/app/code/core/Mage/Page/Block/Html/Topmenu.php

<?php
/**
 * Magento
 *
 * NOTICE OF LICENSE
 *
 * This source file is subject to the Open Software License (OSL 3.0)
 * that is bundled with this package in the file LICENSE.txt.
 * It is also available through the world-wide-web at this URL:
 * http://opensource.org/licenses/osl-3.0.php
 * If you did not receive a copy of the license and are unable to
 * obtain it through the world-wide-web, please send an email
 * to license@magento.com so we can send you a copy immediately.
 *
 * DISCLAIMER
 *
 * Do not edit or add to this file if you wish to upgrade Magento to newer
 * versions in the future. If you wish to customize Magento for your
 * needs please refer to http://www.magento.com for more information.
 *
 * @category    Mage
 * @package     Mage_Page
 * @copyright  Copyright (c) 2006-2016 X.commerce, Inc. and affiliates (http://www.magento.com)
 * @license    http://opensource.org/licenses/osl-3.0.php  Open Software License (OSL 3.0)
 */

/**
 * Top menu block
 *
 * @category    Mage
 * @package     Mage_Page
 * @author      Magento Core Team <core@magentocommerce.com>
 */
class Mage_Page_Block_Html_Topmenu extends Mage_Core_Block_Template
{
    /**
     * Top menu data tree
     *
     * @var Varien_Data_Tree_Node
     */
    protected $_menu;

    /**
     * Current entity key
     *
     * @var string|int
     */
    protected $_currentEntityKey;

    /**
     * Init top menu tree structure and cache
     */
    public function _construct()
    {
        $this->_menu = new Varien_Data_Tree_Node(array(), 'root', new Varien_Data_Tree());
        /*
        * setting cache to save the topmenu block
        */
        $this->setCacheTags(array(Mage_Catalog_Model_Category::CACHE_TAG));
        $this->setCacheLifetime(false);
    }

    /**
     * Get top menu html
     *
     * @param string $outermostClass
     * @param string $childrenWrapClass
     * @return string
     */
    public function getHtml($outermostClass = '', $childrenWrapClass = '')
    {
        Mage::dispatchEvent('page_block_html_topmenu_gethtml_before', array(
            'menu' => $this->_menu,
            'block' => $this
        ));

        $this->_menu->setOutermostClass($outermostClass);
        $this->_menu->setChildrenWrapClass($childrenWrapClass);

        if ($renderer = $this->getChild('catalog.topnav.renderer')) {
            $renderer->setMenuTree($this->_menu)->setChildrenWrapClass($childrenWrapClass);
            $html = $renderer->toHtml();
        } else {
            $html = $this->_getHtml($this->_menu, $childrenWrapClass);
        }

        Mage::dispatchEvent('page_block_html_topmenu_gethtml_after', array(
            'menu' => $this->_menu,
            'html' => $html
        ));

        return $html;
    }

    /**
     * Recursively generates top menu html from data that is specified in $menuTree
     *
     * @param Varien_Data_Tree_Node $menuTree
     * @param string $childrenWrapClass
     * @return string
     * @deprecated since 1.8.2.0 use child block catalog.topnav.renderer instead
     */
    protected function _getHtml(Varien_Data_Tree_Node $menuTree, $childrenWrapClass)
    {
        $html = '';

        $children = $menuTree->getChildren();
        $parentLevel = $menuTree->getLevel();
        $childLevel = is_null($parentLevel) ? 0 : $parentLevel + 1;

        $counter = 1;
        $childrenCount = $children->count();

        $parentPositionClass = $menuTree->getPositionClass();
        $itemPositionClassPrefix = $parentPositionClass ? $parentPositionClass . '-' : 'nav-';

        foreach ($children as $child) {

            $child->setLevel($childLevel);
            $child->setIsFirst($counter == 1);
            $child->setIsLast($counter == $childrenCount);
            $child->setPositionClass($itemPositionClassPrefix . $counter);

            $outermostClassCode = '';
            $outermostClass = $menuTree->getOutermostClass();

            if ($childLevel == 0 && $outermostClass) {
                $outermostClassCode = ' class="' . $outermostClass . '" ';
                $child->setClass($outermostClass);
            }

            $html .= '<li ' . $this->_getRenderedMenuItemAttributes($child) . '>';
            $html .= '<a href="' . $child->getUrl() . '" ' . $outermostClassCode . '><span>'
                . $this->escapeHtml($child->getName()) . '</span></a>';

            if ($child->hasChildren()) {
                if (!empty($childrenWrapClass)) {
                    $html .= '<div class="' . $childrenWrapClass . '">';
                }
                $html .= '<ul class="level' . $childLevel . '">';
                $html .= $this->_getHtml($child, $childrenWrapClass);
                $html .= '</ul>';

                if (!empty($childrenWrapClass)) {
                    $html .= '</div>';
                }
            }
            $html .= '</li>';

            $counter++;
        }

        return $html;
    }

    /**
     * Generates string with all attributes that should be present in menu item element
     *
     * @param Varien_Data_Tree_Node $item
     * @return string
     */
    protected function _getRenderedMenuItemAttributes(Varien_Data_Tree_Node $item)
    {
        $html = '';
        $attributes = $this->_getMenuItemAttributes($item);

        foreach ($attributes as $attributeName => $attributeValue) {
            $html .= ' ' . $attributeName . '="' . str_replace('"', '\"', $attributeValue) . '"';
        }

        return $html;
    }

    /**
     * Returns array of menu item's attributes
     *
     * @param Varien_Data_Tree_Node $item
     * @return array
     */
    protected function _getMenuItemAttributes(Varien_Data_Tree_Node $item)
    {
        $menuItemClasses = $this->_getMenuItemClasses($item);
        $attributes = array(
            'class' => implode(' ', $menuItemClasses)
        );

        return $attributes;
    }

    /**
     * Returns array of menu item's classes
     *
     * @param Varien_Data_Tree_Node $item
     * @return array
     */
    protected function _getMenuItemClasses(Varien_Data_Tree_Node $item)
    {
        $classes = array();

        $classes[] = 'level' . $item->getLevel();
        $classes[] = $item->getPositionClass();

        if ($item->getIsFirst()) {
            $classes[] = 'first';
        }

        if ($item->getIsActive()) {
            $classes[] = 'active';
        }

        if ($item->getIsLast()) {
            $classes[] = 'last';
        }

        if ($item->getClass()) {
            $classes[] = $item->getClass();
        }

        if ($item->hasChildren()) {
            $classes[] = 'parent';
        }

        return $classes;
    }

    /**
     * Retrieve cache key data
     *
     * @return array
     */
    public function getCacheKeyInfo()
    {
        $shortCacheId = array(
            'TOPMENU',
            Mage::app()->getStore()->getId(),
            Mage::getDesign()->getPackageName(),
            Mage::getDesign()->getTheme('template'),
            Mage::getSingleton('customer/session')->getCustomerGroupId(),
            'template' => $this->getTemplate(),
            'name' => $this->getNameInLayout(),
            $this->getCurrentEntityKey()
        );
        $cacheId = $shortCacheId;

        $shortCacheId = array_values($shortCacheId);
        $shortCacheId = implode('|', $shortCacheId);
        $shortCacheId = md5($shortCacheId);

        $cacheId['entity_key'] = $this->getCurrentEntityKey();
        $cacheId['short_cache_id'] = $shortCacheId;

        return $cacheId;
    }

    /**
     * Retrieve current entity key
     *
     * @return int|string
     */
    public function getCurrentEntityKey()
    {
        if (null === $this->_currentEntityKey) {
            $this->_currentEntityKey = Mage::registry('current_entity_key')
                ? Mage::registry('current_entity_key') : Mage::app()->getStore()->getRootCategoryId();
        }
        return $this->_currentEntityKey;
    }
}