import { check } from "./helpers/check.js";
/**
* @function rewind2
* @summary Rewind a geoJSON (Mapbox). The function allows to rewind the winding order of a GeoJSON object. The winding order of a polygon is the order in which the vertices are visited by the path that defines the polygon. The winding order of a polygon is significant because it determines the interior of the polygon. The winding order of a polygon is typically either clockwise or counterclockwise.
* @description Adapted from MapBox geojson-rewind code (https://github.com/mapbox/grojson-rewind) under ISC license.
* @param {object|array} data - A GeoJSON FeatureCollection, an array of features, an array of geometries, a single feature or a single geometry.
* @property {boolean} [options.outer = false] - rewind Rings Outer
* @returns {object|array} - A GeoJSON FeatureCollection, an array of features, an array of geometries, a single feature or a single geometry (it depends on what you've set as `data`)
* @example
* geotoolbox.rewind2(*a geojson*)
*/
export function rewind2(data, { outer = false } = {}) {
const handle = check(data);
let geo = handle.import(data);
for (let i = 0; i < geo.features.length; i++) {
if (geo.features[i].geometry.type === "Polygon") {
rewindRings(geo.features[i].geometry.coordinates, outer);
} else if (geo.features[i].geometry.type === "MultiPolygon") {
for (let j = 0; j < geo.features[i].geometry.coordinates.length; j++) {
rewindRings(geo.features[i].geometry.coordinates[j], outer);
}
}
}
return handle.export(geo);
}
function rewindRings(rings, outer) {
if (rings.length === 0) return;
rewindRing(rings[0], outer);
for (let i = 1; i < rings.length; i++) {
rewindRing(rings[i], !outer);
}
}
function rewindRing(ring, dir) {
let tArea = 0;
let err = 0;
for (let i = 0, len = ring.length, j = len - 1; i < len; j = i++) {
const k = (ring[i][0] - ring[j][0]) * (ring[j][1] + ring[i][1]);
const m = tArea + k;
err += Math.abs(tArea) >= Math.abs(k) ? tArea - m + k : k - m + tArea;
tArea = m;
}
if (tArea + err >= 0 !== !!dir) ring.reverse();
}