Expose fork choice node (#4819)

* Expose node

* Comments

* Extra line

Co-authored-by: prylabs-bulldozer[bot] <58059840+prylabs-bulldozer[bot]@users.noreply.github.com>

beacon-chain/forkchoice/interfaces.go

@@ -38,5 +38,6 @@ type Pruner interface {
 // Getter returns fork choice related information.
 type Getter interface {
 	Nodes() []*protoarray.Node
+	Node([32]byte) *protoarray.Node
 	HasNode([32]byte) bool
 }

beacon-chain/forkchoice/protoarray/helpers.go

@@ -70,3 +70,24 @@ func computeDeltas(
 
 	return deltas, votes, nil
 }
+
+// This return a copy of the proto array node object.
+func copyNode(node *Node) *Node {
+	if node == nil {
+		return &Node{}
+	}
+
+	copiedRoot := [32]byte{}
+	copy(copiedRoot[:], node.root[:])
+
+	return &Node{
+		Slot:           node.Slot,
+		root:           copiedRoot,
+		Parent:         node.Parent,
+		justifiedEpoch: node.justifiedEpoch,
+		finalizedEpoch: node.finalizedEpoch,
+		Weight:         node.Weight,
+		bestChild:      node.bestChild,
+		BestDescendent: node.BestDescendent,
+	}
+}

beacon-chain/forkchoice/protoarray/store.go

@@ -106,6 +106,19 @@ func (f *ForkChoice) Nodes() []*Node {
 	return cpy
 }
 
+// Node returns the copied node in the fork choice store.
+func (f *ForkChoice) Node(root [32]byte) *Node {
+	f.store.nodeIndicesLock.RLock()
+	defer f.store.nodeIndicesLock.RUnlock()
+
+	index, ok := f.store.nodeIndices[root]
+	if !ok {
+		return nil
+	}
+
+	return copyNode(f.store.nodes[index])
+}
+
 // HasNode returns true if the node exists in fork choice store,
 // false else wise.
 func (f *ForkChoice) HasNode(root [32]byte) bool {