Mobile Q&A App Backend

A complete Node.js backend API for a mobile Q&A application with AI integration.

Features

Core Functionality

• User Authentication - Registration, login, email verification, JWT tokens, password reset
• Questions & Answers - Full CRUD operations with voting and search
• Comments System - Add comments to questions and answers
• Bookmarks - Save questions for later reference
• File Uploads - Support for image and document attachments
• AI Integration - Powered by Google Gemini AI for suggestions and improvements

Advanced Features

• Admin Panel - Content moderation, user management, and reporting system
• Reputation System - User reputation based on community engagement
• Search & Filtering - Full-text search with advanced filtering options
• Pagination - Efficient data loading for mobile clients
• Error Handling - Comprehensive error handling and validation

Technology Stack

• Runtime: Node.js
• Framework: Express.js
• Database: MongoDB with Mongoose ODM
• Authentication: JWT (JSON Web Tokens)
• AI Integration: Google Gemini AI
• File Upload: Multer
• Email: Nodemailer
• Security: bcryptjs for password hashing

Prerequisites

• Node.js (v14 or higher)
• MongoDB (local or cloud)
• Google Gemini API key (for AI features)
• Email service credentials (for email verification)

Quick Start

1. Install Dependencies

   npm install

2. Environment Setup

   • Copy .env file and update with your credentials
   • Set your MongoDB URI
   • Add your Gemini API key
   • Configure email settings

3. Start the Server

   npm start

   For development with auto-reload:

   npm run dev

4. Verify Installation

   • Open http://localhost:3000
   • You should see the API status page

API Endpoints

Authentication

• POST /api/auth/register - Register new user
• POST /api/auth/login - User login
• GET /api/auth/verify/:token - Email verification
• GET /api/auth/me - Get current user profile
• PUT /api/auth/profile - Update user profile

Questions

• GET /api/questions - Get all questions (with pagination)
• POST /api/questions - Create new question
• GET /api/questions/:id - Get specific question
• PUT /api/questions/:id - Update question
• DELETE /api/questions/:id - Delete question
• GET /api/questions/search - Search questions
• POST /api/questions/:id/vote - Vote on question

Answers

• GET /api/answers/question/:questionId - Get answers for question
• POST /api/answers/:questionId - Create new answer
• PUT /api/answers/:id - Update answer
• DELETE /api/answers/:id - Delete answer
• POST /api/answers/:id/vote - Vote on answer
• POST /api/answers/:id/accept - Accept answer as solution

Comments

• GET /api/comments/question/:questionId - Get question comments
• GET /api/comments/answer/:answerId - Get answer comments
• POST /api/comments/question/:questionId - Add comment to question
• POST /api/comments/answer/:answerId - Add comment to answer
• PUT /api/comments/:id - Update comment
• DELETE /api/comments/:id - Delete comment

AI Features

• GET /api/ai/status - Check AI service status
• POST /api/ai/answer-suggestion - Get AI answer suggestions
• POST /api/ai/tag-suggestions - Get tag suggestions
• POST /api/ai/chatbot - AI chatbot interaction
• POST /api/ai/question-improvements - Get question improvement suggestions
• POST /api/ai/similar-questions - Find similar questions

Users

• GET /api/users/me - Get current user profile
• GET /api/users/:id - Get user profile by ID
• PUT /api/users/profile - Update user profile
• GET /api/users/leaderboard - Get top users by reputation
• GET /api/users/search - Search users
• GET /api/users/:id/activity - Get user activity feed

Bookmarks

• GET /api/bookmarks - Get user bookmarks
• POST /api/bookmarks/:questionId - Add bookmark
• DELETE /api/bookmarks/:questionId - Remove bookmark
• GET /api/bookmarks/check/:questionId - Check bookmark status

File Upload

• POST /api/upload - Upload file (images, documents)

Admin (Admin access required)

• GET /api/admin/reports - Get all reports
• POST /api/admin/reports - Create new report
• PUT /api/admin/reports/:id/resolve - Resolve report
• GET /api/admin/stats - Get admin dashboard statistics
• DELETE /api/admin/content/:type/:id - Delete content as admin
• PUT /api/admin/users/:id - Manage user (ban/promote/etc.)

Mobile App Integration

This backend is specifically designed for mobile applications with:

• RESTful API - Clean, predictable endpoints
• JSON Responses - Lightweight data format
• CORS Support - Cross-origin requests enabled
• Token Authentication - Stateless authentication perfect for mobile
• Pagination - Efficient data loading for mobile networks
• Error Handling - Consistent error response format

Security Features

• JWT Authentication - Secure token-based authentication
• Password Hashing - bcryptjs for secure password storage
• Input Validation - Comprehensive request validation
• Role-based Access - Admin and user roles
• CORS Protection - Controlled cross-origin access
• File Upload Security - File type and size restrictions

Business Logic Examples

Reputation System

• Question upvote: +5 reputation
• Answer upvote: +10 reputation
• Accepted answer: +15 reputation bonus
• Downvotes: -2 to -5 reputation

AI Integration

• Answer Suggestions: AI analyzes questions and provides helpful answers
• Tag Suggestions: Automatic tag recommendations based on content
• Question Improvements: AI feedback for better question formulation
• Chatbot: General programming help and guidance

Content Moderation

• User Reports: Community-driven content reporting
• Admin Dashboard: Centralized moderation tools
• Automated Actions: Bulk content management
• User Management: Ban, promote, and manage user accounts

Testing the API

You can test the API using tools like:

• Postman - Import the API endpoints
• curl - Command line testing
• Mobile App - Direct integration testing

Example login request:

curl -X POST http://https://devoverflow-backend.onrender.com/api/auth/login \
  -H "Content-Type: application/json" \
  -d '{"email": "user@example.com", "password": "password123"}'

Architecture Overview

This backend follows the Monolithic Architecture pattern, which is perfect for getting started:

• Single Codebase - All functionality in one application
• Shared Database - All models use the same MongoDB instance
• Unified API - Single entry point for all mobile app requests
• Easy Deployment - Simple deployment and scaling

The structure follows the MVC Pattern:

• Models (/models) - Data schemas and database interactions
• Controllers (/controllers) - Business logic and request handling
• Routes (/routes) - API endpoint definitions and middleware
• Middleware (/middleware) - Authentication and validation

Configuration

Key environment variables to configure:

# Database
MONGO_URI=mongodb://devoverflow-backend.onrender.com/mobile_app_db

# JWT
JWT_SECRET=your_super_secret_jwt_key
JWT_EXPIRE=30d

# Email
EMAIL_SERVICE=gmail
EMAIL_USER=your_email@gmail.com
EMAIL_PASS=your_app_password

# AI
GEMINI_API_KEY=your_gemini_api_key

# Server
PORT=3000
NODE_ENV=development

Deployment

This backend can be deployed to:

• Heroku - Easy deployment with MongoDB Atlas
• AWS EC2 - Full control over the environment
• DigitalOcean - Simple cloud deployment
• Vercel - Serverless deployment option

Documentation

The backend is fully documented with:

• Inline Comments - Detailed code documentation
• API Comments - Every endpoint documented
• Error Handling - Comprehensive error responses
• Examples - Real-world usage examples

Contributing

This is a complete, production-ready backend. Key areas for potential enhancement:

• Real-time features (WebSocket integration)
• Caching layer (Redis)
• Email templates
• Push notifications
• Advanced AI features

License

This project is provided as educational material for mobile app development.

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Built for Mobile App Development Course