import Feature from 'ol/Feature';
import Map from 'ol/Map';
import View from 'ol/View';
import {circular as circularPolygon} from 'ol/geom/Polygon';
import {Tile as TileLayer, Vector as VectorLayer} from 'ol/layer';
import TileWMS from 'ol/source/TileWMS';
import VectorSource from 'ol/source/Vector';

const vectorLayer4326 = new VectorLayer({
  source: new VectorSource()
});

const vectorLayer3857 = new VectorLayer({
  source: new VectorSource()
});

const map4326 = new Map({
  layers: [
    new TileLayer({
      source: new TileWMS({
        url: 'https://ahocevar.com/geoserver/wms',
        params: {
          'LAYERS': 'ne:NE1_HR_LC_SR_W_DR',
          'TILED': true
        }
      })
    }),
    vectorLayer4326
  ],
  target: 'map4326',
  view: new View({
    projection: 'EPSG:4326',
    center: [0, 0],
    zoom: 2
  })
});

const map3857 = new Map({
  layers: [
    new TileLayer({
      source: new TileWMS({
        url: 'https://ahocevar.com/geoserver/wms',
        params: {
          'LAYERS': 'ne:NE1_HR_LC_SR_W_DR',
          'TILED': true
        }
      })
    }),
    vectorLayer3857
  ],
  target: 'map3857',
  view: new View({
    center: [0, 0],
    zoom: 2
  })
});

const radius = 800000;
let x, y;
for (x = -180; x < 180; x += 30) {
  for (y = -90; y < 90; y += 30) {
    const circle4326 = circularPolygon([x, y], radius, 64);
    const circle3857 = circle4326.clone().transform('EPSG:4326', 'EPSG:3857');
    vectorLayer4326.getSource().addFeature(new Feature(circle4326));
    vectorLayer3857.getSource().addFeature(new Feature(circle3857));
  }
}