Example with cookie auth (#5821)

Fixes #153

This is my attempt at #153

Following @rauchg instructions:

- it uses an authentication helper across pages which returns a token if there's one
- it has session synchronization across tabs
- <strike>I deployed a passwordless backend on `now.sh` (https://with-cookie-api.now.sh, [src](https://github.com/j0lv3r4/next.js-with-cookies-api))</strike> The backend is included in the repository and you can deploy everything together by running `now`

Also, from reviewing other PRs, I made sure to:

- use [isomorphic-unfetch](https://www.npmjs.com/package/isomorphic-unfetch).
- use [next-cookies](https://www.npmjs.com/package/next-cookies).

Here's a little demo:

![GIF](https://i.imgur.com/067Ph56.gif)

examples/with-cookie-auth/README.md

@@ -0,0 +1,47 @@
+[![Deploy to now](https://deploy.now.sh/static/button.svg)](https://deploy.now.sh/?repo=https://github.com/zeit/next.js/tree/master/examples/with-cookie-auth)
+# Example app utilizing cookie-based authentication
+
+## How to use
+
+### Using `create-next-app`
+
+Download [`create-next-app`](https://github.com/segmentio/create-next-app) to bootstrap the example:
+
+```
+npm i -g create-next-app
+create-next-app --example with-cookie-auth with-cookie-auth-app
+```
+
+### Download manually
+
+Download the example [or clone the repo](https://github.com/zeit/next.js):
+
+```bash
+curl https://codeload.github.com/zeit/next.js/tar.gz/canary | tar -xz --strip=2 next.js-canary/examples/with-cookie-auth
+cd with-cookie-auth
+```
+
+Install it and run:
+
+```bash
+npm install
+npm run dev
+```
+
+Deploy it to the cloud with [now](https://zeit.co/now) ([download](https://zeit.co/download))
+
+```bash
+now
+```
+
+## The idea behind the example
+
+In this example, we authenticate users and store a token in a cookie. The example only shows how the user session works, keeping a user logged in between pages.
+
+This example is backend agnostic and uses [isomorphic-unfetch](https://www.npmjs.com/package/isomorphic-unfetch) to do the API calls on the client and the server.
+
+The repo includes a minimal passwordless backend built with [Micro](https://www.npmjs.com/package/micro) and it logs the user in with a GitHub username and saves the user id from the API call as token. 
+
+Session is syncronized across tabs. If you logout your session gets logged out on all the windows as well. We use the HOC `withAuthSync` for this.
+
+The helper function `auth` helps to retrieve the token across pages and redirects the user if not token was found.

examples/with-cookie-auth/api/login.js

@@ -0,0 +1,21 @@
+const { json, send, createError, run } = require('micro')
+const fetch = require('isomorphic-unfetch')
+
+const login = async (req, res) => {
+  const { username } = await json(req)
+  const url = `https://api.github.com/users/${username}`
+
+  try {
+    const response = await fetch(url)
+    if (response.ok) {
+      const { id } = await response.json()
+      send(res, 200, { token: id })
+    } else {
+      send(res, response.status, response.statusText)
+    }
+  } catch (error) {
+    throw createError(error.statusCode, error.statusText)
+  }
+}
+
+module.exports = (req, res) => run(req, res, login)

examples/with-cookie-auth/api/package.json

@@ -0,0 +1,20 @@
+{
+  "name": "api",
+  "version": "1.0.0",
+  "description": "",
+  "main": "index.js",
+  "dependencies": {
+    "isomorphic-unfetch": "^3.0.0",
+    "micro": "^9.3.3"
+  },
+  "devDependencies": {
+    "micro-dev": "^3.0.0"
+  },
+  "scripts": {
+    "start": "micro",
+    "dev": "micro-dev"
+  },
+  "keywords": [],
+  "author": "",
+  "license": "ISC"
+}

examples/with-cookie-auth/api/profile.js

@@ -0,0 +1,29 @@
+const { send, createError, run } = require('micro')
+const fetch = require('isomorphic-unfetch')
+
+const profile = async (req, res) => {
+  if (!('authorization' in req.headers)) {
+    throw createError(401, 'Authorization header missing')
+  }
+
+  const auth = await req.headers.authorization
+  const { token } = JSON.parse(auth)
+  const url = `https://api.github.com/user/${token}`
+
+  try {
+    const response = await fetch(url)
+
+    if (response.ok) {
+      const js = await response.json()
+      // Need camelcase in the frontend
+      const data = Object.assign({}, { avatarUrl: js.avatar_url }, js)
+      send(res, 200, { data })
+    } else {
+      send(res, response.status, response.statusText)
+    }
+  } catch (error) {
+    throw createError(error.statusCode, error.statusText)
+  }
+}
+
+module.exports = (req, res) => run(req, res, profile)

examples/with-cookie-auth/now.json

@@ -0,0 +1,12 @@
+{
+  "version": 2,
+  "name": "with-cookie-auth",
+  "builds": [
+    { "src": "www/package.json", "use": "@now/next" },
+    { "src": "api/*.js", "use": "@now/node" }
+  ],
+  "routes": [
+    { "src": "/api/(.*)", "dest": "/api/$1" },
+    { "src": "/(.*)", "dest": "/www/$1" }
+  ]
+}

examples/with-cookie-auth/www/components/header.js

@@ -0,0 +1,58 @@
+import Link from 'next/link'
+import { logout } from '../utils/auth'
+
+const Header = props => (
+  <header>
+    <nav>
+      <ul>
+        <li>
+          <Link href='/'>
+            <a>Home</a>
+          </Link>
+        </li>
+        <li>
+          <Link href='/login'>
+            <a>Login</a>
+          </Link>
+        </li>
+        <li>
+          <Link href='/profile'>
+            <a>Profile</a>
+          </Link>
+        </li>
+        <li>
+          <button onClick={logout}>Logout</button>
+        </li>
+      </ul>
+    </nav>
+    <style jsx>{`
+      ul {
+        display: flex;
+        list-style: none;
+        margin-left: 0;
+        padding-left: 0;
+      }
+
+      li {
+        margin-right: 1rem;
+      }
+
+      li:first-child {
+        margin-left: auto;
+      }
+
+      a {
+        color: #fff;
+        text-decoration: none;
+      }
+
+      header {
+        padding: 0.2rem;
+        color: #fff;
+        background-color: #333;
+      }
+    `}</style>
+  </header>
+)
+
+export default Header

examples/with-cookie-auth/www/components/layout.js

@@ -0,0 +1,40 @@
+import React from 'react'
+import Head from 'next/head'
+import Header from './header'
+
+const Layout = props => (
+  <React.Fragment>
+    <Head>
+      <title>With Cookies</title>
+    </Head>
+    <style jsx global>{`
+      *,
+      *::before,
+      *::after {
+        box-sizing: border-box;
+      }
+
+      body {
+        margin: 0;
+        color: #333;
+        font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto,
+          'Helvetica Neue', Arial, Noto Sans, sans-serif, 'Apple Color Emoji',
+          'Segoe UI Emoji', 'Segoe UI Symbol', 'Noto Color Emoji';
+      }
+
+      .container {
+        max-width: 65rem;
+        margin: 1.5rem auto;
+        padding-left: 1rem;
+        padding-right: 1rem;
+      }
+    `}</style>
+    <Header />
+
+    <main>
+      <div className='container'>{props.children}</div>
+    </main>
+  </React.Fragment>
+)
+
+export default Layout

examples/with-cookie-auth/www/package.json

@@ -0,0 +1,16 @@
+{
+  "name": "with-cookie-auth",
+  "scripts": {
+    "dev": "next",
+    "build": "next build",
+    "start": "next start"
+  },
+  "dependencies": {
+    "isomorphic-unfetch": "^3.0.0",
+    "js-cookie": "^2.2.0",
+    "next": "^7.0.2",
+    "next-cookies": "^1.0.4",
+    "react": "^16.6.3",
+    "react-dom": "^16.6.3"
+  }
+}

examples/with-cookie-auth/www/pages/index.js

@@ -0,0 +1,29 @@
+import React from 'react'
+import Layout from '../components/layout'
+
+const Home = props => (
+  <Layout>
+    <h1>Cookie-based authentication example</h1>
+
+    <p>Steps to test the functionality:</p>
+
+    <ol>
+      <li>Click login and enter your GitHub username.</li>
+      <li>
+        Click home and click profile again, notice how your session is being
+        used through a token stored in a cookie.
+      </li>
+      <li>
+        Click logout and try to go to profile again. You'll get redirected to
+        the `/login` route.
+      </li>
+    </ol>
+    <style jsx>{`
+      li {
+        margin-bottom: 0.5rem;
+      }
+    `}</style>
+  </Layout>
+)
+
+export default Home

examples/with-cookie-auth/www/pages/login.js

@@ -0,0 +1,97 @@
+import { Component } from 'react'
+import Layout from '../components/layout'
+import { login } from '../utils/auth'
+
+class Login extends Component {
+  static getInitialProps ({ req }) {
+    const apiUrl = process.browser
+      ? `https://${window.location.host}/api/login.js`
+      : `https://${req.headers.host}/api/login.js`
+
+    return { apiUrl }
+  }
+
+  constructor (props) {
+    super(props)
+
+    this.state = { username: '', error: '' }
+    this.handleChange = this.handleChange.bind(this)
+    this.handleSubmit = this.handleSubmit.bind(this)
+  }
+
+  handleChange (event) {
+    this.setState({ username: event.target.value })
+  }
+
+  async handleSubmit (event) {
+    event.preventDefault()
+    const username = this.state.username
+    const url = this.props.apiUrl
+    login({ username, url }).catch(() =>
+      this.setState({ error: 'Login failed.' })
+    )
+  }
+
+  render () {
+    return (
+      <Layout>
+        <div className='login'>
+          <form onSubmit={this.handleSubmit}>
+            <label htmlFor='username'>GitHub username</label>
+
+            <input
+              type='text'
+              id='username'
+              name='username'
+              value={this.state.username}
+              onChange={this.handleChange}
+            />
+
+            <button type='submit'>Login</button>
+
+            <p className={`error ${this.state.error && 'show'}`}>
+              {this.state.error && `Error: ${this.state.error}`}
+            </p>
+          </form>
+        </div>
+        <style jsx>{`
+          .login {
+            max-width: 340px;
+            margin: 0 auto;
+            padding: 1rem;
+            border: 1px solid #ccc;
+            border-radius: 4px;
+          }
+
+          form {
+            display: flex;
+            flex-flow: column;
+          }
+
+          label {
+            font-weight: 600;
+          }
+
+          input {
+            padding: 8px;
+            margin: 0.3rem 0 1rem;
+            border: 1px solid #ccc;
+            border-radius: 4px;
+          }
+
+          .error {
+            margin: 0.5rem 0 0;
+            display: none;
+            color: brown;
+          }
+
+          .error.show {
+            display: block;
+          }
+        `}</style>
+      </Layout>
+    )
+  }
+}
+
+export default Login