import type { CpNode } from "../cp-node.js";
import { tangent } from "flo-bezier3";
import { cross, toUnitVector } from "flo-vector2d";
import { getMatCurveToNext } from "./get-mat-curve-to-next.js";

const { abs, asin, min, max, PI: π } = Math;


/**
 * 
 * @param cpNode1 
 * @param cpNode2 
 * @returns 
 */
function getInitialDegAngleBetweenMatCurves(
        cpNode1: CpNode,
        cpNode2: CpNode) {

    const tan1 = toUnitVector(tangent(
        getMatCurveToNext(cpNode1)[0], 
        0
    ));
    const tan2 = toUnitVector(tangent(
        getMatCurveToNext(cpNode2)[0], 
        0
    ));

    // clamp: rounding can push the cross product of two unit vectors just
    // outside [-1,1], which would make `asin` return `NaN`
    const cross_ = max(-1, min(1, cross(tan1, tan2)));
    const angle = abs(asin( cross_ ) * (180/π));

    return angle;
}


export { getInitialDegAngleBetweenMatCurves }