Transform your raw DSA submissions into beautifully structured, exam-ready revision cards and code portfolios.

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✨ Screenshots & UI Preview

📸 Desktop & Mobile App Previews — click to expand

🖥️ Desktop Dashboard & Revision Hub

View and search your solved problems, track progression tiers, and access AI-generated solutions.

📊 Deep Analysis Panel

Visualize space/time complexity metrics, step-by-step logic breakdown, edge cases, and code improvement suggestions.

📱 Premium Mobile Experience

Practice, review, and track your revision on the go with a fully responsive layout.

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🚀 Key Features

• AI-Powered Solution Generator: Instantly generates Brute Force, Better, and Optimal solutions with clean, compilable, and inline-commented code. Powered by NVIDIA NIM (meta/llama-3.3-70b-instruct).
• Smart Revision Tracking: Save your solved problems, categorize them by primary DSA patterns, and generate spaced-repetition revision notes automatically.
• Dual Caching System: Integrates Upstash Redis (for lightning-fast variant and base caching) and MongoDB (for persistent storage and recovery), minimizing API costs.
• Complexity Validation Stack: Features an advanced validation pipeline that checks AI time/space complexities against a database of 3,680+ verified LeetCode problems to guarantee accuracy.
• Secure Authentication: Includes Email OTP verification, Google OAuth, GitHub OAuth, and session management using JWT.
• Freemium & Payment Integration: Daily usage rate limits for free tier, upgradeable to Pro using Razorpay payments.
• Admin Control Center: Built-in panel for cache invalidation, user usage analytics, and MongoDB status tracking.

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🗺️ Architecture & Data Flow

⚙️ System Architecture — click to expand

graph TD
    Client["🌐 React 19 Client (Vite)"]
    Backend["☁️ Serverless API (Node.js / Vercel)"]
    DB[("🗄️ MongoDB (Mongoose)")]
    Cache[("⚡ Upstash Redis")]
    AI["🤖 NVIDIA NIM API (Llama 3.3 70B)"]
    Razorpay["💳 Razorpay Gateway"]
    SMTP["📧 Nodemailer (SMTP)"]

    Client -->|API Requests| Backend
    Backend -->|Data Persistence| DB
    Backend -->|Caching & Rate Locks| Cache
    Backend -->|AI Reasoning & Solutions| AI
    Backend -->|Subscription Billing| Razorpay
    Backend -->|Email OTP & Reset| SMTP

    style Client fill:#1e1b4b,stroke:#4338ca,color:#fff
    style Backend fill:#0f172a,stroke:#334155,color:#fff
    style DB fill:#064e3b,stroke:#059669,color:#fff
    style Cache fill:#701a75,stroke:#c084fc,color:#fff
    style AI fill:#14532d,stroke:#22c55e,color:#fff
    style Razorpay fill:#4c1d95,stroke:#8b5cf6,color:#fff
    style SMTP fill:#7c2d12,stroke:#ea580c,color:#fff

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Data Flow: Get Solution

[Client Request] ──► [Check Redis / MongoDB Cache] ──► [Cache Hit: Return Solution]
                               │ Cache Miss
                               ▼
                        [NVIDIA NIM API] ──► [Save to Cache & Return]

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🛠️ Technology Stack

Layer	Technology	Description
Frontend	React 19, TypeScript, Vite, TailwindCSS	High-performance user interface
Backend	Vercel Serverless Functions (Node.js)	Serverless API routes
AI Engine	NVIDIA NIM (meta/llama-3.3-70b-instruct)	Context-aware code generation & logic analysis
Database	MongoDB + Mongoose	Persistent revision storage & base caching
Cache Layer	Upstash Redis	Fast, distributed, low-latency temporary cache
Email	Nodemailer	Password resets & OTP codes
Payments	Razorpay	Subscription order creation and webhooks

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📦 Getting Started

Prerequisites

• Node.js (v18+)
• MongoDB Instance (Atlas or Local)
• NVIDIA NIM API Key (Sign up at build.nvidia.com)
• Upstash Redis (Optional)

Installation

1. Clone the repo:

   git clone https://github.com/WillyEverGreen/ReCode.git
   cd ReCode

2. Install dependencies:

   npm install

3. Configure the environment: Create a .env file in the root based on .env.example:

   cp .env.example .env

   Add your keys:

   MONGO_URI=mongodb://127.0.0.1:27017/recode
   JWT_SECRET=your_jwt_secret_at_least_32_characters
   NVIDIA_API_KEY=nvapi-xxxxxx
   VITE_NVIDIA_API_KEY=nvapi-xxxxxx

4. Launch the development environments:

   • Recommended (tests serverless API + client simultaneously):

     npm install -g vercel
     vercel dev

   • Alternative (launches server and client independently):

     npm run server   # Node Express server on port 5000
     npm run dev      # Vite Dev server on port 3000

5. Open http://localhost:3000 in your browser.

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⚙️ Environment Configuration

Variable	Type	Description
MONGO_URI	Required	Connection string for MongoDB
JWT_SECRET	Required	Used for token encryption (min 32 chars)
NVIDIA_API_KEY	Required	Backend API key for NIM completion
VITE_NVIDIA_API_KEY	Required	Frontend API key for browser-based code analysis
ADMIN_PASSWORD	Required	Admin dashboard credentials
UPSTASH_REDIS_REST_URL	Optional	Upstash Redis connection endpoint
UPSTASH_REDIS_REST_TOKEN	Optional	Upstash Redis connection token
NVIDIA_MODEL	Optional	Override NIM model (defaults to meta/llama-3.3-70b-instruct)

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📝 API Endpoints

Endpoint	Method	Authentication	Description
/api/health	GET	Public	System status check
/api/auth/signup	POST	Public	Registers a new account
/api/auth/login	POST	Public	Authenticates and returns JWT
/api/auth/verify-email	POST	Public	Verifies account via Nodemailer OTP
/api/solution	POST	User JWT	Generates the 3-approach code solution
/api/ai/analyze	POST	User JWT	Analyzes code complexity and structure
/api/questions	GET/POST	User JWT	Reads/writes saved user questions
/api/usage	GET	User JWT	Returns remaining daily rate limits
/api/admin/stats	GET	Admin Pass	Displays global analytics and cache rates

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Made with ❤️ by WillyEverGreen