silverstripe-googlesitemaps/code/extensions/GoogleSitemapSiteTreeExtension.php

<?php

/**
 * @package googlesitemaps
 */
class GoogleSitemapSiteTreeExtension extends GoogleSitemapExtension
{

    /**
     * @var array
     */
    private static $db = array(
        "Priority" => "Varchar(5)"
    );

    /**
     * @param FieldList
     */
    public function updateSettingsFields(&$fields)
    {
        $prorities = array(
            '-1' => _t('GoogleSitemaps.PRIORITYNOTINDEXED', "Not indexed"),
            '1.0' => '1 - ' . _t('GoogleSitemaps.PRIORITYMOSTIMPORTANT', "Most important"),
            '0.9' => '2',
            '0.8' => '3',
            '0.7' => '4',
            '0.6' => '5',
            '0.5' => '6',
            '0.4' => '7',
            '0.3' => '8',
            '0.2' => '9',
            '0.1' => '10 - ' . _t('GoogleSitemaps.PRIORITYLEASTIMPORTANT', "Least important")
        );

        $tabset = $fields->findOrMakeTab('Root.Settings');
        
        $message = "<p>";
        $message .= sprintf(_t('GoogleSitemaps.METANOTEPRIORITY', "Manually specify a Google Sitemaps priority for this page (%s)"),
            '<a href="http://www.google.com/support/webmasters/bin/answer.py?hl=en&answer=71936#prioritize" target="_blank">?</a>'
        );
        $message .=  "</p>";
        
        $tabset->push(new Tab('GoogleSitemap', _t('GoogleSitemaps.TABGOOGLESITEMAP', 'Google Sitemap'),
            new LiteralField("GoogleSitemapIntro", $message),
            $priority = new DropdownField("Priority", $this->owner->fieldLabel('Priority'), $prorities, $this->owner->Priority)
        ));

        $priority->setEmptyString(_t('GoogleSitemaps.PRIORITYAUTOSET', 'Auto-set based on page depth'));
    }

    /**
     * @param FieldList
     *
     * @return void
     */
    public function updateFieldLabels(&$labels)
    {
        parent::updateFieldLabels($labels);

        $labels['Priority'] = _t('GoogleSitemaps.METAPAGEPRIO', "Page Priority");
    }
    
    /**
     * Ensure that all parent pages of this page (if any) are published
     * 
     * @return boolean
     */
    public function hasPublishedParent()
    {
        
        // Skip root pages
        if (empty($this->owner->ParentID)) {
            return true;
        }
        
        // Ensure direct parent exists
        $parent = $this->owner->Parent();
        if (empty($parent) || !$parent->exists()) {
            return false;
        }
        
        // Check ancestry
        return $parent->hasPublishedParent();
    }

    /**
     * @return boolean
     */
    public function canIncludeInGoogleSitemap()
    {
        
        // Check that parent page is published
        if (!$this->owner->hasPublishedParent()) {
            return false;
        }
        
        $result = parent::canIncludeInGoogleSitemap();
        $result = ($this->owner instanceof ErrorPage) ? false : $result;

        return $result;
    }

    /**
     * @return mixed
     */
    public function getGooglePriority()
    {
        setlocale(LC_ALL, "en_US.UTF8");
        $priority = $this->owner->getField('Priority');

        if (!$priority) {
            $parentStack = $this->owner->parentStack();
            $numParents = is_array($parentStack) ? count($parentStack) - 1 : 0;
            
            $num = max(0.1, 1.0 - ($numParents / 10));
            $result = str_replace(",", ".", $num);

            return $result;
        } elseif ($priority == -1) {
            return false;
        } else {
            return (is_numeric($priority) && $priority <= 1.0) ? $priority : 0.5;
        }
    }
}