Add sorting and client-side caching for instant switching

- Add sort dropdown: Newest/Oldest/Title A-Z/Z-A
- Client-side cache with 30s TTL for instant section switching
- Re-sorting uses cached data for immediate response
- Cache clears on data modifications (add/archive/delete)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/app/page.tsx

@@ -1,6 +1,6 @@
 "use client";
 
-import { useState, useEffect, useCallback } from "react";
+import { useState, useEffect, useCallback, useRef } from "react";
 import { Article, Folder } from "@/lib/types";
 import { useReaderSettings, useTTSSettings } from "@/hooks/useSettings";
 import { useTTS } from "@/hooks/useTTS";
@@ -20,10 +20,16 @@ import {
   X,
   CheckSquare,
   ArchiveRestore,
+  ArrowUpDown,
 } from "lucide-react";
 import Link from "next/link";
 
 type FilterType = "all" | "favorites" | "archived" | "folder" | "search";
+type SortType = "newest" | "oldest" | "title-asc" | "title-desc";
+
+// Simple client-side cache for instant section switching
+const articleCache = new Map<string, { data: Article[]; timestamp: number }>();
+const CACHE_TTL = 30000; // 30 seconds
 
 export default function Home() {
   const [articles, setArticles] = useState<Article[]>([]);
@@ -40,6 +46,8 @@ export default function Home() {
   const [isSelectMode, setIsSelectMode] = useState(false);
   const [selectedIds, setSelectedIds] = useState<Set<string>>(new Set());
   const [isBulkUpdating, setIsBulkUpdating] = useState(false);
+  const [sortBy, setSortBy] = useState<SortType>("newest");
+  const [showSortMenu, setShowSortMenu] = useState(false);
 
   const [readerSettings, setReaderSettings] = useReaderSettings();
   const [ttsSettings, setTTSSettings] = useTTSSettings();
@@ -61,8 +69,37 @@ export default function Home() {
     }
   }, [readerSettings]);
 
-  // Fetch articles
-  const fetchArticles = useCallback(async () => {
+  // Sort articles client-side
+  const sortArticles = useCallback((articles: Article[], sort: SortType): Article[] => {
+    const sorted = [...articles];
+    switch (sort) {
+      case "newest":
+        return sorted.sort((a, b) => new Date(b.createdAt).getTime() - new Date(a.createdAt).getTime());
+      case "oldest":
+        return sorted.sort((a, b) => new Date(a.createdAt).getTime() - new Date(b.createdAt).getTime());
+      case "title-asc":
+        return sorted.sort((a, b) => a.title.localeCompare(b.title));
+      case "title-desc":
+        return sorted.sort((a, b) => b.title.localeCompare(a.title));
+      default:
+        return sorted;
+    }
+  }, []);
+
+  // Fetch articles with caching
+  const fetchArticles = useCallback(async (skipCache = false) => {
+    const cacheKey = filter === "folder" ? `folder-${selectedFolderId}` : filter;
+
+    // Check cache first for instant display
+    if (!skipCache) {
+      const cached = articleCache.get(cacheKey);
+      if (cached && Date.now() - cached.timestamp < CACHE_TTL) {
+        setArticles(sortArticles(cached.data, sortBy));
+        setIsLoading(false);
+        return;
+      }
+    }
+
     try {
       let url = `/api/articles?filter=${filter}`;
       if (filter === "folder" && selectedFolderId) {
@@ -71,14 +108,16 @@ export default function Home() {
       const response = await fetch(url);
       if (response.ok) {
         const data = await response.json();
-        setArticles(data);
+        // Cache the raw data
+        articleCache.set(cacheKey, { data, timestamp: Date.now() });
+        setArticles(sortArticles(data, sortBy));
       }
     } catch (error) {
       console.error("Failed to fetch articles:", error);
     } finally {
       setIsLoading(false);
     }
-  }, [filter, selectedFolderId]);
+  }, [filter, selectedFolderId, sortBy, sortArticles]);
 
   // Fetch folders
   const fetchFolders = useCallback(async () => {
@@ -116,6 +155,15 @@ export default function Home() {
     fetchStats();
   }, [fetchArticles, fetchFolders, fetchStats]);
 
+  // Re-sort when sort changes (use cached data for instant response)
+  useEffect(() => {
+    const cacheKey = filter === "folder" ? `folder-${selectedFolderId}` : filter;
+    const cached = articleCache.get(cacheKey);
+    if (cached) {
+      setArticles(sortArticles(cached.data, sortBy));
+    }
+  }, [sortBy, filter, selectedFolderId, sortArticles]);
+
   // Search
   const handleSearch = async () => {
     if (!searchQuery.trim()) {
@@ -151,7 +199,8 @@ export default function Home() {
       throw new Error(data.error || "Failed to add article");
     }
 
-    await fetchArticles();
+    articleCache.clear();
+    await fetchArticles(true);
     fetchStats();
   };
 
@@ -180,7 +229,8 @@ export default function Home() {
       body: JSON.stringify({ isArchived }),
     });
 
-    await fetchArticles();
+    articleCache.clear();
+    await fetchArticles(true);
     fetchStats();
 
     if (selectedArticle?.id === id) {
@@ -191,7 +241,8 @@ export default function Home() {
   // Delete article
   const handleDelete = async (id: string) => {
     await fetch(`/api/articles/${id}`, { method: "DELETE" });
-    await fetchArticles();
+    articleCache.clear();
+    await fetchArticles(true);
 
     if (selectedArticle?.id === id) {
       setSelectedArticle(null);
@@ -252,7 +303,9 @@ export default function Home() {
           updates: { isArchived: archive },
         }),
       });
-      await fetchArticles();
+      // Clear cache to force refresh
+      articleCache.clear();
+      await fetchArticles(true);
       setSelectedIds(new Set());
       setIsSelectMode(false);
       fetchStats();
@@ -489,6 +542,51 @@ export default function Home() {
               {articles.length} articles
             </span>
 
+            {/* Sort dropdown */}
+            <div className="relative">
+              <button
+                onClick={() => setShowSortMenu(!showSortMenu)}
+                className="flex items-center gap-2 px-3 py-2 rounded-lg text-sm text-[var(--muted)] hover:text-[var(--foreground)] hover:bg-[var(--surface)] transition-colors"
+              >
+                <ArrowUpDown className="w-4 h-4" />
+                <span className="hidden sm:inline">
+                  {sortBy === "newest" && "Newest"}
+                  {sortBy === "oldest" && "Oldest"}
+                  {sortBy === "title-asc" && "A-Z"}
+                  {sortBy === "title-desc" && "Z-A"}
+                </span>
+              </button>
+              {showSortMenu && (
+                <>
+                  <div
+                    className="fixed inset-0 z-10"
+                    onClick={() => setShowSortMenu(false)}
+                  />
+                  <div className="absolute right-0 top-full mt-1 bg-[var(--background)] border border-[var(--border)] rounded-lg shadow-lg z-20 py-1 min-w-[140px]">
+                    {[
+                      { value: "newest", label: "Newest first" },
+                      { value: "oldest", label: "Oldest first" },
+                      { value: "title-asc", label: "Title A-Z" },
+                      { value: "title-desc", label: "Title Z-A" },
+                    ].map((option) => (
+                      <button
+                        key={option.value}
+                        onClick={() => {
+                          setSortBy(option.value as SortType);
+                          setShowSortMenu(false);
+                        }}
+                        className={`w-full px-4 py-2 text-left text-sm hover:bg-[var(--surface)] transition-colors ${
+                          sortBy === option.value ? "text-[var(--accent)] font-medium" : ""
+                        }`}
+                      >
+                        {option.label}
+                      </button>
+                    ))}
+                  </div>
+                </>
+              )}
+            </div>
+
             {articles.length > 0 && (
               <button
                 onClick={() => setIsSelectMode(true)}