⚡ Bolt: [performance improvement] Pre-calculate search index and dates for faster render loops

.jules/bolt.md

@@ -0,0 +1,3 @@
+## 2024-05-24 - Pre-calculating search strings and dates for render loops
+**Learning:** Repeated Date formatting, object instantiations, and string lowercasing operations inside the `renderPDFs` loop and its filter functions cause significant CPU overhead and UI lag during user search typing, as these operations run for every item on every keystroke/render cycle.
+**Action:** Implement `prepareSearchIndex` to pre-calculate `_searchStr` (a lowercased concatenation of searchable fields), `_formattedDate`, and `_isNew` once when the PDF database is loaded. Use these cached properties in `renderPDFs` and `createPDFCard` along with early returns in the filter callback to speed up filtering and rendering.

script.js

@@ -335,6 +335,33 @@ function getAdData(slotName) {
 /* =========================================
    5. DATA LOADING WITH CACHING
    ========================================= */
+
+// OPTIMIZATION: Pre-calculate expensive values for search and rendering
+function prepareSearchIndex(pdfs) {
+    const now = new Date();
+    const sevenDaysMs = 7 * 24 * 60 * 60 * 1000;
+
+    pdfs.forEach(pdf => {
+        // Handle both raw Date strings and Firestore Timestamps
+        const uploadDateObj = pdf.uploadDate && typeof pdf.uploadDate.toDate === 'function'
+            ? pdf.uploadDate.toDate()
+            : new Date(pdf.uploadDate);
+
+        // Pre-calculate search string
+        pdf._searchStr = `${pdf.title} ${pdf.description} ${pdf.category} ${pdf.author || ''}`.toLowerCase();
+
+        // Pre-calculate formatted date
+        pdf._formattedDate = uploadDateObj.toLocaleDateString('en-US', {
+            year: 'numeric', month: 'short', day: 'numeric'
+        });
+
+        // Pre-calculate isNew boolean
+        const timeDiff = now - uploadDateObj;
+        pdf._isNew = timeDiff < sevenDaysMs;
+    });
+    return pdfs;
+}
+
 function renderSemesterTabs() {
     const container = document.getElementById('semesterTabsContainer');
     if (!container) return;
@@ -451,6 +478,10 @@ async function loadPDFDatabase() {
 
         if (shouldUseCache) {
             pdfDatabase = cachedData;
+            // The cached data already went through prepareSearchIndex when it was saved,
+            // but we need to re-run it in case `now` has changed to update `_isNew`.
+            prepareSearchIndex(pdfDatabase);
+
             // --- FIX: CALL THIS TO POPULATE UI ---
             syncClassSwitcher();
             renderSemesterTabs();
@@ -469,13 +500,20 @@ async function loadPDFDatabase() {
             pdfDatabase.push({ id: doc.id, ...doc.data() });
         });
 
+        // Pre-calculate expensive properties before saving to cache
+        prepareSearchIndex(pdfDatabase);
+
         localStorage.setItem(CACHE_KEY, JSON.stringify({
             timestamp: new Date().getTime(),
             data: pdfDatabase
         }));
 
         // --- FIX: CALL THIS TO POPULATE UI ---
         syncClassSwitcher();
+        // Missing render calls for fresh fetch (similar to cache hit):
+        renderSemesterTabs();
+        renderCategoryFilters();
+
         renderPDFs();
         hidePreloader();
 
@@ -902,26 +940,25 @@ function renderPDFs() {
 
     // Locate renderPDFs() in script.js and update the filter section
     const filteredPdfs = pdfDatabase.filter(pdf => {
-        const matchesSemester = pdf.semester === currentSemester;
+        // OPTIMIZATION: Early returns for cheap equality checks first
+
+        // 1. Check Class
+        if (pdf.class !== currentClass) return false;
 
-        // NEW: Check if the PDF class matches the UI's current class selection
-        // Note: If old documents don't have this field, they will be hidden.
-        const matchesClass = pdf.class === currentClass;
+        // 2. Check Semester
+        if (pdf.semester !== currentSemester) return false;
 
-        let matchesCategory = false;
+        // 3. Check Category / Favorites
         if (currentCategory === 'favorites') {
-            matchesCategory = favorites.includes(pdf.id);
-        } else {
-            matchesCategory = currentCategory === 'all' || pdf.category === currentCategory;
+            if (!favorites.includes(pdf.id)) return false;
+        } else if (currentCategory !== 'all') {
+            if (pdf.category !== currentCategory) return false;
         }
 
-        const matchesSearch = pdf.title.toLowerCase().includes(searchTerm) ||
-            pdf.description.toLowerCase().includes(searchTerm) ||
-            pdf.category.toLowerCase().includes(searchTerm) ||
-            pdf.author.toLowerCase().includes(searchTerm);
+        // 4. Check Search (using pre-calculated lowercased string)
+        if (searchTerm && !pdf._searchStr.includes(searchTerm)) return false;
 
-        // Update return statement to include matchesClass
-        return matchesSemester && matchesClass && matchesCategory && matchesSearch;
+        return true;
     });
 
     updatePDFCount(filteredPdfs.length);
@@ -991,11 +1028,7 @@ function createPDFCard(pdf, favoritesList, index = 0, highlightRegex = null) {
     const heartIconClass = isFav ? 'fas' : 'far';
     const btnActiveClass = isFav ? 'active' : '';
 
-    const uploadDateObj = new Date(pdf.uploadDate);
-    const timeDiff = new Date() - uploadDateObj;
-    const isNew = timeDiff < (7 * 24 * 60 * 60 * 1000); // 7 days
-
-    const newBadgeHTML = isNew
+    const newBadgeHTML = pdf._isNew
         ? `<span style="background:var(--error-color); color:white; font-size:0.6rem; padding:2px 6px; border-radius:4px; margin-left:8px; vertical-align:middle;">NEW</span>`
         : '';
 
@@ -1007,10 +1040,8 @@ function createPDFCard(pdf, favoritesList, index = 0, highlightRegex = null) {
     };
     const categoryIcon = categoryIcons[pdf.category] || 'fa-file-pdf';
 
-    // Formatting Date
-    const formattedDate = new Date(pdf.uploadDate).toLocaleDateString('en-US', {
-        year: 'numeric', month: 'short', day: 'numeric'
-    });
+    // OPTIMIZATION: Use pre-calculated date string
+    const formattedDate = pdf._formattedDate;
 
     // Uses global escapeHtml() now