seo improvements

server.js

@@ -30,7 +30,24 @@ if (!isProduction) {
   const compression = (await import("compression")).default;
   const sirv = (await import("sirv")).default;
   app.use(compression());
-  app.use(base, sirv(clientDir, { extensions: [] }));
+  app.use(
+    base,
+    sirv(clientDir, {
+      extensions: [],
+      setHeaders(res, pathname) {
+        if (pathname.startsWith("/assets/")) {
+          // vite hashes these filenames, so the content can never change
+          // under a given url
+          res.setHeader("Cache-Control", "public, max-age=31536000, immutable");
+        } else if (pathname.startsWith("/fonts/")) {
+          // stable but unhashed, so cache for a while rather than forever
+          res.setHeader("Cache-Control", "public, max-age=2592000");
+        } else {
+          res.setHeader("Cache-Control", "public, max-age=3600");
+        }
+      },
+    }),
+  );
   // a hashed asset that sirv did not find is genuinely gone, usually a stale
   // cached document asking for a previous build. 404 it here, otherwise it
   // falls through to the catch-all and answers a .js request with html
@@ -43,26 +60,74 @@ if (!isProduction) {
   });
 }
 
+/** load the SSR bundle, from source in dev and from the build in production */
+async function loadServerEntry() {
+  if (!isProduction) {
+    return await vite.ssrLoadModule("/src/entry-server.tsx");
+  }
+  return await import("./dist/server/entry-server.js");
+}
+
+/**
+ * Strip the deploy base from a request url, always leaving a rooted path.
+ * The previous `originalUrl.replace(base, "")` dropped the leading slash when
+ * base was "/", which would hand the router a relative location.
+ */
+function stripBase(originalUrl) {
+  if (!originalUrl) return "/";
+  if (base === "/") return originalUrl;
+  if (originalUrl.startsWith(base)) {
+    const rest = originalUrl.slice(base.length);
+    return rest.startsWith("/") ? rest : `/${rest}`;
+  }
+  return originalUrl;
+}
+
+// generated from the route table rather than checked in, so it cannot go stale
+app.get(`${base.replace(/\/$/, "")}/sitemap.xml`, async (req, res) => {
+  try {
+    const { renderSitemap } = await loadServerEntry();
+    res
+      .status(200)
+      .set({
+        "Content-Type": "application/xml; charset=utf-8",
+        "Cache-Control": "public, max-age=3600",
+      })
+      .send(renderSitemap());
+  } catch (e) {
+    vite?.ssrFixStacktrace(e);
+    console.error(e.stack);
+    res.status(500).end();
+  }
+});
+
 app.use("*all", async (req, res) => {
   try {
-    const url = req.originalUrl.replace(base, "");
+    const url = stripBase(req.originalUrl);
 
     let template;
-    let render;
     if (!isProduction) {
       template = await fs.readFile(path.resolve(root, "index.html"), "utf-8");
       template = await vite.transformIndexHtml(url, template);
-      render = (await vite.ssrLoadModule("/src/entry-server.tsx")).render;
     } else {
       template = templateHtml;
-      render = (await import("./dist/server/entry-server.js")).render;
     }
 
+    const { render } = await loadServerEntry();
     const rendered = await render(url);
     const html = template
       ?.replace("<!--app-head-->", rendered.head ?? "")
       .replace("<!--app-html-->", rendered.html ?? "");
-    res.status(200).set({ "Content-Type": "text/html" }).send(html);
+
+    res
+      .status(rendered.statusCode ?? 200)
+      .set({
+        "Content-Type": "text/html",
+        // short shared cache window; the page embeds live-ish data
+        "Cache-Control":
+          "public, max-age=0, s-maxage=60, stale-while-revalidate=300",
+      })
+      .send(html);
   } catch (e) {
     vite?.ssrFixStacktrace(e);
     console.log(e.stack);