# NetWatch

Real-time network latency monitor SPA designed to be served from a static bucket or Docker container.

## Features

- **Real-time monitoring**: Updates every 2s with 300s history sparklines
- **9 WAN hosts**: Google Cloud, AWS, GitHub, Cloudflare, Azure, DigitalOcean, Fastly, Akamai, datavi.be
- **Local network group**: Local gateway (192.168.100.1) tracked separately
- **Health indicator**: Overall status box — green (HEALTHY) or red (DEGRADED) based on WAN reachability
- **Summary stats**: Reachable count, min/max/avg latency across WAN hosts only
- **Visual latency display**: Large color-coded figures with canvas sparkline graphs
- **Color coding**:
  - Green: <50ms (excellent)
  - Lime: <100ms (good)
  - Yellow: <200ms (moderate)
  - Orange: <500ms (poor)
  - Red: >500ms (bad)
  - Gray: offline/unreachable
- **Fixed chart axes**: Y-axis 0–1000ms, X-axis 0–300s
- **Play/pause**: Pause stops probes but history keeps scrolling (blank gaps, no false outage)
- **Clickable URLs**: Service URLs open in new tabs
- **>1000ms clamped**: Anything over 1s is treated as unreachable
- **Zero runtime dependencies**: All resources bundled into build artifacts
- **IPv4 only**: Designed for IPv4 connectivity testing

## Technical Details

- Latency measured via HEAD requests with cache-busting
- Uses `mode: 'no-cors'` to allow cross-origin requests where CORS headers aren't present
- 1-second timeout for unresponsive hosts (>1000ms clamped to unreachable)
- Canvas-based sparkline rendering with fixed axes
- Tailwind CSS v4 for styling
- Local gateway excluded from WAN summary statistics

## Build

```bash
# Install dependencies
yarn install

# Development server
yarn dev

# Production build
yarn build

# Preview production build
yarn preview
```

## Docker

```bash
docker build -t netwatch .
docker run -p 8080:80 netwatch
```

The nginx config:
- Trusts `X-Forwarded-For` from RFC1918 reverse proxies (10/8, 172.16/12, 192.168/16)
- Access log goes to stdout
- Static assets cached with immutable headers

## Deployment

After running `yarn build`, deploy the contents of the `dist/` directory to any static file host:

- AWS S3
- Google Cloud Storage
- Cloudflare Pages
- Vercel
- Netlify
- GitHub Pages

Or use the Docker image behind a reverse proxy.

## Output Structure

```
dist/
├── index.html
└── assets/
    ├── index-*.css
    └── index-*.js
```

All assets are bundled and minified. No external dependencies at runtime.

## Browser Compatibility

Requires modern browser with:
- ES modules support
- Fetch API
- Canvas API
- CSS custom properties

## Limitations

- **CORS**: Some hosts may block cross-origin HEAD requests. The app uses `no-cors` mode which allows the request but provides opaque responses. Latency is still measurable based on request timing.
- **Local gateway**: The 192.168.100.1 endpoint requires the host to be accessible from your network.
- **Network conditions**: Measurements reflect browser-to-endpoint latency, which includes your local network, ISP, and internet routing.

## License

MIT