Apply GCPair to TreeNode, TextNode (#866)

This commit is a follow-up task of #864, applying GCPair for TextNode
and TreeNode. Additionally, when generating a document from the root,
this commit registers GCPair in the cache.

api/converter/from_pb.go

@@ -658,10 +658,11 @@ func fromTreeNode(pbNode *api.TreeNode) (*crdt.TreeNode, error) {
 		}
 	}
 
-	node.RemovedAt, err = fromTimeTicket(pbNode.RemovedAt)
+	removedAt, err := fromTimeTicket(pbNode.RemovedAt)
 	if err != nil {
 		return nil, err
 	}
+	node.SetRemovedAt(removedAt)
 
 	return node, nil
 }

api/converter/to_bytes.go

@@ -310,10 +310,10 @@ func toTreeNode(treeNode *crdt.TreeNode, depth int) *api.TreeNode {
 	}
 
 	pbNode := &api.TreeNode{
-		Id:         toTreeNodeID(treeNode.ID),
+		Id:         toTreeNodeID(treeNode.ID()),
 		Type:       treeNode.Type(),
 		Value:      treeNode.Value,
-		RemovedAt:  ToTimeTicket(treeNode.RemovedAt),
+		RemovedAt:  ToTimeTicket(treeNode.RemovedAt()),
 		Depth:      int32(depth),
 		Attributes: attrs,
 	}

pkg/document/change/context.go

@@ -80,11 +80,6 @@ func (c *Context) RegisterRemovedElementPair(parent crdt.Container, deleted crdt
 	c.root.RegisterRemovedElementPair(parent, deleted)
 }
 
-// RegisterElementHasRemovedNodes register the given text element with garbage to hash table.
-func (c *Context) RegisterElementHasRemovedNodes(element crdt.GCElement) {
-	c.root.RegisterElementHasRemovedNodes(element)
-}
-
 // RegisterGCPair registers the given GC pair to the root.
 func (c *Context) RegisterGCPair(pair crdt.GCPair) {
 	c.root.RegisterGCPair(pair)

pkg/document/crdt/element.go

@@ -39,13 +39,6 @@ type Container interface {
 	DeleteByCreatedAt(createdAt *time.Ticket, deletedAt *time.Ticket) (Element, error)
 }
 
-// GCElement represents Element which has GC.
-type GCElement interface {
-	Element
-	removedNodesLen() int
-	purgeRemovedNodesBefore(ticket *time.Ticket) (int, error)
-}
-
 // Element represents JSON element.
 type Element interface {
 	// Marshal returns the JSON encoding of this element.

pkg/document/crdt/gc.go

@@ -32,6 +32,6 @@ type GCParent interface {
 
 // GCChild is an interface for the child of the garbage collection target.
 type GCChild interface {
-	ID() string
+	IDString() string
 	RemovedAt() *time.Ticket
 }

pkg/document/crdt/rga_tree_split.go

@@ -173,6 +173,11 @@ func (s *RGATreeSplitNode[V]) ID() *RGATreeSplitNodeID {
 	return s.id
 }
 
+// IDString returns the string representation of the ID.
+func (s *RGATreeSplitNode[V]) IDString() string {
+	return s.id.key()
+}
+
 // InsPrevID returns previous node ID at the time of this node insertion.
 func (s *RGATreeSplitNode[V]) InsPrevID() *RGATreeSplitNodeID {
 	if s.insPrev == nil {
@@ -254,11 +259,14 @@ func (s *RGATreeSplitNode[V]) toTestString() string {
 // Remove removes this node if it created before the time of deletion are
 // deleted. It only marks the deleted time (tombstone).
 func (s *RGATreeSplitNode[V]) Remove(removedAt *time.Ticket, maxCreatedAt *time.Ticket) bool {
+	justRemoved := s.removedAt == nil
+
 	if !s.createdAt().After(maxCreatedAt) &&
 		(s.removedAt == nil || removedAt.After(s.removedAt)) {
 		s.removedAt = removedAt
-		return true
+		return justRemoved
 	}
+
 	return false
 }
 
@@ -281,10 +289,6 @@ type RGATreeSplit[V RGATreeSplitValue] struct {
 	initialHead *RGATreeSplitNode[V]
 	treeByIndex *splay.Tree[*RGATreeSplitNode[V]]
 	treeByID    *llrb.Tree[*RGATreeSplitNodeID, *RGATreeSplitNode[V]]
-
-	// removedNodeMap is a map to store removed nodes. It is used to
-	// delete the node physically when the garbage collection is executed.
-	removedNodeMap map[string]*RGATreeSplitNode[V]
 }
 
 // NewRGATreeSplit creates a new instance of RGATreeSplit.
@@ -294,10 +298,9 @@ func NewRGATreeSplit[V RGATreeSplitValue](initialHead *RGATreeSplitNode[V]) *RGA
 	treeByID.Put(initialHead.ID(), initialHead)
 
 	return &RGATreeSplit[V]{
-		initialHead:    initialHead,
-		treeByIndex:    treeByIndex,
-		treeByID:       treeByID,
-		removedNodeMap: make(map[string]*RGATreeSplitNode[V]),
+		initialHead: initialHead,
+		treeByIndex: treeByIndex,
+		treeByID:    treeByID,
 	}
 }
 
@@ -448,20 +451,20 @@ func (s *RGATreeSplit[V]) edit(
 	maxCreatedAtMapByActor map[string]*time.Ticket,
 	content V,
 	editedAt *time.Ticket,
-) (*RGATreeSplitNodePos, map[string]*time.Ticket, error) {
+) (*RGATreeSplitNodePos, map[string]*time.Ticket, []GCPair, error) {
 	// 01. Split nodes with from and to
 	toLeft, toRight, err := s.findNodeWithSplit(to, editedAt)
 	if err != nil {
-		return nil, nil, err
+		return nil, nil, nil, err
 	}
 	fromLeft, fromRight, err := s.findNodeWithSplit(from, editedAt)
 	if err != nil {
-		return nil, nil, err
+		return nil, nil, nil, err
 	}
 
 	// 02. delete between from and to
 	nodesToDelete := s.findBetween(fromRight, toRight)
-	maxCreatedAtMap, removedNodeMapByNodeKey := s.deleteNodes(nodesToDelete, maxCreatedAtMapByActor, editedAt)
+	maxCreatedAtMap, removedNodes := s.deleteNodes(nodesToDelete, maxCreatedAtMapByActor, editedAt)
 
 	var caretID *RGATreeSplitNodeID
 	if toRight == nil {
@@ -478,11 +481,15 @@ func (s *RGATreeSplit[V]) edit(
 	}
 
 	// 04. add removed node
-	for key, removedNode := range removedNodeMapByNodeKey {
-		s.removedNodeMap[key] = removedNode
+	var pairs []GCPair
+	for _, removedNode := range removedNodes {
+		pairs = append(pairs, GCPair{
+			Parent: s,
+			Child:  removedNode,
+		})
 	}
 
-	return caretPos, maxCreatedAtMap, nil
+	return caretPos, maxCreatedAtMap, pairs, nil
 }
 
 func (s *RGATreeSplit[V]) findBetween(from, to *RGATreeSplitNode[V]) []*RGATreeSplitNode[V] {
@@ -617,29 +624,10 @@ func (s *RGATreeSplit[V]) ToTestString() string {
 	return builder.String()
 }
 
-// removedNodesLen returns length of removed nodes
-func (s *RGATreeSplit[V]) removedNodesLen() int {
-	return len(s.removedNodeMap)
-}
-
-// purgeRemovedNodesBefore physically purges nodes that have been removed.
-func (s *RGATreeSplit[V]) purgeRemovedNodesBefore(ticket *time.Ticket) (int, error) {
-	count := 0
-	for _, node := range s.removedNodeMap {
-		if node.removedAt != nil && ticket.Compare(node.removedAt) >= 0 {
-			s.treeByIndex.Delete(node.indexNode)
-			s.purge(node)
-			s.treeByID.Remove(node.id)
-			delete(s.removedNodeMap, node.id.key())
-			count++
-		}
-	}
+// Purge physically purge the given node from RGATreeSplit.
+func (s *RGATreeSplit[V]) Purge(child GCChild) error {
+	node := child.(*RGATreeSplitNode[V])
 
-	return count, nil
-}
-
-// purge physically purge the given node from RGATreeSplit.
-func (s *RGATreeSplit[V]) purge(node *RGATreeSplitNode[V]) {
 	node.prev.next = node.next
 	if node.next != nil {
 		node.next.prev = node.prev
@@ -653,4 +641,6 @@ func (s *RGATreeSplit[V]) purge(node *RGATreeSplitNode[V]) {
 		node.insNext.insPrev = node.insPrev
 	}
 	node.insPrev, node.insNext = nil, nil
+
+	return nil
 }

pkg/document/crdt/rht.go

@@ -41,8 +41,8 @@ func newRHTNode(key, val string, updatedAt *time.Ticket, isRemoved bool) *RHTNod
 	}
 }
 
-// ID returns the ID of this node.
-func (n *RHTNode) ID() string {
+// IDString returns the string representation of this node.
+func (n *RHTNode) IDString() string {
 	return n.updatedAt.Key() + ":" + n.key
 }
 
@@ -231,8 +231,8 @@ func (rht *RHT) Marshal() string {
 
 // Purge purges the given child node.
 func (rht *RHT) Purge(child *RHTNode) error {
-	if node, ok := rht.nodeMapByKey[child.key]; !ok || node.ID() != child.ID() {
-		//return ErrChildNotFound
+	if node, ok := rht.nodeMapByKey[child.key]; !ok || node.IDString() != child.IDString() {
+		// TODO(hackerwins): Should we return an error when the child is not found?
 		return nil
 	}