chore(docs): Add google auth hook guide

docs/guides/google-auth-hook.md

@@ -0,0 +1,227 @@
+---
+id: google_auth
+title: Google Auth Hook
+---
+
+This part of the tutorial shows how to create a sign-in flow for users and integrate with Unleash server project. The implementation assumes that I am working in `localhost` with `4242` port.
+
+This is a simple `index.js` server file.
+```javascript
+const unleash = require('unleash-server');
+
+if (process.env.DATABASE_URL_FILE) {
+  options.databaseUrl = fs.readFileSync(process.env.DATABASE_URL_FILE);
+}
+
+unleash.start(options).then(unleash => {
+  console.log(`Unleash started on http://localhost:${unleash.app.get('port')}`);
+});;
+```
+
+### Creating a web application client ID
+
+1. Go to the credentials section in the [Google Cloud Platform Console](https://console.cloud.google.com/apis/credentials?_ga=2.77615956.-1991581217.1542834301).
+
+2. Click **OAuth consent screen**. Type a product name. Fill in any relevant optional fields. Click **Save**.
+
+3. Click **Create credentials > OAuth client ID**.
+
+4. Under **Application type**, select **Web Application**.
+
+5. Type the **Name**.
+
+6. Under **Authorized redirect URIs** enter the following URLs, one at a time.
+```
+http://localhost:4242/api/auth/callback
+```
+
+7. Click **Create**.
+
+8. Copy the **CLIENT ID** and **CLIENT SECRET** and save them for later use.
+
+
+### Add dependencies
+
+Add two dependencies [`passport`](https://www.npmjs.com/package/passport) and [`passport-google-oauth20`](https://www.npmjs.com/package/passport-google-oauth20) inside `index.js` file 
+```js
+const unleash = require('unleash-server');
+const passport = require('passport');
+const GoogleStrategy = require('passport-google-oauth20').Strategy;
+```
+### Configure the Google strategy for use by Passport.js
+
+OAuth 2-based strategies require a `verify` function which receives the credential (`accessToken`) for accessing the Google API on the user's behalf, along with the user's profile. The function must invoke `cb` with a user object, which will be set at `req.user` in route handlers after authentication.
+```js
+const GOOGLE_CLIENT_ID = '...';
+const GOOGLE_CLIENT_SECRET = '...';
+const GOOGLE_CALLBACK_URL = 'http://localhost:4242/api/auth/callback';
+
+passport.use(new GoogleStrategy(
+  {
+	clientID: GOOGLE_CLIENT_ID,
+	clientSecret: GOOGLE_CLIENT_SECRET,
+	callbackURL: GOOGLE_CALLBACK_URL
+  },
+  function(accessToken, refreshToken, profile, cb) {
+    // Extract the minimal profile information we need from the profile object
+    // and connect with Unleash to get name and email.
+    cb(null, new unleash.User({
+      name: profile.displayName,
+      email: profile.emails[0].value,
+    }));
+  }
+));
+```
+
+Add `googleAdminAuth()` function and other options
+```js
+function googleAdminAuth(app) {}
+
+let options = {
+  enableLegacyRoutes: false,
+  adminAuthentication: 'custom',
+  preRouterHook: googleAdminAuth
+};
+
+unleash.start(options).then(unleash => {
+  console.log(`Unleash started on http://localhost:${unleash.app.get('port')}`);
+});;
+```
+
+### In `googleAdminAuth` function
+
+Configure `passport` package.
+```js
+function googleAdminAuth(app) {
+  app.use(passport.initialize());
+  app.use(passport.session());
+  passport.serializeUser((user, done) => done(null, user));
+  passport.deserializeUser((user, done) => done(null, user));
+  // ...
+}
+```
+
+Implement a preRouter hook for `/api/admin/login`. It's neccesary for login with Google.
+```js
+function googleAdminAuth(app) {
+  // ...
+  app.get('/api/admin/login', passport.authenticate('google', { scope: ['profile', 'email'] }));
+  // ...
+}
+```
+
+Implement a preRouter hook for `/api/auth/callback`. It's a callback when the login is executed.
+```js
+function googleAdminAuth(app) {
+  // ...
+  app.get('/api/auth/callback',
+    passport.authenticate('google', {
+      failureRedirect: '/api/admin/error-login',
+    }),
+    (req, res) => {
+      // Successful authentication, redirect to your app.
+      res.redirect('/');
+    }
+  );
+  // ...
+}
+```
+
+Implement a preRouter hook for `/api/admin`.
+```js
+function googleAdminAuth(app) {
+  // ...
+  app.use('/api/admin/', (req, res, next) => {
+    if (req.user) {
+      next();
+    } else {
+      // Instruct unleash-frontend to pop-up auth dialog
+      return res
+        .status('401')
+        .json(
+          new unleash.AuthenticationRequired({
+            path: '/api/admin/login',
+            type: 'custom',
+            message: `You have to identify yourself in order to use Unleash. Click the button and follow the instructions.`,
+        })
+      ).end();
+    }
+  });
+  // ...
+}
+```
+
+### The complete code
+The `index.js` server file.
+```js
+'use strict';
+
+const unleash = require('unleash-server');
+const passport = require('passport');
+const GoogleStrategy = require('passport-google-oauth20').Strategy;
+
+const GOOGLE_CLIENT_ID = '...';
+const GOOGLE_CLIENT_SECRET = '...';
+const GOOGLE_CALLBACK_URL = 'http://localhost:4242/api/auth/callback';
+
+passport.use(new GoogleStrategy(
+  {
+	clientID: GOOGLE_CLIENT_ID,
+	clientSecret: GOOGLE_CLIENT_SECRET,
+	callbackURL: GOOGLE_CALLBACK_URL
+  },
+  function(accessToken, refreshToken, profile, cb) {
+    cb(null, new unleash.User({
+      name: profile.displayName,
+      email: profile.emails[0].value,
+    }));
+  }
+));
+
+function googleAdminAuth(app) {
+  app.use(passport.initialize());
+  app.use(passport.session());
+  passport.serializeUser((user, done) => done(null, user));
+  passport.deserializeUser((user, done) => done(null, user));
+
+  app.get('/api/admin/login', passport.authenticate('google', { scope: ['profile', 'email'] }));
+	app.get('/api/auth/callback',
+    passport.authenticate('google', {
+      failureRedirect: '/api/admin/error-login',
+    }),
+    (req, res) => {
+      res.redirect('/');
+    }
+  );
+
+  app.use('/api/admin/', (req, res, next) => {
+    if (req.user) {
+      next();
+    } else {
+      return res
+        .status('401')
+        .json(
+          new unleash.AuthenticationRequired({
+            path: '/api/admin/login',
+            type: 'custom',
+            message: `You have to identify yourself in order to use Unleash. Click the button and follow the instructions.`,
+        })
+      ).end();
+    }
+  });
+}
+
+let options = {
+  enableLegacyRoutes: false,
+  adminAuthentication: 'custom',
+  preRouterHook: googleAdminAuth
+};
+
+if (process.env.DATABASE_URL_FILE) {
+  options.databaseUrl = fs.readFileSync(process.env.DATABASE_URL_FILE);
+}
+
+unleash.start(options).then(unleash => {
+  console.log(`Unleash started on http://localhost:${unleash.app.get('port')}`);
+});;
+```

website/sidebars.json

@@ -1,12 +1,13 @@
 {
   "documentation": {
     "Getting Started": ["getting_started", "securing_unleash", "unleash_context", "activation_strategy", "client_specification", "migration_guide"],
-    "Developer Guide": ["developer_guide", "database_schema", "database_backup"]
+    "Developer Guide": ["developer_guide", "database_schema", "database_backup"],
+    "Guides": ["guides/google_auth"]
   },
   "api": {
     "Client": ["api/client/features", "api/client/register", "api/client/metrics"],
     "Admin": ["api/admin/features", "api/admin/strategies", "api/admin/metrics", "api/admin/events" ],
     "Internal": ["api/internal" ]
-    
+
   }
 }