fix(reader): optimize rendering performance, prevent browser freeze on large technical books

- extract_outline_entries: filter PDF bookmarks by depth and major structural headings, avoiding 550 micro-snippets
- renderContinuousBook: load current chapter and seamlessly append next chapters on scroll (virtual continuous) instead of dumping all chapters into DOM synchronously
- renderInteractiveSpans: use native HTML template fragment instead of new DOMParser per paragraph
- event delegation: handle word clicks on readerContentBody instead of adding hundreds of thousands of individual DOM event listeners
- consolidate existing CCNA book in DB into 68 clean chapters

app/reader.py

@@ -513,15 +513,17 @@ CLI_PROMPT_RE = re.compile(
 
 def extract_outline_entries(outline, reader) -> List[Tuple[str, int]]:
     """
-    Recursively extracts bookmarks / outline entries from PDF.
-    Returns a list of (title, 0-indexed page_number).
+    Recursively extracts bookmarks / outline entries from PDF respecting hierarchy depth.
+    For books with deep trees (Parts -> Chapters -> Sections -> Subsections),
+    prioritizes major structural headings and prevents fragmenting chapters into
+    hundreds of tiny 1-page snippets.
     """
-    entries: List[Tuple[str, int]] = []
+    raw_entries: List[Tuple[str, int, int]] = []
 
-    def _traverse(items):
+    def _traverse(items, depth=0):
         for item in items:
             if isinstance(item, list):
-                _traverse(item)
+                _traverse(item, depth + 1)
             else:
                 try:
                     title = getattr(item, "title", None) or (item.get("/Title") if hasattr(item, "get") else None)
@@ -529,13 +531,44 @@ def extract_outline_entries(outline, reader) -> List[Tuple[str, int]]:
                     if title and page_num is not None:
                         clean_title = str(title).strip()
                         if clean_title:
-                            entries.append((clean_title, int(page_num)))
+                            raw_entries.append((clean_title, int(page_num), depth))
                 except Exception:
                     continue
 
     if outline:
-        _traverse(outline)
-    return entries
+        _traverse(outline, 0)
+
+    if not raw_entries:
+        return []
+
+    # If total entries is reasonable (<= 50), return all
+    if len(raw_entries) <= 50:
+        return [(t, p) for t, p, _ in raw_entries]
+
+    # Check depth distribution
+    d0_entries = [e for e in raw_entries if e[2] == 0]
+    d1_entries = [e for e in raw_entries if e[2] <= 1]
+
+    # If top-level (depth 0) already has >= 10 chapters, use depth 0
+    if len(d0_entries) >= 10:
+        return [(t, p) for t, p, _ in d0_entries]
+
+    # Otherwise, if depth <= 1 gives a good number of chapters (10 to 80), use depth <= 1
+    if len(d1_entries) <= 80:
+        return [(t, p) for t, p, _ in d1_entries]
+
+    # If still too many entries (> 80), filter by major chapter keywords
+    major_re = re.compile(
+        r"^(cover|title\s+page|copyright|contents|introduction|your\s+study\s+plan|"
+        r"part\s+[0-9ivxlcdm]+|chapter\s+\d+|appendix\s+[a-z]|glossary|index)",
+        re.IGNORECASE
+    )
+    major_entries = [e for e in d1_entries if major_re.match(e[0])]
+    if len(major_entries) >= 10:
+        return [(t, p) for t, p, _ in major_entries]
+
+    return [(t, p) for t, p, _ in d1_entries[:80]]
+
 
 
 def clean_page_lines(raw_pages_text: List[str]) -> List[str]:

app/static/index.html

@@ -1075,7 +1075,7 @@
     <!-- Audio Element for native streaming -->
     <audio id="global-audio-player" preload="none"></audio>
 
-    <script src="/static/js/app.js?v=3.9"></script>
+    <script src="/static/js/app.js?v=4.0"></script>
 </body>
 </html>
 

app/static/js/app.js

@@ -2515,7 +2515,7 @@ document.addEventListener('DOMContentLoaded', () => {
         if (!currentBook || !currentBook.chapters) return;
 
         currentChapterIndex = Math.max(0, Math.min(targetChapter, currentBook.chapters.length - 1));
-        readerChapterSelect.value = currentChapterIndex;
+        if (readerChapterSelect) readerChapterSelect.value = currentChapterIndex;
 
         readerPrevChBtn.disabled = currentChapterIndex <= 0;
         readerNextChBtn.disabled = currentChapterIndex >= currentBook.chapters.length - 1;
@@ -2528,15 +2528,13 @@ document.addEventListener('DOMContentLoaded', () => {
             if (c.term) knownWordsMap.set(c.term.trim().toLowerCase(), c);
         });
 
-        currentBook.chapters.forEach((_, idx) => {
-            loadedChaptersSet.add(idx);
-            const chFrag = buildChapterDOM(idx, knownWordsMap, idx > 0);
-            readerContentBody.appendChild(chFrag);
-        });
+        loadedChaptersSet.add(currentChapterIndex);
+        const chFrag = buildChapterDOM(currentChapterIndex, knownWordsMap, false);
+        readerContentBody.appendChild(chFrag);
 
-        const finalFooter = buildChapterFooterDOM(currentBook.chapters.length - 1);
-        if (finalFooter) {
-            readerContentBody.appendChild(finalFooter);
+        const footer = buildChapterFooterDOM(currentChapterIndex);
+        if (footer) {
+            readerContentBody.appendChild(footer);
         }
 
         applyScroll(restoreAnchorIdx, restoreScrollTop, restoreFraction, currentChapterIndex);
@@ -2871,9 +2869,9 @@ document.addEventListener('DOMContentLoaded', () => {
         processed = processed.replace(/(?<!\*)\*([^*]+)\*(?!\*)/g, '<em>$1</em>');
         processed = processed.replace(/(?<!_)_([^_]+)_(?!_)/g, '<em>$1</em>');
 
-        // 3. Parse into DOM tree
-        const parser = new DOMParser();
-        const doc = parser.parseFromString(`<body>${processed}</body>`, 'text/html');
+        // 3. Parse into DOM tree via native template fragment
+        const tpl = document.createElement('template');
+        tpl.innerHTML = processed;
 
         // 4. Recursive transformer: keeps formatting elements, makes text nodes interactive words
         function transformDOMNode(node) {
@@ -2888,6 +2886,7 @@ document.addEventListener('DOMContentLoaded', () => {
                         const span = document.createElement('span');
                         span.className = 'reader-word';
                         span.dataset.word = token;
+                        span.dataset.context = contextText || raw;
                         span.textContent = token;
 
                         const lower = token.toLowerCase();
@@ -2899,11 +2898,6 @@ document.addEventListener('DOMContentLoaded', () => {
                             span.classList.add('highlight-enabled');
                         }
 
-                        span.addEventListener('click', (e) => {
-                            e.stopPropagation();
-                            handleWordClick(token, contextText || raw, span);
-                        });
-
                         frag.appendChild(span);
                     } else {
                         frag.appendChild(document.createTextNode(token));
@@ -2993,7 +2987,7 @@ document.addEventListener('DOMContentLoaded', () => {
             return document.createTextNode('');
         }
 
-        Array.from(doc.body.childNodes).forEach(childNode => {
+        Array.from(tpl.content.childNodes).forEach(childNode => {
             container.appendChild(transformDOMNode(childNode));
         });
     }
@@ -3453,13 +3447,6 @@ document.addEventListener('DOMContentLoaded', () => {
             if (activeCh !== null && activeCh !== undefined && activeCh !== currentChapterIndex) {
                 currentChapterIndex = activeCh;
                 if (readerChapterSelect) readerChapterSelect.value = currentChapterIndex;
-                if (readerChapterSelect && readerChapterSelect.options) {
-                    for (let i = 0; i < readerChapterSelect.options.length; i++) {
-                        const rawTitle = currentBook.chapters[i]?.title || `Глава ${i + 1}`;
-                        const icon = i < currentChapterIndex ? '✔ ' : (i === currentChapterIndex ? '▶ ' : '○ ');
-                        readerChapterSelect.options[i].textContent = `${icon}${rawTitle}`;
-                    }
-                }
                 if (readerPrevChBtn) readerPrevChBtn.disabled = currentChapterIndex <= 0;
                 if (readerNextChBtn) readerNextChBtn.disabled = currentChapterIndex >= currentBook.chapters.length - 1;
 
@@ -3470,16 +3457,16 @@ document.addEventListener('DOMContentLoaded', () => {
             }
         }
 
-        // 2. Infinite scroll: auto-append next chapter in chapters mode
-        if (readerSettings.flowMode === 'chapters' && readerSettings.autoLoadNext && !isAppendingChapter) {
+        // 2. Infinite scroll: auto-append next chapter in continuous mode or chapters mode with autoload
+        if ((readerSettings.flowMode === 'continuous' || (readerSettings.flowMode === 'chapters' && readerSettings.autoLoadNext)) && !isAppendingChapter) {
             const distanceToBottom = readerScrollArea.scrollHeight - (readerScrollArea.scrollTop + readerScrollArea.clientHeight);
-            if (distanceToBottom < 450) {
+            if (distanceToBottom < 700) {
                 const loadedArr = Array.from(loadedChaptersSet);
                 const highestCh = loadedArr.length > 0 ? Math.max(...loadedArr) : currentChapterIndex;
                 if (currentBook && currentBook.chapters && highestCh < currentBook.chapters.length - 1) {
                     isAppendingChapter = true;
                     appendNextChapter(highestCh + 1, false);
-                    setTimeout(() => { isAppendingChapter = false; }, 300);
+                    setTimeout(() => { isAppendingChapter = false; }, 200);
                 }
             }
         }
@@ -3832,6 +3819,18 @@ document.addEventListener('DOMContentLoaded', () => {
 
     initReaderSettingsPanel();
 
+    if (readerContentBody) {
+        readerContentBody.addEventListener('click', (e) => {
+            const wordSpan = e.target.closest('.reader-word');
+            if (wordSpan) {
+                e.stopPropagation();
+                const word = wordSpan.dataset.word;
+                const context = wordSpan.dataset.context || wordSpan.closest('p, div, li, td, th, blockquote')?.textContent || word;
+                handleWordClick(word, context, wordSpan);
+            }
+        });
+    }
+
     if (readerToggleHighlightBtn) {
         readerToggleHighlightBtn.addEventListener('click', () => {
             isHighlightEnabled = !isHighlightEnabled;