Electronics-Astra Backend

A full-featured REST API backend for managing coding problems, testcases, and admin authentication. Built with Node.js, Express, PostgreSQL, and MongoDB.

🎯 Overview

Electronics-Astra Backend is a RESTful API service designed for managing coding problem platforms. It provides secure admin authentication with 2FA, problem management with image uploads, and comprehensive testcase handling for problem evaluation.

Current Status: Development/Beta - Not production-ready

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✨ Features

Authentication & Authorization

• ✅ Admin signup with email-based OTP verification (2FA)
• ✅ JWT-based authentication
• ✅ Secure password hashing (bcrypt)
• ✅ Protected admin routes
• ✅ Profile management (view, edit, delete)

Problem Management

• ✅ CRUD operations for coding problems
• ✅ Multi-image upload support
• ✅ Rich problem metadata (title, difficulty, tags, description, constraints)
• ✅ Public and admin-only endpoints
• ✅ Cascade deletion (problems → testcases → files)

Testcase Management

• ✅ Create visible and hidden testcases
• ✅ Link testcases to specific problems
• ✅ Public vs. admin-only testcase visibility
• ✅ Individual testcase CRUD operations
• ✅ Automatic cleanup on problem deletion

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🛠 Tech Stack

Category	Technology
Runtime	Node.js (v18+)
Framework	Express.js
Databases	PostgreSQL (admin data), MongoDB (problem data)
ORMs	Sequelize (PostgreSQL), Mongoose (MongoDB)
Authentication	JWT, bcryptjs
File Upload	Multer
Email	Nodemailer
Dev Tools	nodemon, dotenv

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📦 Prerequisites

Before you begin, ensure you have the following installed: commit the changes

Required Software

1. Node.js (v18.0.0 or higher)

   node --version  # Should output v18.x.x or higher

   Download Node.js

2. PostgreSQL (v12 or higher)

   psql --version  # Should output PostgreSQL 12.x or higher

   Download PostgreSQL

3. MongoDB (v5.0 or higher)

   mongod --version  # Should output v5.x.x or higher

   Download MongoDB Community Server

4. Git

   git --version

Account Setup

• Gmail Account: Required for sending OTP emails (you'll need an App Password)
• MongoDB Atlas (Optional): For cloud MongoDB hosting

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🚀 Installation

Step 1: Clone the Repository

# Clone the repository
git clone https://github.com/mohith1976/electronics-astra.git

# Navigate to backend directory
cd electronics-astra/backend

Step 2: Install Dependencies

npm install

This installs all required packages:

• express, cors, dotenv - Server essentials
• sequelize, pg, pg-hstore - PostgreSQL ORM
• mongoose - MongoDB ODM
• jsonwebtoken, bcryptjs - Authentication
• nodemailer - Email OTP delivery
• multer, uuid - File uploads
• nodemon - Development auto-reload

Step 3: Database Setup

PostgreSQL Setup

# Login to PostgreSQL
psql -U postgres

# Create database
CREATE DATABASE electronics_astra;

# Exit psql
\q

MongoDB Setup (Local)

# Start MongoDB service (Windows)
net start MongoDB

# Start MongoDB service (macOS/Linux)
sudo systemctl start mongod

# Verify MongoDB is running
mongosh
# Should connect successfully

MongoDB Setup (Atlas - Cloud)

1. Create account at MongoDB Atlas
2. Create a new cluster (free tier available)
3. Add database user with password
4. Whitelist your IP address (or use 0.0.0.0/0 for development)
5. Get connection string (looks like: mongodb+srv://username:password@cluster0.mongodb.net/electronics-astra)

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⚙️ Configuration

Step 1: Create Environment File

Create a .env file in the backend/ directory:

# In backend/ directory
touch .env  # macOS/Linux
# OR
type nul > .env  # Windows

Step 2: Configure Environment Variables

Add the following to your .env file:

# PostgreSQL Configuration
PG_HOST=localhost
PG_PORT=5432
PG_DATABASE=electronics_astra
PG_USER=postgres
PG_PASSWORD=your_postgres_password

# MongoDB Configuration (choose one)
# Local MongoDB
MONGO_URI=mongodb://localhost:27017/electronics-astra
# OR Atlas MongoDB
# MONGO_URI=mongodb+srv://<username>:<password>@cluster0.mongodb.net/electronics-astra?retryWrites=true&w=majority

# Server Configuration
PORT=5000
JWT_SECRET=your_very_long_random_secret_key_here_min_32_characters

# Email Configuration (Gmail)
EMAIL_USER=your-email@gmail.com
EMAIL_PASS=your_16_character_app_password

Step 3: Generate Secure JWT Secret

# Generate a secure random string (Node.js)
node -e "console.log(require('crypto').randomBytes(32).toString('hex'))"

Copy the output and use it as your JWT_SECRET.

Step 4: Get Gmail App Password

1. Go to Google Account Security
2. Enable 2-Step Verification
3. Go to App Passwords
4. Select "Mail" and "Other (Custom name)"
5. Generate password (16 characters, no spaces)
6. Use this as EMAIL_PASS in .env

MongoDB and Images

• Add MONGO_URI to your .env. Example:
  • Local: mongodb://localhost:27017/electronics-astra
  • Atlas: mongodb+srv://<user>:<password>@cluster0.mongodb.net/electronics-astra?retryWrites=true&w=majority
• Problems API stores images as URLs in the images array on the Problem document.
• For local testing we save uploaded images to /uploads and serve them statically at http://localhost:5000/uploads/<filename>.
• For production, replace the upload handling with S3 or other object storage and save public URLs.

Install dependencies

⚠️ Security Warning: Never commit .env to version control. It's already in .gitignore.

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🏃 Running the Application

Development Mode (with auto-reload)

npm run dev

You should see:

Server running on port 5000
PostgreSQL connected
MongoDB connected successfully

Production Mode

npm start

Verify Server is Running

Open browser and navigate to:

http://localhost:5000

You should see the Express welcome message or 404 (depending on root route configuration).

Troubleshooting

PostgreSQL connection fails

# Check PostgreSQL is running
# Windows
net start postgresql-x64-14

# macOS/Linux
sudo systemctl status postgresql

MongoDB connection fails

# Check MongoDB is running
# Windows
net start MongoDB

# macOS/Linux
sudo systemctl status mongod

# Check connection string
mongosh "your_MONGO_URI_here"

Port 5000 already in use

• Change PORT=5000 to another port in .env (e.g., PORT=5001)

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📚 API Documentation

Base URL

http://localhost:5000

Authentication Flow

1. Request OTP for Signup

POST /api/otp/request
Content-Type: application/json

{
  "email": "admin@example.com"
}

Response (200):

{
  "message": "OTP sent successfully"
}

2. Verify OTP and Complete Signup

POST /api/admin/signup/verify
Content-Type: application/json

{
  "name": "Admin Name",
  "email": "admin@example.com",
  "password": "SecurePassword123!",
  "otp": "123456"
}

Response (201):

{
  "message": "Admin registered successfully",
  "admin": {
    "id": "uuid-here",
    "name": "Admin Name",
    "email": "admin@example.com"
  }
}

3. Login

POST /api/admin/login
Content-Type: application/json

{
  "email": "admin@example.com",
  "password": "SecurePassword123!"
}

Response (200):

{
  "message": "Login successful",
  "token": "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9...",
  "admin": {
    "id": "uuid-here",
    "name": "Admin Name",
    "email": "admin@example.com"
  }
}

3.b Admin Reset Password (Admin only)

POST /api/admin/reset-password
Authorization: Bearer <your_jwt_token>
Content-Type: application/json

{
  "email": "admin@example.com",
  "newPassword": "NewSecurePassword123!"
}

Response (200):

{
  "message": "Password updated successfully"
}

Problem Management

4. Create Problem (Admin Only)

POST /api/problems
Authorization: Bearer <your_jwt_token>
Content-Type: multipart/form-data

title: "Two Sum"
difficulty: "Easy"
tags: ["Array", "Hash Table"]
description: "Given an array of integers..."
constraints: "1 <= nums.length <= 10^4"
images: [File1, File2]

Response (201):

{
  "problem": {
    "_id": "problem_id_here",
    "title": "Two Sum",
    "difficulty": "Easy",
    "tags": ["Array", "Hash Table"],
    "description": "Given an array of integers...",
    "constraints": "1 <= nums.length <= 10^4",
    "images": ["/uploads/image1.jpg", "/uploads/image2.jpg"],
    "createdBy": "admin_id",
    "createdAt": "2025-10-20T10:30:00.000Z"
  }
}

5. Get All Problems (Public)

GET /api/problems

6. Get Single Problem (Public)

GET /api/problems/:id

7. Update Problem (Admin Only)

PUT /api/problems/:id
Authorization: Bearer <your_jwt_token>
Content-Type: multipart/form-data

title: "Updated Title"
difficulty: "Medium"

8. Delete Problem (Admin Only)

DELETE /api/problems/:id
Authorization: Bearer <your_jwt_token>

Response (200):

{
  "message": "Problem and all related data deleted successfully",
  "deletedTestcases": 5,
  "deletedFiles": {
    "success": 3,
    "failed": 0
  }
}

Testcase Management

9. Add Testcases to Problem (Admin Only)

POST /api/problems/:id/testcases
Authorization: Bearer <your_jwt_token>
Content-Type: application/json

{
  "visible": [
    {
      "input": "[2,7,11,15]\n9",
      "output": "[0,1]"
    }
  ],
  "hidden": [
    {
      "input": "[3,2,4]\n6",
      "output": "[1,2]"
    }
  ]
}

Response (201):

{
  "message": "Testcases added successfully",
  "visible": [...],
  "hidden": [...]
}

10. Get All Testcases (Admin Only)

GET /api/problems/:id/testcases
Authorization: Bearer <your_jwt_token>

11. Get Public Testcases (No Auth Required)

GET /api/problems/:id/testcases/public

12. Update Single Testcase (Admin Only)

PUT /api/problems/:id/testcases/:testcase_id
Authorization: Bearer <your_jwt_token>
Content-Type: application/json

{
  "input": "updated input",
  "output": "updated output"
}

13. Delete Single Testcase (Admin Only)

DELETE /api/problems/:id/testcases/:testcase_id
Authorization: Bearer <your_jwt_token>

---

🧪 Testing Guide

Manual Testing with Postman

Setup Postman Environment

1. Create new environment in Postman
2. Add variables:
   • base_url: http://localhost:5000
   • admin_token: (will be set after login)

Test Sequence

Test 1: Complete Authentication Flow

1. Request OTP

   • Method: POST
   • URL: {{base_url}}/api/otp/request
   • Body: {"email": "test@example.com"}
   • ✅ Expect: 200, "OTP sent successfully"
   • Check your email for OTP

2. Complete Signup

   • Method: POST
   • URL: {{base_url}}/api/admin/signup/verify
   • Body: Include name, email, password, and OTP from email
   • ✅ Expect: 201, admin object returned

3. Login

   • Method: POST
   • URL: {{base_url}}/api/admin/login
   • Body: {"email": "test@example.com", "password": "your_password"}
   • ✅ Expect: 200, JWT token returned
   • Save the token to admin_token environment variable

Test 2: Problem Lifecycle

4. Create Problem

   • Method: POST
   • URL: {{base_url}}/api/problems
   • Headers: Authorization: Bearer {{admin_token}}
   • Body: form-data with title, difficulty, description
   • ✅ Expect: 201, problem object with _id
   • Save problem _id for next tests

5. Get All Problems

   • Method: GET
   • URL: {{base_url}}/api/problems
   • ✅ Expect: 200, array containing your problem

6. Get Single Problem

   • Method: GET
   • URL: {{base_url}}/api/problems/{{problem_id}}
   • ✅ Expect: 200, problem details

Test 3: Testcase Management

7. Add Testcases

   • Method: POST
   • URL: {{base_url}}/api/problems/{{problem_id}}/testcases
   • Headers: Authorization: Bearer {{admin_token}}
   • Body: JSON with visible and hidden arrays
   • ✅ Expect: 201, testcases created
   • Save a testcase _id

8. Get Public Testcases

   • Method: GET
   • URL: {{base_url}}/api/problems/{{problem_id}}/testcases/public
   • ✅ Expect: 200, only visible testcases returned

9. Get All Testcases (Admin)

   • Method: GET
   • URL: {{base_url}}/api/problems/{{problem_id}}/testcases
   • Headers: Authorization: Bearer {{admin_token}}
   • ✅ Expect: 200, both visible and hidden testcases

Test 4: Cleanup & Cascade Deletion

10. Delete Problem

    • Method: DELETE
    • URL: {{base_url}}/api/problems/{{problem_id}}
    • Headers: Authorization: Bearer {{admin_token}}
    • ✅ Expect: 200, deletedTestcases count > 0

11. Verify Cleanup

    • Try to GET the problem again
    • ✅ Expect: 404, problem not found

Expected Error Responses

Scenario	Status	Response
Invalid OTP	400	{"error": "Invalid OTP"}
Expired OTP	400	{"error": "OTP expired"}
Missing JWT	401	{"error": "Unauthorized"}
Invalid JWT	403	{"error": "Invalid token"}
Problem not found	404	{"error": "Problem not found"}
Duplicate email	409	{"error": "Email already exists"}

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📁 Project Structure

backend/
├── src/
│   ├── config/
│   │   ├── db.js              # Sequelize/PostgreSQL configuration
│   │   └── mongo.js           # Mongoose/MongoDB connection
│   │
│   ├── controllers/
│   │   ├── adminController.js # Admin auth logic
│   │   ├── otpController.js   # OTP generation/verification
│   │   └── problemController.js # Problem & testcase CRUD
│   │
│   ├── middlewares/
│   │   ├── auth.js            # JWT verification middleware
│   │   └── upload.js          # Multer file upload config
│   │
│   ├── models/
│   │   ├── User.js            # Sequelize User model (PostgreSQL)
│   │   ├── Problem.js         # Mongoose Problem model
│   │   └── Testcase.js        # Mongoose Testcase model
│   │
│   ├── routes/
│   │   ├── admin.js           # /api/admin/* routes
│   │   ├── otp.js             # /api/otp/* routes
│   │   └── problems.js        # /api/problems/* routes
│   │
│   ├── services/
│   │   ├── otpService.js      # OTP email sending logic
│   │   └── pendingSignupService.js # Temporary signup data store
│   │
│   └── server.js              # Express app entry point
│
├── uploads/                   # Local file storage (dev only)
├── .env                       # Environment variables (DO NOT COMMIT)
├── .env.example               # Example environment file
├── .gitignore
├── package.json
├── package-lock.json
└── README.md

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⚠️ Known Limitations

🔴 CRITICAL - Not Production Ready

This project is currently in development/beta stage. Do NOT deploy to production without addressing:

Security Issues

1. In-Memory OTP Storage

   • OTPs are stored in application memory
   • Lost on server restart
   • Not suitable for distributed systems
   • Fix: Use Redis or database with TTL

2. File Deletion Vulnerability

   • Current implementation allows deletion of any file server has access to
   • No path traversal protection
   • Fix: Restrict deletions to uploads/ directory only

3. No Rate Limiting

   • APIs can be abused (OTP spam, brute force)
   • Fix: Implement express-rate-limit

4. Local File Storage

   • Files stored on server filesystem
   • Not scalable for multiple servers
   • Fix: Use S3, Cloudinary, or similar cloud storage

Missing Features

• Input validation (no express-validator or Joi)
• API request logging
• Automated tests (unit, integration)
• Database migrations system
• API versioning
• CORS configuration for production
• Error monitoring (Sentry, etc.)
• Health check endpoints

Recommendations Before Production

1. Implement Redis for OTP storage
2. Add comprehensive input validation
3. Switch to cloud file storage (S3/GCS)
4. Add request rate limiting
5. Implement proper logging (Winston, Morgan)
6. Add integration tests
7. Set up CI/CD pipeline
8. Configure production CORS policies
9. Add API documentation (Swagger/OpenAPI)
10. Implement database backup strategy

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🤝 Contributing

Contributions are welcome! Please follow these steps:

1. Fork the repository
2. Create a feature branch (git checkout -b feature/AmazingFeature)
3. Commit your changes (git commit -m 'Add some AmazingFeature')
4. Push to the branch (git push origin feature/AmazingFeature)
5. Open a Pull Request

Contribution Guidelines

• Follow existing code style
• Add tests for new features
• Update documentation as needed
• Ensure all tests pass before submitting PR

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👤 Author

Mohith

• GitHub: @mohith1976

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Happy Coding! 🚀

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📝 Hints (new feature)

Admins can attach hints to problems. Hints are rich objects with: text, order, and visibleToStudents (boolean). Admins can add, update and delete hints; students/public callers will only see hints where visibleToStudents: true.

Endpoints added:

• Add hint (admin only):

  POST /api/problems/:id/hints Authorization: Bearer <your_jwt_token> Content-Type: application/json

  Body example: { "text": "Consider using a hash map to reduce complexity.", "order": 1, "visibleToStudents": true }

• List visible hints (public):

  GET /api/problems/:id/hints

• List all hints (admin):

  GET /api/problems/:id/hints/admin Authorization: Bearer <your_jwt_token>

• Update a hint (admin):

  PUT /api/problems/:id/hints/:hintId Authorization: Bearer <your_jwt_token> Content-Type: application/json

  Body example: { "text": "Updated hint text", "visibleToStudents": false }

• Delete a hint (admin):

  DELETE /api/problems/:id/hints/:hintId Authorization: Bearer <your_jwt_token>

Notes:

• The Problem model stores hints as an array of subdocuments. Existing documents remain compatible (no migration required). New endpoints are protected with the existing auth middleware for admin actions.