<?php

interface NodeInfo
{
    public function getLeftValue();
    public function setLeftValue($value);

    public function getRightValue();
    public function setRightValue($value);

    public function getLevel();
    public function setLevel($value);

    public function getRootValue();
    public function setRootValue($value);
}


interface Node extends NodeInfo
{
    public function __construct($entity);

    public function hasPrevSibling();
    public function hasNextSibling();
    public function hasChildren();
    public function hasParent();
    public function isRoot();

    public function unwrap();

    public function getPrevSibling();
    public function getNextSibling();
    public function getChildren();
    public function getParent();
    public function getFirstChild();
    public function getLastChild();

    public function delete();

    public function addChild(Node $node);

    public function insertAsLastChildOf(Node $node);
    public function insertAsFirstChildOf(Node $node);
    public function insertAsNextSiblingOf(Node $node);
    public function insertAsPrevSiblingOf(Node $node);
    public function moveAsLastChildOf(Node $node);
    public function moveAsFirstChildOf(Node $node);
    public function moveAsNextSiblingOf(Node $node);
    public function moveAsPrevSiblingOf(Node $node);
}


class AbstractDecorator
{
    protected $entity;

    public function __construct($entity)
    {
        $this->entity = $entity;

        $this->_initMetadata();
    }

    public function unwrap()
    {
        return $this->entity;
    }

    // ...
}


class NestedSetDecorator extends AbstractDecorator implements Node
{
    public function hasChildren()
    {
        $rgtValue = $this->_getEntityValue('rightFieldName');
        $lftValue = $this->_getEntityValue('leftFieldName');

        return ($rgtValue - $lftValue) > 1;
    }

    // ...
}


class AdjacencyListDecorator extends AbstractDecorator implements Node
{
    // ...
}


class MaterializedPathDecorator extends AbstractDecorator implements Node
{
    // ...
}


class HierarchicalManager
{
    private $em;

    public function __construct(EntityManager $em)
    {
        $this->em = $em;
    }

    public function getNode($entity)
    {
        return new NestedSetDecorator($entity);
    }

    public function createRoot($entity)
    {
        // ...
    }

    // ...
}