Improve localized page path resolution

- Resolve page locale from source paths instead of IDs
- Deduplicate localized fallback paths and pass page descriptions to layout

src/pages/[...slug].astro

@@ -1,46 +1,76 @@
 ---
 import { getCollection, render, type CollectionEntry } from "astro:content";
-import { astroI18n, createGetStaticPaths, stripLocaleFromPath } from "$lib/i18n";
+import { astroI18n, createGetStaticPaths, l, stripLocaleFromPath } from "$lib/i18n";
 import PageLayout from "../layouts/PageLayout.astro";
 import LanguageWarning from "../components/LanguageWarning.astro";
 import "@styles/table.css";
 
 export const getStaticPaths = createGetStaticPaths(async () => {
     const allPages = await getCollection("pages");
-    let posts = allPages.filter((value) => value.id.split("/")[0] === astroI18n.locale);
+    const locale = astroI18n.locale;
 
-    const germanPosts = allPages.filter((entry) => entry.id.split("/")[0] === astroI18n.fallbackLocale);
+    function getPageLocale(page: CollectionEntry<"pages">): string {
+        const sourcePath = page.filePath ?? "";
+        const match = sourcePath.match(/(?:^|[/\\])src[/\\]content[/\\]pages[/\\]([^/\\]+)/);
 
-    germanPosts.forEach((value) => {
-        if (posts.find((post) => post.id.split("/")[1] !== value.id.split("/")[1])) {
-            posts.push(value);
+        return match?.[1] ?? page.id.split("/")[0] ?? astroI18n.primaryLocale;
+    }
+
+    const posts = allPages.filter((page) => getPageLocale(page) === locale);
+
+    const germanPosts = allPages.filter((page) => getPageLocale(page) === astroI18n.fallbackLocale);
+
+    germanPosts.forEach((page) => {
+        const fallbackSlug = fixLink(page);
+
+        if (!posts.some((post) => fixLink(post) === fallbackSlug)) {
+            posts.push(page);
         }
     });
 
     function fixLink(page: CollectionEntry<"pages">): string {
-        if (astroI18n.locale != astroI18n.primaryLocale && Object.keys(page.data.slugs ?? {}).includes(astroI18n.locale)) {
-            return page.data.slugs[astroI18n.locale];
+        if (locale !== astroI18n.primaryLocale) {
+            const translatedSlug = page.data.slugs?.[locale];
+
+            if (translatedSlug) {
+                return translatedSlug;
+            }
         }
 
-        return page.data.slug ?? stripLocaleFromPath(page.id);
+        const slug = page.data.slug ?? stripLocaleFromPath(page.id);
+
+        if (locale !== astroI18n.primaryLocale && getPageLocale(page) === astroI18n.primaryLocale) {
+            return stripLocaleFromPath(l(`/${slug}`, undefined, { targetLocale: locale }));
+        }
+
+        return slug;
     }
 
-    return posts.map((page) => ({
+    const paths = posts.map((page) => ({
         props: {
             page,
-            german: astroI18n.locale !== astroI18n.primaryLocale && page.id.split("/")[0] !== astroI18n.locale,
+            german: locale !== astroI18n.primaryLocale && getPageLocale(page) !== locale,
         },
         params: {
             slug: fixLink(page),
         },
     }));
+
+    const uniquePaths = new Map<string, (typeof paths)[number]>();
+    paths.forEach((path) => {
+        if (!uniquePaths.has(path.params.slug)) {
+            uniquePaths.set(path.params.slug, path);
+        }
+    });
+
+    return Array.from(uniquePaths.values());
 });
 
 const { page, german } = Astro.props as { page: CollectionEntry<"pages">; german: boolean };
 const { Content } = await render(page);
 ---
 
-<PageLayout title={page.data.title}>
+<PageLayout title={page.data.title} description={page.data.description}>
     <article>
         {german && <LanguageWarning />}
         <h1 class="text-left" style="font-family: 'Barlow Condensed', sans-serif; letter-spacing: 0.04em;">{page.data.title}</h1>