Middlewares

// this function below is an example of a middleware in express.js
// its responsible for handling any requests needed to create a new user in our application.
const signupUserController = async (req, res) => {
    // map data to create schema
    const userData = {
        userName: req.body.userName,
        password: hashPassword,
        email: req.body.email,
    };

    const user = new UserModel(userData);

    try {
        const savedUser = await user.save();
        // response with the new user 
        res.status(200).json(savedUser);
    } catch (err) {
      // or resoponse with any error
        res.status(400).json(err);
    }
};

// we run the middleware when the user hits that endpoint.
router.post("/users/signup", signupUserController);

// with the function we can read the incoming request. 
// or make updates to the request.
const logReq = async (req, res) => {
  // read the request
  console.log(`request method is ${req.method} to ${res.url}`);

  // modify the request to use in next middleware in the stack
  req.isLogged = true;

  // modify the outgoing resposnse
  res.send('req is modified')
};

// we use the middleware for all routs. 
router.use("/", logReq);

// first middleware in stack
// we call the res.end() method to end the current request and stoping it from the going to the next middleware in the stack
const firstMiddleWare = async (req, res) => {
  res.end();
};

const secondMiddleWare = async (req, res) => {
  res.send('second middleware');
};

const thirdMiddleWare = async (req, res) => {
  res.send('third middleware');
};

// sice we end the request in the first middleware we never excute the second and third middlewares in the stack.
router.use("/", firstMiddleWare, secondMiddleWare, thirdMiddleWare);

// first middleware in stack
// we call the res.end() method to end the current request and stoping it from going to the next middleware in the stack
const firstMiddleWare = async (req, res, next) => {
  req.firstMiddleWareRan = true;

  // invoking the next fn lets express know to go to the next middleware in the stack.
  next();
};

const secondMiddleWare = async (req, res, next) => {
    req.secondMiddleWareRan = true;
    // invoking the next fn lets express know to go to the next middleware in the stack.
  next();
};

const thirdMiddleWare = async (req, res) => {
  console.log(req) // {firstMiddleWareRan: true, secondMiddleWareRan: true}

    // invoking the next fn lets express know to go to the next middleware in the stack.
  res.send("all middlewares ran");
};

// we execute all middlewares in the stack [firstMiddleWare, secondMiddleWare, thirdMiddleware]
router.use("/", firstMiddleWare, secondMiddleWare, thirdMiddleWare);