fix: lang switch

app/[locale]/products/[...slug]/page.tsx

@@ -14,7 +14,7 @@ import { getTranslations, setRequestLocale } from 'next-intl/server';
 import { getProductOGImageMetadata } from '@/lib/metadata';
 import Image from 'next/image';
 import Link from 'next/link';
-import { notFound } from 'next/navigation';
+import { notFound, redirect } from 'next/navigation';
 import ProductEngagementTracker from '@/components/analytics/ProductEngagementTracker';
 import PayloadRichText from '@/components/PayloadRichText';
 
@@ -53,7 +53,7 @@ export async function generateMetadata({ params }: ProductPageProps): Promise<Me
       title: categoryTitle,
       description: categoryDesc,
       alternates: {
-        canonical: `${SITE_URL}/${locale}/${await mapFileSlugToTranslated('products', locale)}/${productSlug}`,
+        canonical: `${SITE_URL}/${locale}/${await mapFileSlugToTranslated('products', locale)}/${await mapFileSlugToTranslated(fileSlug, locale)}`,
         languages: {
           de: `${SITE_URL}/de/${await mapFileSlugToTranslated('products', 'de')}/${await mapFileSlugToTranslated(fileSlug, 'de')}`,
           en: `${SITE_URL}/en/${await mapFileSlugToTranslated('products', 'en')}/${await mapFileSlugToTranslated(fileSlug, 'en')}`,
@@ -75,11 +75,13 @@ export async function generateMetadata({ params }: ProductPageProps): Promise<Me
   const product = await getProductBySlug(productSlug, locale);
   if (!product) return {};
 
+  const currentLocalePath = await getLocalizedPath(locale);
+
   return {
     title: product.frontmatter.title,
     description: product.frontmatter.description,
     alternates: {
-      canonical: `${SITE_URL}/${locale}/${await mapFileSlugToTranslated('products', locale)}/${slug.join('/')}`,
+      canonical: `${SITE_URL}/${locale}/${currentLocalePath}`,
       languages: {
         de: `${SITE_URL}/de/${await getLocalizedPath('de')}`,
         en: `${SITE_URL}/en/${await getLocalizedPath('en')}`,
@@ -90,7 +92,7 @@ export async function generateMetadata({ params }: ProductPageProps): Promise<Me
       title: product.frontmatter.title,
       description: product.frontmatter.description,
       type: 'website',
-      url: `${SITE_URL}/${locale}/products/${slug.join('/')}`,
+      url: `${SITE_URL}/${locale}/${currentLocalePath}`,
       images: getProductOGImageMetadata(productSlug, product.frontmatter.title, locale),
     },
     twitter: {
@@ -114,7 +116,19 @@ export default async function ProductPage({ params }: ProductPageProps) {
     'high-voltage-cables',
     'solar-cables',
   ];
-  const fileSlug = await mapSlugToFileSlug(productSlug, locale);
+
+  const fileSlugs = await Promise.all(slug.map((s) => mapSlugToFileSlug(s, locale)));
+  const translatedSlugsForLocale = await Promise.all(
+    fileSlugs.map((fs) => mapFileSlugToTranslated(fs, locale)),
+  );
+
+  // If the requested slugs don't exactly match the translated slugs for the current locale
+  // (i.e. if the user used the static language switcher but kept the original locale's slugs)
+  if (slug.join('/') !== translatedSlugsForLocale.join('/')) {
+    redirect(`/${locale}/${productsSlug}/${translatedSlugsForLocale.join('/')}`);
+  }
+
+  const fileSlug = fileSlugs[fileSlugs.length - 1];
 
   if (categories.includes(fileSlug)) {
     const allProducts = await getAllProducts(locale);