import {LatLng} from '../LatLng';
import {Bounds} from '../../geometry/Bounds';
import {Point} from '../../geometry/Point';

/*
 * @namespace Projection
 * @projection L.Projection.Mercator
 *
 * Elliptical Mercator projection — more complex than Spherical Mercator. Takes into account that Earth is a geoid, not a perfect sphere. Used by the EPSG:3395 CRS.
 */

export var Mercator = {
	R: 6378137,
	R_MINOR: 6356752.314245179,

	bounds: new Bounds([-20037508.34279, -15496570.73972], [20037508.34279, 18764656.23138]),

	project: function (latlng) {
		var d = Math.PI / 180,
		    r = this.R,
		    y = latlng.lat * d,
		    tmp = this.R_MINOR / r,
		    e = Math.sqrt(1 - tmp * tmp),
		    con = e * Math.sin(y);

		var ts = Math.tan(Math.PI / 4 - y / 2) / Math.pow((1 - con) / (1 + con), e / 2);
		y = -r * Math.log(Math.max(ts, 1E-10));

		return new Point(latlng.lng * d * r, y);
	},

	unproject: function (point) {
		var d = 180 / Math.PI,
		    r = this.R,
		    tmp = this.R_MINOR / r,
		    e = Math.sqrt(1 - tmp * tmp),
		    ts = Math.exp(-point.y / r),
		    phi = Math.PI / 2 - 2 * Math.atan(ts);

		for (var i = 0, dphi = 0.1, con; i < 15 && Math.abs(dphi) > 1e-7; i++) {
			con = e * Math.sin(phi);
			con = Math.pow((1 - con) / (1 + con), e / 2);
			dphi = Math.PI / 2 - 2 * Math.atan(ts * con) - phi;
			phi += dphi;
		}

		return new LatLng(phi * d, point.x * d / r);
	}
};