[#30] add object name resolving

Signed-off-by: Pavel Pogodaev <p.pogodaev@yadro.com>

tree/tree.go

@@ -0,0 +1,156 @@
+package tree
+
+import (
+	"context"
+	"fmt"
+	"strings"
+
+	"git.frostfs.info/TrueCloudLab/frostfs-http-gw/api"
+	"git.frostfs.info/TrueCloudLab/frostfs-http-gw/api/layer"
+	cid "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/container/id"
+	oid "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object/id"
+)
+
+type (
+	Tree struct {
+		service ServiceClient
+	}
+
+	// ServiceClient is a client to interact with tree service.
+	// Each method must return ErrNodeNotFound or ErrNodeAccessDenied if relevant.
+	ServiceClient interface {
+		GetNodes(ctx context.Context, p *GetNodesParams) ([]NodeResponse, error)
+	}
+
+	treeNode struct {
+		ObjID oid.ID
+		Meta  map[string]string
+	}
+
+	GetNodesParams struct {
+		CnrID      cid.ID
+		TreeID     string
+		Path       []string
+		Meta       []string
+		LatestOnly bool
+		AllAttrs   bool
+	}
+)
+
+var (
+	// ErrNodeNotFound is returned from ServiceClient in case of not found error.
+	ErrNodeNotFound = layer.ErrNodeNotFound
+
+	// ErrNodeAccessDenied is returned from ServiceClient service in case of access denied error.
+	ErrNodeAccessDenied = layer.ErrNodeAccessDenied
+)
+
+const (
+	FileNameKey = "FileName"
+)
+
+const (
+	oidKV = "OID"
+
+	// keys for delete marker nodes.
+	isDeleteMarkerKV = "IsDeleteMarker"
+
+	// versionTree -- ID of a tree with object versions.
+	versionTree = "version"
+
+	separator = "/"
+)
+
+// NewTree creates instance of Tree using provided address and create grpc connection.
+func NewTree(service ServiceClient) *Tree {
+	return &Tree{service: service}
+}
+
+type Meta interface {
+	GetKey() string
+	GetValue() []byte
+}
+
+type NodeResponse interface {
+	GetMeta() []Meta
+}
+
+func newTreeNode(nodeInfo NodeResponse) (*treeNode, error) {
+	treeNode := &treeNode{
+		Meta: make(map[string]string, len(nodeInfo.GetMeta())),
+	}
+
+	for _, kv := range nodeInfo.GetMeta() {
+		switch kv.GetKey() {
+		case oidKV:
+			if err := treeNode.ObjID.DecodeString(string(kv.GetValue())); err != nil {
+				return nil, err
+			}
+		default:
+			treeNode.Meta[kv.GetKey()] = string(kv.GetValue())
+		}
+	}
+
+	return treeNode, nil
+}
+
+func (n *treeNode) Get(key string) (string, bool) {
+	value, ok := n.Meta[key]
+	return value, ok
+}
+
+func (n *treeNode) FileName() (string, bool) {
+	value, ok := n.Meta[FileNameKey]
+	return value, ok
+}
+
+func newNodeVersion(node NodeResponse) (*api.NodeVersion, error) {
+	treeNode, err := newTreeNode(node)
+	if err != nil {
+		return nil, fmt.Errorf("invalid tree node: %w", err)
+	}
+
+	return newNodeVersionFromTreeNode(treeNode), nil
+}
+
+func newNodeVersionFromTreeNode(treeNode *treeNode) *api.NodeVersion {
+	_, isDeleteMarker := treeNode.Get(isDeleteMarkerKV)
+
+	version := &api.NodeVersion{
+		BaseNodeVersion: api.BaseNodeVersion{
+			OID: treeNode.ObjID,
+		},
+		DeleteMarker: isDeleteMarker,
+	}
+
+	return version
+}
+
+func (c *Tree) GetLatestVersion(ctx context.Context, cnrID *cid.ID, objectName string) (*api.NodeVersion, error) {
+	meta := []string{oidKV, isDeleteMarkerKV}
+	path := pathFromName(objectName)
+
+	p := &GetNodesParams{
+		CnrID:      *cnrID,
+		TreeID:     versionTree,
+		Path:       path,
+		Meta:       meta,
+		LatestOnly: true,
+		AllAttrs:   false,
+	}
+	nodes, err := c.service.GetNodes(ctx, p)
+	if err != nil {
+		return nil, err
+	}
+
+	if len(nodes) == 0 {
+		return nil, layer.ErrNodeNotFound
+	}
+
+	return newNodeVersion(nodes[0])
+}
+
+// pathFromName splits name by '/'.
+func pathFromName(objectName string) []string {
+	return strings.Split(objectName, separator)
+}