2(ctx context.Context, p *DeleteObjectParams, opts ...CallOption) (*v2object.DeleteResponse, error) {
+func (c *clientImpl) deleteObjectV2(ctx context.Context, p *DeleteObjectParams, opts ...CallOption) (*v2object.DeleteResponse, error) {
 	// create V2 Object client
 	cli, err := v2ObjectClient(c.remoteNode.Protocol, c.opts)
 	if err != nil {
@@ -481,7 +501,7 @@ func (p *GetObjectParams) RawFlag() bool {
 	return false
 }
 
-func (c *Client) GetObject(ctx context.Context, p *GetObjectParams, opts ...CallOption) (*object.Object, error) {
+func (c *clientImpl) GetObject(ctx context.Context, p *GetObjectParams, opts ...CallOption) (*object.Object, error) {
 	// check remote node version
 	switch c.remoteNode.Version.Major() {
 	case 2:
@@ -491,7 +511,7 @@ func (c *Client) GetObject(ctx context.Context, p *GetObjectParams, opts ...Call
 	}
 }
 
-func (c *Client) getObjectV2(ctx context.Context, p *GetObjectParams, opts ...CallOption) (*object.Object, error) {
+func (c *clientImpl) getObjectV2(ctx context.Context, p *GetObjectParams, opts ...CallOption) (*object.Object, error) {
 	// create V2 Object client
 	cli, err := v2ObjectClient(c.remoteNode.Protocol, c.opts)
 	if err != nil {
@@ -653,7 +673,7 @@ func (p *ObjectHeaderParams) RawFlag() bool {
 	return false
 }
 
-func (c *Client) GetObjectHeader(ctx context.Context, p *ObjectHeaderParams, opts ...CallOption) (*object.Object, error) {
+func (c *clientImpl) GetObjectHeader(ctx context.Context, p *ObjectHeaderParams, opts ...CallOption) (*object.Object, error) {
 	// check remote node version
 	switch c.remoteNode.Version.Major() {
 	case 2:
@@ -663,7 +683,7 @@ func (c *Client) GetObjectHeader(ctx context.Context, p *ObjectHeaderParams, opt
 	}
 }
 
-func (c *Client) getObjectHeaderV2(ctx context.Context, p *ObjectHeaderParams, opts ...CallOption) (*object.Object, error) {
+func (c *clientImpl) getObjectHeaderV2(ctx context.Context, p *ObjectHeaderParams, opts ...CallOption) (*object.Object, error) {
 	// create V2 Object client
 	cli, err := v2ObjectClient(c.remoteNode.Protocol, c.opts)
 	if err != nil {
@@ -850,7 +870,7 @@ func (p *RangeDataParams) DataWriter() io.Writer {
 	return nil
 }
 
-func (c *Client) ObjectPayloadRangeData(ctx context.Context, p *RangeDataParams, opts ...CallOption) ([]byte, error) {
+func (c *clientImpl) ObjectPayloadRangeData(ctx context.Context, p *RangeDataParams, opts ...CallOption) ([]byte, error) {
 	// check remote node version
 	switch c.remoteNode.Version.Major() {
 	case 2:
@@ -860,7 +880,7 @@ func (c *Client) ObjectPayloadRangeData(ctx context.Context, p *RangeDataParams,
 	}
 }
 
-func (c *Client) objectPayloadRangeV2(ctx context.Context, p *RangeDataParams, opts ...CallOption) ([]byte, error) {
+func (c *clientImpl) objectPayloadRangeV2(ctx context.Context, p *RangeDataParams, opts ...CallOption) ([]byte, error) {
 	// create V2 Object client
 	cli, err := v2ObjectClient(c.remoteNode.Protocol, c.opts)
 	if err != nil {
@@ -1009,7 +1029,7 @@ func (p *RangeChecksumParams) withChecksumType(t checksumType) *RangeChecksumPar
 	return p
 }
 
-func (c *Client) ObjectPayloadRangeSHA256(ctx context.Context, p *RangeChecksumParams, opts ...CallOption) ([][sha256.Size]byte, error) {
+func (c *clientImpl) ObjectPayloadRangeSHA256(ctx context.Context, p *RangeChecksumParams, opts ...CallOption) ([][sha256.Size]byte, error) {
 	res, err := c.objectPayloadRangeHash(ctx, p.withChecksumType(checksumSHA256), opts...)
 	if err != nil {
 		return nil, err
@@ -1018,7 +1038,7 @@ func (c *Client) ObjectPayloadRangeSHA256(ctx context.Context, p *RangeChecksumP
 	return res.([][sha256.Size]byte), nil
 }
 
-func (c *Client) ObjectPayloadRangeTZ(ctx context.Context, p *RangeChecksumParams, opts ...CallOption) ([][TZSize]byte, error) {
+func (c *clientImpl) ObjectPayloadRangeTZ(ctx context.Context, p *RangeChecksumParams, opts ...CallOption) ([][TZSize]byte, error) {
 	res, err := c.objectPayloadRangeHash(ctx, p.withChecksumType(checksumTZ), opts...)
 	if err != nil {
 		return nil, err
@@ -1027,7 +1047,7 @@ func (c *Client) ObjectPayloadRangeTZ(ctx context.Context, p *RangeChecksumParam
 	return res.([][TZSize]byte), nil
 }
 
-func (c *Client) objectPayloadRangeHash(ctx context.Context, p *RangeChecksumParams, opts ...CallOption) (interface{}, error) {
+func (c *clientImpl) objectPayloadRangeHash(ctx context.Context, p *RangeChecksumParams, opts ...CallOption) (interface{}, error) {
 	// check remote node version
 	switch c.remoteNode.Version.Major() {
 	case 2:
@@ -1037,7 +1057,7 @@ func (c *Client) objectPayloadRangeHash(ctx context.Context, p *RangeChecksumPar
 	}
 }
 
-func (c *Client) objectPayloadRangeHashV2(ctx context.Context, p *RangeChecksumParams, opts ...CallOption) (interface{}, error) {
+func (c *clientImpl) objectPayloadRangeHashV2(ctx context.Context, p *RangeChecksumParams, opts ...CallOption) (interface{}, error) {
 	// create V2 Object client
 	cli, err := v2ObjectClient(c.remoteNode.Protocol, c.opts)
 	if err != nil {
@@ -1176,7 +1196,7 @@ func (p *SearchObjectParams) SearchFilters() object.SearchFilters {
 	return nil
 }
 
-func (c *Client) SearchObject(ctx context.Context, p *SearchObjectParams, opts ...CallOption) ([]*object.ID, error) {
+func (c *clientImpl) SearchObject(ctx context.Context, p *SearchObjectParams, opts ...CallOption) ([]*object.ID, error) {
 	// check remote node version
 	switch c.remoteNode.Version.Major() {
 	case 2:
@@ -1186,7 +1206,7 @@ func (c *Client) SearchObject(ctx context.Context, p *SearchObjectParams, opts .
 	}
 }
 
-func (c *Client) searchObjectV2(ctx context.Context, p *SearchObjectParams, opts ...CallOption) ([]*object.ID, error) {
+func (c *clientImpl) searchObjectV2(ctx context.Context, p *SearchObjectParams, opts ...CallOption) ([]*object.ID, error) {
 	// create V2 Object client
 	cli, err := v2ObjectClient(c.remoteNode.Protocol, c.opts)
 	if err != nil {
@@ -1297,7 +1317,7 @@ func v2ObjectClient(proto TransportProtocol, opts *clientOptions) (*v2object.Cli
 	}
 }
 
-func (c Client) attachV2SessionToken(opts callOptions, hdr *v2session.RequestMetaHeader, info v2SessionReqInfo) error {
+func (c clientImpl) attachV2SessionToken(opts callOptions, hdr *v2session.RequestMetaHeader, info v2SessionReqInfo) error {
 	if opts.session == nil {
 		return nil
 	}

pkg/client/opts.go

@@ -68,7 +68,7 @@ func (e errOptionsLack) Error() string {
 	return fmt.Sprintf("lack of sdk client options to create %s client", string(e))
 }
 
-func (c Client) defaultCallOptions() callOptions {
+func (c clientImpl) defaultCallOptions() callOptions {
 	return callOptions{
 		ttl:     2,
 		version: pkg.SDKVersion(),

pkg/client/session.go

@@ -11,9 +11,19 @@ import (
 	"github.com/pkg/errors"
 )
 
+// Session contains session-related methods.
+type Session interface {
+	// CreateSession creates session using provided expiration time.
+	CreateSession(context.Context, uint64, ...CallOption) (*token.SessionToken, error)
+	// AttachSessionToken attaches session token to be used by default for following requests.
+	AttachSessionToken(*token.SessionToken)
+	// AttachBearerToken attaches bearer token to be used by default for following requests.
+	AttachBearerToken(*token.BearerToken)
+}
+
 var errMalformedResponseBody = errors.New("malformed response body")
 
-func (c Client) CreateSession(ctx context.Context, expiration uint64, opts ...CallOption) (*token.SessionToken, error) {
+func (c clientImpl) CreateSession(ctx context.Context, expiration uint64, opts ...CallOption) (*token.SessionToken, error) {
 	switch c.remoteNode.Version.Major() {
 	case 2:
 		return c.createSessionV2(ctx, expiration, opts...)
@@ -22,7 +32,7 @@ func (c Client) CreateSession(ctx context.Context, expiration uint64, opts ...Ca
 	}
 }
 
-func (c Client) createSessionV2(ctx context.Context, expiration uint64, opts ...CallOption) (*token.SessionToken, error) {
+func (c clientImpl) createSessionV2(ctx context.Context, expiration uint64, opts ...CallOption) (*token.SessionToken, error) {
 	// apply all available options
 	callOptions := c.defaultCallOptions()
 
@@ -119,7 +129,7 @@ func v2SessionClientFromOptions(opts *clientOptions) (cli *v2session.Client, err
 //
 // Provided token is attached to all requests without WithSession option.
 // Use WithSession(nil) option in order to send request without session token.
-func (c *Client) AttachSessionToken(token *token.SessionToken) {
+func (c *clientImpl) AttachSessionToken(token *token.SessionToken) {
 	c.sessionToken = token
 }
 
@@ -127,6 +137,6 @@ func (c *Client) AttachSessionToken(token *token.SessionToken) {
 //
 // Provided bearer is attached to all requests without WithBearer option.
 // Use WithBearer(nil) option in order to send request without bearer token.
-func (c *Client) AttachBearerToken(token *token.BearerToken) {
+func (c *clientImpl) AttachBearerToken(token *token.BearerToken) {
 	c.bearerToken = token
 }