URL Shortener Service

Overview

A lightweight and efficient URL shortening service implemented in Python using Flask. This service provides URL shortening, redirection, and analytics capabilities with thread-safe operations and in-memory storage.

Features

• Generate short URLs with 6-character alphanumeric codes
• Redirect to original URLs with click tracking
• View analytics (click counts and creation timestamps)
• Thread-safe operations for concurrent access
• Comprehensive test coverage

Prerequisites

• Python 3.8+
• Flask 2.3.2

Installation & Setup

# Clone the repository
git clone https://github.com/suryanshgargbpgc/url_shortener.git
cd url_shortener

# Install dependencies
pip install -r requirements.txt

# Start the application
python -m flask --app app.main run

# Run tests
pytest

The API will be available at http://localhost:5000

Project Structure

url_shortener/
├── app/
│   ├── __init__.py
│   ├── main.py        # API endpoints and Flask application
│   ├── models.py      # Data storage and thread-safe operations
│   └── utils.py       # URL validation and code generation
├── tests/
│   └── test_basic.py  # Comprehensive test suite
└── requirements.txt   # Project dependencies

API Documentation

1. Shorten URL

POST /api/shorten
Content-Type: application/json

{
    "url": "https://www.example.com/very/long/url"
}

Response:

{
    "short_code": "abc123",
    "short_url": "http://localhost:5000/abc123"
}

2. URL Redirection

GET /<short_code>

Redirects to the original URL or returns 404 if not found.

3. URL Analytics

GET /api/stats/<short_code>

Response:

{
    "url": "https://www.example.com/very/long/url",
    "clicks": 5,
    "created_at": "2025-07-24T11:55:45"
}

## Technical Implementation

### Key Features
- Thread-safe operations using `threading.Lock`
- URL validation using `urllib.parse`
- In-memory storage with Python dictionary
- 6-character alphanumeric short codes
- Comprehensive error handling
- Full test coverage

### Example Usage with curl
```bash
# Create a short URL
curl -X POST http://localhost:5000/api/shorten \
  -H "Content-Type: application/json" \
  -d '{"url": "https://www.google.com"}'

# Visit the URL (use -L to follow redirects)
curl -L http://localhost:5000/<short_code>

# Get statistics
curl http://localhost:5000/api/stats/<short_code>

Testing

The project includes comprehensive tests covering:

• URL shortening functionality
• URL validation
• Redirection behavior
• Analytics tracking
• Concurrent access handling

Run tests using:

pytest -v

Error Handling

• Invalid URLs return 400 Bad Request
• Non-existent short codes return 404 Not Found
• All errors return appropriate HTTP status codes and messages

Design Decisions

1. In-Memory Storage: Used Python dictionary for fast access and simplicity
2. Thread Safety: Implemented using threading.Lock for concurrent access
3. URL Validation: Robust validation using urllib.parse
4. Short Code Generation: Random 6-character alphanumeric codes
5. Error Handling: Comprehensive HTTP status codes and messages

Contributing

Pull requests are welcome. For major changes, please open an issue first to discuss what you would like to change.

License

MIT