src/Mod/CAM/libarea/Adaptive.cpp

// SPDX-License-Identifier: LGPL-2.1-or-later

/**************************************************************************
 *   Copyright (c) 2018 Kresimir Tusek <kresimir.tusek@gmail.com>          *
 *                                                                         *
 *   This file is part of the FreeCAD CAx development system.              *
 *                                                                         *
 *   This library is free software; you can redistribute it and/or         *
 *   modify it under the terms of the GNU Library General Public           *
 *   License as published by the Free Software Foundation; either          *
 *   version 2 of the License, or (at your option) any later version.      *
 *                                                                         *
 *   This library  is distributed in the hope that it will be useful,      *
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
 *   GNU Library General Public License for more details.                  *
 *                                                                         *
 *   You should have received a copy of the GNU Library General Public     *
 *   License along with this library; see the file COPYING.LIB. If not,    *
 *   write to the Free Software Foundation, Inc., 59 Temple Place,         *
 *   Suite 330, Boston, MA  02111-1307, USA                                *
 *                                                                         *
 ***************************************************************************/

#include "Adaptive.hpp"
#include <iostream>
#include <cmath>
#include <cstring>
#include <ctime>
#include <algorithm>
#include <numbers>
#include <optional>

namespace ClipperLib
{
void TranslatePath(const Path& input, Path& output, IntPoint delta);
}

namespace AdaptivePath
{
using namespace ClipperLib;
using namespace std;
#define SAME_POINT_TOL_SQRD_SCALED 4.0
#define UNUSED(expr) (void)(expr)

//*****************************************
// Utils - inline
//*****************************************

inline double DistanceSqrd(const IntPoint& pt1, const IntPoint& pt2)
{
    double Dx = double(pt1.X - pt2.X);
    double dy = double(pt1.Y - pt2.Y);
    return (Dx * Dx + dy * dy);
}

inline bool SetSegmentLength(const IntPoint& pt1, IntPoint& pt2, double new_length)
{
    double Dx = double(pt2.X - pt1.X);
    double dy = double(pt2.Y - pt1.Y);
    double l = sqrt(Dx * Dx + dy * dy);
    if (l > 0.0) {
        pt2.X = long(pt1.X + new_length * Dx / l);
        pt2.Y = long(pt1.Y + new_length * dy / l);
        return true;
    }
    return false;
}

inline bool HasAnyPath(const Paths& paths)
{
    for (Paths::size_type i = 0; i < paths.size(); i++) {
        if (!paths[i].empty()) {
            return true;
        }
    }
    return false;
}

inline double averageDV(const vector<double>& vec)
{
    double s = 0;
    std::size_t size = vec.size();
    if (size == 0) {
        return 0;
    }
    for (std::size_t i = 0; i < size; i++) {
        s += vec[i];
    }
    return s / double(size);
}

inline DoublePoint rotate(const DoublePoint& in, double rad)
{
    double c = cos(rad);
    double s = sin(rad);
    return DoublePoint(c * in.X - s * in.Y, s * in.X + c * in.Y);
}

// calculates path length for open path
inline double PathLength(const Path& path)
{
    double len = 0;
    if (path.size() < 2) {
        return len;
    }
    for (size_t i = 1; i < path.size(); i++) {
        len += sqrt(DistanceSqrd(path[i - 1], path[i]));
    }
    return len;
}

inline double PointSideOfLine(const IntPoint& p1, const IntPoint& p2, const IntPoint& pt)
{
    return double((pt.X - p1.X) * (p2.Y - p1.Y) - (pt.Y - p2.Y) * (p2.X - p1.X));
}

inline double Angle3Points(const DoublePoint& p1, const DoublePoint& p2, const DoublePoint& p3)
{
    double t1 = atan2(p2.Y - p1.Y, p2.X - p1.X);
    double t2 = atan2(p3.Y - p2.Y, p3.X - p2.X);
    double a = fabs(t2 - t1);
    return min(a, 2 * std::numbers::pi - a);
}

inline DoublePoint DirectionV(const IntPoint& pt1, const IntPoint& pt2)
{
    double DX = double(pt2.X - pt1.X);
    double DY = double(pt2.Y - pt1.Y);
    double l = sqrt(DX * DX + DY * DY);
    if (l < NTOL) {
        return DoublePoint(0, 0);
    }
    return DoublePoint(DX / l, DY / l);
}

inline void NormalizeV(DoublePoint& pt)
{
    double len = sqrt(pt.X * pt.X + pt.Y * pt.Y);
    if (len > NTOL) {
        pt.X /= len;
        pt.Y /= len;
    }
}

inline DoublePoint GetPathDirectionV(const Path& pth, size_t pointIndex)
{
    if (pth.size() < 2) {
        return DoublePoint(0, 0);
    }
    const IntPoint& p1 = pth.at(pointIndex > 0 ? pointIndex - 1 : pth.size() - 1);
    const IntPoint& p2 = pth.at(pointIndex);
    return DirectionV(p1, p2);
}

// Returns true if points 'a' and 'b' are coincident or nearly so.
bool isClose(const IntPoint& a, const IntPoint& b)
{
    return abs(a.X - b.X) <= 1 && abs(a.Y - b.Y) <= 1;
}

// Remove coincident and almost-coincident points from Paths.
void filterCloseValues(Paths& ppg)
{
    for (auto& pth : ppg) {
        while (true) {
            auto i = std::adjacent_find(pth.begin(), pth.end(), isClose);
            if (i == pth.end()) {
                break;
            }
            pth.erase(i);
        }
        // adjacent_find doesn't compare first with last element, so
        // do that manually.
        while (pth.size() > 1 && isClose(pth.front(), pth.back())) {
            pth.pop_back();
        }
    }
}

//*****************************************
// Utils
//*****************************************

class BoundBox
{
public:
    BoundBox()
    {
        minX = 0;
        maxX = 0;
        minY = 0;
        maxY = 0;
    }

    // generic: first point
    BoundBox(const IntPoint& p1)
    {
        minX = p1.X;
        maxX = p1.X;
        minY = p1.Y;
        maxY = p1.Y;
    }

    void SetFirstPoint(const IntPoint& p1)
    {
        minX = p1.X;
        maxX = p1.X;
        minY = p1.Y;
        maxY = p1.Y;
    }

    // generic: subsequent points
    void AddPoint(const IntPoint& pt)
    {
        minX = min(pt.X, minX);
        maxX = max(pt.X, maxX);
        minY = min(pt.Y, minY);
        maxY = max(pt.Y, maxY);
    }

    // line segment: two points
    BoundBox(const IntPoint& p1, const IntPoint& p2)
    {
        if (p1.X < p2.X) {
            minX = p1.X;
            maxX = p2.X;
        }
        else {
            minX = p2.X;
            maxX = p1.X;
        }
        if (p1.Y < p2.Y) {
            minY = p1.Y;
            maxY = p2.Y;
        }
        else {
            minY = p2.Y;
            maxY = p1.Y;
        }
    }

    // for circle: center and radius
    BoundBox(const IntPoint& center, long radius)
    {
        minX = center.X - radius;
        maxX = center.X + radius;
        minY = center.Y - radius;
        maxY = center.Y + radius;
    }

    // bounds check - intersection
    inline bool CollidesWith(const BoundBox& bb2)
    {
        return minX <= bb2.maxX && maxX >= bb2.minX && minY <= bb2.maxY && maxY >= bb2.minY;
    }

    // bounds check -  contains
    inline bool Contains(const BoundBox& bb2)
    {
        return minX <= bb2.minX && maxX >= bb2.maxX && minY <= bb2.minY && maxY >= bb2.maxY;
    }

    ClipperLib::cInt minX;
    ClipperLib::cInt maxX;
    ClipperLib::cInt minY;
    ClipperLib::cInt maxY;
};

std::ostream& operator<<(std::ostream& s, const BoundBox& p)
{
    s << "(" << p.minX << "," << p.minY << ") - (" << p.maxX << "," << p.maxY << ")";
    return s;
}

int getPathNestingLevel(const Path& path, const Paths& paths)
{
    int nesting = 0;
    for (const auto& other : paths) {
        if (!path.empty() && PointInPolygon(path.front(), other) != 0) {
            nesting++;
        }
    }
    return nesting;
}

void appendDirectChildPaths(Paths& outPaths, const Path& path, const Paths& paths)
{
    int nesting = getPathNestingLevel(path, paths);
    for (const auto& other : paths) {
        if (!path.empty() && !other.empty() && PointInPolygon(other.front(), path) != 0) {
            if (getPathNestingLevel(other, paths) == nesting + 1) {
                outPaths.push_back(other);
            }
        }
    }
}

void AverageDirection(const vector<DoublePoint>& unityVectors, DoublePoint& output)
{
    std::size_t size = unityVectors.size();
    output.X = 0;
    output.Y = 0;
    // sum vectors
    for (std::size_t i = 0; i < size; i++) {
        DoublePoint v = unityVectors[i];
        output.X += v.X;
        output.Y += v.Y;
    }
    // normalize
    double magnitude = sqrt(output.X * output.X + output.Y * output.Y);
    output.X /= magnitude;
    output.Y /= magnitude;
}

double DistancePointToLineSegSquared(
    const IntPoint& p1,
    const IntPoint& p2,
    const IntPoint& pt,
    IntPoint& closestPoint,
    double& ptParameter,
    bool clamp = true
)
{
    double D21X = double(p2.X - p1.X);
    double D21Y = double(p2.Y - p1.Y);
    double DP1X = double(pt.X - p1.X);
    double DP1Y = double(pt.Y - p1.Y);
    double lsegLenSqr = D21X * D21X + D21Y * D21Y;
    if (lsegLenSqr == 0) {  // segment is zero length, return point to point distance
        closestPoint = p1;
        ptParameter = 0;
        return DP1X * DP1X + DP1Y * DP1Y;
    }
    double parameter = DP1X * D21X + DP1Y * D21Y;
    if (clamp) {
        // clamp the parameter
        if (parameter < 0) {
            parameter = 0;
        }
        else if (parameter > lsegLenSqr) {
            parameter = lsegLenSqr;
        }
    }
    // point on line at parameter
    ptParameter = parameter / lsegLenSqr;
    closestPoint.X = long(p1.X + ptParameter * D21X);
    closestPoint.Y = long(p1.Y + ptParameter * D21Y);
    // calculate distance from point on line to pt
    double DX = double(pt.X - closestPoint.X);
    double DY = double(pt.Y - closestPoint.Y);
    return DX * DX + DY * DY;  // return distance squared
}

void ScaleUpPaths(Paths& paths, long scaleFactor)
{
    for (auto& pth : paths) {
        for (auto& pt : pth) {
            pt.X *= scaleFactor;
            pt.Y *= scaleFactor;
        }
    }
}

void ScaleDownPaths(Paths& paths, long scaleFactor)
{
    for (auto& pth : paths) {
        for (auto& pt : pth) {
            pt.X /= scaleFactor;
            pt.Y /= scaleFactor;
        }
    }
}


double DistancePointToPathsSqrd(
    const Paths& paths,
    const IntPoint& pt,
    IntPoint& closestPointOnPath,
    size_t& clpPathIndex,
    size_t& clpSegmentIndex,
    double& clpParameter
)
{
    double minDistSq = __DBL_MAX__;
    IntPoint clp;
    // iterate though paths
    for (Path::size_type i = 0; i < paths.size(); i++) {
        const Path* path = &paths[i];
        Path::size_type size = path->size();
        // iterate through segments
        for (Path::size_type j = 0; j < size; j++) {
            double ptPar;
            double distSq = DistancePointToLineSegSquared(
                path->at(j > 0 ? j - 1 : size - 1),
                path->at(j),
                pt,
                clp,
                ptPar
            );
            if (distSq < minDistSq) {
                clpPathIndex = i;
                clpSegmentIndex = j;
                clpParameter = ptPar;
                closestPointOnPath = clp;
                minDistSq = distSq;
            }
        }
    }
    return minDistSq;
}

// joins collinear segments (within the tolerance)
void CleanPath(const Path& inp, Path& outpt, double tolerance)
{
    if (inp.size() < 3) {
        outpt = inp;
        return;
    }
    outpt.clear();
    Path tmp;
    CleanPolygon(inp, tmp, tolerance);
    long size = long(tmp.size());

    // CleanPolygon will have empty result if all points are collinear,
    // 	need to add first and last point to the output
    if (size <= 2) {
        outpt.push_back(inp.front());
        outpt.push_back(inp.back());
        return;
    }

    // restore starting point
    double clpPar = 0;
    size_t clpSegmentIndex = 0;
    size_t clpPathIndex = 0;
    Paths tmpPaths;
    tmpPaths.push_back(tmp);
    IntPoint clp;
    // find point on cleaned poly that is closest to original starting point
    DistancePointToPathsSqrd(tmpPaths, inp.front(), clp, clpPathIndex, clpSegmentIndex, clpPar);


    // if closes point is not one of the polygon points, add it as separate first point
    if (DistanceSqrd(clp, tmp.at(clpSegmentIndex)) > 0
        && DistanceSqrd(clp, tmp.at(clpSegmentIndex > 0 ? clpSegmentIndex - 1 : size - 1)) > 0) {
        outpt.push_back(clp);
    }

    // add remaining points starting from closest
    long index;
    for (long i = 0; i < size; i++) {
        index = static_cast<long>(clpSegmentIndex + i);
        if (index >= size) {
            index -= size;
        }
        outpt.push_back(tmp.at(index));
    }


    if (DistanceSqrd(outpt.front(), inp.front()) > SAME_POINT_TOL_SQRD_SCALED) {
        outpt.insert(outpt.begin(), inp.front());
    }

    if (DistanceSqrd(outpt.back(), inp.back()) > SAME_POINT_TOL_SQRD_SCALED) {
        outpt.push_back(inp.back());
    }
}

bool Circle2CircleIntersect(
    const IntPoint& c1,
    const IntPoint& c2,
    double radius,
    pair<DoublePoint, DoublePoint>& intersections
)
{
    double DX = double(c2.X - c1.X);
    double DY = double(c2.Y - c1.Y);
    double d = sqrt(DX * DX + DY * DY);
    if (d < NTOL) {
        return false;  // same center
    }
    if (d >= radius) {
        return false;  // do not intersect, or intersect in one point (this case not relevant here)
    }
    double a_2 = sqrt(4 * radius * radius - d * d) / 2.0;
    intersections.first
        = DoublePoint(0.5 * (c1.X + c2.X) - DY * a_2 / d, 0.5 * (c1.Y + c2.Y) + DX * a_2 / d);
    intersections.second
        = DoublePoint(0.5 * (c1.X + c2.X) + DY * a_2 / d, 0.5 * (c1.Y + c2.Y) - DX * a_2 / d);
    return true;
}

bool Line2CircleIntersect(
    const IntPoint& c,
    double radius,
    const IntPoint& p1,
    const IntPoint& p2,
    vector<DoublePoint>& result,
    bool clamp = true
)
{
    // if more intersections returned, first is closer to p1

    // box  check for performance
    if (clamp) {
        BoundBox cBB(c, (ClipperLib::cInt)radius + 1);  // circle bound box
        BoundBox sBB(p1, p2);
        if (!sBB.CollidesWith(cBB)) {
            return false;
        }
    }

    double dx = double(p2.X - p1.X);
    double dy = double(p2.Y - p1.Y);
    double lcx = double(p1.X - c.X);
    double lcy = double(p1.Y - c.Y);
    double a = dx * dx + dy * dy;
    double b = 2 * dx * lcx + 2 * dy * lcy;
    double C = lcx * lcx + lcy * lcy - radius * radius;
    double sq = b * b - 4 * a * C;
    if (sq < 0) {
        return false;  // no solution
    }
    sq = sqrt(sq);
    double t1 = (-b - sq) / (2 * a);
    double t2 = (-b + sq) / (2 * a);
    result.clear();
    if (clamp) {
        if (t1 >= 0.0 && t1 <= 1.0) {
            result.emplace_back(p1.X + t1 * dx, p1.Y + t1 * dy);
        }
        if (t2 >= 0.0 && t2 <= 1.0) {
            result.emplace_back(p1.X + t2 * dx, p1.Y + t2 * dy);
        }
    }
    else {
        result.emplace_back(p1.X + t2 * dx, p1.Y + t2 * dy);
        result.emplace_back(p1.X + t2 * dx, p1.Y + t2 * dy);
    }
    return !result.empty();
}

// calculate center point of polygon
IntPoint Compute2DPolygonCentroid(const Path& vertices)
{
    DoublePoint centroid(0, 0);
    double signedArea = 0.0;
    double x0 = 0.0;  // Current vertex X
    double y0 = 0.0;  // Current vertex Y
    double x1 = 0.0;  // Next vertex X
    double y1 = 0.0;  // Next vertex Y
    double a = 0.0;   // Partial signed area

    // For all vertices
    size_t i = 0;
    Path::size_type size = vertices.size();
    for (i = 0; i < size; ++i) {
        x0 = double(vertices[i].X);
        y0 = double(vertices[i].Y);
        x1 = double(vertices[(i + 1) % size].X);
        y1 = double(vertices[(i + 1) % size].Y);
        a = x0 * y1 - x1 * y0;
        signedArea += a;
        centroid.X += (x0 + x1) * a;
        centroid.Y += (y0 + y1) * a;
    }

    signedArea *= 0.5;
    centroid.X /= (6.0 * signedArea);
    centroid.Y /= (6.0 * signedArea);
    return IntPoint(long(centroid.X), long(centroid.Y));
}

// point must be within first path (boundary) and must not be within all other paths (holes)
bool IsPointWithinCutRegion(const Paths& toolBoundPaths, const IntPoint& point)
{
    for (size_t i = 0; i < toolBoundPaths.size(); i++) {
        int pip = PointInPolygon(point, toolBoundPaths[i]);
        if (i == 0 && pip == 0) {
            return false;  // is outside or on boundary
        }
        if (i > 0 && pip != 0) {
            return false;  // is inside hole
        }
    }
    return true;
}

/* finds intersection of line segment with line segment */
bool IntersectionPoint(
    const IntPoint& s1p1,
    const IntPoint& s1p2,
    const IntPoint& s2p1,
    const IntPoint& s2p2,
    IntPoint& intersection
)
{
    double S1DX = double(s1p2.X - s1p1.X);
    double S1DY = double(s1p2.Y - s1p1.Y);
    double S2DX = double(s2p2.X - s2p1.X);
    double S2DY = double(s2p2.Y - s2p1.Y);
    double d = S1DY * S2DX - S2DY * S1DX;
    if (fabs(d) < NTOL) {
        return false;  // lines are parallel
    }

    double LPDX = double(s1p1.X - s2p1.X);
    double LPDY = double(s1p1.Y - s2p1.Y);
    double p1d = S2DY * LPDX - S2DX * LPDY;
    double p2d = S1DY * LPDX - S1DX * LPDY;
    if ((d < 0) && (p1d < d || p1d > 0 || p2d < d || p2d > 0)) {
        return false;  // intersection not within segment1
    }
    if ((d > 0) && (p1d < 0 || p1d > d || p2d < 0 || p2d > d)) {
        return false;  // intersection not within segment2
    }
    double t = p1d / d;
    intersection = IntPoint(long(s1p1.X + S1DX * t), long(s1p1.Y + S1DY * t));
    return true;
}

/* finds one/first intersection of line segment with paths */
bool IntersectionPoint(const Paths& paths, const IntPoint& p1, const IntPoint& p2, IntPoint& intersection)
{
    BoundBox segBB(p1, p2);
    for (size_t i = 0; i < paths.size(); i++) {
        const Path* path = &paths[i];
        size_t size = path->size();
        if (size < 2) {
            continue;
        }
        BoundBox pathBB(path->front());
        for (size_t j = 0; j < size; j++) {

            const IntPoint* pp2 = &path->at(j);

            // box check for performance
            pathBB.AddPoint(*pp2);
            if (!pathBB.CollidesWith(segBB)) {
                continue;
            }

            const IntPoint* pp1 = &path->at(j > 0 ? j - 1 : size - 1);
            double LDY = double(p2.Y - p1.Y);
            double LDX = double(p2.X - p1.X);
            double PDX = double(pp2->X - pp1->X);
            double PDY = double(pp2->Y - pp1->Y);
            double d = LDY * PDX - PDY * LDX;
            if (fabs(d) < NTOL) {
                continue;  // lines are parallel
            }

            double LPDX = double(p1.X - pp1->X);
            double LPDY = double(p1.Y - pp1->Y);
            double p1d = PDY * LPDX - PDX * LPDY;
            double p2d = LDY * LPDX - LDX * LPDY;
            if ((d < 0) && (p1d < d || p1d > 0 || p2d < d || p2d > 0)) {
                continue;  // intersection not within segment
            }
            if ((d > 0) && (p1d < 0 || p1d > d || p2d < 0 || p2d > d)) {
                continue;  // intersection not within segment
            }
            double t = p1d / d;
            intersection = IntPoint(long(p1.X + LDX * t), long(p1.Y + LDY * t));
            return true;
        }
    }
    return false;
}

void SmoothPaths(Paths& paths, double stepSize, long pointCount, long iterations)
{
    Paths output;
    output.resize(paths.size());
    const long scale = 1000;
    const double stepScaled = stepSize * scale;

    ScaleUpPaths(paths, scale);
    vector<pair<size_t /*path index*/, IntPoint>> points;
    for (size_t i = 0; i < paths.size(); i++) {
        for (const auto& pt : paths[i]) {
            if (points.empty()) {
                points.emplace_back(i, pt);
                continue;
            }
            const auto back = points.back();
            const IntPoint& lastPt = back.second;


            const double l = sqrt(DistanceSqrd(lastPt, pt));

            if (l < 0.5 * stepScaled) {
                if (points.size() > 1) {
                    points.pop_back();
                }
                points.emplace_back(i, pt);
                continue;
            }
            size_t lastPathIndex = back.first;
            const long steps = max(long(l / stepScaled), 1L);
            const long left = pointCount * iterations * 2;
            const long right = steps - pointCount * iterations * 2;
            for (long idx = 0; idx <= steps; idx++) {
                if (idx > left && idx < right) {
                    idx = right;
                    continue;
                }
                const double p = double(idx) / steps;
                const IntPoint ptx(
                    long(lastPt.X + double(pt.X - lastPt.X) * p),
                    long(lastPt.Y + double(pt.Y - lastPt.Y) * p)
                );

                if (idx == 0 && DistanceSqrd(back.second, ptx) < scale && points.size() > 1) {
                    points.pop_back();
                }

                if (p < 0.5) {
                    points.emplace_back(lastPathIndex, ptx);
                }
                else {
                    points.emplace_back(i, ptx);
                }
            }
        }
    }
    if (points.empty()) {
        return;
    }
    const long size = long(points.size());
    for (long iter = 0; iter < iterations; iter++) {
        for (long i = 1; i < size - 1; i++) {
            IntPoint& cp = points[i].second;
            IntPoint avgPoint(cp);
            long cnt = 1;

            long ptsToAverage = pointCount;
            if (i <= ptsToAverage) {
                ptsToAverage = max(i - 1, 0L);
            }
            else if (i + ptsToAverage >= size - 1) {
                ptsToAverage = size - 1 - i;
            }
            for (long j = i - ptsToAverage; j <= i + ptsToAverage; j++) {
                if (j == i) {
                    continue;
                }
                long index = j;
                if (index < 0) {
                    index = 0;
                }
                if (index >= size) {
                    index = size - 1;
                }
                IntPoint& p = points[index].second;
                avgPoint.X += p.X;
                avgPoint.Y += p.Y;
                cnt++;
            }
            cp.X = avgPoint.X / cnt;
            cp.Y = avgPoint.Y / cnt;
        }
    }

    for (const auto& pr : points) {
        output[pr.first].push_back(pr.second);
    }
    for (size_t i = 0; i < paths.size(); i++) {
        CleanPath(output[i], paths[i], 1.4 * scale);
    }
    ScaleDownPaths(paths, scale);
}

bool PopPathWithClosestPoint(
    Paths& paths /*closest path is removed from collection and shifted to
                    start with closest point */
    ,
    IntPoint p1,
    Path& result
)
{

    if (paths.empty()) {
        return false;
    }

    double minDistSqrd = __DBL_MAX__;
    size_t closestPathIndex = 0;
    long closestPointIndex = 0;
    for (size_t pathIndex = 0; pathIndex < paths.size(); pathIndex++) {
        Path& path = paths.at(pathIndex);
        for (size_t i = 0; i < path.size(); i++) {
            double dist = DistanceSqrd(p1, path.at(i));
            if (dist < minDistSqrd) {
                minDistSqrd = dist;
                closestPathIndex = pathIndex;
                closestPointIndex = long(i);
            }
        }
    }

    result.clear();
    // make new path starting with that point
    Path& closestPath = paths.at(closestPathIndex);
    for (size_t i = 0; i < closestPath.size(); i++) {
        long index = closestPointIndex + long(i);
        if (index >= long(closestPath.size())) {
            index -= long(closestPath.size());
        }
        result.push_back(closestPath.at(index));
    }
    // remove the closest path
    paths.erase(paths.begin() + closestPathIndex);
    return true;
}

void DeduplicatePaths(const Paths& inputs, Paths& outputs)
{
    outputs.clear();
    for (const auto& new_pth : inputs) {
        bool duplicate = false;
        // if all points of new path exist on some of the old paths, path is considered duplicate
        for (const auto& old_pth : outputs) {
            bool all_points_exists = true;
            for (const auto pt1 : new_pth) {
                bool pointExists = false;
                for (const auto pt2 : old_pth) {
                    if (DistanceSqrd(pt1, pt2) < SAME_POINT_TOL_SQRD_SCALED) {
                        pointExists = true;
                        break;
                    }
                }
                if (!pointExists) {
                    all_points_exists = false;
                    break;
                }
            }
            if (all_points_exists) {
                duplicate = true;
                break;
            }
        }

        if (!duplicate && !new_pth.empty()) {
            outputs.push_back(new_pth);
        }
    }
}

void ConnectPaths(Paths input, Paths& output)
{
    output.clear();
    bool newPath = true;
    Path joined;
    while (!input.empty()) {
        if (newPath) {
            if (!joined.empty()) {
                output.push_back(joined);
            }
            joined.clear();
            for (auto pt : input.front()) {
                joined.push_back(pt);
            }
            input.erase(input.begin());
            newPath = false;
        }
        bool anyMatch = false;
        for (size_t i = 0; i < input.size(); i++) {
            Path& n = input.at(i);
            if (DistanceSqrd(n.front(), joined.back()) < SAME_POINT_TOL_SQRD_SCALED) {
                for (auto pt : n) {
                    joined.push_back(pt);
                }
                input.erase(input.begin() + i);
                anyMatch = true;
                break;
            }
            else if (DistanceSqrd(n.back(), joined.back()) < SAME_POINT_TOL_SQRD_SCALED) {
                ReversePath(n);
                for (auto pt : n) {
                    joined.push_back(pt);
                }
                input.erase(input.begin() + i);
                anyMatch = true;
                break;
            }
            else if (DistanceSqrd(n.front(), joined.front()) < SAME_POINT_TOL_SQRD_SCALED) {
                for (auto pt : n) {
                    joined.insert(joined.begin(), pt);
                }
                input.erase(input.begin() + i);
                anyMatch = true;
                break;
            }
            else if (DistanceSqrd(n.back(), joined.front()) < SAME_POINT_TOL_SQRD_SCALED) {
                ReversePath(n);
                for (auto pt : n) {
                    joined.insert(joined.begin(), pt);
                }
                input.erase(input.begin() + i);
                anyMatch = true;
                break;
            }
        }
        if (!anyMatch) {
            newPath = true;
        }
    }
    if (!joined.empty()) {
        output.push_back(joined);
    }
}

// helper class for measuring performance
class PerfCounter
{
public:
    PerfCounter(string p_name)
    {
        name = p_name;
        count = 0;
        running = false;
        start_ticks = 0;
        total_ticks = 0;
    }
    inline void Start()
    {
#ifdef DEV_MODE
        start_ticks = clock();
        if (running) {
            cerr << "PerfCounter already running:" << name << endl;
        }
        running = true;
#endif
    }
    inline void Stop()
    {
#ifdef DEV_MODE
        if (!running) {
            cerr << "PerfCounter not running:" << name << endl;
        }
        total_ticks += clock() - start_ticks;
        start_ticks = clock();
        count++;
        running = false;
#endif
    }
    void DumpResults()
    {
        double total_time = double(total_ticks) / CLOCKS_PER_SEC;
        cout << "Perf: " << name.c_str() << " total_time: " << total_time
             << " sec, call_count:" << count << " per_call:" << double(total_time / count) << endl;
        start_ticks = clock();
        total_ticks = 0;
        count = 0;
    }

private:
    string name;
    clock_t start_ticks;
    clock_t total_ticks;
    size_t count;
    bool running = false;
};

PerfCounter Perf_ProcessPolyNode("ProcessPolyNode");
PerfCounter Perf_CalcCutAreaCirc("CalcCutArea");
PerfCounter Perf_CalcCutAreaClip("CalcCutAreaClip");
PerfCounter Perf_NextEngagePoint("NextEngagePoint");
PerfCounter Perf_PointIterations("PointIterations");
PerfCounter Perf_ExpandCleared("ExpandCleared");
PerfCounter Perf_DistanceToBoundary("DistanceToBoundary");
PerfCounter Perf_AppendToolPath("AppendToolPath");
PerfCounter Perf_IsAllowedToCutTrough("IsAllowedToCutTrough");
PerfCounter Perf_IsClearPath("IsClearPath");

//***********************************
// Cleared area bounding support
//***********************************
class ClearedArea
{
public:
    ClearedArea(ClipperLib::cInt p_toolRadiusScaled)
    {
        toolRadiusScaled = p_toolRadiusScaled;
    };

    void SetClearedPaths(const Paths& paths)
    {
        clearedPaths = paths;
        bboxPathsInvalid = true;
        bboxClippedInvalid = true;
    }
    void ExpandCleared(const Path toClearToolPath)
    {
        if (toClearToolPath.empty()) {
            return;
        }
        Perf_ExpandCleared.Start();
        clipof.Clear();
        clipof.AddPath(toClearToolPath, JoinType::jtRound, EndType::etOpenRound);
        Paths toolCoverPoly;
        clipof.Execute(toolCoverPoly, toolRadiusScaled + 1);
        clip.Clear();
        clip.AddPaths(clearedPaths, PolyType::ptSubject, true);
        clip.AddPaths(toolCoverPoly, PolyType::ptClip, true);
        clip.Execute(ClipType::ctUnion, clearedPaths);
        CleanPolygons(clearedPaths);
        bboxPathsInvalid = true;
        bboxClippedInvalid = true;
        Perf_ExpandCleared.Stop();
    }

    // gets the path sections inside the ext. tool bounding box
    Paths& GetBoundedClearedPaths(const IntPoint& toolPos)
    {
        BoundBox toolBB(toolPos, toolRadiusScaled);
        if (!bboxPathsInvalid && clearedBBPathsInFocus.Contains(toolBB)) {
            return clearedBoundedPaths;
        }
        ClipperLib::cInt delta = focusBBFactor1 * toolRadiusScaled;
        clearedBBPathsInFocus.SetFirstPoint(IntPoint(toolPos.X - delta, toolPos.Y - delta));
        clearedBBPathsInFocus.AddPoint(IntPoint(toolPos.X + delta, toolPos.Y + delta));

        BoundBox bb(toolPos, focusBBFactor2 * toolRadiusScaled);
        clearedBoundedPaths.clear();
        for (const auto& pth : clearedPaths) {
            if (pth.size() < 2) {
                continue;
            }
            Path bPath;
            size_t size = pth.size();
            for (size_t i = 0; i < size + 1; i++) {
                IntPoint last = (i > 0 ? pth[i - 1] : pth.back());
                IntPoint next = i < size ? pth[i] : pth.front();
                BoundBox ptbox(last, next);
                if (ptbox.CollidesWith(bb)) {
                    if (bPath.empty() || bPath.back() != last) {
                        bPath.push_back(last);
                    }
                    bPath.push_back(next);
                }
                else {
                    if (!bPath.empty()) {
                        clearedBoundedPaths.push_back(bPath);
                        bPath.clear();
                    }
                }
            }
            if (!bPath.empty()) {
                clearedBoundedPaths.push_back(bPath);
                bPath.clear();
            }
        }
        bboxPathsInvalid = false;
        return clearedBoundedPaths;
    }

    // get cleared area/poly bounded to toolbox
    Paths& GetBoundedClearedAreaClipped(const IntPoint& toolPos)
    {
        BoundBox toolBB(toolPos, toolRadiusScaled);
        if (!bboxClippedInvalid && clearedBBClippedInFocus.Contains(toolBB)) {
            return clearedBoundedClipped;
        }
        ClipperLib::cInt delta = focusBBFactor1 * toolRadiusScaled;
        clearedBBClippedInFocus.SetFirstPoint(IntPoint(toolPos.X - delta, toolPos.Y - delta));
        clearedBBClippedInFocus.AddPoint(IntPoint(toolPos.X + delta, toolPos.Y + delta));

        // a little larger area is bounded than checked
        ClipperLib::cInt delta2 = focusBBFactor2 * toolRadiusScaled;
        Path bbPath;
        bbPath.push_back(IntPoint(toolPos.X - delta2, toolPos.Y - delta2));
        bbPath.push_back(IntPoint(toolPos.X + delta2, toolPos.Y - delta2));
        bbPath.push_back(IntPoint(toolPos.X + delta2, toolPos.Y + delta2));
        bbPath.push_back(IntPoint(toolPos.X - delta2, toolPos.Y + delta2));
        clip.Clear();
        clip.AddPath(bbPath, PolyType::ptSubject, true);
        clip.AddPaths(clearedPaths, PolyType::ptClip, true);
        clip.Execute(ClipType::ctIntersection, clearedBoundedClipped);
        bboxClippedInvalid = false;
        return clearedBoundedClipped;
    }

    // get full cleared area
    Paths& GetCleared()
    {
        return clearedPaths;
    }

private:
    Clipper clip;
    ClipperOffset clipof;
    Paths clearedPaths;
    Paths clearedBoundedClipped;
    Paths clearedBoundedPaths;

    ClipperLib::cInt toolRadiusScaled;
    BoundBox clearedBBClippedInFocus;
    BoundBox clearedBBPathsInFocus;

    bool bboxClippedInvalid = false;
    bool bboxPathsInvalid = false;
    // size of the focus BB
    const ClipperLib::cInt focusBBFactor1 = 8;
    const ClipperLib::cInt focusBBFactor2 = 9;
};

//***************************************
// Linear Interpolation - area vs angle
//***************************************
class Interpolation
{
public:
    const double MIN_ANGLE = -std::numbers::pi / 4;
    const double MAX_ANGLE = std::numbers::pi / 4;

    void clear()
    {
        m_min.reset();
        m_max.reset();
    }
    bool bothSides()
    {
        return m_min && m_max && m_min->second < 0 && m_max->second >= 0;
    }
    // adds point keeping the incremental order of areas for interpolation to work correctly
    void addPoint(double error, std::pair<double, IntPoint> angle, bool allowSkip = false)
    {
        if (!m_min) {
            m_min = {angle, error};
        }
        else if (!m_max) {
            m_max = {angle, error};
            if (m_min->second > m_max->second) {
                auto tmp = m_min;
                m_min = m_max;
                m_max = tmp;
            }
        }
        else if (bothSides()) {
            if (error < 0) {
                m_min = {angle, error};
            }
            else {
                m_max = {angle, error};
            }
        }
        else {
            if (allowSkip && abs(error) > abs(m_min->second) && abs(error) > abs(m_max->second)) {
                return;
            }
            if (abs(m_min->second) > abs(m_max->second)) {
                m_min.reset();
            }
            else {
                m_max.reset();
            }
            addPoint(error, angle);
        }
    }

    double interpolateAngle()
    {
        if (!m_min) {
            return MIN_ANGLE;
        }

        if (!m_max) {
            return MAX_ANGLE;
        }
        double p = (0 - m_min->second) / (m_max->second - m_min->second);

        // Ensure search is sufficiently efficient -- this is a compromise
        // between binary search (p = 0.5, guaranteed search completion in log
        // time) and following linear interpolation completely (often faster
        // since area cut is locally linear in movement angle)
        const double minInterp = .2;
        p = max(min(p, 1 - minInterp), minInterp);

        return m_min->first.first * (1 - p) + m_max->first.first * p;
    }

    double clampAngle(double angle)
    {
        return max(min(angle, MAX_ANGLE), MIN_ANGLE);
    }

    size_t getPointCount()
    {
        return (m_min ? 1 : 0) + (m_max ? 1 : 0);
    }

public:
    // {{angle, clipper point}, error}
    std::optional<std::pair<std::pair<double, IntPoint>, double>> m_min;
    std::optional<std::pair<std::pair<double, IntPoint>, double>> m_max;
};

//***************************************
// Engage Point
//***************************************

class EngagePoint
{
public:
    struct EngageState
    {
        size_t currentPathIndex = 0;
        size_t currentSegmentIndex = 0;
        double segmentPos = 0;
        double totalDistance = 0;
        double currentPathLength = 0;
        int passes = 0;

        double metric = 0;  // engage point metric

        bool operator<(const EngageState& other) const
        {
            return (metric < other.metric);
        }
    };
    EngagePoint(const Paths& p_toolBoundPaths)
    {
        SetPaths(p_toolBoundPaths);

        state.currentPathIndex = 0;
        state.currentSegmentIndex = 0;
        state.segmentPos = 0;
        state.totalDistance = 0;
        calculateCurrentPathLength();
    }

    void SetPaths(const Paths& paths)
    {
        toolBoundPaths = paths;
        state.currentPathIndex = 0;
        state.currentSegmentIndex = 0;
        state.segmentPos = 0;
        state.totalDistance = 0;
        state.passes = 0;
        calculateCurrentPathLength();
    }

    EngageState GetState()
    {
        return state;
    }

    void SetState(const EngageState& new_state)
    {
        state = new_state;
    }

    void ResetPasses()
    {
        state.passes = 0;
    }
    void moveToClosestPoint(const IntPoint& pt, double step)
    {

        Path result;
        IntPoint current = pt;
        // chain paths according to distance in between
        Paths toChain = toolBoundPaths;
        toolBoundPaths.clear();
        // if(toChain.size()>0) {
        // 	toolBoundPaths.push_back(toChain.front());
        // 	toChain.erase(toChain.begin());
        // }
        while (PopPathWithClosestPoint(toChain, current, result)) {
            toolBoundPaths.push_back(result);
            if (!result.empty()) {
                current = result.back();
            }
        }

        double minDistSq = __DBL_MAX__;
        size_t minPathIndex = state.currentPathIndex;
        size_t minSegmentIndex = state.currentSegmentIndex;
        double minSegmentPos = state.segmentPos;
        state.totalDistance = 0;
        for (;;) {
            while (moveForward(step)) {
                double distSqrd = DistanceSqrd(pt, getCurrentPoint());
                if (distSqrd < minDistSq) {
                    minDistSq = distSqrd;
                    minPathIndex = state.currentPathIndex;
                    minSegmentIndex = state.currentSegmentIndex;
                    minSegmentPos = state.segmentPos;
                }
            }
            if (!nextPath()) {
                break;
            }
        }
        state.currentPathIndex = minPathIndex;
        state.currentSegmentIndex = minSegmentIndex;
        state.segmentPos = minSegmentPos;
        calculateCurrentPathLength();
        ResetPasses();
    }
    bool nextEngagePoint(
        Adaptive2d* parent,
        ClearedArea& clearedArea,
        double step,
        double minCutArea,
        double maxCutArea,
        int maxPases = 2
    )
    {
        Perf_NextEngagePoint.Start();
        double prevArea = 0;  // we want to make sure that we catch the point where the area is on
                              // raising slope
        IntPoint initialPoint(-1000000000, -1000000000);
        for (;;) {
            if (!moveForward(step)) {
                if (!nextPath()) {
                    state.passes++;
                    if (state.passes >= maxPases) {
                        Perf_NextEngagePoint.Stop();
                        return false;  // nothing more to cut
                    }
                    prevArea = 0;
                }
            }
            IntPoint cpt = getCurrentPoint();
            double area = parent->CalcCutArea(clip, initialPoint, cpt, clearedArea);
            if (area > minCutArea && area < maxCutArea && area > prevArea) {
                Perf_NextEngagePoint.Stop();
                return true;
            }
            prevArea = area;
        }
    }
    IntPoint getCurrentPoint()
    {
        const Path* pth = &toolBoundPaths.at(state.currentPathIndex);
        const IntPoint* p1 = &pth->at(
            state.currentSegmentIndex > 0 ? state.currentSegmentIndex - 1 : pth->size() - 1
        );
        const IntPoint* p2 = &pth->at(state.currentSegmentIndex);
        double segLength = sqrt(DistanceSqrd(*p1, *p2));
        return IntPoint(
            long(p1->X + state.segmentPos * double(p2->X - p1->X) / segLength),
            long(p1->Y + state.segmentPos * double(p2->Y - p1->Y) / segLength)
        );
    }

    DoublePoint getCurrentDir()
    {
        const Path* pth = &toolBoundPaths.at(state.currentPathIndex);
        const IntPoint* p1 = &pth->at(
            state.currentSegmentIndex > 0 ? state.currentSegmentIndex - 1 : pth->size() - 1
        );
        const IntPoint* p2 = &pth->at(state.currentSegmentIndex);
        double segLength = sqrt(DistanceSqrd(*p1, *p2));
        return DoublePoint(double(p2->X - p1->X) / segLength, double(p2->Y - p1->Y) / segLength);
    }

    bool moveForward(double distance)
    {
        const Path* pth = &toolBoundPaths.at(state.currentPathIndex);
        if (distance < NTOL) {
            throw std::invalid_argument("distance must be positive");
        }
        state.totalDistance += distance;
        double segmentLength = currentSegmentLength();
        while (state.segmentPos + distance > segmentLength) {
            state.currentSegmentIndex++;
            if (state.currentSegmentIndex >= pth->size()) {
                state.currentSegmentIndex = 0;
            }
            distance = distance - (segmentLength - state.segmentPos);
            state.segmentPos = 0;
            segmentLength = currentSegmentLength();
        }
        state.segmentPos += distance;
        return state.totalDistance <= 1.2 * state.currentPathLength;
    }

    bool nextPath()
    {
        state.currentPathIndex++;
        state.currentSegmentIndex = 0;
        state.segmentPos = 0;
        state.totalDistance = 0;
        if (state.currentPathIndex >= toolBoundPaths.size()) {
            state.currentPathIndex = 0;
            calculateCurrentPathLength();
            return false;
        }
        calculateCurrentPathLength();
        return true;
    }

private:
    Paths toolBoundPaths;
    EngageState state;
    Clipper clip;
    void calculateCurrentPathLength()
    {
        const Path* pth = &toolBoundPaths.at(state.currentPathIndex);
        size_t size = pth->size();
        state.currentPathLength = 0;
        for (size_t i = 0; i < size; i++) {
            const IntPoint* p1 = &pth->at(i > 0 ? i - 1 : size - 1);
            const IntPoint* p2 = &pth->at(i);
            state.currentPathLength += sqrt(DistanceSqrd(*p1, *p2));
        }
    }

    double currentSegmentLength()
    {
        const Path* pth = &toolBoundPaths.at(state.currentPathIndex);
        const IntPoint* p1 = &pth->at(
            state.currentSegmentIndex > 0 ? state.currentSegmentIndex - 1 : pth->size() - 1
        );
        const IntPoint* p2 = &pth->at(state.currentSegmentIndex);
        return sqrt(DistanceSqrd(*p1, *p2));
    }
};

//***************************************
// Adaptive2d main class - implementation
//***************************************

Adaptive2d::Adaptive2d()
{}

double Adaptive2d::CalcCutArea(
    Clipper& clip,
    const IntPoint& c1,
    const IntPoint& c2,
    ClearedArea& clearedArea,
    bool preventConventional
)
{

    double dist = DistanceSqrd(c1, c2);
    if (dist < NTOL) {
        return 0;
    }

    Perf_CalcCutAreaCirc.Start();

    /// new alg
    double rsqrd = toolRadiusScaled * toolRadiusScaled;
    double area = 0;
    Paths interPaths;
    IntPoint clp;                // to hold closest point
    vector<DoublePoint> inters;  // to hold intersection results
    BoundBox c2BB(c2, toolRadiusScaled);
    BoundBox c1BB(c1, toolRadiusScaled);
    Paths& clearedBounded = clearedArea.GetBoundedClearedAreaClipped(c2);
    for (const Path& path : clearedBounded) {
        size_t size = path.size();
        if (size == 0) {
            continue;
        }

        //** bound box check
        // construct bound box for path
        BoundBox pathBB(path.front());
        for (const auto& pt : path) {
            pathBB.AddPoint(pt);
        }
        if (!c2BB.CollidesWith(c2)) {
            continue;  // this path cannot colide with tool
        }
        //** end of BB check

        size_t curPtIndex = 0;
        bool found = false;
        // step 1: we find the starting point on the cleared path that is outside new tool shape
        // (c2)
        for (size_t i = 0; i < size; i++) {
            if (DistanceSqrd(path[curPtIndex], c2) > rsqrd) {
                found = true;
                break;
            }
            curPtIndex++;
            if (curPtIndex >= size) {
                curPtIndex = 0;
            }
        }
        if (!found) {
            continue;  // try another path
        }

        // step 2: iterate through path from starting point and find the part of the path inside the
        // c2
        size_t prevPtIndex = curPtIndex;
        Path* interPath = NULL;
        bool prev_inside = false;
        const IntPoint* p1 = &path[prevPtIndex];
        double par;  // to hold parameter output
        for (size_t i = 0; i < size; i++) {
            curPtIndex++;
            if (curPtIndex >= size) {
                curPtIndex = 0;
            }
            const IntPoint* p2 = &path[curPtIndex];
            BoundBox segBB(*p1, *p2);
            if (!prev_inside) {  // prev state: outside, find first point inside C2
                if (segBB.CollidesWith(c2BB)
                    && DistancePointToLineSegSquared(*p1, *p2, c2, clp, par)
                        <= rsqrd) {  // current segment inside, start
                    prev_inside = true;
                    interPaths.push_back(Path());
                    if (interPaths.size() > 1) {
                        break;  // we will use poly clipping alg. if there are more intersecting
                                // paths
                    }
                    interPath = &interPaths.back();
                    // current segment inside c2, prev point outside, find intersection:
                    if (Line2CircleIntersect(c2, toolRadiusScaled, *p1, *p2, inters)) {
                        interPath->push_back(IntPoint(long(inters[0].X), long(inters[0].Y)));
                        if (inters.size() > 1) {
                            interPath->push_back(IntPoint(long(inters[1].X), long(inters[1].Y)));
                            prev_inside = false;
                        }
                        else {
                            interPath->push_back(IntPoint(*p2));
                        }
                    }
                    else {  // no intersection - must be edge case, add p2
                        interPath->push_back(IntPoint(*p2));
                    }
                }
            }
            else if (interPath != NULL) {                // state: inside
                if ((DistanceSqrd(c2, *p2) <= rsqrd)) {  // next point still inside, add it and
                                                         // continue, no state change
                    interPath->push_back(IntPoint(*p2));
                }
                else {  // prev point inside, current point outside, find intersection
                    if (Line2CircleIntersect(c2, toolRadiusScaled, *p1, *p2, inters)) {
                        if (inters.size() > 1) {
                            interPath->push_back(IntPoint(long(inters[1].X), long(inters[1].Y)));
                        }
                        else {
                            interPath->push_back(IntPoint(long(inters[0].X), long(inters[0].Y)));
                        }
                    }
                    prev_inside = false;
                }
            }
            prevPtIndex = curPtIndex;
            p1 = p2;
        }
        if (interPaths.size() > 1) {
            break;  // we will use poly clipping alg. if there are more intersecting paths with the
                    // tool (rare case)
        }
    }
    Perf_CalcCutAreaCirc.Stop();
    if (interPaths.size() == 1 && interPaths.front().size() > 1) {
        Perf_CalcCutAreaCirc.Start();
        Path* interPath = &interPaths.front();
        // interPath - now contains the part of cleared path inside the C2
        size_t ipc2_size = interPath->size();
        const IntPoint& fpc2 = interPath->front();  // first point
        const IntPoint& lpc2 = interPath->back();   // last point
        // path length
        double interPathLen = 0;
        for (size_t j = 1; j < ipc2_size; j++) {
            interPathLen += sqrt(DistanceSqrd(interPath->at(j - 1), interPath->at(j)));
        }

        Paths inPaths;
        inPaths.reserve(200);
        inPaths.push_back(*interPath);
        Path pthToSubtract;
        pthToSubtract.push_back(fpc2);

        double fi1 = atan2(fpc2.Y - c2.Y, fpc2.X - c2.X);
        double fi2 = atan2(lpc2.Y - c2.Y, lpc2.X - c2.X);
        double minFi = fi1;
        double maxFi = fi2;
        if (maxFi < minFi) {
            maxFi += 2 * std::numbers::pi;
        }

        if (preventConventional && interPathLen >= MIN_STEP_CLIPPER) {
            // detect conventional mode cut - we want only climb mode
            IntPoint midPoint(
                long(c2.X + toolRadiusScaled * cos(0.5 * (maxFi + minFi))),
                long(c2.Y + toolRadiusScaled * sin(0.5 * (maxFi + minFi)))
            );
            if (PointSideOfLine(c1, c2, midPoint) < 0) {
                area = __DBL_MAX__;
                Perf_CalcCutAreaCirc.Stop();
                // #ifdef DEV_MODE
                // 	cout << "Break: @(" << double(c2.X)/scaleFactor << "," <<
                // double(c2.Y)/scaleFactor  << ") conventional mode" << endl; #endif
                return area;
            }
        }

        double scanDistance = 2.5 * toolRadiusScaled;
        // stepping through path discretized to stepDistance
        double stepDistance = min(double(MIN_STEP_CLIPPER), interPathLen / 24) + 1;
        const IntPoint* prevPt = &interPath->front();
        double distance = 0;
        for (size_t j = 1; j < ipc2_size; j++) {
            const IntPoint* cpt = &interPath->at(j);
            double segLen = sqrt(DistanceSqrd(*cpt, *prevPt));
            if (segLen < NTOL) {
                continue;  // skip point - segment too short
            }
            for (double pos_unclamped = 0.0; pos_unclamped < segLen + stepDistance;
                 pos_unclamped += stepDistance) {
                double pos = pos_unclamped;
                if (pos > segLen) {
                    distance += stepDistance - (pos - segLen);
                    pos = segLen;  // make sure we get exact end point
                }
                else {
                    distance += stepDistance;
                }
                double dx = double(cpt->X - prevPt->X);
                double dy = double(cpt->Y - prevPt->Y);
                IntPoint segPoint(
                    long(prevPt->X + dx * pos / segLen),
                    long(prevPt->Y + dy * pos / segLen)
                );
                IntPoint scanPoint(
                    long(c2.X + scanDistance * cos(minFi + distance * (maxFi - minFi) / interPathLen)),
                    long(c2.Y + scanDistance * sin(minFi + distance * (maxFi - minFi) / interPathLen))
                );

                IntPoint intersC2(segPoint.X, segPoint.Y);
                IntPoint intersC1(segPoint.X, segPoint.Y);

                // there should be intersection with C2
                if (Line2CircleIntersect(c2, toolRadiusScaled, segPoint, scanPoint, inters)) {
                    if (inters.size() > 1) {
                        intersC2.X = long(inters[1].X);
                        intersC2.Y = long(inters[1].Y);
                    }
                    else {
                        intersC2.X = long(inters[0].X);
                        intersC2.Y = long(inters[0].Y);
                    }
                }
                else {
                    pthToSubtract.push_back(segPoint);
                }

                if (Line2CircleIntersect(c1, toolRadiusScaled, segPoint, scanPoint, inters)) {
                    if (inters.size() > 1) {
                        intersC1.X = long(inters[1].X);
                        intersC1.Y = long(inters[1].Y);
                    }
                    else {
                        intersC1.X = long(inters[0].X);
                        intersC1.Y = long(inters[0].Y);
                    }
                    if (DistanceSqrd(segPoint, intersC2) < DistanceSqrd(segPoint, intersC1)) {
                        pthToSubtract.push_back(intersC2);
                    }
                    else {
                        pthToSubtract.push_back(intersC1);
                    }
                }
                else {  // add the segpoint if no intersection with C1
                    pthToSubtract.push_back(segPoint);
                }
            }
            prevPt = cpt;
        }

        pthToSubtract.push_back(lpc2);  // add last point
        pthToSubtract.push_back(c2);

        double segArea = Area(pthToSubtract);
        double A = (maxFi - minFi) * rsqrd / 2;  // sector area
        area += A - fabs(segArea);
        Perf_CalcCutAreaCirc.Stop();
    }
    else if (interPaths.size() > 1) {
        Perf_CalcCutAreaClip.Start();
        // old way of calculating cut area based on polygon clipping
        // used in case when there are multiple intersections of tool with cleared poly (very rare
        // case, but important)
        // 1. find difference between old and new tool shape
        Path oldTool;
        Path newTool;
        TranslatePath(toolGeometry, oldTool, c1);
        TranslatePath(toolGeometry, newTool, c2);
        clip.Clear();
        clip.AddPath(newTool, PolyType::ptSubject, true);
        clip.AddPath(oldTool, PolyType::ptClip, true);
        Paths toolDiff;
        clip.Execute(ClipType::ctDifference, toolDiff);

        // 2. difference to cleared
        clip.Clear();
        clip.AddPaths(toolDiff, PolyType::ptSubject, true);
        clip.AddPaths(clearedBounded, PolyType::ptClip, true);
        Paths cutAreaPoly;
        clip.Execute(ClipType::ctDifference, cutAreaPoly);

        // calculate resulting area
        area = 0;
        for (Path& path : cutAreaPoly) {
            area += fabs(Area(path));
        }
        Perf_CalcCutAreaClip.Stop();
    }
    return area;
}

void Adaptive2d::ApplyStockToLeave(Paths& inputPaths)
{
    ClipperOffset clipof;
    if (stockToLeave > NTOL) {
        clipof.Clear();
        clipof.AddPaths(inputPaths, JoinType::jtRound, EndType::etClosedPolygon);
        if (opType == OperationType::otClearingOutside
            || opType == OperationType::otProfilingOutside) {
            clipof.Execute(inputPaths, stockToLeave * scaleFactor);
        }
        else {
            clipof.Execute(inputPaths, -stockToLeave * scaleFactor);
        }
    }
    else {
        // fix for clipper glitches
        clipof.Clear();
        clipof.AddPaths(inputPaths, JoinType::jtRound, EndType::etClosedPolygon);
        clipof.Execute(inputPaths, -1);
        filterCloseValues(inputPaths);
        clipof.Clear();
        clipof.AddPaths(inputPaths, JoinType::jtRound, EndType::etClosedPolygon);
        clipof.Execute(inputPaths, 1);
        filterCloseValues(inputPaths);
    }
}

//********************************************
// Adaptive2d - Execute
//********************************************

std::list<AdaptiveOutput> Adaptive2d::Execute(
    const DPaths& stockPaths,
    const DPaths& paths,
    std::function<bool(TPaths)> progressCallbackFn
)
{
    //**********************************
    // Initializations
    //**********************************

    // keep the tolerance in workable range
    tolerance = max(tolerance, 0.01);
    tolerance = min(tolerance, 1.0);

    // 1/"tolerance" = number of min-size adaptive steps per stepover
    scaleFactor = MIN_STEP_CLIPPER / tolerance / min(1.0, stepOverFactor * toolDiameter);

    current_region = 0;
    cout << "Tool Diameter: " << toolDiameter << endl;
    cout << "Min step size: " << round(MIN_STEP_CLIPPER / scaleFactor * 1000 * 10) / 10 << " um"
         << endl;
    cout << flush;

    toolRadiusScaled = long(toolDiameter * scaleFactor / 2);
    stepOverScaled = toolRadiusScaled * stepOverFactor;
    progressCallback = &progressCallbackFn;
    lastProgressTime = clock();
    stopProcessing = false;

    if (helixRampTargetDiameter < NTOL) {
        helixRampTargetDiameter = toolDiameter;
    }
    helixRampTargetDiameter = min(helixRampTargetDiameter, toolDiameter);
    helixRampMinDiameter = max(helixRampMinDiameter, toolDiameter / 8);
    helixRampTargetDiameter = max(helixRampTargetDiameter, helixRampMinDiameter);

    helixRampMaxRadiusScaled = long(helixRampTargetDiameter * scaleFactor / 2);
    helixRampMinRadiusScaled = long(helixRampMinDiameter * scaleFactor / 2);
    if (finishingProfile) {
        finishPassOffsetScaled = long(stepOverScaled / 10);
    }

    ClipperOffset clipof;
    Clipper clip;

    // generate tool shape
    clipof.Clear();
    Path p;
    p << IntPoint(0, 0);
    clipof.AddPath(p, JoinType::jtRound, EndType::etOpenRound);
    Paths toolGeometryPaths;
    clipof.Execute(toolGeometryPaths, toolRadiusScaled);
    toolGeometry = toolGeometryPaths[0];
    // calculate reference area
    Path slotCut;
    TranslatePath(toolGeometryPaths[0], slotCut, IntPoint(toolRadiusScaled / 2, 0));
    clip.Clear();
    clip.AddPath(toolGeometryPaths[0], PolyType::ptSubject, true);
    clip.AddPath(slotCut, PolyType::ptClip, true);
    Paths crossing;
    clip.Execute(ClipType::ctDifference, crossing);
    referenceCutArea = fabs(Area(crossing[0]));
    optimalCutAreaPD = 2 * stepOverFactor * referenceCutArea / toolRadiusScaled;
#ifdef DEV_MODE
    cout << "optimalCutAreaPD:" << optimalCutAreaPD << " scaleFactor:" << scaleFactor
         << " toolRadiusScaled:" << toolRadiusScaled
         << " helixRampMaxRadiusScaled:" << helixRampMaxRadiusScaled << endl;
#endif
    //******************************
    // Convert input paths to clipper
    //******************************
    Paths converted;
    for (size_t i = 0; i < paths.size(); i++) {
        Path cpth;
        for (size_t j = 0; j < paths[i].size(); j++) {
            std::pair<double, double> pt = paths[i][j];
            cpth.push_back(IntPoint(long(pt.first * scaleFactor), long(pt.second * scaleFactor)));
        }
        Path cpth2;
        CleanPath(cpth, cpth2, FINISHING_CLEAN_PATH_TOLERANCE);
        converted.push_back(cpth2);
    }

    DeduplicatePaths(converted, inputPaths);
    ConnectPaths(inputPaths, inputPaths);
    SimplifyPolygons(inputPaths);
    ApplyStockToLeave(inputPaths);

    //*************************
    // convert stock paths
    //*************************
    stockInputPaths.clear();
    for (size_t i = 0; i < stockPaths.size(); i++) {
        Path cpth;
        for (size_t j = 0; j < stockPaths[i].size(); j++) {
            std::pair<double, double> pt = stockPaths[i][j];
            cpth.push_back(IntPoint(long(pt.first * scaleFactor), long(pt.second * scaleFactor)));
        }

        stockInputPaths.push_back(cpth);
    }

    SimplifyPolygons(stockInputPaths);
    // CleanPolygons(stockInputPaths,0.707);

    //***************************************
    //	Resolve hierarchy and run processing
    //***************************************
    double cornerRoundingOffset = 0.15 * toolRadiusScaled / 2;
    if (opType == OperationType::otClearingInside || opType == OperationType::otClearingOutside) {

        // prepare stock boundary overshooted paths
        clipof.Clear();
        clipof.AddPaths(stockInputPaths, JoinType::jtSquare, EndType::etClosedPolygon);
        double overshootDistance = 4 * toolRadiusScaled + stockToLeave * scaleFactor;
        if (forceInsideOut) {
            overshootDistance = 0;
        }
        Paths stockOvershoot;
        clipof.Execute(stockOvershoot, overshootDistance);
        ReversePaths(stockOvershoot);

        if (opType == OperationType::otClearingOutside) {
            // add stock paths, with overshooting
            for (const auto& p : stockOvershoot) {
                inputPaths.push_back(p);
            }
        }
        else if (opType == OperationType::otClearingInside) {
            // potential TODO: check if there are open paths, and try to close it through
            // overshooted stock boundary
        }

        clipof.Clear();
        clipof.AddPaths(inputPaths, JoinType::jtRound, EndType::etClosedPolygon);
        Paths paths;
        clipof.Execute(paths, -toolRadiusScaled - finishPassOffsetScaled - cornerRoundingOffset);
        for (const auto& current : paths) {
            int nesting = getPathNestingLevel(current, paths);
            if (nesting % 2 != 0 && (polyTreeNestingLimit == 0 || nesting <= polyTreeNestingLimit)) {
                Paths toolBoundPaths;
                toolBoundPaths.push_back(current);
                if (polyTreeNestingLimit != nesting) {
                    appendDirectChildPaths(toolBoundPaths, current, paths);
                }

                // offset back outwards - corner rounding
                clipof.Clear();
                clipof.AddPaths(toolBoundPaths, JoinType::jtRound, EndType::etClosedPolygon);
                clipof.Execute(toolBoundPaths, cornerRoundingOffset);

                // restore original bound paths
                // bounding paths - i.e. area that must be cleared inside
                // it's not the same as input paths due to filtering (nesting logic) and corner
                // rounding
                Paths boundPaths;
                clipof.Clear();
                clipof.AddPaths(toolBoundPaths, JoinType::jtRound, EndType::etClosedPolygon);
                clipof.Execute(boundPaths, toolRadiusScaled + finishPassOffsetScaled);
                ProcessPolyNode(boundPaths, toolBoundPaths);
            }
        }
    }

    if (opType == OperationType::otProfilingInside || opType == OperationType::otProfilingOutside) {
        double offset = opType == OperationType::otProfilingInside
            ? -2 * (helixRampMaxRadiusScaled + toolRadiusScaled) - MIN_STEP_CLIPPER
            : 2 * (helixRampMaxRadiusScaled + toolRadiusScaled) + MIN_STEP_CLIPPER;
        for (const auto& current : inputPaths) {
            int nesting = getPathNestingLevel(current, inputPaths);
            if (nesting % 2 != 0 && (polyTreeNestingLimit == 0 || nesting <= polyTreeNestingLimit)) {
                Paths profilePaths;
                profilePaths.push_back(current);
                if (polyTreeNestingLimit != nesting) {
                    appendDirectChildPaths(profilePaths, current, inputPaths);
                }
                for (size_t i = 0; i < profilePaths.size(); i++) {
                    double efOffset = i == 0 ? offset : -offset;
                    clipof.Clear();
                    clipof.AddPath(profilePaths[i], JoinType::jtSquare, EndType::etClosedPolygon);
                    Paths off1;
                    clipof.Execute(off1, efOffset);
                    // make poly between original path and offset path
                    Paths boundPaths;
                    clip.Clear();
                    if (efOffset < 0) {
                        clip.AddPath(profilePaths[i], PolyType::ptSubject, true);
                        clip.AddPaths(off1, PolyType::ptClip, true);
                    }
                    else {
                        clip.AddPaths(off1, PolyType::ptSubject, true);
                        clip.AddPath(profilePaths[i], PolyType::ptClip, true);
                    }
                    clip.Execute(ClipType::ctDifference, boundPaths, PolyFillType::pftEvenOdd);

                    /** tool bounds */
                    Paths toolBoundPaths;
                    clipof.Clear();
                    clipof.AddPaths(boundPaths, JoinType::jtRound, EndType::etClosedPolygon);
                    clipof.Execute(
                        toolBoundPaths,
                        -toolRadiusScaled - finishPassOffsetScaled - cornerRoundingOffset
                    );

                    /** offset back outwards - corner rounding */
                    clipof.Clear();
                    clipof.AddPaths(toolBoundPaths, JoinType::jtRound, EndType::etClosedPolygon);
                    clipof.Execute(toolBoundPaths, cornerRoundingOffset);

                    // restore original bound paths
                    // bounding paths - i.e. area that must be cleared inside
                    // it's not the same as above due to corner rounding
                    clipof.Clear();
                    clipof.AddPaths(toolBoundPaths, JoinType::jtRound, EndType::etClosedPolygon);
                    clipof.Execute(boundPaths, toolRadiusScaled + finishPassOffsetScaled);

                    ProcessPolyNode(boundPaths, toolBoundPaths);
                }
            }
        }
    }
    return results;
}

bool Adaptive2d::FindEntryPoint(
    TPaths& progressPaths,
    const Paths& toolBoundPaths,
    const Paths& boundPaths,
    ClearedArea& clearedArea /*output-initial cleared area by helix*/,
    IntPoint& entryPoint /*output*/,
    IntPoint& toolPos,
    DoublePoint& toolDir,
    long& helixRadiusScaled
)
{
    Paths incOffset;
    Paths lastValidOffset;
    Clipper clip;
    ClipperOffset clipof;
    bool found = false;
    Paths clearedPaths;
    Paths checkPaths = toolBoundPaths;
    for (int iter = 0; iter < 10; iter++) {
        clipof.Clear();
        clipof.AddPaths(checkPaths, JoinType::jtSquare, EndType::etClosedPolygon);
        double step = MIN_STEP_CLIPPER;
        double currentDelta = -1;
        clipof.Execute(incOffset, currentDelta);
        while (!incOffset.empty()) {
            clipof.Execute(incOffset, currentDelta);
            if (!incOffset.empty()) {
                lastValidOffset = incOffset;
            }
            currentDelta -= step;
        }
        for (size_t i = 0; i < lastValidOffset.size(); i++) {
            if (!lastValidOffset[i].empty()) {
                entryPoint = Compute2DPolygonCentroid(lastValidOffset[i]);
                found = true;
                break;
            }
        }
        // check if the start point is in any of the holes
        // this may happen in case when toolBoundPaths are symmetric (boundary + holes)
        // we need to break simetry and try again
        for (size_t j = 0; j < checkPaths.size(); j++) {
            int pip = PointInPolygon(entryPoint, checkPaths[j]);
            if ((j == 0 && pip == 0) || (j > 0 && pip != 0)) {
                found = false;
                break;
            }
        }
        // check if helix fits
        const auto checkHelixFit = [&](long testHelixRadiusScaled) {
            clipof.Clear();
            Path p1;
            p1.push_back(entryPoint);
            clipof.AddPath(p1, JoinType::jtRound, EndType::etOpenRound);
            clipof.Execute(clearedPaths, (double)(testHelixRadiusScaled + toolRadiusScaled));
            CleanPolygons(clearedPaths);
            // we got first cleared area - check if it is crossing boundary
            clip.Clear();
            clip.AddPaths(clearedPaths, PolyType::ptSubject, true);
            clip.AddPaths(boundPaths, PolyType::ptClip, true);
            Paths crossing;
            clip.Execute(ClipType::ctDifference, crossing);

            return crossing.empty();
        };

        if (found) {
            // check that helix fits, and make initial polygon cleared by helix ramp
            if (!checkHelixFit(helixRampMinRadiusScaled)) {
                // min-size helix does not fit
                found = false;
            }
            else {
                // find the largest helix that fits
                // minSize = largest known fit; maxSize = largest possible fit
                long minSize = helixRampMinRadiusScaled;
                long maxSize = helixRampMaxRadiusScaled;
                while (minSize < maxSize) {
                    long testSize = (minSize + maxSize + 1) / 2;  // always testSize > minSize
                    if (checkHelixFit(testSize)) {
                        minSize = testSize;
                    }
                    else {
                        maxSize = testSize - 1;  // always maxSize >= minSize
                    }
                }
                helixRadiusScaled = minSize;
                checkHelixFit(helixRadiusScaled);  // set clearedPaths for final size
                clearedArea.SetClearedPaths(clearedPaths);
            }
        }

        if (!found) {  // break simetry and try again
            clip.Clear();
            clip.AddPaths(checkPaths, PolyType::ptSubject, true);
            auto bounds = clip.GetBounds();
            clip.Clear();
            Path rect;
            rect << IntPoint(bounds.left, bounds.bottom);
            rect << IntPoint(bounds.left, (bounds.top + bounds.bottom) / 2);
            rect << IntPoint((bounds.left + bounds.right) / 2, (bounds.top + bounds.bottom) / 2);
            rect << IntPoint((bounds.left + bounds.right) / 2, bounds.bottom);
            clip.AddPath(rect, PolyType::ptSubject, true);
            clip.AddPaths(checkPaths, PolyType::ptClip, true);
            clip.Execute(ClipType::ctIntersection, checkPaths);
        }
        if (found) {
            break;
        }
    }

    if (!found) {
        cerr << "Start point not found!" << endl;
    }
    if (found) {
        // visualize/progress for helix
        clipof.Clear();
        Path hp;
        hp << entryPoint;
        clipof.AddPath(hp, JoinType::jtRound, EndType::etOpenRound);
        Paths hps;
        clipof.Execute(hps, helixRadiusScaled);
        AddPathsToProgress(progressPaths, hps);

        toolPos = IntPoint(entryPoint.X, entryPoint.Y - helixRadiusScaled);
        toolDir = DoublePoint(1.0, 0.0);
    }
    return found;
}

bool Adaptive2d::FindEntryPointOutside(
    TPaths& progressPaths,
    const Paths& toolBoundPaths,
    const Paths& boundPaths,
    ClearedArea& clearedArea /*output-initial cleared area by helix*/,
    IntPoint& entryPoint /*output*/,
    IntPoint& toolPos,
    DoublePoint& toolDir
)
{

    UNUSED(progressPaths);  // to silence compiler warning
    UNUSED(boundPaths);     // to silence compiler warning

    Clipper clip;
    ClipperOffset clipof;
    Paths clearedPaths;
    // check if boundary shape to cut is outside the stock
    for (const auto& pth : toolBoundPaths) {
        for (size_t i = 0; i < pth.size(); i++) {
            IntPoint checkPoint = pth[i];
            IntPoint lastPoint = i > 0 ? pth[i - 1] : pth.back();
            // if point is outside the stock
            if (PointInPolygon(checkPoint, stockInputPaths.front()) == 0) {

                clipof.Clear();
                clipof.AddPaths(stockInputPaths, JoinType::jtSquare, EndType::etClosedPolygon);
                clipof.Execute(clearedPaths, 1000 * toolRadiusScaled);

                clip.Clear();
                clip.AddPaths(clearedPaths, PolyType::ptSubject, true);
                clip.AddPaths(stockInputPaths, PolyType::ptClip, true);
                clip.Execute(ClipType::ctDifference, clearedPaths);
                CleanPolygons(clearedPaths);
                SimplifyPolygons(clearedPaths);
                clearedArea.SetClearedPaths(clearedPaths);
                entryPoint = checkPoint;
                toolPos = entryPoint;
                // find tool dir
                double len = sqrt(DistanceSqrd(lastPoint, checkPoint));
                toolDir = DoublePoint(
                    (checkPoint.X - lastPoint.X) / len,
                    (checkPoint.Y - lastPoint.Y) / len
                );
                return true;
            }
        }
    }
    return false;
}

//************************************************************
//  IsClearPath - returns true if path is clear from obstacles
//***********************************************************
bool Adaptive2d::IsClearPath(const Path& tp, ClearedArea& cleared, double safetyClearance)
{
    Perf_IsClearPath.Start();
    Clipper clip;
    ClipperOffset clipof;
    clipof.AddPath(tp, JoinType::jtRound, EndType::etOpenRound);
    Paths toolShape;
    clipof.Execute(toolShape, toolRadiusScaled + safetyClearance);
    clip.AddPaths(toolShape, PolyType::ptSubject, true);
    clip.AddPaths(cleared.GetCleared(), PolyType::ptClip, true);
    Paths crossing;
    clip.Execute(ClipType::ctDifference, crossing);
    double collisionArea = 0;
    for (auto& p : crossing) {
        collisionArea += fabs(Area(p));
    }
    Perf_IsClearPath.Stop();
    return collisionArea < 1.0;
}

bool Adaptive2d::IsAllowedToCutTrough(
    const IntPoint& p1,
    const IntPoint& p2,
    ClearedArea& cleared,
    const Paths& toolBoundPaths,
    double areaFactor,
    bool skipBoundsCheck
)
{
    Perf_IsAllowedToCutTrough.Start();

    if (!skipBoundsCheck && !IsPointWithinCutRegion(toolBoundPaths, p2)) {
        // last point outside boundary - its not clear to cut
        Perf_IsAllowedToCutTrough.Stop();
        return false;
    }
    else if (!skipBoundsCheck && !IsPointWithinCutRegion(toolBoundPaths, p1)) {
        // first point outside boundary - its not clear to cut
        Perf_IsAllowedToCutTrough.Stop();
        return false;
    }
    else {
        Clipper clip;
        double distance = sqrt(DistanceSqrd(p1, p2));
        double stepSize = min(0.5 * stepOverScaled, 8 * MIN_STEP_CLIPPER);
        if (distance < stepSize / 2) {  // not significant cut
            Perf_IsAllowedToCutTrough.Stop();
            return true;
        }
        if (distance < stepSize) {  // adjust for numeric instability with small distances
            areaFactor *= 2;
        }

        IntPoint toolPos1 = p1;
        long steps = long(distance / stepSize) + 1;
        stepSize = distance / steps;
        for (long i = 1; i <= steps; i++) {
            double p = double(i) / steps;
            IntPoint toolPos2(
                long(p1.X + double(p2.X - p1.X) * p),
                long(p1.Y + double(p2.Y - p1.Y) * p)
            );
            double area = CalcCutArea(clip, toolPos1, toolPos2, cleared, false);
            // if we are cutting above optimal -> not clear to cut
            if (area > areaFactor * stepSize * optimalCutAreaPD) {
                Perf_IsAllowedToCutTrough.Stop();
                return false;
            }
            // if tool is outside boundary -> its not clear to cut
            if (!skipBoundsCheck && !IsPointWithinCutRegion(toolBoundPaths, toolPos2)) {
                Perf_IsAllowedToCutTrough.Stop();
                return false;
            }
            toolPos1 = toolPos2;
        }
    }
    Perf_IsAllowedToCutTrough.Stop();
    return true;
}

bool Adaptive2d::ResolveLinkPath(
    const IntPoint& startPoint,
    const IntPoint& endPoint,
    ClearedArea& clearedArea,
    Path& output
)
{
    vector<pair<IntPoint, IntPoint>> queue;
    queue.emplace_back(startPoint, endPoint);
    Path checkPath;
    double totalLength = 0;
    double directDistance = sqrt(DistanceSqrd(startPoint, endPoint));
    Paths linkPaths;

    double scanStep = 2 * MIN_STEP_CLIPPER;
    if (scanStep > scaleFactor * 0.1) {
        scanStep = scaleFactor * 0.1;
    }
    if (scanStep < scaleFactor * 0.01) {
        scanStep = scaleFactor * 0.01;
    }
    long limit = 10000;

    double clearance = stepOverScaled;
    double offClearance = 2 * stepOverScaled;
    if (offClearance > directDistance / 2) {
        offClearance = directDistance / 2;
        clearance = 0;
    }

    long cnt = 0;

    // to hold CLP results
    IntPoint clp;
    size_t pindex;
    size_t sindex;
    double par;

    // put a time limit on the resolving the link path
    clock_t time_limit = (clock_t)(max(keepToolDownDistRatio, 3.0) * CLOCKS_PER_SEC / 6);

    clock_t time_out = clock() + time_limit;

    while (!queue.empty()) {
        if (stopProcessing) {
            return false;
        }
        if (clock() > time_out) {
            cout << "Unable to resolve tool down linking path (limit reached)." << endl;
            return false;
        }

        cnt++;
        if (cnt > limit) {
            cout << "Unable to resolve tool down linking path @(" << endPoint.X / scaleFactor << ","
                 << endPoint.Y / scaleFactor << ") (" << limit << " points limit reached)." << endl;
            return false;
        }
        pair<IntPoint, IntPoint> pointPair = queue.back();
        queue.pop_back();

        // check for self intersections - if found discard the link path
        for (size_t i = 0; i < linkPaths.size(); i++) {
            if (linkPaths[i].front() != pointPair.first && linkPaths[i].back() != pointPair.first
                && linkPaths[i].front() != pointPair.second && linkPaths[i].back() != pointPair.second
                && IntersectionPoint(
                    linkPaths[i].front(),
                    linkPaths[i].back(),
                    pointPair.first,
                    pointPair.second,
                    clp
                )) {
                cout << "Unable to resolve tool down linking path (self-intersects)." << endl;
                return false;
            }
        }

        DoublePoint direction = DirectionV(pointPair.first, pointPair.second);
        checkPath.clear();
        if (pointPair.first == startPoint) {
            checkPath.push_back(IntPoint(
                pointPair.first.X + offClearance * direction.X,
                pointPair.first.Y + offClearance * direction.Y
            ));
        }
        else {
            checkPath.push_back(pointPair.first);
        }
        if (pointPair.second == endPoint) {
            checkPath.push_back(IntPoint(
                pointPair.second.X - offClearance * direction.X,
                pointPair.second.Y - offClearance * direction.Y
            ));
        }
        else {
            checkPath.push_back(pointPair.second);
        }

        if (IsClearPath(checkPath, clearedArea, clearance)) {
            totalLength += sqrt(DistanceSqrd(pointPair.first, pointPair.second));
            if (totalLength > keepToolDownDistRatio * directDistance) {
                return false;
            }
            Path link;
            link.push_back(pointPair.first);
            link.push_back(pointPair.second);
            linkPaths.push_back(link);
        }
        else {
            if (sqrt(DistanceSqrd(pointPair.first, pointPair.second)) < 4) {
                // segment became too short but still not clear
                return false;
            }
            DoublePoint pDir(-direction.Y, direction.X);
            // find mid point
            IntPoint midPoint(
                0.5 * double(pointPair.first.X + pointPair.second.X),
                0.5 * double(pointPair.first.Y + pointPair.second.Y)
            );
            for (long i = 1;; i++) {
                if (stopProcessing) {
                    return false;
                }
                double offset = i * scanStep;
                IntPoint checkPoint1(midPoint.X + offset * pDir.X, midPoint.Y + offset * pDir.Y);
                IntPoint checkPoint2(midPoint.X - offset * pDir.X, midPoint.Y - offset * pDir.Y);

                if (DistancePointToPathsSqrd(clearedArea.GetCleared(), checkPoint1, clp, pindex, sindex, par)
                    < DistancePointToPathsSqrd(
                        clearedArea.GetCleared(),
                        checkPoint2,
                        clp,
                        pindex,
                        sindex,
                        par
                    )) {
                    // exchange points
                    IntPoint tmp = checkPoint2;
                    checkPoint2 = checkPoint1;
                    checkPoint1 = tmp;
                }

                checkPath.clear();
                checkPath.push_back(checkPoint1);
                if (IsClearPath(checkPath, clearedArea, clearance + 1)) {  // check if point clear
                    queue.emplace_back(pointPair.first, checkPoint1);
                    queue.emplace_back(checkPoint1, pointPair.second);
                    break;
                }
                else {  // check the other side

                    checkPath.clear();
                    checkPath.push_back(checkPoint2);
                    if (IsClearPath(checkPath, clearedArea, clearance + 1)) {
                        queue.emplace_back(pointPair.first, checkPoint2);
                        queue.emplace_back(checkPoint2, pointPair.second);
                        break;
                    }
                }
                if (offset > keepToolDownDistRatio * directDistance) {
                    return false;  // can't find keep tool down link
                }
            }
        }
    }
    if (linkPaths.empty()) {
        return false;
    }
    ConnectPaths(linkPaths, linkPaths);
    output = linkPaths[0];
    return true;
}

bool Adaptive2d::MakeLeadPath(
    bool leadIn,
    const IntPoint& startPoint,
    const DoublePoint& startDir,
    const IntPoint& beaconPoint,
    ClearedArea& clearedArea,
    const Paths& toolBoundPaths,
    Path& output
)
{
    IntPoint currentPoint = startPoint;
    DoublePoint targetDir = DirectionV(currentPoint, beaconPoint);
    double distanceToBeacon = sqrt(DistanceSqrd(startPoint, beaconPoint));
    double stepSize = 0.2 * stepOverScaled + 1;
    double maxPathLen = stepOverScaled;
    DoublePoint nextDir = startDir;
    IntPoint nextPoint
        = IntPoint(currentPoint.X + nextDir.X * stepSize, currentPoint.Y + nextDir.Y * stepSize);
    Path checkPath;
    double adaptFactor = 0.4;
    double alfa = std::numbers::pi / 64;
    double pathLen = 0;
    checkPath.push_back(nextPoint);
    for (int i = 0; i < 10000; i++) {
        if (IsAllowedToCutTrough(
                IntPoint(
                    currentPoint.X + MIN_STEP_CLIPPER * nextDir.X,
                    currentPoint.Y + MIN_STEP_CLIPPER * nextDir.Y
                ),
                nextPoint,
                clearedArea,
                toolBoundPaths
            )) {
            if (output.empty()) {
                output.push_back(currentPoint);
            }
            output.push_back(nextPoint);
            currentPoint = nextPoint;
            pathLen += stepSize;
            targetDir = DirectionV(currentPoint, beaconPoint);
            nextDir = DoublePoint(
                nextDir.X + adaptFactor * targetDir.X,
                nextDir.Y + adaptFactor * targetDir.Y
            );
            NormalizeV(nextDir);
            if (pathLen > maxPathLen) {
                break;
            }
            if (pathLen > distanceToBeacon / 2) {
                break;
            }
        }
        else {
            nextDir = rotate(nextDir, leadIn ? -alfa : alfa);
        }
        nextPoint
            = IntPoint(currentPoint.X + nextDir.X * stepSize, currentPoint.Y + nextDir.Y * stepSize);
    }
    if (output.empty()) {
        output.push_back(startPoint);
    }
    return true;
}
void Adaptive2d::AppendToolPath(
    TPaths& progressPaths,
    AdaptiveOutput& output,
    const Path& passToolPath,
    ClearedArea& clearedBefore,
    ClearedArea& clearedAfter,
    const Paths& toolBoundPaths
)
{
    if (passToolPath.size() < 2) {
        return;
    }
    Perf_AppendToolPath.Start();
    UNUSED(progressPaths);  // to silence compiler warning,var is occasionally used in dev. for
                            // debugging

    IntPoint endPoint(passToolPath[0]);
    // if there is a previous path - need to resolve linking move to new path
    if (!output.AdaptivePaths.empty() && output.AdaptivePaths.back().second.size() > 1) {
        auto& lastTPath = output.AdaptivePaths.back();

        auto& lastPrevTPoint = lastTPath.second.at(lastTPath.second.size() - 2);
        auto& lastTPoint = lastTPath.second.back();

        IntPoint startPrevPoint(
            long(lastPrevTPoint.first * scaleFactor),
            long(lastPrevTPoint.second * scaleFactor)
        );
        IntPoint startPoint(long(lastTPoint.first * scaleFactor), long(lastTPoint.second * scaleFactor));

        // first we try to cut through the linking move for short distances
        bool linkFound = false;
        double linkDistance = sqrt(DistanceSqrd(startPoint, endPoint));
        if (linkDistance < NTOL) {
            linkFound = true;
        }

        if (!linkFound) {
            size_t clpPathIndex;
            size_t clpSegmentIndex;
            double clpParameter;
            IntPoint clp;

            double beaconOffset = stepOverScaled;
            if (beaconOffset > linkDistance) {
                beaconOffset = linkDistance;
            }

            double pathLen = PathLength(passToolPath);
            if (beaconOffset > pathLen / 2) {
                beaconOffset = pathLen / 2;
            }
            if (beaconOffset > linkDistance / 2) {
                beaconOffset = linkDistance / 2;
            }

            DistancePointToPathsSqrd(
                toolBoundPaths,
                startPoint,
                clp,
                clpPathIndex,
                clpSegmentIndex,
                clpParameter
            );
            DoublePoint startDir = GetPathDirectionV(toolBoundPaths[clpPathIndex], clpSegmentIndex);

            DistancePointToPathsSqrd(
                toolBoundPaths,
                endPoint,
                clp,
                clpPathIndex,
                clpSegmentIndex,
                clpParameter
            );
            DoublePoint endDir = GetPathDirectionV(toolBoundPaths[clpPathIndex], clpSegmentIndex);

            IntPoint startBeacon(
                startPoint.X - beaconOffset * (startDir.Y - startDir.X),
                startPoint.Y + beaconOffset * (startDir.X + startDir.Y)
            );
            IntPoint endBeacon(
                endPoint.X - beaconOffset * (endDir.X + endDir.Y),
                endPoint.Y + beaconOffset * (endDir.X - endDir.Y)
            );
            Path leadOutPath;
            MakeLeadPath(false, startPoint, startDir, startBeacon, clearedBefore, toolBoundPaths, leadOutPath);

            Path leadInPath;
            MakeLeadPath(
                true,
                endPoint,
                DoublePoint(-endDir.X, -endDir.Y),
                endBeacon,
                clearedBefore,
                toolBoundPaths,
                leadInPath
            );
            ReversePath(leadInPath);

            Path linkPath;
            MotionType linkType = MotionType::mtCutting;

            // this is not needed:
            // clearedBefore.ExpandCleared(leadInPath);
            // clearedBefore.ExpandCleared(leadOutPath);

            if (ResolveLinkPath(leadOutPath.back(), leadInPath.front(), clearedBefore, linkPath)) {
                linkType = MotionType::mtLinkClear;
                double remainingLeadInExtension = stepOverScaled / 2;
                while (linkPath.size() >= 2 && remainingLeadInExtension > NTOL) {
                    IntPoint p1 = linkPath.at(linkPath.size() - 2);
                    IntPoint p2 = linkPath.at(linkPath.size() - 1);
                    double l = sqrt(DistanceSqrd(p1, p2));
                    if (l >= remainingLeadInExtension) {
                        IntPoint splitPoint(
                            p1.X + (p2.X - p1.X) * (l - remainingLeadInExtension) / l,
                            p1.Y + (p2.Y - p1.Y) * (l - remainingLeadInExtension) / l
                        );
                        linkPath.pop_back();
                        linkPath.push_back(splitPoint);
                        leadInPath.insert(leadInPath.begin(), splitPoint);
                        remainingLeadInExtension = 0;
                        Path checkPath;
                        checkPath.push_back(p2);
                        checkPath.push_back(splitPoint);
                        if (!IsClearPath(checkPath, clearedBefore, 0)) {
                            remainingLeadInExtension = stepOverScaled / 2;
                        }
                    }
                    else {
                        linkPath.pop_back();
                        leadInPath.insert(leadInPath.begin(), p1);
                        remainingLeadInExtension -= l;
                        if (remainingLeadInExtension < NTOL) {
                            Path checkPath;
                            checkPath.push_back(p2);
                            checkPath.push_back(p1);
                            if (!IsClearPath(checkPath, clearedBefore, 0)) {
                                remainingLeadInExtension = stepOverScaled / 2;
                            }
                        }
                    }
                }
            }
            else {
                linkType = MotionType::mtLinkNotClear;
                double dist = sqrt(DistanceSqrd(leadOutPath.back(), leadInPath.front()));
                if (dist < 2 * stepOverScaled
                    && IsAllowedToCutTrough(
                        IntPoint(
                            leadOutPath.back().X + (leadInPath.front().X - leadOutPath.back().X) / dist,
                            leadOutPath.back().Y + (leadInPath.front().Y - leadOutPath.back().Y) / dist
                        ),
                        IntPoint(
                            leadInPath.front().X - (leadInPath.front().X - leadOutPath.back().X) / dist,
                            leadInPath.front().Y - (leadInPath.front().Y - leadOutPath.back().Y) / dist
                        ),
                        clearedBefore,
                        toolBoundPaths
                    )) {
                    linkType = MotionType::mtCutting;
                }
                // add direct linking move at clear height

                linkPath.clear();
                linkPath.push_back(leadOutPath.back());
                linkPath.push_back(leadInPath.front());
            }

            /* paths smoothing*/
            Paths linkPaths;
            linkPaths.push_back(leadOutPath);
            linkPaths.push_back(linkPath);
            linkPaths.push_back(leadInPath);

            if (linkType == MotionType::mtLinkClear) {
                SmoothPaths(linkPaths, 0.1 * stepOverScaled, 1, 4);
            }

            leadOutPath = linkPaths[0];
            linkPath = linkPaths[1];
            leadInPath = linkPaths[2];

            // add lead-out move
            TPath linkPath1;
            linkPath1.first = MotionType::mtCutting;
            for (const auto& pt : leadOutPath) {
                linkPath1.second.emplace_back(double(pt.X) / scaleFactor, double(pt.Y) / scaleFactor);
            }
            output.AdaptivePaths.push_back(linkPath1);

            // add linking path
            TPath linkPath2;
            linkPath2.first = linkType;
            for (const auto& pt : linkPath) {
                linkPath2.second.emplace_back(double(pt.X) / scaleFactor, double(pt.Y) / scaleFactor);
            }
            output.AdaptivePaths.push_back(linkPath2);

            // add lead-in move
            TPath linkPath3;
            linkPath3.first = MotionType::mtCutting;
            for (const auto& pt : leadInPath) {
                linkPath3.second.emplace_back(double(pt.X) / scaleFactor, double(pt.Y) / scaleFactor);
            }

            output.AdaptivePaths.push_back(linkPath3);

            clearedAfter.ExpandCleared(leadInPath);
            clearedAfter.ExpandCleared(leadOutPath);

            linkFound = true;
        }
        if (!linkFound) {  // nothing clear so far - check direct link with no interim points -
                           // either this is clear or we need to raise the tool
            Path tp;
            tp << startPoint;
            tp << endPoint;
            MotionType mt = IsClearPath(tp, clearedBefore) ? MotionType::mtLinkClear
                                                           : MotionType::mtLinkNotClear;

            // make cutting move through small clear links
            if (mt == MotionType::mtLinkClear && linkDistance < toolRadiusScaled) {
                mt = MotionType::mtCutting;
                clearedAfter.ExpandCleared(tp);
            }

            TPath linkPath;
            linkPath.first = mt;
            linkPath.second.emplace_back(
                double(startPoint.X) / scaleFactor,
                double(startPoint.Y) / scaleFactor
            );
            linkPath.second.emplace_back(
                double(endPoint.X) / scaleFactor,
                double(endPoint.Y) / scaleFactor
            );
            output.AdaptivePaths.push_back(linkPath);
        }
    }
    TPath cutPath;
    cutPath.first = MotionType::mtCutting;
    for (const auto& p : passToolPath) {
        DPoint nextT;
        nextT.first = double(p.X) / scaleFactor;
        nextT.second = double(p.Y) / scaleFactor;
        cutPath.second.push_back(nextT);
    }

    if (!cutPath.second.empty()) {
        output.AdaptivePaths.push_back(cutPath);
    }
    Perf_AppendToolPath.Stop();
}

void Adaptive2d::CheckReportProgress(TPaths& progressPaths, bool force)
{
    if (!force && (clock() - lastProgressTime < PROGRESS_TICKS)) {
        return;  // not yet
    }
    lastProgressTime = clock();
    if (progressPaths.empty()) {
        return;
    }
    if (progressCallback) {
        if ((*progressCallback)(progressPaths)) {
            stopProcessing = true;  // call python function, if returns true signal stop processing
        }
    }
    // clean the paths - keep the last point
    if (progressPaths.back().second.empty()) {
        return;
    }
    TPath* lastPath = &progressPaths.back();
    DPoint* lastPoint = &lastPath->second.back();
    DPoint next(lastPoint->first, lastPoint->second);
    while (progressPaths.size() > 1) {
        progressPaths.pop_back();
    }
    while (!progressPaths.front().second.empty()) {
        progressPaths.front().second.pop_back();
    }
    progressPaths.front().first = MotionType::mtCutting;
    progressPaths.front().second.push_back(next);
}

void Adaptive2d::AddPathsToProgress(TPaths& progressPaths, Paths paths, MotionType mt)
{
    for (const auto& pth : paths) {
        if (!pth.empty()) {
            progressPaths.push_back(TPath());
            progressPaths.back().first = mt;
            for (const auto pt : pth) {
                progressPaths.back().second.emplace_back(
                    double(pt.X) / scaleFactor,
                    double(pt.Y) / scaleFactor
                );
            }
            progressPaths.back().second.emplace_back(
                double(pth.front().X) / scaleFactor,
                double(pth.front().Y) / scaleFactor
            );
        }
    }
}

void Adaptive2d::AddPathToProgress(TPaths& progressPaths, const Path pth, MotionType mt)
{
    if (!pth.empty()) {
        progressPaths.push_back(TPath());
        progressPaths.back().first = mt;
        for (const auto pt : pth) {
            progressPaths.back().second.emplace_back(
                double(pt.X) / scaleFactor,
                double(pt.Y) / scaleFactor
            );
        }
    }
}

void Adaptive2d::ProcessPolyNode(Paths boundPaths, Paths toolBoundPaths)
{
    Perf_ProcessPolyNode.Start();
    current_region++;
    cout << "** Processing region: " << current_region << endl;

    // node paths are already constrained to tool boundary path for adaptive path before finishing
    // pass
    Clipper clip;
    ClipperOffset clipof;

    IntPoint entryPoint;
    long helixRadiusScaled;
    TPaths progressPaths;
    progressPaths.reserve(10000);

    CleanPolygons(toolBoundPaths);
    SimplifyPolygons(toolBoundPaths);

    CleanPolygons(boundPaths);
    SimplifyPolygons(boundPaths);

    AddPathsToProgress(progressPaths, toolBoundPaths, MotionType::mtLinkClear);

    IntPoint toolPos;
    DoublePoint toolDir;
    ClearedArea cleared(toolRadiusScaled);
    bool outsideEntry = false;
    bool firstEngagePoint = true;
    Paths engageBounds = toolBoundPaths;

    if (!forceInsideOut
        && FindEntryPointOutside(
            progressPaths,
            toolBoundPaths,
            boundPaths,
            cleared,
            entryPoint,
            toolPos,
            toolDir
        )) {
        if (!Orientation(engageBounds[0])) {
            ReversePath(engageBounds[0]);
        }
        // add initial offset of cleared area to engage paths
        Paths outsideEngage;
        clipof.Clear();
        clipof.AddPaths(stockInputPaths, JoinType::jtRound, EndType::etClosedPolygon);
        clipof.Execute(outsideEngage, toolRadiusScaled - stepOverFactor * toolRadiusScaled);
        CleanPolygons(outsideEngage);
        ReversePaths(outsideEngage);
        for (const auto& p : outsideEngage) {
            engageBounds.push_back(p);
        }
        outsideEntry = true;
    }
    else {
        if (!FindEntryPoint(
                progressPaths,
                toolBoundPaths,
                boundPaths,
                cleared,
                entryPoint,
                toolPos,
                toolDir,
                helixRadiusScaled
            )) {
            Perf_ProcessPolyNode.Stop();
            return;
        }
    }

    EngagePoint engage(engageBounds);  // engage point stepping instance

    if (outsideEntry) {
        engage.moveToClosestPoint(toolPos, 2 * MIN_STEP_CLIPPER);
        engage.moveForward(MIN_STEP_CLIPPER);
        toolPos = engage.getCurrentPoint();
        toolDir = engage.getCurrentDir();
        entryPoint = toolPos;
    }

    // cout << "Entry point:" << double(entryPoint.X)/scaleFactor << "," <<
    // double(entryPoint.Y)/scaleFactor << endl;

    AdaptiveOutput output;
    output.ReturnMotionType = 0;
    output.HelixCenterPoint.first = double(entryPoint.X) / scaleFactor;
    output.HelixCenterPoint.second = double(entryPoint.Y) / scaleFactor;

    long stepScaled = long(MIN_STEP_CLIPPER);
    IntPoint engagePoint;

    IntPoint newToolPos;
    DoublePoint newToolDir;

    CheckReportProgress(progressPaths, true);

    IntPoint startPoint = toolPos;
    output.StartPoint = DPoint(double(startPoint.X) / scaleFactor, double(startPoint.Y) / scaleFactor);

    Path passToolPath;  // to store pass toolpath
    Path toClearPath;
    IntPoint clp;                 // to store closest point
    vector<DoublePoint> gyro;     // used to average tool direction
    vector<double> angleHistory;  // use to predict deflection angle
    double angle = std::numbers::pi;
    engagePoint = toolPos;
    Interpolation interp;  // interpolation instance

    long total_iterations = 0;
    long total_points = 0;
    long total_exceeded = 0;
    long total_output_points = 0;
    long over_cut_count = 0;
    long bad_engage_count = 0;
    double prevDistFromStart = 0;
    double refinement_factor = 1;
    bool prevDistTrend = false;

    double perf_total_len = 0;
#ifdef DEV_MODE
    clock_t start_clock = clock();
#endif
    ClearedArea clearedBeforePass(toolRadiusScaled);
    clearedBeforePass.SetClearedPaths(cleared.GetCleared());

    //*******************************
    // LOOP - PASSES
    //*******************************
    for (long pass = 0; pass < PASSES_LIMIT; pass++) {
        if (stopProcessing) {
            break;
        }

        passToolPath.clear();
        toClearPath.clear();
        angleHistory.clear();

        // append a new path to progress info paths
        if (progressPaths.empty()) {
            progressPaths.push_back(TPath());
        }
        else {
            // append new path if previous not empty
            if (!progressPaths.back().second.empty()) {
                progressPaths.push_back(TPath());
            }
        }

        angle = std::numbers::pi / 4;  // initial pass angle
        bool recalcArea = false;
        double cumulativeCutArea = 0;
        // init gyro
        gyro.clear();
        for (int i = 0; i < DIRECTION_SMOOTHING_BUFLEN; i++) {
            gyro.push_back(toolDir);
        }

        size_t clpPathIndex;
        size_t clpSegmentIndex;
        double clpParameter;
        double passLength = 0;
        double noCutDistance = 0;
        clearedBeforePass.SetClearedPaths(cleared.GetCleared());
        //*******************************
        // LOOP - POINTS
        //*******************************
        for (long point_index = 0; point_index < POINTS_PER_PASS_LIMIT; point_index++) {
            if (stopProcessing) {
                break;
            }

            total_points++;
            AverageDirection(gyro, toolDir);
            Perf_DistanceToBoundary.Start();

            double distanceToBoundary = sqrt(
                DistancePointToPathsSqrd(toolBoundPaths, toolPos, clp, clpPathIndex, clpSegmentIndex, clpParameter)
            );
            DoublePoint boundaryDir = GetPathDirectionV(toolBoundPaths[clpPathIndex], clpSegmentIndex);
            double distBoundaryPointToEngage = sqrt(DistanceSqrd(clp, engagePoint));

            Perf_DistanceToBoundary.Stop();
            double distanceToEngage = sqrt(DistanceSqrd(toolPos, engagePoint));

            double targetAreaPD = optimalCutAreaPD;

            // set the step size: 1x to 8x base size
            double slowDownDistance = max(double(toolRadiusScaled) / 4, MIN_STEP_CLIPPER * 8);
            if (distanceToBoundary < slowDownDistance || distanceToEngage < slowDownDistance) {
                stepScaled = long(MIN_STEP_CLIPPER);
            }
            else if (fabs(angle) > NTOL) {
                stepScaled = long(MIN_STEP_CLIPPER / fabs(angle));
            }
            else {
                stepScaled = long(MIN_STEP_CLIPPER * 8);
            }

            // clamp the step size - for stability
            if (stepScaled > min(long(toolRadiusScaled / 4), long(MIN_STEP_CLIPPER * 8))) {
                stepScaled = min(long(toolRadiusScaled / 4), long(MIN_STEP_CLIPPER * 8));
            }
            if (stepScaled < MIN_STEP_CLIPPER) {
                stepScaled = long(MIN_STEP_CLIPPER);
            }

            //*****************************
            // ANGLE vs AREA ITERATIONS
            //*****************************
            double predictedAngle = averageDV(angleHistory);
            double maxError = AREA_ERROR_FACTOR * optimalCutAreaPD;
            double area = 0;
            double areaPD = 0;
            interp.clear();
            /******************************/
            Perf_PointIterations.Start();
            int iteration;
            double prev_error = __DBL_MAX__;
            bool pointNotInterp;
            for (iteration = 0; iteration < MAX_ITERATIONS; iteration++) {
                total_iterations++;
                if (iteration == 0) {
                    angle = predictedAngle;
                    pointNotInterp = true;
                }
                else if (iteration == 1) {
                    angle = interp.MIN_ANGLE;  // max engage
                    pointNotInterp = true;
                }
                else if (iteration == 2) {
                    if (interp.bothSides()) {
                        angle = interp.interpolateAngle();
                        pointNotInterp = false;
                    }
                    else {
                        angle = interp.MAX_ANGLE;  // min engage
                        pointNotInterp = true;
                    }
                }
                else {
                    angle = interp.interpolateAngle();
                    pointNotInterp = false;
                }
                angle = interp.clampAngle(angle);

                newToolDir = rotate(toolDir, angle);
                newToolPos = IntPoint(
                    long(toolPos.X + newToolDir.X * stepScaled),
                    long(toolPos.Y + newToolDir.Y * stepScaled)
                );

                // Skip iteration if this IntPoint has already been processed
                bool intRepeat = false;
                if (interp.m_min && newToolPos == interp.m_min->first.second) {
                    interp.m_min = {{angle, newToolPos}, interp.m_min->second};
                    intRepeat = true;
                }
                if (interp.m_max && newToolPos == interp.m_max->first.second) {
                    interp.m_max = {{angle, newToolPos}, interp.m_max->second};
                    intRepeat = true;
                }

                if (intRepeat) {
                    if (interp.m_min && interp.m_max
                        && abs(interp.m_min->first.second.X - interp.m_max->first.second.X) <= 1
                        && abs(interp.m_min->first.second.Y - interp.m_max->first.second.Y) <= 1) {
                        if (pointNotInterp) {
                            // if this happens while testing min/max of the range it doesn't mean
                            // anything; only exit early if interpolation is down to adjacent
                            // integers
                            continue;
                        }
                        // exit early, selecting the better of the two adjacent integers
                        double error;
                        if (abs(interp.m_min->second) < abs(interp.m_max->second)) {
                            newToolDir = rotate(toolDir, interp.m_min->first.first);
                            newToolPos = interp.m_min->first.second;
                            error = interp.m_min->second;
                        }
                        else {
                            newToolDir = rotate(toolDir, interp.m_max->first.first);
                            newToolPos = interp.m_max->first.second;
                            error = interp.m_max->second;
                        }
                        areaPD = error + targetAreaPD;
                        area = areaPD * double(stepScaled);
                        break;
                    }
                    continue;
                }

                area = CalcCutArea(clip, toolPos, newToolPos, cleared);

                areaPD = area / double(stepScaled);  // area per distance
                double error = areaPD - targetAreaPD;
                interp.addPoint(error, {angle, newToolPos}, pointNotInterp);
                // cout << " iter:" << iteration << " angle:" << angle << " area:" << areaPD
                //      << " target:" << targetAreaPD << " error:" << error << " max:" << maxError
                //      << endl;
                if (fabs(error) < maxError) {
                    angleHistory.push_back(angle);
                    if (angleHistory.size() > ANGLE_HISTORY_POINTS) {
                        angleHistory.erase(angleHistory.begin());
                    }
                    break;
                }
                if (iteration == MAX_ITERATIONS - 1) {
                    total_exceeded++;
                }
                prev_error = error;
            }
            Perf_PointIterations.Stop();

            recalcArea = false;
            // approach end boundary tangentially
            double relDistToBoundary = 4 * distanceToBoundary / stepOverScaled;
            if (relDistToBoundary <= 1.0 && passLength > 2 * stepOverFactor
                && distanceToEngage > 2 * stepOverScaled
                && distBoundaryPointToEngage > 2 * stepOverScaled) {
                double wb = 1 - relDistToBoundary;
                newToolDir = DoublePoint(
                    newToolDir.X + wb * boundaryDir.X,
                    newToolDir.Y + wb * boundaryDir.Y
                );
                NormalizeV(newToolDir);
                newToolPos = IntPoint(
                    long(toolPos.X + newToolDir.X * stepScaled),
                    long(toolPos.Y + newToolDir.Y * stepScaled)
                );
                recalcArea = true;
            }

            //**********************************************
            // CHECK AND RECORD NEW TOOL POS
            //**********************************************
            long rotateStep = 0;
            while (!IsPointWithinCutRegion(toolBoundPaths, newToolPos) && rotateStep < 180) {
                rotateStep++;
                // if new tool pos. outside boundary rotate until back in
                recalcArea = true;
                newToolDir = rotate(newToolDir, std::numbers::pi / 90);
                newToolPos = IntPoint(
                    long(toolPos.X + newToolDir.X * stepScaled),
                    long(toolPos.Y + newToolDir.Y * stepScaled)
                );
            }
            if (rotateStep >= 180) {
#ifdef DEV_MODE
                cerr << "Warning: unexpected number of rotate iterations." << endl;
#endif
                break;
            }

            if (recalcArea) {
                area = CalcCutArea(clip, toolPos, newToolPos, cleared);
            }

            // safety condition
            if (area > stepScaled * optimalCutAreaPD && areaPD > 2 * optimalCutAreaPD) {
                over_cut_count++;
                break;
            }

            // update cleared paths when trend of distance from start point changes sign (starts to
            // get closer, or start to get farther)
            double distFromStart = sqrt(DistanceSqrd(toolPos, startPoint));
            bool distanceTrend = distFromStart > prevDistFromStart ? true : false;

            if (distanceTrend != prevDistTrend) {
                cleared.ExpandCleared(toClearPath);
                toClearPath.clear();
            }
            prevDistTrend = distanceTrend;
            prevDistFromStart = distFromStart;

            if (area > 0.5 * MIN_CUT_AREA_FACTOR * optimalCutAreaPD) {  // cut is ok - record it
                noCutDistance = 0;
                if (toClearPath.empty()) {
                    toClearPath.push_back(toolPos);
                }
                toClearPath.push_back(newToolPos);

                cumulativeCutArea += area;

                // append to toolpaths
                if (passToolPath.empty()) {
                    // in outside entry first successful cut defines the "helix center" and start
                    // point in this case helix diameter is 0 (straight line downwards)
                    if (output.AdaptivePaths.empty() && outsideEntry) {
                        entryPoint = toolPos;
                        output.HelixCenterPoint.first = double(entryPoint.X) / scaleFactor;
                        output.HelixCenterPoint.second = double(entryPoint.Y) / scaleFactor;
                        output.StartPoint = DPoint(
                            double(entryPoint.X) / scaleFactor,
                            double(entryPoint.Y) / scaleFactor
                        );
                    }
                    passToolPath.push_back(toolPos);
                }
                passToolPath.push_back(newToolPos);
                perf_total_len += stepScaled;
                passLength += stepScaled;
                toolPos = newToolPos;

                // append to progress info paths
                if (progressPaths.empty()) {
                    progressPaths.push_back(TPath());
                }
                progressPaths.back().second.emplace_back(
                    double(newToolPos.X) / scaleFactor,
                    double(newToolPos.Y) / scaleFactor
                );

                // append gyro
                gyro.push_back(newToolDir);
                gyro.erase(gyro.begin());
                CheckReportProgress(progressPaths);
            }
            else {
#ifdef DEV_MODE
                // if(point_index==0) {
                // 	engage_no_cut_count++;
                // 	cout<<"Break:no cut #" << engage_no_cut_count << ", bad engage, pass:" << pass
                // << " over_cut_count:" << over_cut_count << endl;
                // }
#endif
                // cout<<"Break: no cut @" << point_index << endl;
                if (noCutDistance > stepOverScaled) {
                    break;
                }
                noCutDistance += stepScaled;
            }
        } /* end of points loop*/

        if (!toClearPath.empty()) {
            cleared.ExpandCleared(toClearPath);
            toClearPath.clear();
        }
        if (cumulativeCutArea > MIN_CUT_AREA_FACTOR * optimalCutAreaPD) {
            Path cleaned;
            CleanPath(passToolPath, cleaned, CLEAN_PATH_TOLERANCE);
            total_output_points += long(cleaned.size());
            AppendToolPath(progressPaths, output, cleaned, clearedBeforePass, cleared, toolBoundPaths);
            CheckReportProgress(progressPaths);
            bad_engage_count = 0;
            engage.ResetPasses();
        }
        else {
            bad_engage_count++;
        }

        if (bad_engage_count > 10000) {
            cerr << "Break (next valid engage point not found)." << endl;
            break;
        }

        /*****NEXT ENGAGE POINT******/
        if (firstEngagePoint) {
            engage.moveToClosestPoint(newToolPos, stepScaled + 1);
            firstEngagePoint = false;
        }
        else {
            double moveDistance = ENGAGE_SCAN_DISTANCE_FACTOR * stepOverScaled * refinement_factor;

            if (!engage.nextEngagePoint(
                    this,
                    cleared,
                    moveDistance,
                    ENGAGE_AREA_THR_FACTOR * optimalCutAreaPD,
                    4 * referenceCutArea * stepOverFactor
                )) {
                // check if there are any uncleared area left
                Paths remaining;
                for (const auto& p : cleared.GetCleared()) {
                    if (!p.empty() && IsPointWithinCutRegion(toolBoundPaths, p.front())
                        && DistancePointToPathsSqrd(
                               boundPaths,
                               p.front(),
                               clp,
                               clpPathIndex,
                               clpSegmentIndex,
                               clpParameter
                           ) > 4 * toolRadiusScaled * toolRadiusScaled) {
                        remaining.push_back(p);
                    }
                };
                if (remaining.empty()) {
                    cout << "All cleared." << endl;
                    break;
                }
                else {
                    cout << "Clearing " << remaining.size() << " remaining internal path(s)." << endl;
                }

                // try to find new engage point along the remaining
                clipof.Clear();
                clipof.AddPaths(remaining, JoinType::jtRound, EndType::etClosedPolygon);
                clipof.Execute(remaining, toolRadiusScaled - 0.5 * stepOverScaled);

                ReversePaths(remaining);
                engage.SetPaths(remaining);
                engage.moveToClosestPoint(newToolPos, stepScaled + 1);
                if (!engage.nextEngagePoint(
                        this,
                        cleared,
                        moveDistance,
                        ENGAGE_AREA_THR_FACTOR * optimalCutAreaPD,
                        4 * referenceCutArea * stepOverFactor
                    )) {
                    break;
                }
            }
        }
        toolPos = engage.getCurrentPoint();
        toolDir = engage.getCurrentDir();
    }

    //**********************************
    //*  FINISHING PASS                *
    //**********************************
    if (finishingProfile) {
        Paths finishingPaths;
        clipof.Clear();
        clipof.AddPaths(boundPaths, JoinType::jtRound, EndType::etClosedPolygon);
        clipof.Execute(finishingPaths, -toolRadiusScaled);

        clipof.Clear();
        clipof.AddPaths(finishingPaths, JoinType::jtRound, EndType::etClosedPolygon);
        clipof.Execute(toolBoundPaths, -1);

        IntPoint lastPoint = toolPos;
        Path finShiftedPath;

        bool allCutsAllowed = true;
        while (!stopProcessing && PopPathWithClosestPoint(finishingPaths, lastPoint, finShiftedPath)) {
            if (finShiftedPath.empty()) {
                continue;
            }
            // skip finishing passes outside the stock boundary - no sense to cut where is no
            // material
            bool allPointsOutside = true;
            IntPoint p1 = finShiftedPath.front();
            for (const auto& pt : finShiftedPath) {

                // midpoint
                if (IsPointWithinCutRegion(
                        stockInputPaths,
                        IntPoint((p1.X + pt.X) / 2, (p1.Y + pt.Y) / 2)
                    )) {
                    allPointsOutside = false;
                    break;
                }
                // current point
                if (IsPointWithinCutRegion(stockInputPaths, pt)) {
                    allPointsOutside = false;
                    break;
                }

                p1 = pt;
            }
            if (allPointsOutside) {
                continue;
            }

            progressPaths.push_back(TPath());
            // show in progress cb
            for (auto& pt : finShiftedPath) {
                progressPaths.back().second.emplace_back(
                    double(pt.X) / scaleFactor,
                    double(pt.Y) / scaleFactor
                );
            }

            if (!finShiftedPath.empty()) {
                finShiftedPath << finShiftedPath.front();  // make sure its closed
            }

            Path finCleaned;
            CleanPath(finShiftedPath, finCleaned, FINISHING_CLEAN_PATH_TOLERANCE);

            // sanity check for finishing paths - check the area of finishing cut
            for (size_t i = 1; i < finCleaned.size(); i++) {
                if (!IsAllowedToCutTrough(
                        finCleaned.at(i - 1),
                        finCleaned.at(i),
                        cleared,
                        toolBoundPaths,
                        2.0,
                        true
                    )) {
                    allCutsAllowed = false;
                }
            }

            // make sure it's closed
            finCleaned.push_back(finCleaned.front());
            AppendToolPath(progressPaths, output, finCleaned, cleared, cleared, toolBoundPaths);

            cleared.ExpandCleared(finCleaned);

            if (!finCleaned.empty()) {
                lastPoint.X = finCleaned.back().X;
                lastPoint.Y = finCleaned.back().Y;
            }
        }

        Path returnPath;
        returnPath << lastPoint;
        returnPath << entryPoint;
        output.ReturnMotionType = IsClearPath(returnPath, cleared) ? MotionType::mtLinkClear
                                                                   : MotionType::mtLinkNotClear;

        // dump performance results
#ifdef DEV_MODE
        Perf_ProcessPolyNode.Stop();
        Perf_ProcessPolyNode.DumpResults();
        Perf_PointIterations.DumpResults();
        Perf_CalcCutAreaCirc.DumpResults();
        Perf_CalcCutAreaClip.DumpResults();
        Perf_NextEngagePoint.DumpResults();
        Perf_ExpandCleared.DumpResults();
        Perf_DistanceToBoundary.DumpResults();
        Perf_AppendToolPath.DumpResults();
        Perf_IsAllowedToCutTrough.DumpResults();
        Perf_IsClearPath.DumpResults();
#endif
        CheckReportProgress(progressPaths, true);
#ifdef DEV_MODE
        double duration = ((double)(clock() - start_clock)) / CLOCKS_PER_SEC;
        cout << "PolyNode perf:" << perf_total_len / double(scaleFactor) / duration << " mm/sec"
             << " processed_points:" << total_points << " output_points:" << total_output_points
             << " total_iterations:" << total_iterations
             << " iter_per_point:" << (double(total_iterations) / ((double(total_points) + 0.001)))
             << " total_exceeded:" << total_exceeded << " ("
             << 100 * double(total_exceeded) / double(total_points) << "%)" << endl;
#else
        (void)total_output_points;
        (void)over_cut_count;
        (void)total_exceeded;
        (void)total_points;
        (void)total_iterations;
        (void)perf_total_len;
#endif

        // warn about invalid paths being detected
        if (!allCutsAllowed) {
            cerr << "Warning: some cuts may be above optimal step-over. Please double check the "
                    "results."
                 << endl
                 << "Hint: try to modify accuracy and/or step-over." << endl;
        }
    }
    results.push_back(output);
}

}  // namespace AdaptivePath