Calculate ray and circle reflection points

gistfile1.txt

/**
 * Calculates whether a ray intersects a circle. If it does, it returns the intersection point, the angle of reflection, and the distance from the origin of the ray.
 * @param {Object} origin {x, y}
 * @param {Number} angle 
 * @param {Object} circle {x, y, r}
 * @returns {Object} {x, y, angle, dist} | null
 * 
 */
const rayCircleIntersection = (origin, angle, circle) => {
    let x1 = origin.x;
    let y1 = origin.y;
    let x2 = origin.x + cos(angle);
    let y2 = origin.y + sin(angle);

    let cx = circle.x;
    let cy = circle.y;
    let r = circle.r / 4;

    let dx = x2 - x1;
    let dy = y2 - y1;

    let fx = x1 - cx;
    let fy = y1 - cy;

    let a = dx * dx + dy * dy;
    let b = 2 * (fx * dx + fy * dy);
    let c = fx * fx + fy * fy - r * r;

    let discriminant = b * b - 4 * a * c;

    if (discriminant >= 0) {
        discriminant = sqrt(discriminant);
        let t1 = (-b - discriminant) / (2 * a);
        let t2 = (-b + discriminant) / (2 * a);
        //console.log(t1, t2)
        //if (t1 >= 0 && t1 <= 1) {
        if (t1 >= 0 && t2 <= 1) {
            let intersectionPoint = {
                x: x1 + t1 * dx,
                y: y1 + t1 * dy
            };
            let normal = {
                x: (intersectionPoint.x - cx) / r,
                y: (intersectionPoint.y - cy) / r
            };
            let incidentAngle = atan2(dy, dx);
            let reflectionAngle = 2 * atan2(normal.y, normal.x) - incidentAngle + PI;
            //console.log('incident', incidentAngle)
            return {
                x: intersectionPoint.x,
                y: intersectionPoint.y,
                angle: reflectionAngle,
                dist: dist(origin.x, origin.y, intersectionPoint.x, intersectionPoint.y)
            };
        }
        else if (t1 <= 0 && t2 >= 1) {
            let intersectionPoint = {
                x: x1 + t2 * dx,
                y: y1 + t2 * dy
            };
            let normal = {
                x: (intersectionPoint.x - cx) / r,
                y: (intersectionPoint.y - cy) / r
            };
            let incidentAngle = atan2(dy, dx);
            let reflectionAngle = 2 * atan2(normal.y, normal.x) - incidentAngle;
            console.log('incident', incidentAngle)
            return {
                x: intersectionPoint.x,
                y: intersectionPoint.y,
                angle: reflectionAngle,
                dist: dist(origin.x, origin.y, intersectionPoint.x, intersectionPoint.y)
            };
        }
    }
    return null;
}