feat: implement sitemap generation with locale support and BASE_URL configuration

Author: echoja

src/app/test/sitemap.ts

@@ -0,0 +1,45 @@
+import type { MetadataRoute } from "next";
+import { articleLocales } from "@modules/i18n/available";
+import items from "@modules/article/items";
+
+const BASE = process.env.BASE_URL;
+
+if (!BASE) {
+  throw new Error("BASE_URL is not defined");
+}
+
+export default function sitemap(): MetadataRoute.Sitemap {
+  const urls: MetadataRoute.Sitemap = [
+    { url: `${BASE}/`, changeFrequency: "weekly" },
+    { url: `${BASE}/portfolio`, changeFrequency: "monthly" },
+  ];
+
+  for (const item of items) {
+    const locales = articleLocales[item.slug] ?? [];
+
+    // If there are locales available for the article, add entries for each locale
+    if (locales.length > 0) {
+      const languages = Object.fromEntries(
+        locales.map((l) => [l, `${BASE}/${l}/${item.slug}`]),
+      );
+      for (const l of locales) {
+        urls.push({
+          url: `${BASE}/${l}/${item.slug}`,
+          changeFrequency: "monthly",
+          lastModified: item.updatedAt,
+          alternates: { languages },
+        });
+      }
+      continue;
+    }
+
+    //  Default entry without locale
+    urls.push({
+      url: `${BASE}/${item.slug}`,
+      changeFrequency: "monthly",
+      lastModified: item.updatedAt,
+    });
+  }
+
+  return urls;
+}