From 83f933010ec783603bbe7e327196db9efd592a5f Mon Sep 17 00:00:00 2001
From: Tobias Leinss <7684178+leinss@users.noreply.github.com>
Date: Tue, 18 Aug 2026 11:33:17 +0200
Subject: [PATCH] feat(blog): remember the chosen post language across visits

The blog index toggles between English and German panels client-side but
reset to English on every visit, so a German reader re-selected the
language on every arrival. The theme already persists; the language now
does too.

- Store the choice under `blogLang` on click and restore it on init
- Only restore a language that still has a panel, so a stored value that
  outlives its posts cannot hide every panel and leave an empty page
- Guard reads and writes: localStorage throws rather than returning null
  when a browser blocks storage, and a toggle that stops working is worse
  than one that forgets
---
 src/pages/blog/index.astro | 36 +++++++++++++++++++++++++++++++++++-
 1 file changed, 35 insertions(+), 1 deletion(-)

diff --git a/src/pages/blog/index.astro b/src/pages/blog/index.astro
index 137b6b9fc..bbb2ef610 100644
--- a/src/pages/blog/index.astro
+++ b/src/pages/blog/index.astro
@@ -93,6 +93,28 @@ const sections = langsWithPosts.map((lang) => ({
 </PageLayout>
 
 <script>
+  // The chosen language survives the visit, the way the theme does. Reading and
+  // writing are wrapped because localStorage throws rather than returning null
+  // when a browser blocks storage, and a language toggle that stops working is
+  // a worse outcome than one that forgets.
+  const STORAGE_KEY = "blogLang";
+
+  function readStoredLang(): string | null {
+    try {
+      return localStorage.getItem(STORAGE_KEY);
+    } catch {
+      return null;
+    }
+  }
+
+  function storeLang(lang: string) {
+    try {
+      localStorage.setItem(STORAGE_KEY, lang);
+    } catch {
+      // Storage unavailable; the toggle still works for this page view.
+    }
+  }
+
   function initBlogLang() {
     const toggles = Array.from(
       document.querySelectorAll<HTMLButtonElement>("[data-lang-toggle]")
@@ -116,8 +138,20 @@ const sections = langsWithPosts.map((lang) => ({
     };
 
     toggles.forEach((btn) => {
-      btn.addEventListener("click", () => show(btn.dataset.langToggle!));
+      btn.addEventListener("click", () => {
+        const lang = btn.dataset.langToggle!;
+        storeLang(lang);
+        show(lang);
+      });
     });
+
+    // Only restore a language that still has a panel. A stored value can
+    // outlive the posts it pointed at, and restoring it blindly would hide
+    // every panel and leave an empty page.
+    const stored = readStoredLang();
+    if (stored && toggles.some((btn) => btn.dataset.langToggle === stored)) {
+      show(stored);
+    }
   }
 
   initBlogLang();