import GeoJSON from '../src/ol/format/GeoJSON.js';
import Map from '../src/ol/Map.js';
import View from '../src/ol/View.js';
import {Fill, Style} from '../src/ol/style.js';
import {OSM, Stamen, Vector as VectorSource} from '../src/ol/source.js';
import {Tile as TileLayer, Vector as VectorLayer} from '../src/ol/layer.js';
import {fromLonLat} from '../src/ol/proj.js';
import {getVectorContext} from '../src/ol/render.js';
import {intersects} from '../src/ol/extent.js';

//A distinct className is required to use another canvas for the background
const background = new TileLayer({
  className: 'stamen',
  source: new Stamen({
    layer: 'toner',
  }),
});

const base = new TileLayer({
  source: new OSM(),
});

const clipLayer = new VectorLayer({
  style: null,
  source: new VectorSource({
    url: './data/geojson/switzerland.geojson',
    format: new GeoJSON(),
  }),
});

const style = new Style({
  fill: new Fill({
    color: 'black',
  }),
});

base.on('postrender', function (e) {
  const vectorContext = getVectorContext(e);
  e.context.globalCompositeOperation = 'destination-in';
  //Checking interect is required so the base layer is totally hidden when not clipped
  if (intersects(e.frameState.extent, clipLayer.getSource().getExtent())) {
    clipLayer.getSource().forEachFeature(function (feature) {
      vectorContext.drawFeature(feature, style);
    });
  } else {
    e.context.fillStyle = 'transparent';
    e.context.fillRect(0, 0, 1, 1);
  }
  e.context.globalCompositeOperation = 'source-over';
});

const map = new Map({
  layers: [background, base, clipLayer],
  target: 'map',
  view: new View({
    center: fromLonLat([8.23, 46.86]),
    zoom: 7,
  }),
});