Complete public brief locale switching

frontend/app/sources/[slug]/page.tsx

@@ -1,16 +1,37 @@
 import type { Metadata } from "next";
+import { cookies, headers } from "next/headers";
 import { notFound } from "next/navigation";
 import { SourceDetailPageView } from "@/components/public-content/PublicContentPages";
+import {
+  LANDING_LOCALE_COOKIE,
+  LANDING_LOCALE_QUERY_PARAM,
+  pickLandingLocale,
+  type LandingLocale,
+} from "@/components/landing/landingLocale";
 import {
   SOURCE_PAGES,
   absolutePublicUrl,
   getSourcePage,
+  localizeSourcePage,
   sourcePath,
 } from "@/content/public-content";
 
 type SourcePageParams = {
   slug: string;
 };
+type SourceSearchParams = Promise<Record<string, string | string[] | undefined>>;
+
+async function resolvePublicContentLocale(searchParams: SourceSearchParams): Promise<LandingLocale> {
+  const params = await searchParams;
+  const rawLocale = params[LANDING_LOCALE_QUERY_PARAM];
+  const queryLocale = Array.isArray(rawLocale) ? rawLocale[0] : rawLocale;
+  const [cookieStore, headerStore] = await Promise.all([cookies(), headers()]);
+  return pickLandingLocale(
+    queryLocale,
+    cookieStore.get(LANDING_LOCALE_COOKIE)?.value,
+    headerStore.get("accept-language"),
+  );
+}
 
 export function generateStaticParams() {
   return SOURCE_PAGES.map((source) => ({ slug: source.slug }));
@@ -18,10 +39,15 @@ export function generateStaticParams() {
 
 export async function generateMetadata({
   params,
+  searchParams,
 }: {
   params: Promise<SourcePageParams>;
+  searchParams: SourceSearchParams;
 }): Promise<Metadata> {
-  const { slug } = await params;
+  const [{ slug }, locale] = await Promise.all([
+    params,
+    resolvePublicContentLocale(searchParams),
+  ]);
   const source = getSourcePage(slug);
 
   if (!source) {
@@ -29,17 +55,18 @@ export async function generateMetadata({
       title: "Source not found",
     };
   }
+  const localizedSource = localizeSourcePage(source, locale);
 
   return {
-    title: source.title,
-    description: source.description,
+    title: localizedSource.title,
+    description: localizedSource.description,
     alternates: {
       canonical: sourcePath(source),
     },
     openGraph: {
       type: "article",
-      title: source.title,
-      description: source.description,
+      title: localizedSource.title,
+      description: localizedSource.description,
       url: sourcePath(source),
       modifiedTime: source.updatedAt,
     },
@@ -48,22 +75,28 @@ export async function generateMetadata({
 
 export default async function SourceDetailPage({
   params,
+  searchParams,
 }: {
   params: Promise<SourcePageParams>;
+  searchParams: SourceSearchParams;
 }) {
-  const { slug } = await params;
+  const [{ slug }, locale] = await Promise.all([
+    params,
+    resolvePublicContentLocale(searchParams),
+  ]);
   const source = getSourcePage(slug);
 
   if (!source) {
     notFound();
   }
 
+  const localizedSource = localizeSourcePage(source, locale);
   const pathname = sourcePath(source);
   const jsonLd = {
     "@context": "https://schema.org",
     "@type": "Dataset",
-    name: source.title,
-    description: source.description,
+    name: localizedSource.title,
+    description: localizedSource.description,
     url: absolutePublicUrl(pathname),
     dateModified: source.updatedAt,
     creator: {
@@ -83,7 +116,7 @@ export default async function SourceDetailPage({
         type="application/ld+json"
         dangerouslySetInnerHTML={{ __html: JSON.stringify(jsonLd) }}
       />
-      <SourceDetailPageView source={source} />
+      <SourceDetailPageView source={source} locale={locale} />
     </>
   );
 }