feat(auth, epub): enhance Google token verification and EPUB chapter extraction

- Added Google token verification logic to improve security and ensure valid tokens are processed.
- Introduced functions for extracting chapters from EPUB files based on HTML tags, including support for chapter markers.
- Updated `.env.example` to include configuration for an OpenAI-compatible router.
- Refactored existing functions for better readability and maintainability.

app/epub_parser.py

@@ -1,5 +1,7 @@
 from __future__ import annotations
 
+import html as html_lib
+import re
 from pathlib import Path
 from typing import Any
 
@@ -7,8 +9,13 @@ import html2text
 from ebooklib import ITEM_DOCUMENT
 from ebooklib import epub as epublib
 
+_CHAPTER_MARKER_TEXT_RE = re.compile(
+    r"(?:ch(?:u(?:ơng|ong))?|chapter|hồi|hoi|phần|phan|tập|tap|quyển|quyen)\s*\d+",
+    re.IGNORECASE,
+)
 
-def _html_to_text(html_content: str) -> str:
+
+def html_to_text(html_content: str) -> str:
     h = html2text.HTML2Text()
     h.ignore_links = True
     h.ignore_images = True
@@ -17,6 +24,20 @@ def _html_to_text(html_content: str) -> str:
     return h.handle(html_content).strip()
 
 
+def _html_to_text(html_content: str) -> str:
+    return html_to_text(html_content)
+
+
+def build_merged_html_from_epub(epub_path: Path) -> str:
+    book = epublib.read_epub(str(epub_path), options={"ignore_ncx": False})
+    parts: list[str] = []
+    for item in book.get_items_of_type(ITEM_DOCUMENT):
+        content = item.get_content().decode("utf-8", errors="replace")
+        if content.strip():
+            parts.append(content)
+    return "\n".join(parts)
+
+
 def build_chapters_from_epub(epub_path: Path) -> list[dict[str, Any]]:
     book = epublib.read_epub(str(epub_path), options={"ignore_ncx": False})
     out: list[dict[str, Any]] = []
@@ -36,3 +57,135 @@ def build_chapters_from_epub(epub_path: Path) -> list[dict[str, Any]]:
         )
         idx += 1
     return out
+
+
+def count_html_tag_opens(html: str, tag: str) -> int:
+    tag_re = re.escape(tag.strip().lower())
+    return len(re.findall(rf"<{tag_re}\b", html, flags=re.IGNORECASE))
+
+
+def _strip_tags_to_text(fragment: str) -> str:
+    return html_lib.unescape(re.sub(r"<[^>]+>", " ", fragment or "")).strip()
+
+
+def _title_from_tag_opening(opening_attrs: str, fragment: str, tag: str) -> str:
+    tag_re = re.escape(tag)
+    for attr in ("title", "alt"):
+        match = re.search(rf'{attr}\s*=\s*["\']([^"\']+)["\']', opening_attrs, flags=re.IGNORECASE)
+        if match:
+            title = html_lib.unescape(match.group(1)).strip()
+            if title and len(title) <= 160:
+                return title
+    for attr in ("id", "name"):
+        match = re.search(rf'{attr}\s*=\s*["\']([^"\']+)["\']', opening_attrs, flags=re.IGNORECASE)
+        if match:
+            title = html_lib.unescape(match.group(1)).strip()
+            if title and not title.startswith("#") and len(title) <= 160:
+                return title
+    close_match = re.search(
+        rf"<{tag_re}\b[^>]*>(.*?)</{tag_re}>",
+        fragment,
+        flags=re.IGNORECASE | re.DOTALL,
+    )
+    if not close_match:
+        return ""
+    inner = _strip_tags_to_text(close_match.group(1))
+    if inner and len(inner) <= 160:
+        return inner
+    return ""
+
+
+def _anchor_seems_chapter_marker(opening_attrs: str, inner_text: str) -> bool:
+    text = (inner_text or "").strip()
+    if text and _CHAPTER_MARKER_TEXT_RE.search(text):
+        return True
+    attrs = opening_attrs or ""
+    if re.search(r'\bhref\s*=\s*["\'][^"\']*\.xhtml', attrs, flags=re.IGNORECASE):
+        return True
+    if re.search(
+        r'\b(?:id|name)\s*=\s*["\'][^"\']*(?:chuong|chương|chapter|ch\d|c\d|hoi|hồi)',
+        attrs,
+        flags=re.IGNORECASE,
+    ):
+        return True
+    # TOC / nav links thường có text ngắn.
+    if text and len(text) <= 120:
+        return True
+    return False
+
+
+def _derive_simple_chapter_title(txt: str, number: int) -> str:
+    for line in (txt or "").splitlines():
+        cleaned = line.strip()
+        if cleaned:
+            return cleaned[:160]
+    return f"Chương {number}"
+
+
+def extract_chapters_by_html_tag(
+    epub_path: Path,
+    tag: str,
+) -> tuple[list[dict[str, Any]], dict[str, int]]:
+    """Tách chương tại mỗi thẻ mở `<tag ...>`. Trả về (chapters, stats)."""
+    merged_html = build_merged_html_from_epub(epub_path)
+    stats = {"tagOpens": 0, "tagOpensUsed": 0, "tagOpensFiltered": 0}
+    if not merged_html.strip():
+        return [], stats
+
+    tag_name = tag.strip().lower()
+    tag_re = re.escape(tag_name)
+    opener_re = re.compile(rf"<({tag_re})\b([^>]*)>", re.IGNORECASE)
+    matches = list(opener_re.finditer(merged_html))
+    stats["tagOpens"] = len(matches)
+    if not matches:
+        return [], stats
+
+    if tag_name == "a" and len(matches) > 300:
+        filtered: list[re.Match[str]] = []
+        for match in matches:
+            attrs = match.group(2) or ""
+            rest = merged_html[match.end() : match.end() + 800]
+            close = re.search(rf"</{tag_re}>", rest, flags=re.IGNORECASE)
+            inner_html = rest[: close.start()] if close else rest
+            inner_text = _strip_tags_to_text(inner_html)
+            if _anchor_seems_chapter_marker(attrs, inner_text):
+                filtered.append(match)
+        if filtered:
+            stats["tagOpensFiltered"] = len(matches) - len(filtered)
+            matches = filtered
+
+    chapters: list[dict[str, Any]] = []
+    for index, match in enumerate(matches):
+        start = match.start()
+        end = matches[index + 1].start() if index + 1 < len(matches) else len(merged_html)
+        raw_html = merged_html[start:end].strip()
+        if not raw_html:
+            continue
+
+        opening_attrs = match.group(2) or ""
+        txt = html_to_text(raw_html)
+        inline_title = _title_from_tag_opening(opening_attrs, raw_html, tag_name)
+        number = len(chapters) + 1
+        title = inline_title or _derive_simple_chapter_title(txt, number)
+
+        # Bỏ qua anchor rỗng không có tiêu đề và không có nội dung theo sau.
+        if not txt.strip() and not inline_title:
+            tag_only = re.fullmatch(
+                rf"<{tag_re}\b[^>]*>\s*(?:</{tag_re}>\s*)?",
+                raw_html,
+                flags=re.IGNORECASE | re.DOTALL,
+            )
+            if tag_only:
+                continue
+
+        chapters.append(
+            {
+                "number": number,
+                "title": title,
+                "raw_html": raw_html,
+                "txt": txt,
+            }
+        )
+
+    stats["tagOpensUsed"] = len(matches)
+    return chapters, stats