Passport JS push

BackEnd/concepts.md

@@ -124,6 +124,39 @@ Know more about mongoose: [OFFCIAL DOCUMENTATION](https://mongoosejs.com/docs/in
 
 The `versionKey` is a property set on each document when first created by Mongoose. This keys value contains the internal [revision](http://aaronheckmann.blogspot.com/2012/06/mongoose-v3-part-1-versioning.html) of the document. The `versionKey` option is a string that represents the path to use for versioning. The default is `__v`.
 
-## Some Backend Code Concepts in Express: 
+## Some Backend Code Concepts in Express:
 
-How to use the req Object in Express: [Here](https://www.digitalocean.com/community/tutorials/nodejs-req-object-in-expressjs)
+#### How to use the req Object in Express: [Here](https://www.digitalocean.com/community/tutorials/nodejs-req-object-in-expressjs)
+
+#### Serialize and deserialize in passport js
+
+
+To maintain a login session, Passport serializes and deserializes user information to and from the session. The information that is stored is determined by the application, which supplies a `serializeUser` and a `deserializeUser` function.
+
+```
+passport.serializeUser(function(user, cb) {
+  process.nextTick(function() {
+    return cb(null, {
+      id: user.id,
+      username: user.username,
+      picture: user.picture
+    });
+  });
+});
+
+passport.deserializeUser(function(user, cb) {
+  process.nextTick(function() {
+    return cb(null, user);
+  });
+});
+```
+
+A login session is established upon a user successfully authenticating using a credential. The following route will authenticate a user using a username and password. If successfully verified, Passport will call the `serializeUser` function, which in the above example is storing the user's ID, username, and picture. Any other properties of the user, such as an address or birthday, are not stored.
+
+```
+app.post('/login/password',
+  passport.authenticate('local', { failureRedirect: '/login', failureMessage: true }),
+  function(req, res) {
+    res.redirect('/~' + req.user.username);
+  });
+```

ConnectIO/config/passport-local-strategy.js

@@ -0,0 +1,51 @@
+const passport  =  require("passport");
+
+const LocalStrategy = require("passport-local").Strategy;
+const User  = require('../models/user');
+
+//authentication using passport: 
+passport.use(new LocalStrategy({
+        usernameField: 'email'
+    },
+
+
+    //here done is a callback function. 
+    function(email,password,done){
+        //find user and establish identity: 
+        User.findOne({email:email}, function(err,user){
+            if(err){
+                console.log("Error in finding user --> Passport");
+                return done(err);  
+            }
+
+            //if user does not exist or password incorrect: 
+            if(!user || user.password!= password){
+                console.log("Invalid Credentials!!");
+                return done(err,false); //done takes 2 arguments.
+            }
+
+            return done(null,user); //if user is found then return done().
+        });
+    }
+
+
+));
+
+//serializing user to decide which key is to be kept in the cookies
+
+passport.serializeUser(function(user,done){
+    done(null,user.id); //this encrypts the id. 
+});
+
+//deserializing user from thr key in the cookies
+
+passport.deserializeUser(function(id,done){
+    User.findById(id, function(err,user){
+        if(err){
+            console.log("Error in finding user --> Passport");
+            return done(err);  
+        }
+
+        return done(null,user);
+    })
+})