added sample auth controller for login

Author: gauravprwl14

server/controllers/auth.controller.js

@@ -0,0 +1,51 @@
+import jwt from 'jsonwebtoken';
+import httpStatus from 'http-status';
+import APIError from '../helpers/APIError';
+import config from '../../config/config';
+
+// sample user, used for authentication
+const user = {
+    username: 'react',
+    password: 'express',
+};
+
+/**
+ * Returns jwt token if valid username and password is provided
+ * @param req
+ * @param res
+ * @param next
+ * @returns {*}
+ */
+function login(req, res, next) {
+    // Ideally you'll fetch this from the db
+    // Idea here was to show how jwt works with simplicity
+    if (req.body.username === user.username && req.body.password === user.password) {
+        const token = jwt.sign({
+            username: user.username,
+            expiresIn: 3600,
+        }, config.jwtSecret);
+        return res.json({
+            token,
+            username: user.username,
+        });
+    }
+
+    const err = new APIError('Authentication error', httpStatus.UNAUTHORIZED, true);
+    return next(err);
+}
+
+/**
+ * This is a protected route. Will return random number only if jwt token is provided in header.
+ * @param req
+ * @param res
+ * @returns {*}
+ */
+function getRandomNumber(req, res) {
+    // req.user is assigned by jwt middleware if valid token is provided
+    return res.json({
+        user: req.user,
+        num: Math.random() * 100,
+    });
+}
+
+export default { login, getRandomNumber };