Added the auth header verification to fetch the users

README.md

@@ -1,2 +1,2 @@
 
-## Build a basic version of PayTM
+## Build a basic Payments App

backend/.gitignore

@@ -1 +1,2 @@
 node_modules
+.env

backend/config.js

@@ -0,0 +1,6 @@
+const dotenv = require('dotenv')
+dotenv.config();
+
+module.exports = {
+    JWT_SECRET : process.env.JWT_SECRET
+};

backend/db.js

@@ -0,0 +1,28 @@
+const mongoose = require("mongoose");
+const dotenv = require('dotenv')
+dotenv.config();
+
+mongoose.connect(process.env.MONGO_URL)
+
+const userSchema = new mongoose.Schema({
+    username: String,
+    password: String,
+    firstName: String,
+    lastName: String
+})
+const AccountSchema = new mongoose.Schema({
+    userId: {
+        type: mongoose.Schema.Types.ObjectId,
+        ref: "User"
+    },
+    balance: Number
+})
+
+
+const User = mongoose.model("User", userSchema)
+const Account = mongoose.model("Account",AccountSchema);
+
+module.exports = {
+    User,
+    Account
+}

backend/index.js

@@ -1,3 +1,14 @@
 const express = require("express");
+const cors = require("cors")
+const app = express();
 
+app.use(cors());
+app.use(express.json());
+
+const mainRouter = require("./routes/index")
+
+
+app.use("/api/v1/", mainRouter);
+
+app.listen(3000);
 

backend/middleware.js

@@ -0,0 +1,26 @@
+const { JWT_SECRET } = require("./config");
+const jwt = require("jsonwebtoken");
+
+const authMiddleware = (req, res, next) => {
+    const authHeader = req.headers.authorization;
+
+    if (!authHeader || !authHeader.startsWith('Bearer ')) {
+        return res.status(403).json({});
+    }
+
+    const token = authHeader.split(' ')[1];
+
+    try {
+        const decoded = jwt.verify(token, JWT_SECRET);
+
+        req.userId = decoded.userId;
+
+        next();
+    } catch (err) {
+        return res.status(403).json({});
+    }
+};
+
+module.exports = {
+    authMiddleware
+}

backend/package.json

@@ -10,7 +10,10 @@
   "author": "",
   "license": "ISC",
   "dependencies": {
+    "cors": "^2.8.5",
+    "dotenv": "^16.4.5",
     "express": "^4.18.2",
+    "jsonwebtoken": "^9.0.2",
     "mongoose": "^8.1.0",
     "zod": "^3.22.4"
   }

backend/routes/account.js

@@ -0,0 +1,55 @@
+const express = require("express");
+const { authMiddleware } = require("../middleware");
+const { Account } = require("../db");
+const mongoose = require("mongoose");
+
+const router = express.Router();
+
+router.get("/balance", authMiddleware, async(req,res) => {
+    const account = await Account.findOne({
+        userId : req.userId
+
+    });
+
+    res.json({
+        balance : account.balance
+    })
+});
+
+router.post("/transfer", authMiddleware, async (req,res) =>{
+// async function transfer(req) {
+
+    const session = await mongoose.startSession();
+
+
+    session.startTransaction();
+    const { amount, to } = req.body;
+
+    const account = await Account.findOne({userId : req.userId}).session(session);
+
+    if(!account || account.balance < amount){
+        await session.abortTransaction();
+        return res.status(400).json({
+            message : "Insufficient balance"
+        });
+    }
+
+    const toAccount = await Account.findOne({userId: to}).session(session);
+
+    if(!account){
+        await session.abortTransaction();
+        return res.status(400).json({
+            message: " Invalid account"
+        });
+    }
+
+    await Account.updateOne({ userId : req.userId }, {$inc : {balance : -amount} }).session(session);
+    await Account.updateOne({ userId : to}, {$inc : {balance : amount} }).session(session);
+
+    await session.commitTransaction();
+    res.json({
+        message: "Transfer successful"
+    }); 
+});
+
+module.exports = router;

backend/routes/index.js

@@ -0,0 +1,10 @@
+const express = require("express")
+const userRouter = require("./user")
+const accountRouter = require("./account");
+
+const router = express.Router();
+
+router.use("/user",userRouter)
+router.use("/account",accountRouter)
+
+module.exports = router;