reworked structure and improved performance to handle 500 concurrent users

app/blueprints/slides/__init__.py

@@ -0,0 +1,5 @@
+from flask import Blueprint
+
+slides_bp = Blueprint('slides', __name__, url_prefix='/slides')
+
+from . import routes  # import routes after blueprint is created

app/blueprints/slides/routes.py

@@ -0,0 +1,158 @@
+from . import slides_bp
+from flask import current_app, abort, redirect, url_for, request, send_from_directory
+from app.utils import get_cached_deck_info, token_required
+from app.models import Deck, db, Course
+import os
+import flask_login
+import re
+
+
+slidev_deck_pattern = re.compile(
+    r"^\/slides\/[^\/]+\/[^\/]+\/(?:\d+|index\.html)(?:\?.*)?$"
+)
+slidev_all_pattern = re.compile(
+    r"^\/slides\/([^\/]+)\/([^\/]+)(?:\/presenter)?\/(\d+)(?:\?.*)?$"
+)
+
+
+def log_404(reason: str, deck: str, course: str, path: str, token):
+    """
+    Helper function to log 404 errors with the user's identity.
+    Uses current_app.logger to ensure logs are handled by the app's config.
+    """
+    user_identity = f"User: {token.name} (ID: {token.id})"
+    current_app.logger.warning(
+        f"404 Not Found [{reason}] | {user_identity} | Resource: {course}/{deck}/{path}"
+    )
+
+
+@slides_bp.after_request
+def inject_confused_button(response):
+    if (
+        (slidev_deck_pattern.match(request.path) or request.path == "/")
+        and response.content_type.startswith("text/html")
+        and not flask_login.current_user.is_authenticated
+    ):
+        if response.direct_passthrough:
+            response.direct_passthrough = False
+        body = response.get_data(as_text=True)
+        insert_at = body.find("</body>")
+        if insert_at != -1:
+            button_html = """
+            <button id="confused-button" style="
+                position: fixed;
+                bottom: 1.5rem;
+                right: 1.5rem;
+                z-index: 9999;
+                background-color: #4f8cff;
+                color: white;
+                font-size: 1rem;
+                font-weight: bold;
+                border: none;
+                border-radius: 9999px;
+                padding: 1rem;
+                box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
+                cursor: pointer;
+                transition: background-color 0.3s, transform 0.2s;"
+                title="Didn't understand? Click!">
+              Ich habe das nicht verstanden
+            </button>
+            <script>
+            document.getElementById('confused-button').addEventListener('click', () => {
+                fetch('/confused', {method: 'POST'})
+                  .then(response => {
+                    if (response.ok) {
+                      alert('Alles klar! Ich versuche es besser zu erklären. Melde dich, wenn du eine spezifische Frage hast oder noch etwas unklar bleibt.');
+                    }
+                  }).catch(error => console.error('Error:', error));
+            });
+            </script>
+            """
+            body = body[:insert_at] + button_html + body[insert_at:]
+            response.set_data(body)
+    return response
+
+
+@slides_bp.route("/<course_folder>/<deck>/")
+@slides_bp.route("/<course_folder>/<deck>/<path:path>")
+@token_required
+def serve_deck(course_folder, deck, token, path="index.html"):
+    # 1. Ask the cache for the deck data (0 DB queries on a cache hit!)
+    deck_info = get_cached_deck_info(token.id, course_folder, deck)
+
+    # 2. Handle missing data
+    if not deck_info["course_exists"]:
+        log_404("Course not found", deck, course_folder, path, token)
+        abort(404)
+
+    if not deck_info["deck_exists"]:
+        log_404("Deck not in database", deck, course_folder, path, token)
+        abort(404)
+
+    # 3. Handle authorization
+    if not deck_info["auth"]:
+        current_app.logger.warning(
+            f"Access denied (locked) for user {token.name} -> {deck_info.get('deck_name', deck)}"
+        )
+        return redirect(url_for("main.index"))
+
+    # 4. Resolve the file path entirely using strings
+    slides_dir = os.path.join(current_app.config["SLIDES_DIR"], course_folder)
+    deck_path = os.path.join(slides_dir, deck)
+
+    if not os.path.exists(deck_path):
+        log_404("Deck directory missing on disk", deck, course_folder, path, token)
+        return f"Deck '{deck_info['deck_name']}' not found.", 404
+
+    # 5. Serve the file
+    if slidev_all_pattern.match(request.path):
+        current_app.logger.info(f"User reloaded in deck {deck_info['deck_name']}")
+        return send_from_directory(deck_path, deck_info["index_file"])
+
+    requested_file = os.path.join(deck_path, path)
+    if os.path.isfile(requested_file):
+        if path == deck_info["index_file"]:
+            current_app.logger.info(
+                f"User {token.name} accessed deck {deck_info['deck_name']}"
+            )
+        return send_from_directory(deck_path, path)
+
+    log_404("File missing within deck", deck, course_folder, path, token)
+    abort(404)
+
+
+@slides_bp.route("/<course_folder>/<deck>/export")
+@token_required
+def serve_export(deck, course_folder, token):
+    course = db.session.execute(
+        db.select(Course).where(Course.folder == course_folder)
+    ).scalar()
+    if not course:
+        log_404("Export: Course not found", deck, course_folder, "", token)
+        abort(404)
+    assert isinstance(course, Course)
+
+    deck_obj = db.session.execute(
+        db.select(Deck).where(Deck.deck == deck, Deck.course_id == course.id)
+    ).scalar()
+    if not deck_obj:
+        log_404("Export: Deck not in database", deck, course_folder, "", token)
+        abort(404)
+    assert isinstance(deck_obj, Deck)
+
+    if not deck_obj.export_file:
+        log_404("Export: Deck has no export_file set", deck, course_folder, "", token)
+        abort(404)
+
+    if not token.is_unlocked(deck_obj.deck):
+        return redirect(url_for("main.index"))
+
+    exports_dir = os.path.join(current_app.config["EXPORTS_DIR"], course.folder)
+    deck_path = os.path.join(exports_dir, deck_obj.deck)
+    requested_file = os.path.join(deck_path, deck_obj.export_file)
+    if os.path.isfile(requested_file):
+        current_app.logger.info(f"User {token.name} exported deck {deck_obj.name}")
+        return send_from_directory(deck_path, deck_obj.export_file)
+
+    log_404("Export file missing", deck, course_folder, deck_obj.export_file, token)
+    abort(404)