mr-crocs-adventures/js/geometry/GeometryLine.js

import GeometryPoint from "./GeometryPoint.js";
import GeometryStroke from "./GeometryStroke.js";

export default class GeometryLine
{
    constructor(pointA, pointB)
    {
        this.pointA = pointA;
        this.pointB = pointB;
    }

    getIntersectionWithLine(line)
    {
        try {
            let xa = (line.pointB.x - line.pointA.x) * (this.pointB.x * this.pointA.y - this.pointA.x * this.pointB.y);
            let xb = (this.pointB.x - this.pointA.x) * (line.pointB.x * line.pointA.y - line.pointA.x * line.pointB.y);
            let xc = (line.pointB.y - line.pointA.y) * (this.pointB.x - this.pointA.x);
            let xd = (this.pointB.y - this.pointA.y) * (line.pointB.x - line.pointA.x);

            let x  = (xa - xb) / (xc - xd);

            if (isNaN(x)) {
                return null;
            }

            let ya = (this.pointA.y - this.pointB.y) *(line.pointB.x * line.pointA.y - line.pointA.x * line.pointB.y);
            let yb = (line.pointA.y - line.pointB.y) *(this.pointB.x * this.pointA.y - this.pointA.x * this.pointB.y);
            let yc = (line.pointB.y - line.pointA.y) * (this.pointB.x - this.pointA.x);
            let yd = (this.pointB.y - this.pointA.y) * (line.pointB.x - line.pointA.x);

            let y = (ya - yb) / (yc - yd);

            if (isNaN(y)) {
                return null;
            }

            return new GeometryPoint(x, y);
        } catch (error) {
            return null;
        }
    }

    getStroke()
    {
        return new GeometryStroke(this.pointA, this.pointB);
    }

    draw(context)
    {
        context.beginPath();
        context.moveTo(this.pointA.x, this.pointA.y);
        context.lineTo(this.pointB.x, this.pointB.y);
        context.stroke();
    }
}