import type { CurvePiece } from '../mat/curve-piece.js';
import { getMedialPointCoeffsBez0 } from "flo-bezier3";
import { lengthSquared, squaredDistanceBetween } from "flo-vector2d";

const { abs } = Math;


const TOLERANCE = 1 + 2**-20;


/**
 * Reduces the circle radius initially as an optimization step.
 * 
 * @param rO maximum possible initial radius
 * 
 * @internal
 */
function reduceRadius(
        maxCoordPowerOf2: number,
        rO: number,
        curvePieces: CurvePiece[], 
        y: number[],
        nnorm: number[]): number {

    let minRadiusSqrd = rO**2;
    let x = [y[0] + nnorm[0], y[1] + nnorm[1]];

    for (let i=0; i<curvePieces.length; i++) {
        const curvePiece = curvePieces[i];

        const { ps } = curvePiece.curve;

        const pS = ps[0];
        const pE = ps[ps.length - 1];

        for (const P of [pS,pE]) {
            if (squaredDistanceBetween(x,P) > minRadiusSqrd) {
                continue;  // short-circuit
            }

            const { a0, b0 } = getMedialPointCoeffsBez0(y, nnorm, P);

            if (abs(a0) <= 2**-40 || abs(b0) <= 2**-40) {
                continue;
            }

            const w = -b0 / a0;

            // too close to point of origin *or* negative;
            if (w < 2**-40) { continue; }

            const N = [w*nnorm[0], w*nnorm[1]];
            const r = lengthSquared(N);

            if (r < minRadiusSqrd) {
                minRadiusSqrd = r;
                x = [y[0] + N[0], y[1] + N[1]];
            }
        }
    }

    // The extra bit is to account for floating point precision.
    return TOLERANCE*minRadiusSqrd;
}


export { reduceRadius }