From 35a252299e099f8450117f886b42e9da46ee9942 Mon Sep 17 00:00:00 2001
From: FatimaSami <84532632+fatima-Sami55@users.noreply.github.com>
Date: Mon, 27 Jul 2026 19:10:09 +0500
Subject: [PATCH] fix: ensure sitemap.xml emits a single XML declaration

Google Search Console rejects duplicated <?xml?> prologs that browsers still accept. Strip any declarations, emit exactly one, validate <urlset>, and fail the build if the invariant breaks.
---
 public/sitemap.xml           | 64 ++++++++++++++++++------------------
 scripts/sitemap-generator.js | 29 +++++++++++++---
 2 files changed, 57 insertions(+), 36 deletions(-)

diff --git a/public/sitemap.xml b/public/sitemap.xml
index 2d85e11..7c7b036 100644
--- a/public/sitemap.xml
+++ b/public/sitemap.xml
@@ -2,193 +2,193 @@
 <urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
   <url>
     <loc>https://physicshub.github.io/</loc>
-    <lastmod>2026-07-21T00:00:00.000Z</lastmod>
+    <lastmod>2026-07-27T00:00:00.000Z</lastmod>
     <changefreq>weekly</changefreq>
     <priority>1.0</priority>
   </url>
   <url>
     <loc>https://physicshub.github.io/contribute</loc>
-    <lastmod>2026-07-21T00:00:00.000Z</lastmod>
+    <lastmod>2026-07-27T00:00:00.000Z</lastmod>
     <changefreq>monthly</changefreq>
     <priority>0.8</priority>
   </url>
   <url>
     <loc>https://physicshub.github.io/simulations</loc>
-    <lastmod>2026-07-21T00:00:00.000Z</lastmod>
+    <lastmod>2026-07-27T00:00:00.000Z</lastmod>
     <changefreq>weekly</changefreq>
     <priority>0.9</priority>
   </url>
   <url>
     <loc>https://physicshub.github.io/about</loc>
-    <lastmod>2026-07-21T00:00:00.000Z</lastmod>
+    <lastmod>2026-07-27T00:00:00.000Z</lastmod>
     <changefreq>monthly</changefreq>
     <priority>0.7</priority>
   </url>
   <url>
     <loc>https://physicshub.github.io/blog</loc>
-    <lastmod>2026-07-21T00:00:00.000Z</lastmod>
+    <lastmod>2026-07-27T00:00:00.000Z</lastmod>
     <changefreq>weekly</changefreq>
     <priority>0.9</priority>
   </url>
   <url>
     <loc>https://physicshub.github.io/blog/create</loc>
-    <lastmod>2026-07-21T00:00:00.000Z</lastmod>
+    <lastmod>2026-07-27T00:00:00.000Z</lastmod>
     <changefreq>monthly</changefreq>
     <priority>0.7</priority>
   </url>
   <url>
     <loc>https://physicshub.github.io/blog/what-is-physics</loc>
-    <lastmod>2026-07-21T00:00:00.000Z</lastmod>
+    <lastmod>2026-07-27T00:00:00.000Z</lastmod>
     <changefreq>monthly</changefreq>
     <priority>0.8</priority>
   </url>
   <url>
     <loc>https://physicshub.github.io/blog/class-12-physics-complete-guide</loc>
-    <lastmod>2026-07-21T00:00:00.000Z</lastmod>
+    <lastmod>2026-07-27T00:00:00.000Z</lastmod>
     <changefreq>monthly</changefreq>
     <priority>0.8</priority>
   </url>
   <url>
     <loc>https://physicshub.github.io/blog/physics-bouncing-ball-comprehensive-educational-guide</loc>
-    <lastmod>2026-07-21T00:00:00.000Z</lastmod>
+    <lastmod>2026-07-27T00:00:00.000Z</lastmod>
     <changefreq>monthly</changefreq>
     <priority>0.8</priority>
   </url>
   <url>
     <loc>https://physicshub.github.io/blog/comprehensive-guide-to-vector-operations</loc>
-    <lastmod>2026-07-21T00:00:00.000Z</lastmod>
+    <lastmod>2026-07-27T00:00:00.000Z</lastmod>
     <changefreq>monthly</changefreq>
     <priority>0.8</priority>
   </url>
   <url>
     <loc>https://physicshub.github.io/blog/ball-uniformly-accelerated-motion</loc>
-    <lastmod>2026-07-21T00:00:00.000Z</lastmod>
+    <lastmod>2026-07-27T00:00:00.000Z</lastmod>
     <changefreq>monthly</changefreq>
     <priority>0.8</priority>
   </url>
   <url>
     <loc>https://physicshub.github.io/blog/ball-free-fall-comprehensive-guide</loc>
-    <lastmod>2026-07-21T00:00:00.000Z</lastmod>
+    <lastmod>2026-07-27T00:00:00.000Z</lastmod>
     <changefreq>monthly</changefreq>
     <priority>0.8</priority>
   </url>
   <url>
     <loc>https://physicshub.github.io/blog/spring-connection</loc>
-    <lastmod>2026-07-21T00:00:00.000Z</lastmod>
+    <lastmod>2026-07-27T00:00:00.000Z</lastmod>
     <changefreq>monthly</changefreq>
     <priority>0.8</priority>
   </url>
   <url>
     <loc>https://physicshub.github.io/blog/physics-of-pendulum-explained</loc>
-    <lastmod>2026-07-21T00:00:00.000Z</lastmod>
+    <lastmod>2026-07-27T00:00:00.000Z</lastmod>
     <changefreq>monthly</changefreq>
     <priority>0.8</priority>
   </url>
   <url>
     <loc>https://physicshub.github.io/blog/projectile-parabolic-motion</loc>
-    <lastmod>2026-07-21T00:00:00.000Z</lastmod>
+    <lastmod>2026-07-27T00:00:00.000Z</lastmod>
     <changefreq>monthly</changefreq>
     <priority>0.8</priority>
   </url>
   <url>
     <loc>https://physicshub.github.io/blog/physics-behind-three-body-problem</loc>
-    <lastmod>2026-07-21T00:00:00.000Z</lastmod>
+    <lastmod>2026-07-27T00:00:00.000Z</lastmod>
     <changefreq>monthly</changefreq>
     <priority>0.8</priority>
   </url>
   <url>
     <loc>https://physicshub.github.io/blog/pi-from-block-collisions-explained</loc>
-    <lastmod>2026-07-21T00:00:00.000Z</lastmod>
+    <lastmod>2026-07-27T00:00:00.000Z</lastmod>
     <changefreq>monthly</changefreq>
     <priority>0.8</priority>
   </url>
   <url>
     <loc>https://physicshub.github.io/simulations/BouncingBall</loc>
-    <lastmod>2026-07-21T00:00:00.000Z</lastmod>
+    <lastmod>2026-07-27T00:00:00.000Z</lastmod>
     <changefreq>weekly</changefreq>
     <priority>0.7</priority>
   </url>
   <url>
     <loc>https://physicshub.github.io/simulations/VectorsOperations</loc>
-    <lastmod>2026-07-21T00:00:00.000Z</lastmod>
+    <lastmod>2026-07-27T00:00:00.000Z</lastmod>
     <changefreq>weekly</changefreq>
     <priority>0.7</priority>
   </url>
   <url>
     <loc>https://physicshub.github.io/simulations/BallAcceleration</loc>
-    <lastmod>2026-07-21T00:00:00.000Z</lastmod>
+    <lastmod>2026-07-27T00:00:00.000Z</lastmod>
     <changefreq>weekly</changefreq>
     <priority>0.7</priority>
   </url>
   <url>
     <loc>https://physicshub.github.io/simulations/BallGravity</loc>
-    <lastmod>2026-07-21T00:00:00.000Z</lastmod>
+    <lastmod>2026-07-27T00:00:00.000Z</lastmod>
     <changefreq>weekly</changefreq>
     <priority>0.7</priority>
   </url>
   <url>
     <loc>https://physicshub.github.io/simulations/SpringConnection</loc>
-    <lastmod>2026-07-21T00:00:00.000Z</lastmod>
+    <lastmod>2026-07-27T00:00:00.000Z</lastmod>
     <changefreq>weekly</changefreq>
     <priority>0.7</priority>
   </url>
   <url>
     <loc>https://physicshub.github.io/simulations/SimplePendulum</loc>
-    <lastmod>2026-07-21T00:00:00.000Z</lastmod>
+    <lastmod>2026-07-27T00:00:00.000Z</lastmod>
     <changefreq>weekly</changefreq>
     <priority>0.7</priority>
   </url>
   <url>
     <loc>https://physicshub.github.io/simulations/ParabolicMotion</loc>
-    <lastmod>2026-07-21T00:00:00.000Z</lastmod>
+    <lastmod>2026-07-27T00:00:00.000Z</lastmod>
     <changefreq>weekly</changefreq>
     <priority>0.7</priority>
   </url>
   <url>
     <loc>https://physicshub.github.io/simulations/InclinedPlane</loc>
-    <lastmod>2026-07-21T00:00:00.000Z</lastmod>
+    <lastmod>2026-07-27T00:00:00.000Z</lastmod>
     <changefreq>weekly</changefreq>
     <priority>0.7</priority>
   </url>
   <url>
     <loc>https://physicshub.github.io/simulations/CircularMotion</loc>
-    <lastmod>2026-07-21T00:00:00.000Z</lastmod>
+    <lastmod>2026-07-27T00:00:00.000Z</lastmod>
     <changefreq>weekly</changefreq>
     <priority>0.7</priority>
   </url>
   <url>
     <loc>https://physicshub.github.io/simulations/ThreeBody</loc>
-    <lastmod>2026-07-21T00:00:00.000Z</lastmod>
+    <lastmod>2026-07-27T00:00:00.000Z</lastmod>
     <changefreq>weekly</changefreq>
     <priority>0.7</priority>
   </url>
   <url>
     <loc>https://physicshub.github.io/simulations/HorizontalSpring</loc>
-    <lastmod>2026-07-21T00:00:00.000Z</lastmod>
+    <lastmod>2026-07-27T00:00:00.000Z</lastmod>
     <changefreq>weekly</changefreq>
     <priority>0.7</priority>
   </url>
   <url>
     <loc>https://physicshub.github.io/simulations/DoublePendulum</loc>
-    <lastmod>2026-07-21T00:00:00.000Z</lastmod>
+    <lastmod>2026-07-27T00:00:00.000Z</lastmod>
     <changefreq>weekly</changefreq>
     <priority>0.7</priority>
   </url>
   <url>
     <loc>https://physicshub.github.io/simulations/CollisionSimulation</loc>
-    <lastmod>2026-07-21T00:00:00.000Z</lastmod>
+    <lastmod>2026-07-27T00:00:00.000Z</lastmod>
     <changefreq>weekly</changefreq>
     <priority>0.7</priority>
   </url>
   <url>
     <loc>https://physicshub.github.io/simulations/test</loc>
-    <lastmod>2026-07-21T00:00:00.000Z</lastmod>
+    <lastmod>2026-07-27T00:00:00.000Z</lastmod>
     <changefreq>weekly</changefreq>
     <priority>0.7</priority>
   </url>
   <url>
     <loc>https://physicshub.github.io/simulations/PiCollisions</loc>
-    <lastmod>2026-07-21T00:00:00.000Z</lastmod>
+    <lastmod>2026-07-27T00:00:00.000Z</lastmod>
     <changefreq>weekly</changefreq>
     <priority>0.7</priority>
   </url>
diff --git a/scripts/sitemap-generator.js b/scripts/sitemap-generator.js
index ce435cc..d8cfc9e 100644
--- a/scripts/sitemap-generator.js
+++ b/scripts/sitemap-generator.js
@@ -74,14 +74,35 @@ async function generateSitemap() {
 
   const rawXml = (await streamToPromise(sitemap)).toString();
 
-  // Add XML declaration and format
+  // Format only — SitemapStream already emits an XML declaration.
+  // A previous version prepended a second <?xml ...?>, which browsers
+  // tolerate but Google Search Console rejects as invalid XML (#107).
   const formatted = xmlFormat(rawXml, {
     indentation: "  ",
     collapseContent: true,
     lineSeparator: "\n",
   });
 
-  const xmlOutput = formatted;
+  // Guarantee exactly one XML declaration, even if a dependency starts
+  // emitting none or more than one. (GSC rejects duplicated prologs.)
+  const body = formatted.replace(/<\?xml[^?]*\?>\s*/gi, "").trimStart();
+  if (!body.startsWith("<urlset")) {
+    throw new Error(
+      "Sitemap body must start with <urlset> after stripping XML declarations"
+    );
+  }
+
+  let xmlOutput = `<?xml version="1.0" encoding="UTF-8"?>\n${body}`;
+  if (!xmlOutput.endsWith("\n")) {
+    xmlOutput += "\n";
+  }
+
+  const declarationCount = (xmlOutput.match(/<\?xml\b/gi) || []).length;
+  if (declarationCount !== 1) {
+    throw new Error(
+      `Sitemap must contain exactly one XML declaration, found ${declarationCount}`
+    );
+  }
 
   // Ensure public directory exists
   const publicDir = join(__dirname, "../public");
@@ -91,13 +112,13 @@ async function generateSitemap() {
 
   // Write to public directory
   const publicPath = join(publicDir, `${sitemapName}.xml`);
-  writeFileSync(publicPath, xmlOutput);
+  writeFileSync(publicPath, xmlOutput, "utf8");
   console.log(`✅ Sitemap generated with ${allRoutes.length} links in public/`);
 
   // Also write to out/ if it exists (for deployment consistency)
   const outDir = join(__dirname, "../out");
   if (existsSync(outDir)) {
-    writeFileSync(join(outDir, `${sitemapName}.xml`), xmlOutput);
+    writeFileSync(join(outDir, `${sitemapName}.xml`), xmlOutput, "utf8");
     console.log(`✅ Sitemap copied to ./out/`);
   }