Add cache headers, real 404s, social meta, JSON-LD, robots and sitemap

src/lib/seo.ts

@@ -0,0 +1,17 @@
+// Plain-text excerpt of a markdown body for description meta tags: the first
+// paragraph that isn't a heading or a bare media URL, trimmed to `max` chars.
+export function excerpt(markdown: string, max = 160): string {
+  const lines = markdown.split("\n").map((l) => l.trim());
+  const line = lines.find(
+    (l) => l && !l.startsWith("#") && !/^https?:\/\/\S+$/.test(l),
+  );
+  if (!line) return "";
+  const text = line
+    .replace(/!\[[^\]]*\]\([^)]*\)/g, "") // images
+    .replace(/\[([^\]]*)\]\([^)]*\)/g, "$1") // links → label
+    .replace(/[*_`~]+/g, "")
+    .replace(/nostr:([a-z0-9]{12})[a-z0-9]*/g, "@$1…") // keep a short handle
+    .replace(/\s+/g, " ")
+    .trim();
+  return text.length > max ? text.slice(0, max - 1).trimEnd() + "…" : text;
+}