import Map from '../src/ol/Map.js';
import OSM from '../src/ol/source/OSM.js';
import TileLayer from '../src/ol/layer/Tile.js';
import View from '../src/ol/View.js';
import {ScaleLine, defaults as defaultControls} from '../src/ol/control.js';
import {
  getPointResolution,
  get as getProjection,
  transform,
} from '../src/ol/proj.js';

const viewProjSelect = document.getElementById('view-projection');
const projection = getProjection(viewProjSelect.value);

const scaleControl = new ScaleLine({
  units: 'metric',
  bar: true,
  steps: 4,
  text: true,
  minWidth: 140,
});

const map = new Map({
  controls: defaultControls().extend([scaleControl]),
  layers: [
    new TileLayer({
      source: new OSM(),
    }),
  ],
  target: 'map',
  view: new View({
    center: transform([0, 52], 'EPSG:4326', projection),
    zoom: 6,
    projection: projection,
  }),
});

function onChangeProjection() {
  const currentView = map.getView();
  const currentProjection = currentView.getProjection();
  const newProjection = getProjection(viewProjSelect.value);
  const currentResolution = currentView.getResolution();
  const currentCenter = currentView.getCenter();
  const currentRotation = currentView.getRotation();
  const newCenter = transform(currentCenter, currentProjection, newProjection);
  const currentPointResolution = getPointResolution(
    currentProjection,
    1,
    currentCenter,
    'm'
  );
  const newPointResolution = getPointResolution(
    newProjection,
    1,
    newCenter,
    'm'
  );
  const newResolution =
    (currentResolution * currentPointResolution) / newPointResolution;
  const newView = new View({
    center: newCenter,
    resolution: newResolution,
    rotation: currentRotation,
    projection: newProjection,
  });
  map.setView(newView);
}
viewProjSelect.addEventListener('change', onChangeProjection);
