import { dot, scale, sub, type Vec } from "./given.ts";

/**
 * Remove the component of `v` that points into a wall with the given (unit)
 * normal, leaving only the motion that runs along the wall.
 *
 *   vSlide = v - normal * dot(v, normal)
 */
export function slide(v: Vec, normal: Vec): Vec {
	return sub(v, scale(normal, dot(v, normal)));
}