import {lngLatToWorld} from '@math.gl/web-mercator';

// https://epsg.io/3857
// +proj=merc +a=6378137 +b=6378137 +lat_ts=0 +lon_0=0 +x_0=0 +y_0=0 +k=1 +units=m +nadgrids=@null +wktext +no_defs +type=crs
const HALF_EARTH_CIRCUMFERENCE = 6378137 * Math.PI;

/** Projects EPSG:4326 to EPSG:3857
 * This is a lightweight replacement of proj4. Use tests to ensure conformance.
 */
export function WGS84ToPseudoMercator(coord: [number, number]): [number, number] {
  const mercator = lngLatToWorld(coord);
  mercator[0] = (mercator[0] / 256 - 1) * HALF_EARTH_CIRCUMFERENCE;
  mercator[1] = (mercator[1] / 256 - 1) * HALF_EARTH_CIRCUMFERENCE;
  return mercator;
}