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A competitive programming platform focused on secure execution, real-time systems, and AI-assisted workflows.

Video Overview of the Platform: Coming Soon...

Table of Contents

• 🏗️ Overview
• ✨ Why CodeArena?
• ⚡ Capabilities
• 🔧 Technical Deep Dive
• 🛠️ Technology Stack
• 🚀 Quick Start
• ⚙️ How It Works
• 💻 Development
• 📦 Deployment
• 📡 API
• 🔒 Security
• 📊 Monitoring
• 👥 Team
• 🤝 Contributing

Overview

CodeArena separates concerns across stateless API servers, background workers, and real-time socket clusters — all coordinated through Redis.

flowchart TB
    Client[Next.js Client] -->|HTTP| API[Next.js API Routes]
    Client -->|WebSocket| Socket[Socket.IO Server]

    API -->|Enqueue| Redis[(Redis)]
    Socket -->|Pub/Sub| Redis

    Redis -->|Process| Workers[BullMQ Workers]
    Workers -->|Execute| Docker[Docker Sandbox]
    Workers -->|Fallback| Judge0[Judge0 API]
    Workers -->|Analyze| Groq[Groq AI]

    API -->|Query| MongoDB[(MongoDB)]
    Workers -->|Read/Write| MongoDB

    style Docker fill:#2496ED,stroke:#fff,stroke-width:2px
    style Redis fill:#DC382D,stroke:#fff,stroke-width:2px
    style MongoDB fill:#47A248,stroke:#fff,stroke-width:2px

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The design prioritizes security (sandboxed execution), scalability (horizontal socket scaling via Redis adapter), and resilience (graceful fallbacks when Docker is unavailable).

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Why CodeArena?

Most platforms in the competitive programming ecosystem specialize in only one part of the workflow — coding challenges, contests, interview preparation, or AI feedback.

CodeArena was built to explore how these systems could coexist within a unified architecture while maintaining secure execution, scalable real-time infrastructure, and low-latency developer interactions.

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Capabilities

Feature	Description
Competitive Programming	Multi-language judge (JS, Python, Java, C/C++, Go) with Docker sandboxing. Verdicts: ACCEPTED • WRONG_ANSWER • TLE • MLE • RUNTIME_ERROR • COMPILATION_ERROR
AI Interviews (Alex)	4-phase mock interviews with streaming AI feedback via Socket.IO. Evaluates algorithms, code quality, and communication
Contests	Real-time ICPC-style leaderboards with plagiarism detection
Community	Developer feed, solution sharing, tag-based recommendations

Problem Browser

Problem Solving

Contests & Leaderboards (75% Zoom-Out)

AI Interview System

User Profile

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Technical Deep Dive

Execution Engine

Dual-mode architecture:

1. Docker Sandbox (primary): Seccomp-filtered containers, no network, read-only rootfs, cgroup limits. Handles compiled (C++, Java) and interpreted (Python, JS) languages.

2. Judge0 API (fallback): Cloud fallback for Railway, Render, and other environments without Docker socket access.

Security: Pattern-based code validation, execution timeouts, auto-removal.

Worker Orchestration

Seven BullMQ workers with idempotency guards:

Worker	Purpose
submission.worker.js	Code execution & verdicts
ai.worker.js	Post-submission analysis (Groq Llama 3.3 70B)
interviewAI.worker.js	Real-time AI streaming
interviewExecution.worker.js	Interview code validation
interviewSummarize.worker.js	Session summarization
plagiarism.worker.js	Similarity detection
stats.worker.js	Performance aggregation

Real-time Infrastructure

Socket.IO with Redis adapter enables horizontal scaling. Multiple server instances share state via Redis pub/sub. JWT tokens secure WebSocket connections; tiered rate limiting protects endpoints.

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Stack

Layer	Technology
Frontend	Next.js 16, React 19, TailwindCSS 4, shadcn/ui, Monaco Editor
Backend	Next.js API Routes, Socket.IO 4, BullMQ 5, JWT, Zod
Data	MongoDB 8 (Mongoose), Redis 7
Execution	Docker 24 + seccomp, Judge0 fallback
AI	Groq SDK (Llama 3.3 70B)
Deploy	Docker Compose, Railway, Render

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Quick Start

Docker (recommended):

git clone https://github.com/yourusername/codearena.git
cd codearena
chmod +x setup.sh && ./setup.sh
# Or: docker-compose up -d

Environment:

MONGODB_URI=mongodb://admin:password@localhost:27017/codearena?authSource=admin
REDIS_URL=redis://:password@localhost:6379
JWT_SECRET=your-secret-key-min-32-characters

Local dev:

npm install && npm run docker:build
npm run dev
node scripts/worker-boot.js  # Separate terminal

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How It Works

Code Submission Flow

sequenceDiagram
    Client->>API: POST /api/submissions
    API->>Redis: Enqueue
    API->>Client: Job ID
    Worker->>Redis: Pick up
    Worker->>MongoDB: Fetch tests
    Worker->>Docker: Execute
    Docker->>Worker: Verdict
    Worker->>Redis: Publish
    Worker->>MongoDB: Save

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Real-time Updates

sequenceDiagram
    Worker->>Redis: Publish score
    Redis->>Socket: Broadcast
    Socket->>Client: Push

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Development

Scripts

Command	Purpose
npm run dev	Dev server
npm run docker:build	Build executors
node scripts/worker-boot.js	Start workers
node scripts/dev-all.js	Concurrent mode

Project Structure

src/
├── app/         # Next.js App Router
├── features/    # Problem-solve, interview, contests
├── services/    # BullMQ workers
├── lib/         # Docker, AI, Socket.IO
├── models/      # Mongoose schemas
└── socket/      # Namespaces

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Deployment

Platform	Command
Railway	railway login && railway link && railway up
Render	Use render.yaml blueprint
Docker	docker build -t codearena . && docker run -p 3000:3000 -e MONGODB_URI=... codearena

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API

REST: Auth, Problems, Submissions, Contests, Interview, Feed, Admin

WebSocket: submission_update, contest_update, notification, interview_ai_stream

Health: GET /api/health

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Security

Layer	Measures
Sandbox	Seccomp, no network, read-only rootfs, resource limits, pattern detection
API	Tiered rate limiting, JWT (httpOnly + Bearer), CORS, Zod validation
Data	bcryptjs, strong secrets, MongoDB authSource, Redis password auth

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Monitoring

Structured logging (auth, database, contest, system), query performance, cache hit rates, worker metrics. Health: GET /api/health

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Team

Role	Member
🏛️ Architecture / Backend	Arafat Salehin
⚙️ Core Systems	AH Muzahid
🎨 UI / UX	Shahnawas Adeel
💻 Frontend / Dashboard	Rabiul Islam
💻 Frontend	Abdullah Noman
✍️ Content	Ummey Salma Tamanna

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Contributing

Fork → branch (feature/name) → commit → PR. Standards: ESLint, Prettier, Husky.

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Built with Next.js, React, MongoDB, Redis, Docker, BullMQ, Socket.IO, Groq