@Override
default Tree<T> replace(T currentElement, T newElement) {
if (isEmpty()) {
return Empty.instance();
} else {
return Replace.apply((Node<T>) this, currentElement, newElement);
}
}
// Idea:
// Traverse (depth-first) until a match is found, then stop and rebuild relevant parts of the
// tree.
// If not found, return the same tree instance.
static <T> Node<T> apply(Node<T> node, T currentElement, T newElement) {
if (Objects.equals(node.getValue(), currentElement)) {
return new Node<>(newElement, node.getChildren());
} else {
for (Node<T> child : node.getChildren()) {
final Node<T> newChild = Replace.apply(child, currentElement, newElement);
final boolean found = newChild != child;
if (found) {
final List<Node<T>> newChildren = node.getChildren().replace(child, newChild);
return new Node<>(node.getValue(), newChildren);
}
}
return node;
}
}