// UserRepository.js -------------------------------------------------------------------------
// ... implementation

module.exports = UserRepository;

// UserService.js  -------------------------------------------------------------------------
// ... implementation

module.exports = UserService;

// createNewUser.js -------------------------------------------------------------------------
const createNewUser = (userService) => (newUser) => {
  // ... implementation that uses userService
}

module.exports = createController;

// app.js -------------------------------------------------------------------------
const express = require('express')
const app = express()
const UserRepository = require('./UserRepository');
const UserService = require('./UserService');

// initialize db and everything
const userRepository = new UserRepository();
const userservice = new UserService(userRepository);

const createNewUser = require('./createNewUser')(userservice);

app.post('/register', (req, res) => {
  const newUser = req.body;
  // prepare other args as well
  createNewUser(newUser)
    .then(result => res.json({ /* ... */ })
    .catch(error => res.json({ /* ... */ });
});

app.listen(3000, () => console.log('Example app listening on port 3000!'))

// Test: createNewUser.spec.js -------------------------------------------------------------------------
describe('createNewUser', function() {
  it('will fail when insert new user', function() {
    const userServiceStub = {
      getByEmail() {
        return Promise.resolve('test@gmail.com');
      },
      insertUser(user) {
        return Promise.reject({ /* error props */ });
      }
    };

    const result = createNewUser(userservice))({ /* user data */ })

    // assert on result ...
  });
});