LeetCode Daily Challenge Tracker - Backend

A production-ready backend application for tracking LeetCode daily challenges with automated evaluation, streak tracking, and penalty management.

🚀 Features

• User Authentication: JWT-based authentication with secure password hashing
• Challenge Management: Create and join challenges with customizable rules
• LeetCode Integration: Fetch submissions from LeetCode GraphQL API
• Automated Evaluation: Daily cron jobs to evaluate challenge progress
• Streak Tracking: Track current and longest streaks
• Penalty System: Virtual penalty tracking for missed days
• Dashboard: Comprehensive progress overview and leaderboards
• Clean Architecture: Service-based structure with separation of concerns

🛠️ Tech Stack

• Runtime: Node.js
• Framework: Express.js
• Database: PostgreSQL
• ORM: Prisma
• Authentication: JWT (jsonwebtoken)
• Encryption: AES-256-GCM (crypto)
• Scheduling: node-cron
• HTTP Client: Axios
• Logging: Winston
• Validation: express-validator

📁 Project Structure

src/
 ├── app.js                      # Express app setup
 ├── server.js                   # Server entry point
 ├── config/
 │    ├── env.js                 # Environment configuration
 │    ├── prisma.js              # Prisma client setup
 │    └── cron.js                # Cron job manager
 ├── routes/
 │    ├── auth.routes.js         # Authentication routes
 │    ├── challenge.routes.js    # Challenge routes
 │    └── dashboard.routes.js    # Dashboard routes
 ├── controllers/
 │    ├── auth.controller.js     # Auth request handlers
 │    ├── challenge.controller.js # Challenge request handlers
 │    └── dashboard.controller.js # Dashboard request handlers
 ├── services/
 │    ├── auth.service.js        # Authentication business logic
 │    ├── challenge.service.js   # Challenge business logic
 │    ├── leetcode.service.js    # LeetCode API integration
 │    ├── penalty.service.js     # Penalty management
 │    └── evaluation.service.js  # Daily evaluation logic
 ├── middlewares/
 │    ├── auth.middleware.js     # JWT authentication
 │    └── error.middleware.js    # Error handling
 ├── utils/
 │    ├── jwt.js                 # JWT utilities
 │    ├── encryption.js          # Encryption utilities
 │    └── logger.js              # Winston logger
 └── prisma/
      └── schema.prisma          # Database schema

🚦 Getting Started

Prerequisites

• Node.js (v16 or higher)
• PostgreSQL (v12 or higher)
• npm or yarn

Installation

1. Clone the repository

   cd "f:\DATA\College\Project and stuff\Leetcode streak"

2. Install dependencies

   npm install

3. Set up environment variables

   cp .env.example .env

   Edit .env and configure:

   • DATABASE_URL: PostgreSQL connection string
   • JWT_SECRET: Generate with node -e "console.log(require('crypto').randomBytes(32).toString('hex'))"
   • ENCRYPTION_KEY: Generate with node -e "console.log(require('crypto').randomBytes(32).toString('hex'))"
   • Other configuration as needed

4. Set up database

   npm run prisma:generate
   npm run prisma:migrate

5. Start the server

   # Development mode with auto-reload
   npm run dev
   
   # Production mode
   npm start

The server will start on http://localhost:3000 (or the port specified in .env).

📡 API Endpoints

Authentication

• POST /api/auth/register - Register new user
• POST /api/auth/login - Login user
• GET /api/auth/profile - Get current user profile (protected)
• PUT /api/auth/profile - Update user profile (protected)

Challenges

• POST /api/challenges - Create new challenge (protected)
• GET /api/challenges - Get user's challenges (protected)
• GET /api/challenges/:id - Get challenge details (protected)
• POST /api/challenges/:id/join - Join a challenge (protected)
• PATCH /api/challenges/:id/status - Update challenge status (protected, owner only)

Dashboard

• GET /api/dashboard - Get dashboard overview (protected)
• GET /api/dashboard/today - Get today's status (protected)
• GET /api/dashboard/challenge/:id - Get detailed challenge progress (protected)
• GET /api/dashboard/challenge/:id/leaderboard - Get challenge leaderboard (protected)

Health Check

• GET /health - Server health status

🗄️ Database Schema

User

• User authentication and profile information
• LeetCode username mapping

Challenge

• Challenge configuration and rules
• Start/end dates, difficulty filters, penalty amounts

ChallengeMember

• User participation in challenges
• Streak tracking and penalty totals

DailyResult

• Daily evaluation results
• Submission counts and problem tracking

PenaltyLedger

• Penalty transaction history

LeetCodeSession

• Encrypted session storage for LeetCode API

⚙️ Configuration

Cron Jobs

Daily evaluation runs automatically based on DAILY_EVALUATION_TIME in .env:

# Run at 1:00 AM daily (recommended)
DAILY_EVALUATION_TIME=0 1 * * *

# For testing - run every 15 minutes
DAILY_EVALUATION_TIME=*/15 * * * *

Challenge Rules

When creating a challenge, configure:

• minSubmissionsPerDay: Minimum accepted submissions required
• difficultyFilter: Array of difficulties (Easy, Medium, Hard)
• uniqueProblemConstraint: Whether to count unique problems only
• penaltyAmount: Virtual penalty for missed days

🔐 Security Features

• Password hashing with bcrypt (12 rounds)
• JWT-based authentication
• AES-256-GCM encryption for sensitive data
• Input validation on all endpoints
• SQL injection protection via Prisma ORM
• Environment variable validation on startup

📝 Development Notes

Adding New Features

1. Service Layer: Add business logic in src/services/
2. Controller: Add request handlers in src/controllers/
3. Routes: Define endpoints in src/routes/
4. Validation: Add input validation in controllers

Database Changes

# Create migration
npm run prisma:migrate

# Regenerate Prisma Client
npm run prisma:generate

# Open Prisma Studio (DB GUI)
npm run prisma:studio

Logging

Uses Winston for structured logging:

• Console logs with colors (development)
• File logs: logs/combined.log, logs/error.log
• Exception/rejection logs

🐛 Troubleshooting

Database Connection Issues

• Verify PostgreSQL is running
• Check DATABASE_URL in .env
• Ensure database exists: createdb leetcode_tracker

LeetCode API Rate Limiting

• LeetCode may rate limit requests
• Consider adding delays between requests
• Store session data for authenticated requests

Cron Jobs Not Running

• Check CRON_ENABLED=true in .env
• Verify cron expression syntax
• Check logs for error messages

🚀 Production Deployment

1. Environment

   • Set NODE_ENV=production
   • Use strong secrets for JWT_SECRET and ENCRYPTION_KEY
   • Configure CORS_ORIGIN to your frontend URL

2. Database

   • Use production PostgreSQL instance
   • Run migrations: npm run prisma:migrate

3. Process Management

   • Use PM2 or similar for process management
   • Enable clustering for high availability

4. Monitoring

   • Monitor logs in logs/ directory
   • Set up error alerting
   • Monitor cron job execution

📄 License

ISC

👤 Author

Built with ❤️ for the LeetCode community