Generate sitemap dynamically

.gitignore

@@ -1,9 +1,10 @@
 # Fetched room info
 output/servers.json
 
-# Generated HTML
+# Generated files
 output/*.html
 output/**/*.html
+output/sitemap.xml
 
 # Downloaded QR codes
 output/qr-codes

sites/sitemap.xml.php

@@ -1,27 +1,40 @@
 <?xml version="1.0" encoding="UTF-8"?>
+<?php
+	require_once '+getenv.php';
+
+	function loc_lastmod(string $rel_loc, ?string $changes_under_root = null) {
+		global $SITE_CANONICAL_URL, $DOCUMENT_ROOT, $TEMPLATES_ROOT;
+		$root = $changes_under_root ?? $TEMPLATES_ROOT;
+		$ext = ($root == $TEMPLATES_ROOT) ? "php" : "html";
+?>
+		<loc><?=$SITE_CANONICAL_URL . $rel_loc?></loc>
+		<lastmod><?=date('c', filemtime("$root$rel_loc/index.$ext"))?></lastmod>
+<?php
+	}
+?>
 <urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
 	<url>
-		<loc>https://sessioncommunities.online/</loc>
+<?=loc_lastmod("", changes_under_root: $DOCUMENT_ROOT)?>
 		<changefreq>hourly</changefreq>
 		<priority>1.0</priority>
 	</url>
 	<url>
-		<loc>https://sessioncommunities.online/about</loc>
+<?=loc_lastmod("/about")?>
 		<changefreq>monthly</changefreq>
 		<priority>0.7</priority>
 	</url>
 	<url>
-		<loc>https://sessioncommunities.online/privacy</loc>
+<?=loc_lastmod("/privacy")?>
 		<changefreq>monthly</changefreq>
 		<priority>0.0</priority>
 	</url>
 	<url>
-		<loc>https://sessioncommunities.online/donate</loc>
+<?=loc_lastmod("/donate")?>
 		<changefreq>monthly</changefreq>
 		<priority>0.0</priority>
 	</url>
 	<url>
-		<loc>https://sessioncommunities.online/instructions</loc>
+<?=loc_lastmod("/instructions")?>
 		<changefreq>monthly</changefreq>
 		<priority>0.0</priority>
 	</url>