feat: add sitemap generation for announcements and static routes

app/sitemap.ts

@@ -0,0 +1,44 @@
+import type { MetadataRoute } from "next";
+
+import { getAllAnnouncements } from "@/lib/announcements";
+
+const SITE_URL =
+  process.env.NEXT_PUBLIC_SITE_URL ??
+  process.env.SITE_URL ??
+  "https://mc.neody.ad.jp";
+
+function toAbsoluteUrl(pathname: string): string {
+  return new URL(pathname, SITE_URL).toString();
+}
+
+export default async function sitemap(): Promise<MetadataRoute.Sitemap> {
+  const announcements = await getAllAnnouncements();
+
+  const staticRoutes: MetadataRoute.Sitemap = [
+    {
+      url: toAbsoluteUrl("/"),
+      lastModified: new Date(),
+      changeFrequency: "weekly",
+      priority: 1,
+    },
+    {
+      url: toAbsoluteUrl("/announcements/"),
+      lastModified: new Date(),
+      changeFrequency: "daily",
+      priority: 0.8,
+    },
+  ];
+
+  const announcementRoutes: MetadataRoute.Sitemap = announcements.map((item) => {
+    const parsedDate = new Date(item.date);
+
+    return {
+      url: toAbsoluteUrl(`/announcements/${item.slug}/`),
+      lastModified: Number.isNaN(parsedDate.getTime()) ? new Date() : parsedDate,
+      changeFrequency: "monthly",
+      priority: 0.7,
+    };
+  });
+
+  return [...staticRoutes, ...announcementRoutes];
+}