diff --git a/ext/sitemap/main.php b/ext/sitemap/main.php
index e481510f..37f494c0 100644
--- a/ext/sitemap/main.php
+++ b/ext/sitemap/main.php
@@ -1,54 +1,135 @@
-<?php
-/*
- * Name: XML Sitemap
- * Author: Sein Kraft <mail@seinkraft.info>
- * License: GPLv2
- * Description: Adds sitemap.xml on request.
- * Documentation:
- */
-
-class XMLSitemap extends Extension {
-	public function onPageRequest(PageRequestEvent $event) {
-		if($event->page_matches("sitemap.xml")) {
-			$images = Image::find_images(0, 50, array());
-			$this->do_xml($images);
-		}
-	}
-	
-	private function do_xml(/*array(Image)*/ $images) {
-		global $page;
-		$page->set_mode("data");
-		$page->set_type("application/xml");
-
-		$data = "";
-		foreach($images as $image) {
-			$link = make_http(make_link("post/view/{$image->id}"));
-			$posted = date("Y-m-d", $image->posted_timestamp);
-			
-			$data .= "
-			<url>
-			<loc>$link</loc>
-			<lastmod>$posted</lastmod>
-			<changefreq>monthly</changefreq>
-			<priority>0.8</priority>
-			</url>
-			";
-		}
-
-		$base_href = make_http(make_link("post/list"));
-
-		$xml = "<"."?xml version=\"1.0\" encoding=\"utf-8\"?".">
-				<urlset xmlns=\"http://www.sitemaps.org/schemas/sitemap/0.9\">
-				<url>
-				<loc>$base_href</loc>
-				<lastmod>2009-01-01</lastmod>
-				<changefreq>monthly</changefreq>
-				<priority>1</priority>
-				</url>
-				$data
-				</urlset>
-				";
-		$page->set_data($xml);
-	}
-}
-?>
+<?php
+/*
+ * Name: XML Sitemap
+ * Author: Sein Kraft <mail@seinkraft.info>, Drudex Software <support@drudexsoftware.com
+ * License: GPLv2
+ * Description: Adds sitemap.xml on request.
+ * Documentation:
+ */
+
+class XMLSitemap extends Extension {
+        private $sitemap_queue = "";
+        private $time_structure = "YmdHis";
+        private $sitemap_creation_interval = 6; // number of hours between sitemap regeneration
+    
+        public function onInitExt(InitExtEvent $event) {
+            global $config;
+            
+            // adds last_sitemap to config
+            $config->set_default_string("last_sitemap", // set initial date to a year ago
+                            date($this->time_structure, strtotime('-1 year',time())));    
+        }
+        
+	public function onPageRequest(PageRequestEvent $event) { 
+            global $database, $config;  
+            if($event->page_matches("sitemap.xml")) 
+            {   
+                // creates default value
+                $config->set_default_string("last_sitemap", // set initial date to a year ago
+                            date($this->time_structure, strtotime('-1 year',time())));
+                
+                // remakes sitemap if needed
+                $lastsitemaptime = date($this->time_structure, $config->get_string("last_sitemap"));
+                $sitemap_creation_allowed_time = date($this->time_structure, strtotime("+$this->sitemap_creation_interval hours", $lastsitemaptime));
+                if ($sitemap_creation_allowed_time < time() || // sitemap is allowed to reset
+                        !file_exists($_SERVER["DOCUMENT_ROOT"]."/sitemap.xml")) // or sitemap can be remade
+                {              
+                    // add index
+                    $index[0] = $base_href = make_http(make_link("post/list"));
+                    $this->add_sitemap_queue($index, "weekly", "1");
+                    
+                    /* --- Add 20 most used tags --- */
+                    $popular_tags = $database->get_all("SELECT tag, count FROM tags ORDER BY `count` DESC LIMIT 0,20");
+                    foreach($popular_tags as $arrayid => $tag) {
+                        $tag = $tag['tag'];
+                        // create url from tags (tagme ignored)
+                        if ($tag != "tagme")
+                            $popular_tags[$arrayid] = "post/list/$tag/";
+                    }
+                    $this->add_sitemap_queue($popular_tags, "monthly", "0.9" /* not sure how to deal with date here */);           
+
+                    /* --- Add latest images to sitemap with higher priority --- */
+                    $latestimages = Image::find_images(0, 50, array());
+                    $latestimages_urllist = array();
+                    foreach($latestimages as $arrayid => $image)
+                        // create url from image id's
+                        $latestimages_urllist[$arrayid] = "post/view/$image->id";
+                    $this->add_sitemap_queue($latestimages_urllist, "monthly", "0.8", date("Y-m-d", $image->posted_timestamp));
+
+                    /* --- Add other tags --- */
+                    $other_tags = $database->get_all("SELECT tag, count FROM tags ORDER BY `count` DESC LIMIT 21,10000000");
+                    foreach($other_tags as $arrayid => $tag) {
+                        $tag = $tag['tag'];
+                        // create url from tags (tagme ignored)
+                        if ($tag != "tagme")
+                            $other_tags[$arrayid] = "post/list/$tag/";
+                    }
+                    $this->add_sitemap_queue($other_tags, "monthly", "0.7" /* not sure how to deal with date here */);
+
+                    /* --- Add all other images to sitemap with lower priority --- */
+                    $otherimages = Image::find_images(51, 10000000, array());
+                    foreach($otherimages as $arrayid => $image)
+                        // create url from image id's
+                        $otherimages[$arrayid] = "post/view/$image->id";             
+                    $this->add_sitemap_queue($otherimages, "monthly", "0.6", date("Y-m-d", $image->posted_timestamp));
+                    
+                    // Creates the sitemap file
+                    $this->create_sitemap();
+                }
+                
+                /* --- Display page --- */
+                // when sitemap is ok, display it from the file
+                $this->display_sitemap();
+            } 
+	}
+	
+        // Adds an array of urls to the sitemap with the given information
+	private function add_sitemap_queue(/*array(urls)*/ $urls, $changefreq="monthly", $priority="0.5", $date="2013-02-01") {
+                foreach($urls as $url) {
+                    $link = make_http(make_link("$url"));
+                    $this->sitemap_queue .= "
+                    <url>
+                    <loc>$link</loc>
+                    <lastmod>$date</lastmod>
+                    <changefreq>$changefreq</changefreq>
+                    <priority>$priority</priority>
+                    </url>";
+            }	
+	}
+        
+        // sets sitemap with entries in the queue
+        private function display_sitemap()
+        {
+            global $page;
+            $page->set_mode("data");
+            $page->set_type("application/xml");
+            
+            // read file
+            $filename = $_SERVER['DOCUMENT_ROOT']."/sitemap.xml";
+            $xmlreader = fopen($filename, 'r') or die("can't open file");
+            $xml = fread($xmlreader, filesize($filename));
+            fclose($xmlreader);
+            
+            // sets
+            $page->set_data($xml);
+        }
+        
+        // creates the xml sitemap file from the queue
+        private function create_sitemap()
+        {
+            global $config;
+            
+            $xml = "<"."?xml version=\"1.0\" encoding=\"utf-8\"?".">
+                <urlset xmlns=\"http://www.sitemaps.org/schemas/sitemap/0.9\">
+                    $this->sitemap_queue
+                </urlset>";
+            
+            $fh = fopen($_SERVER["DOCUMENT_ROOT"]."/sitemap.xml", 'w') or die("can't open file");
+            fwrite($fh, $this->sitemap_queue);
+            fclose($fh);
+            
+            file_put_contents($_SERVER['DOCUMENT_ROOT']."/sitemap.xml", $xml);
+            $config->set_string("last_sitemap", date($this->time_structure, time()));
+        }
+}
+?>