fix: add error handling to all routes, always return JSON

app.py

@@ -26,10 +26,18 @@ CORS(app)
 
 # MongoDB setup
 MONGO_URI = os.getenv("MONGO_URI")
-client = MongoClient(MONGO_URI)
-db = client["screw_inspections"]
-predictions_collection = db["predictions"]
-users_collection = db["users"]
+try:
+    client = MongoClient(MONGO_URI, serverSelectionTimeoutMS=5000)
+    client.server_info()  # Force connection check
+    db = client["screw_inspections"]
+    predictions_collection = db["predictions"]
+    users_collection = db["users"]
+    print("✅ MongoDB connected")
+except Exception as e:
+    print(f"❌ MongoDB connection failed: {e}")
+    client = None
+    predictions_collection = None
+    users_collection = None
 
 # Load ResNet50 model
 model = models.resnet50()
@@ -117,47 +125,59 @@ def predict():
 
 @app.route("/register", methods=["POST"])
 def register():
-    data = request.json
-    username = data.get("username")
-    password = data.get("password")
+    try:
+        data = request.json
+        username = data.get("username")
+        password = data.get("password")
 
-    if not username or not password:
-        return jsonify({"error": "Username and password required"}), 400
+        if not username or not password:
+            return jsonify({"error": "Username and password required"}), 400
 
-    if users_collection.find_one({"username": username}):
-        return jsonify({"error": "User already exists"}), 400
+        if users_collection is None:
+            return jsonify({"error": "Database not connected"}), 500
 
-    hashed_pw = bcrypt.hashpw(password.encode('utf-8'), bcrypt.gensalt())
+        if users_collection.find_one({"username": username}):
+            return jsonify({"error": "User already exists"}), 400
 
-    users_collection.insert_one({
-        "username": username,
-        "password": hashed_pw,
-        "action": "register",
-        "timestamp": datetime.now(timezone.utc)
-    })
+        hashed_pw = bcrypt.hashpw(password.encode('utf-8'), bcrypt.gensalt())
 
-    return jsonify({"message": "User registered successfully"}), 201
+        users_collection.insert_one({
+            "username": username,
+            "password": hashed_pw,
+            "action": "register",
+            "timestamp": datetime.now(timezone.utc)
+        })
+
+        return jsonify({"message": "User registered successfully"}), 201
+    except Exception as e:
+        return jsonify({"error": str(e)}), 500
 
 @app.route("/login", methods=["POST"])
 def login():
-    data = request.json
-    username = data.get("username")
-    password = data.get("password")
+    try:
+        data = request.json
+        username = data.get("username")
+        password = data.get("password")
 
-    if not username or not password:
-        return jsonify({"error": "Username and password required"}), 400
+        if not username or not password:
+            return jsonify({"error": "Username and password required"}), 400
 
-    user = users_collection.find_one({"username": username})
-    if not user or not bcrypt.checkpw(password.encode('utf-8'), user['password']):
-        return jsonify({"error": "Invalid username or password"}), 401
+        if users_collection is None:
+            return jsonify({"error": "Database not connected"}), 500
 
-    users_collection.insert_one({
-        "username": username,
-        "action": "login",
-        "timestamp": datetime.now(timezone.utc)
-    })
+        user = users_collection.find_one({"username": username})
+        if not user or not bcrypt.checkpw(password.encode('utf-8'), user['password']):
+            return jsonify({"error": "Invalid username or password"}), 401
 
-    return jsonify({"message": "Login successful", "user_email": username}), 200
+        users_collection.insert_one({
+            "username": username,
+            "action": "login",
+            "timestamp": datetime.now(timezone.utc)
+        })
+
+        return jsonify({"message": "Login successful", "user_email": username}), 200
+    except Exception as e:
+        return jsonify({"error": str(e)}), 500
 
 @app.route("/get-reports", methods=["POST"])
 def get_reports():