Fix bug failed on await db.documents.insert_one(doc)

app/db.py

@@ -46,10 +46,12 @@ async def save_to_textbook_fs(doc_id: str, file_path: str):
     except Exception as e:
         logger.warning(f"⚠️ textbook GridFS save failed: {e}")
 
+# Fetch to view PDF on frontend
 async def fetch_textbook_pdf(doc_id: str):
     bucket = _get_textbook_fs()
     return await bucket.open_download_stream_by_name(f"{doc_id}.pdf")
 
+# Delete textbook when handshake failed
 async def delete_textbook_pdf(doc_id: str):
     bucket = _get_textbook_fs()
     try:

app/routers/import_doc.py

@@ -80,7 +80,7 @@ async def import_book(req: ImportRequest):
         "metadata": result
     }
     db = get_db()
-    await db.documents.insert_one(doc)
+    await db.documents.replace_one({"_id": req.candidate_id}, doc, upsert=True)
     asyncio.create_task(parse_and_index(req.candidate_id))
     logger.info(f"📚 Document {req.candidate_id} queued for indexing")
     # Head back to frontend