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import { pointsEqual } from "./point";
import { lineSegment, pointOnLineSegment } from "./segment";
import type { GlobalPoint, LocalPoint, Polygon } from "./types";
import { PRECISION } from "./utils";
export function polygon<Point extends GlobalPoint | LocalPoint>(
...points: Point[]
) {
return polygonClose(points) as Polygon<Point>;
}
export function polygonFromPoints<Point extends GlobalPoint | LocalPoint>(
points: Point[],
) {
return polygonClose(points) as Polygon<Point>;
}
export const polygonIncludesPoint = <Point extends LocalPoint | GlobalPoint>(
point: Point,
polygon: Polygon<Point>,
) => {
const x = point[0];
const y = point[1];
let inside = false;
for (let i = 0, j = polygon.length - 1; i < polygon.length; j = i++) {
const xi = polygon[i][0];
const yi = polygon[i][1];
const xj = polygon[j][0];
const yj = polygon[j][1];
if (
((yi > y && yj <= y) || (yi <= y && yj > y)) &&
x < ((xj - xi) * (y - yi)) / (yj - yi) + xi
) {
inside = !inside;
}
}
return inside;
};
export const pointOnPolygon = <Point extends LocalPoint | GlobalPoint>(
p: Point,
poly: Polygon<Point>,
threshold = PRECISION,
) => {
let on = false;
for (let i = 0, l = poly.length - 1; i < l; i++) {
if (pointOnLineSegment(p, lineSegment(poly[i], poly[i + 1]), threshold)) {
on = true;
break;
}
}
return on;
};
function polygonClose<Point extends LocalPoint | GlobalPoint>(
polygon: Point[],
) {
return polygonIsClosed(polygon)
? polygon
: ([...polygon, polygon[0]] as Polygon<Point>);
}
function polygonIsClosed<Point extends LocalPoint | GlobalPoint>(
polygon: Point[],
) {
return pointsEqual(polygon[0], polygon[polygon.length - 1]);
}
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