import { fromTo as fromToVect, dot } from "flo-vector2d";


/** 
 * Returns `true` if the given quadratic bezier is obtuse, `false` otherwise (i.e.
 * `false` if acute).
 * 
 * Obtuse here is defined as follows: let the quad form a triangle through its 
 * control points P0, P1, P2 where P0 and P2 are the endpoints. If both interior
 * angles ∠P0 and ∠P2 are <= 90 degrees then the quad is considered acute,
 * otherwise it is considered obtuse.
 * 
 * @doc mdx
 */
function isQuadObtuse(ps: number[][]) {
    const v0 = fromToVect(ps[0], ps[1]);
    const v1 = fromToVect(ps[1], ps[2]);
    const v2 = fromToVect(ps[2], ps[0]);

    const angleP0Obtuse = dot(v2, v0) > 0;
    const angleP2Obtuse = dot(v1, v2) > 0;

    return angleP0Obtuse || angleP2Obtuse;
}


export { isQuadObtuse }