Handle concurrent editing of Tree.Edit (#607)

Introduced new logical timestamp for identifying the position in
local/remote editing, and ensures commutative editing in concurrent
cases.

This logical timestamp consists of {parentID, leftSiblingID}. This
allows editing at the front of text nodes by using a reference to the
parent, as well as getting rid of the local offset used to access an
element node's children previously by using the leftSiblingID.

---------

Co-authored-by: MoonGyu1 <s201801402@hufs-gsuite.kr>
Co-authored-by: sejongk <sepaper@naver.com>

api/converter/from_pb.go

@@ -491,6 +491,13 @@ func fromTreeEdit(pbTreeEdit *api.Operation_TreeEdit) (*operations.TreeEdit, err
 		return nil, err
 	}
 
+	createdAtMapByActor, err := fromCreatedAtMapByActor(
+		pbTreeEdit.CreatedAtMapByActor,
+	)
+	if err != nil {
+		return nil, err
+	}
+
 	nodes, err := FromTreeNodesWhenEdit(pbTreeEdit.Contents)
 	if err != nil {
 		return nil, err
@@ -500,6 +507,7 @@ func fromTreeEdit(pbTreeEdit *api.Operation_TreeEdit) (*operations.TreeEdit, err
 		parentCreatedAt,
 		from,
 		to,
+		createdAtMapByActor,
 		nodes,
 		executedAt,
 	), nil
@@ -620,7 +628,7 @@ func FromTreeNodesWhenEdit(pbNodes []*api.TreeNodes) ([]*crdt.TreeNode, error) {
 }
 
 func fromTreeNode(pbNode *api.TreeNode) (*crdt.TreeNode, error) {
-	pos, err := fromTreePos(pbNode.Pos)
+	id, err := fromTreeNodeID(pbNode.Id)
 	if err != nil {
 		return nil, err
 	}
@@ -635,20 +643,34 @@ func fromTreeNode(pbNode *api.TreeNode) (*crdt.TreeNode, error) {
 	}
 
 	return crdt.NewTreeNode(
-		pos,
+		id,
 		pbNode.Type,
 		attrs,
 		pbNode.Value,
 	), nil
 }
 
 func fromTreePos(pbPos *api.TreePos) (*crdt.TreePos, error) {
+	parentID, err := fromTreeNodeID(pbPos.ParentId)
+	if err != nil {
+		return nil, err
+	}
+
+	leftSiblingID, err := fromTreeNodeID(pbPos.LeftSiblingId)
+	if err != nil {
+		return nil, err
+	}
+
+	return crdt.NewTreePos(parentID, leftSiblingID), nil
+}
+
+func fromTreeNodeID(pbPos *api.TreeNodeID) (*crdt.TreeNodeID, error) {
 	createdAt, err := fromTimeTicket(pbPos.CreatedAt)
 	if err != nil {
 		return nil, err
 	}
 
-	return crdt.NewTreePos(
+	return crdt.NewTreeNodeID(
 		createdAt,
 		int(pbPos.Offset),
 	), nil

api/converter/to_bytes.go

@@ -298,7 +298,7 @@ func toTreeNode(treeNode *crdt.TreeNode, depth int) *api.TreeNode {
 	}
 
 	pbNode := &api.TreeNode{
-		Pos:        toTreePos(treeNode.Pos),
+		Id:         toTreeNodeID(treeNode.ID),
 		Type:       treeNode.Type(),
 		Value:      treeNode.Value,
 		RemovedAt:  ToTimeTicket(treeNode.RemovedAt),
@@ -307,15 +307,28 @@ func toTreeNode(treeNode *crdt.TreeNode, depth int) *api.TreeNode {
 	}
 
 	if treeNode.InsPrev != nil {
-		pbNode.InsPrevPos = toTreePos(treeNode.InsPrev.Pos)
+		pbNode.InsPrevId = toTreeNodeID(treeNode.InsPrev.ID)
 	}
 
 	return pbNode
 }
 
-func toTreePos(pos *crdt.TreePos) *api.TreePos {
-	return &api.TreePos{
+func toTreeNodeID(pos *crdt.TreeNodeID) *api.TreeNodeID {
+	return &api.TreeNodeID{
 		CreatedAt: ToTimeTicket(pos.CreatedAt),
 		Offset:    int32(pos.Offset),
 	}
 }
+
+func toTreePos(pos *crdt.TreePos) *api.TreePos {
+	return &api.TreePos{
+		ParentId: &api.TreeNodeID{
+			CreatedAt: ToTimeTicket(pos.ParentID.CreatedAt),
+			Offset:    int32(pos.ParentID.Offset),
+		},
+		LeftSiblingId: &api.TreeNodeID{
+			CreatedAt: ToTimeTicket(pos.LeftSiblingID.CreatedAt),
+			Offset:    int32(pos.LeftSiblingID.Offset),
+		},
+	}
+}

api/converter/to_pb.go

@@ -381,11 +381,12 @@ func toIncrease(increase *operations.Increase) (*api.Operation_Increase_, error)
 func toTreeEdit(e *operations.TreeEdit) (*api.Operation_TreeEdit_, error) {
 	return &api.Operation_TreeEdit_{
 		TreeEdit: &api.Operation_TreeEdit{
-			ParentCreatedAt: ToTimeTicket(e.ParentCreatedAt()),
-			From:            toTreePos(e.FromPos()),
-			To:              toTreePos(e.ToPos()),
-			Contents:        ToTreeNodesWhenEdit(e.Contents()),
-			ExecutedAt:      ToTimeTicket(e.ExecutedAt()),
+			ParentCreatedAt:     ToTimeTicket(e.ParentCreatedAt()),
+			From:                toTreePos(e.FromPos()),
+			To:                  toTreePos(e.ToPos()),
+			CreatedAtMapByActor: toCreatedAtMapByActor(e.CreatedAtMapByActor()),
+			Contents:            ToTreeNodesWhenEdit(e.Contents()),
+			ExecutedAt:          ToTimeTicket(e.ExecutedAt()),
 		},
 	}, nil
 }