import { toPowerBasisExact } from "../../../to-power-basis/to-power-basis/exact/to-power-basis-exact.js";
import { eHorner } from 'flo-poly';


/**
 * Returns the *exact* resulting point of evaluating the given bezier curve at
 * the given `t` parameter.
 * 
 * * the result is returned as `[x,y]`, where `x` and `y` are [Shewchuk](https://people.eecs.berkeley.edu/~jrs/papers/robustr.pdf) floating
 * point expansions
 * 
 * @param ps an order 0,1,2 or 3 bezier curve given as an ordered array of its
 * control point coordinates, e.g. `[[0,0], [1,1], [2,1], [2,0]]`
 * @param t 
 * 
 * @doc mdx
 */
function evaluateExact(
        ps: number[][],
        t: number): number[][] {

    if (t === 0) { return [[ps[0][0]], [ps[0][1]]]; }
    if (t === 1) { return [[ps[ps.length-1][0]], [ps[ps.length-1][1]]]; }

    const [X,Y] = toPowerBasisExact(ps);
    
    return [
        eHorner(X,t),
        eHorner(Y,t)
    ];
}


export { evaluateExact }