[#165] Support streaming listing

Signed-off-by: Denis Kirillov <d.kirillov@yadro.com>

pkg/service/tree/tree_client_in_memory.go

@@ -3,6 +3,7 @@ package tree
 import (
 	"context"
 	"fmt"
+	"io"
 	"sort"
 	"time"
 
@@ -146,6 +147,7 @@ func (t *memoryTree) createPathIfNotExist(parent *treeNodeMemory, path []string)
 		}
 		t.idCounter++
 		parent.children = append(parent.children, node)
+		//sortNodes(parent.children)
 	}
 
 	return t.createPathIfNotExist(node, path[1:])
@@ -227,9 +229,45 @@ func (c *ServiceClientMemory) GetSubTree(_ context.Context, bktInfo *data.Bucket
 		return nil, ErrNodeNotFound
 	}
 
+	// we depth-1 in case of uint32 and 0 as mark to get all subtree leads to overflow and depth is getting quite big to walk all tree levels
 	return node.listNodes(nil, depth-1), nil
 }
 
+type SubTreeStreamImpl struct {
+	res    []NodeResponse
+	offset int
+}
+
+func (s *SubTreeStreamImpl) Next() (NodeResponse, error) {
+	if s.offset > len(s.res)-1 {
+		return nil, io.EOF
+	}
+	s.offset++
+	return s.res[s.offset-1], nil
+}
+
+func (c *ServiceClientMemory) GetSubTreeStream(_ context.Context, bktInfo *data.BucketInfo, treeID string, rootID uint64, depth uint32) (SubTreeStream, error) {
+	cnr, ok := c.containers[bktInfo.CID.EncodeToString()]
+	if !ok {
+		return nil, nil
+	}
+
+	tr, ok := cnr.trees[treeID]
+	if !ok {
+		return nil, ErrNodeNotFound
+	}
+
+	node := tr.treeData.getNode(rootID)
+	if node == nil {
+		return nil, ErrNodeNotFound
+	}
+
+	return &SubTreeStreamImpl{
+		res:    node.listNodes(nil, depth-1),
+		offset: 0,
+	}, nil
+}
+
 func newContainerInfo(bktInfo *data.BucketInfo, treeID string) containerInfo {
 	return containerInfo{
 		bkt: bktInfo,
@@ -257,7 +295,11 @@ func newMemoryTree() memoryTree {
 	}
 }
 
-func (c *ServiceClientMemory) AddNode(_ context.Context, bktInfo *data.BucketInfo, treeID string, parent uint64, meta map[string]string) (uint64, error) {
+func (c *ServiceClientMemory) AddNode(ctx context.Context, bktInfo *data.BucketInfo, treeID string, parent uint64, meta map[string]string) (uint64, error) {
+	return c.AddNodeBase(ctx, bktInfo, treeID, parent, meta, true)
+}
+
+func (c *ServiceClientMemory) AddNodeBase(_ context.Context, bktInfo *data.BucketInfo, treeID string, parent uint64, meta map[string]string, needSort bool) (uint64, error) {
 	cnr, ok := c.containers[bktInfo.CID.EncodeToString()]
 	if !ok {
 		cnr = newContainerInfo(bktInfo, treeID)
@@ -289,6 +331,9 @@ func (c *ServiceClientMemory) AddNode(_ context.Context, bktInfo *data.BucketInf
 	}
 
 	parentNode.children = append(parentNode.children, tn)
+	if needSort {
+		//sortNodes(parentNode.children)
+	}
 	cnr.trees[treeID] = tr
 
 	return newID, nil
@@ -326,6 +371,7 @@ func (c *ServiceClientMemory) AddNodeByPath(_ context.Context, bktInfo *data.Buc
 	}
 
 	parentNode.children = append(parentNode.children, tn)
+	//sortNodes(parentNode.children)
 	cnr.trees[treeID] = tr
 
 	return newID, nil
@@ -356,11 +402,38 @@ func (c *ServiceClientMemory) MoveNode(_ context.Context, bktInfo *data.BucketIn
 	node.data.parentID = parentID
 
 	newParent.children = append(newParent.children, node)
+	//sortNodes(newParent.children)
 	node.parent.removeChild(nodeID)
 
 	return nil
 }
 
+func (c *ServiceClientMemory) Sort() {
+	for _, info := range c.containers {
+		for _, tree := range info.trees {
+			sortNode(tree.treeData)
+		}
+	}
+}
+
+func sortNode(node *treeNodeMemory) {
+	if node == nil {
+		return
+	}
+
+	sortNodes(node.children)
+
+	for _, child := range node.children {
+		sortNode(child)
+	}
+}
+
+func sortNodes(list []*treeNodeMemory) {
+	sort.Slice(list, func(i, j int) bool {
+		return list[i].data.getValue(FileNameKey) < list[j].data.getValue(FileNameKey)
+	})
+}
+
 func (c *ServiceClientMemory) RemoveNode(_ context.Context, bktInfo *data.BucketInfo, treeID string, nodeID uint64) error {
 	cnr, ok := c.containers[bktInfo.CID.EncodeToString()]
 	if !ok {