app.js

const express = require('express');
const app = express();
const port = process.env.PORT || 3000;
const morgan = require('morgan');
const bodyParser = require('body-parser');
const mongoose = require('mongoose');

const productRoutes = require('./api/routes/products');
const orderRoutes = require('./api/routes/orders');
const userRoutes = require('./api/routes/users');

mongoose.connect('mongodb://localhost/shop');

app.use(morgan('dev'));
// Making the uploads folder publicly accessible so that we can view images
app.use('/uploads', express.static('uploads'));
app.use(bodyParser.urlencoded({ extended: false }));
app.use(bodyParser.json());

/*
	Handling CORS errors
*/

app.use((req, res, next) => {
	res.header('Access-Control-Allow-Origin', '*');
	res.header('Access-Control-Allow-Headers', '*');
	if(req.method === 'OPTIONS') {
		res.header('Access-Control-Allow-Methods', 
			'PUT, POST, PATCH, DELETE, GET');
		return res.status(200).json({});
	}
	next();
});
/*
This is the middleware
Routes which should handle requests
*/

app.use('/products', productRoutes);
app.use('/orders', orderRoutes);
app.use('/users', userRoutes);

app.use((req, res, next) => {
	const error = new Error('Not found');
	error.status = 404;
	next(error); // Throws the error to the next block
});

/*
	Catches errors from previous block (if initial route
	isn't correct) as well as errors coming from 
	elsewhere.
*/
app.use((error, req, res, next) => {
	res.status(error.status || 500);
	res.json({
		error: {
			message: error.message
		}
	});
});

app.listen(port);
console.log('Running on port ' + port);