import org.apache.maven.api.annotations.Nonnull;

/**
 * Defines a hierarchical visitor for collecting dependency node trees.
 *
 * @since 4.0.0
 */
@Experimental
@Consumer
public interface NodeVisitor {
    /**
     * Starts the visit to the specified dependency node.
     *
     * @param node the dependency node to visit

import org.apache.maven.api.Node;
import org.apache.maven.api.NodeVisitor;
import org.eclipse.aether.artifact.Artifact;
import org.eclipse.aether.graph.Dependency;
import org.eclipse.aether.graph.DependencyNode;

public abstract class AbstractNode implements Node {

    abstract org.eclipse.aether.graph.DependencyNode getDependencyNode();

    @Override
    public boolean accept(NodeVisitor visitor) {
        if (visitor.enter(this)) {

        }

        @VisibleForTesting
        List<String> flatten() {
            final List<String> prefixes = new ArrayList<String>();
            rootNode.visitHierarchy(0, new NodeVisitor() {
                @Override
                public void visitNode(int depth, Node node) {
                    if (depth == 0) {
                        prefixes.add(node.prefix);
                    } else {

     *
     * @param visitor the visitor to call back, must not be {@code null}
     * @return {@code true} to visit siblings nodes of this node as well, {@code false} to skip siblings
     */
    boolean accept(@Nonnull NodeVisitor visitor);

    /**
     * Returns a new tree starting at this node, filtering the children.
     * Note that this node will not be filtered and only the children
     * and its descendant will be checked.
     *