# Wind layer demo

A minimal browser client that renders the predictor's wind field as an
animated particle layer using [Leaflet](https://leafletjs.com/) and
[leaflet-velocity](https://github.com/onaci/leaflet-velocity).

The predictor's `GET /api/v1/wind/field` endpoint emits the
[wind-js-server](https://github.com/danwild/wind-js-server) "gfs.json" format
(a two-element `[U, V]` array of `{header, data}` records), which is exactly
what leaflet-velocity and [sakitam-fdd/wind-layer](https://github.com/sakitam-fdd/wind-layer)
consume — so no transformation is needed in the frontend.

## Running

Serve this directory and the predictor from the same origin (or set `API` in
`index.html` to the predictor's base URL and rely on the predictor's CORS
headers):

```bash
# Terminal 1: the predictor (must have a dataset loaded for real data)
./bin/predictor

# Terminal 2: serve the demo
cd examples/wind-demo && python3 -m http.server 8090
# open http://localhost:8090  (set API="http://localhost:8080" in index.html)
```

## API contract

`GET /api/v1/wind/field` query parameters (all optional):

| Param | Default | Meaning |
|---|---|---|
| `time` | dataset epoch | RFC3339 forecast time to sample |
| `altitude` | `0` | altitude in metres |
| `min_lat`,`max_lat`,`min_lng`,`max_lng` | global | bounding box (degrees) |
| `step` | `1.0` | grid resolution in degrees (min `0.25`) |

`GET /api/v1/wind/meta` returns the active dataset's source, epoch, suggested
altitudes, and bounding box so a client can populate its controls.

The full OpenAPI definition is served at `/openapi.yaml`, with a browsable
ReDoc rendering at `/docs`.

## Minimal fetch

```js
const res = await fetch("/api/v1/wind/field?altitude=10000&step=2");
const data = await res.json();         // [ {header, data}, {header, data} ]
L.velocityLayer({ data }).addTo(map);
```