<?php

namespace app\components;

use DOMDocument;
use yii;
use yii\db\ActiveQueryInterface;

class SitemapGenerator
{
    const ALWAYS = 'always';
    const HOURLY = 'hourly';
    const DAILY = 'daily';
    const WEEKLY = 'weekly';
    const MONTHLY = 'monthly';
    const YEARLY = 'yearly';
    const NEVER = 'never';

    protected $items = array();

    /**
     * @param        $url
     * @param string $changeFreq
     * @param float  $priority
     * @param int    $lastMod
     */
    public function addUrl($url, $changeFreq = self::DAILY, $priority = 0.5, $lastMod = 0)
    {
        $host = Yii::$app->request->hostInfo;
        $item = [
            'loc'        => $host . $url,
            'changefreq' => $changeFreq,
            'priority'   => $priority
        ];
        if ($lastMod) {
            $item['lastmod'] = $this->dateToW3C($lastMod);
        }

        $this->items[] = $item;
    }

    /**
     * @return string XML code
     */
    public function render()
    {
        $dom = new DOMDocument('1.0', 'utf-8');
        $urlset = $dom->createElement('urlset');
        $urlset->setAttribute('xmlns', 'http://www.sitemaps.org/schemas/sitemap/0.9');
        foreach ($this->items as $item) {
            $url = $dom->createElement('url');

            foreach ($item as $key => $value) {
                $elem = $dom->createElement($key);
                $elem->appendChild($dom->createTextNode($value));
                $url->appendChild($elem);
            }

            $urlset->appendChild($url);
        }
        $dom->appendChild($urlset);

        return $dom->saveXML();
    }

    protected function dateToW3C($date)
    {
        if (is_int($date)) {
            return date(DATE_W3C, $date);
        } else {
            return date(DATE_W3C, strtotime($date));
        }
    }

}