reworked structure and improved performance to handle 500 concurrent users

app/utils.py

@@ -1,7 +1,7 @@
 import os
 import logging
 
-from flask import request, session, redirect, url_for, current_app
+from flask import request, session, redirect, url_for, current_app, abort, make_response
 from typing import cast
 from itsdangerous import BadSignature, URLSafeSerializer
 from xkcdpass import xkcd_password
@@ -10,6 +10,7 @@ from urllib.parse import urlparse, urljoin
 
 from .models import Deck, InfoBanner, Token, db, Course
 
+
 # Create a module-level logger per Flask/Python standards
 logger = logging.getLogger(__name__)
 
@@ -96,6 +97,23 @@ def create_token(user_name: str) -> Token:
     return token
 
 
+def set_cookie(token):
+    next_url = session.pop("next_url", None)
+    if not next_url:
+        current_app.logger.debug("next_url not present redirecting to index")
+        next_url = url_for("main.index")
+
+    if not is_safe_url(next_url):
+        current_app.logger.warning(f"Blocked unsafe redirect attempt to: {next_url}")
+        return abort(400)
+
+    resp = make_response(redirect(next_url))
+    resp.set_cookie(
+        "access_token", serialize_token(token), httponly=True, samesite="Lax", path="/", max_age=31536000
+    )
+    return resp
+
+
 def serialize_token(token: Token) -> str:
     return serializer.dumps(token.id)