select-city.js

export function* selectCity({ payload }) {
  const url = `https://nominatim.openstreetmap.org/search/${encodeURIComponent(payload)}?format=json&polygon_geojson=1&type=city`
  const places = yield call(get, url)
  const city = places.find(p => (p.type === 'city' || p.class === 'boundary') && ['MultiPolygon', 'Polygon'].includes(p.geojson.type))
  if (!city) {
    yield put(toggleSnackbar('fail to find the boundaries'))
    yield put(startSearchingNewCity())
  } else {
    const [minLng, maxLng, minLat, maxLat] = city.boundingbox.map(Number)
    yield put(receiveCity(({ ...city, boundingbox: [[minLat, minLng], [maxLat, maxLng]] })))
  }
}