<?php

class App_Sitemap_Xml_Writer extends XmlWriter
{
    protected $_fileIndex = 1;
    protected $_urlCount = 0;
    protected $_size = 0;
    protected $_maxUrlCount = 50000;
    protected $_maxSize = 10485760; // 10 MB
    protected $_fileName = 'sitemap.xml';
    protected $_file;
    protected $_flushed = false;

    public function __construct()
    {
        $this->_file = WWW_PATH . '/' . $this->_fileName;
    }

    public function start()
    {
        $file = str_replace('.xml', '.' . $this->_fileIndex . '.xml', $this->_file);
        $this->_checkFile($file);
        $this->openUri($file);
        $this->setIndent(true);
        $this->setIndentString('    ');
        $this->startDocument('1.0', 'UTF-8');
        $this->startElement('urlset');
        $this->writeAttribute('xmlns', 'http://www.sitemaps.org/schemas/sitemap/0.9');
        $this->_urlCount = 0;
        $this->_size = 0;
        return $this;
    }

    public function startIndex()
    {
        $this->_checkFile($this->_file);
        $this->openUri($this->_file);
        $this->setIndent(true);
        $this->setIndentString('    ');
        $this->startDocument('1.0', 'UTF-8');
        $this->startElement('sitemapindex');
        $this->writeAttribute('xmlns', 'http://www.sitemaps.org/schemas/sitemap/0.9');
        return $this;
    }

    public function endIndex()
    {
        $this->endElement(); // sitemapindex
        $this->endDocument();
    }

    public function writeUrl($url, $lastmod = null)
    {
        $this->_flushed = false;
        $this->startElement('url');
        $this->startElement('loc');
        $this->text($url);
        $this->endElement(); // loc
        if (!empty($lastmod)) {
            $this->startElement('lastmod');
            $this->text($lastmod);
            $this->endElement(); //lastmod
        }
        $this->endElement(); // url
        $this->_urlCount++;
        $this->_size += $this->flush();
        if ($this->_urlCount == $this->_maxUrlCount || ($this->_size >= $this->_maxSize - 256)) {
            $this->end();
            $this->flush();
            $this->_fileIndex++;
            $this->start();
        }
        return $this;
    }

    protected function _checkFile($file)
    {
        if (!is_writable(dirname($file))) {
            throw new App_Sitemap_Xml_Exception('Destination directory "' . dirname($file) . '" is not writable');
        }
        if (file_exists($file) && !is_writable($file)) {
            throw new App_Sitemap_Xml_Exception('Destination file "' . $file . '" is not writable');
        }
        return $this;
    }

    public function end()
    {
        $this->endElement(); // urlset
        $this->endDocument();
        return $this;
    }

    public function finish()
    {
        $this->flush();
        if (1 == $this->_fileIndex) {
            $this->_checkFile($this->_file);
            $file = str_replace('.xml', '.' . $this->_fileIndex . '.xml', $this->_file);
            rename($file, $this->_file);
            return $this;
        }
        $this->startIndex();
        for ($i = 0; $i < $this->_fileIndex; $i++) {
            $this->startElement('sitemap');
            $this->startElement('loc');
            $file = str_replace('.xml', '.' . ($i + 1) . '.xml', $this->_fileName);
            $this->text(BASE_URL . '/' . $file);
            $this->endElement(); // loc
            $this->endElement(); // sitemap
        }
        $this->endIndex();
        $this->flush();
    }

    public function output()
    {
        if (!$handle = fopen($this->_file, 'r')) {
            throw new App_Sitemap_Xml_Exception('Can not open file "' . $file . '"');
        }
        header('Content-type: text/xml');
        fpassthru($handle);
        exit;
    }
}