package lujing;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

/**
 * 凸形草地路径规划 (围边优化版)
 * 优化重点：围边坐标对齐扫描起点、全路径连贯性
 */
public class AoxinglujingNoObstacle {

    private static final double EPSILON = 1e-6;

    public static class Point {
        public double x, y;
        public Point(double x, double y) { this.x = x; this.y = y; }
        @Override
        public String toString() { return String.format("%.6f,%.6f", x, y); }
    }

    public static class PathSegment {
        public Point start, end;
        public boolean isMowing;
        public PathSegment(Point start, Point end, boolean isMowing) {
            this.start = start; this.end = end; this.isMowing = isMowing;
        }
    }

    /**
     * 对外主接口
     */
    public static List<PathSegment> planPath(String boundaryCoordsStr, String mowingWidthStr, String safetyMarginStr) {
        List<Point> originalPolygon = parseCoords(boundaryCoordsStr);
        double width = Double.parseDouble(mowingWidthStr);
        double margin = Double.parseDouble(safetyMarginStr);

        return planPathCore(originalPolygon, width, margin);
    }

    private static List<PathSegment> planPathCore(List<Point> originalPolygon, double width, double margin) {
        if (originalPolygon.size() < 3) return new ArrayList<>();

        // 1. 确保逆时针并进行安全内缩
        ensureCCW(originalPolygon);
        List<Point> workArea = shrinkPolygon(originalPolygon, margin);
        if (workArea.size() < 3) return new ArrayList<>();

        // 2. 预计算最优角度和填充路径的第一个点
        double bestAngle = findOptimalScanAngle(workArea);
        Point firstScanStart = getFirstScanStartPoint(workArea, bestAngle, width);

        // 3. 对齐围边起点：让围边的最后一个点刚好连接扫描填充的起点
        List<Point> alignedWorkArea = alignBoundaryToStart(workArea, firstScanStart);

        List<PathSegment> finalPath = new ArrayList<>();

        // 4. 【第一阶段】添加围边坐标路径
        for (int i = 0; i < alignedWorkArea.size(); i++) {
            Point p1 = alignedWorkArea.get(i);
            Point p2 = alignedWorkArea.get((i + 1) % alignedWorkArea.size());
            finalPath.add(new PathSegment(p1, p2, true));
        }

        // 5. 【第二阶段】生成内部弓字形路径
        // 从围边闭合点（alignedWorkArea.get(0)）开始连接
        Point currentPos = alignedWorkArea.get(0);
        List<PathSegment> zigZagLines = generateZigZagPath(workArea, bestAngle, width, currentPos);
        
        finalPath.addAll(zigZagLines);

        return finalPath;
    }

    /**
     * 寻找弓字形的第一条线的起点
     */
    private static Point getFirstScanStartPoint(List<Point> polygon, double angle, double width) {
        List<Point> rotated = rotatePolygon(polygon, -angle);
        double minY = Double.MAX_VALUE;
        for (Point p : rotated) minY = Math.min(minY, p.y);

        double startY = minY + width + EPSILON;
        List<Double> xIntersections = getXIntersections(rotated, startY);
        if (xIntersections.isEmpty()) return polygon.get(0);
        
        Collections.sort(xIntersections);
        return rotatePoint(new Point(xIntersections.get(0), startY), angle);
    }

    /**
     * 重组多边形顶点，使得索引0的点最靠近填充起点
     */
    private static List<Point> alignBoundaryToStart(List<Point> polygon, Point target) {
        int bestIdx = 0;
        double minDist = Double.MAX_VALUE;
        for (int i = 0; i < polygon.size(); i++) {
            double d = Math.hypot(polygon.get(i).x - target.x, polygon.get(i).y - target.y);
            if (d < minDist) {
                minDist = d;
                bestIdx = i;
            }
        }
        List<Point> aligned = new ArrayList<>();
        for (int i = 0; i < polygon.size(); i++) {
            aligned.add(polygon.get((bestIdx + i) % polygon.size()));
        }
        return aligned;
    }

    private static List<PathSegment> generateZigZagPath(List<Point> polygon, double angle, double width, Point startPoint) {
        List<PathSegment> result = new ArrayList<>();
        List<Point> rotated = rotatePolygon(polygon, -angle);

        double minY = Double.MAX_VALUE, maxY = -Double.MAX_VALUE;
        for (Point p : rotated) {
            minY = Math.min(minY, p.y);
            maxY = Math.max(maxY, p.y);
        }

        Point currentPos = startPoint;
        boolean leftToRight = true;
        // 起点从 minY + width 开始，因为边缘已经围边割过
        for (double y = minY + width; y < maxY - width / 2; y += width) {
            List<Double> xInt = getXIntersections(rotated, y);
            if (xInt.size() < 2) continue;
            Collections.sort(xInt);

            double xStart = leftToRight ? xInt.get(0) : xInt.get(xInt.size() - 1);
            double xEnd = leftToRight ? xInt.get(xInt.size() - 1) : xInt.get(0);

            Point pS = rotatePoint(new Point(xStart, y), angle);
            Point pE = rotatePoint(new Point(xEnd, y), angle);

            // 添加过渡段 (如果是从围边切换过来或者换行)
            if (Math.hypot(currentPos.x - pS.x, currentPos.y - pS.y) > 0.05) {
                result.add(new PathSegment(currentPos, pS, false));
            }
            result.add(new PathSegment(pS, pE, true));
            currentPos = pE;
            leftToRight = !leftToRight;
        }
        return result;
    }

    private static List<Double> getXIntersections(List<Point> rotatedPoly, double y) {
        List<Double> xIntersections = new ArrayList<>();
        int n = rotatedPoly.size();
        for (int i = 0; i < n; i++) {
            Point p1 = rotatedPoly.get(i);
            Point p2 = rotatedPoly.get((i + 1) % n);
            if ((p1.y <= y && p2.y > y) || (p2.y <= y && p1.y > y)) {
                double x = p1.x + (y - p1.y) * (p2.x - p1.x) / (p2.y - p1.y);
                xIntersections.add(x);
            }
        }
        return xIntersections;
    }

    // --- 几何基础工具 ---

    private static List<Point> shrinkPolygon(List<Point> polygon, double margin) {
        List<Point> result = new ArrayList<>();
        int n = polygon.size();
        for (int i = 0; i < n; i++) {
            Point pPrev = polygon.get((i - 1 + n) % n);
            Point pCurr = polygon.get(i);
            Point pNext = polygon.get((i + 1) % n);

            double d1x = pCurr.x - pPrev.x, d1y = pCurr.y - pPrev.y;
            double l1 = Math.hypot(d1x, d1y);
            double d2x = pNext.x - pCurr.x, d2y = pNext.y - pCurr.y;
            double l2 = Math.hypot(d2x, d2y);

            double n1x = -d1y / l1, n1y = d1x / l1;
            double n2x = -d2y / l2, n2y = d2x / l2;

            double bx = n1x + n2x, by = n1y + n2y;
            double bLen = Math.hypot(bx, by);
            if (bLen < EPSILON) { bx = n1x; by = n1y; } 
            else { bx /= bLen; by /= bLen; }

            double cosHalf = n1x * bx + n1y * by;
            double d = margin / Math.max(cosHalf, 0.1);
            result.add(new Point(pCurr.x + bx * d, pCurr.y + by * d));
        }
        return result;
    }

    private static double findOptimalScanAngle(List<Point> polygon) {
        double minH = Double.MAX_VALUE;
        double bestA = 0;
        for (int i = 0; i < polygon.size(); i++) {
            Point p1 = polygon.get(i), p2 = polygon.get((i + 1) % polygon.size());
            double angle = Math.atan2(p2.y - p1.y, p2.x - p1.x);
            double h = calculatePolygonHeightAtAngle(polygon, angle);
            if (h < minH) { minH = h; bestA = angle; }
        }
        return bestA;
    }

    private static double calculatePolygonHeightAtAngle(List<Point> poly, double angle) {
        double minY = Double.MAX_VALUE, maxY = -Double.MAX_VALUE;
        double sin = Math.sin(-angle), cos = Math.cos(-angle);
        for (Point p : poly) {
            double ry = p.x * sin + p.y * cos;
            minY = Math.min(minY, ry); maxY = Math.max(maxY, ry);
        }
        return maxY - minY;
    }

    private static Point rotatePoint(Point p, double angle) {
        double c = Math.cos(angle), s = Math.sin(angle);
        return new Point(p.x * c - p.y * s, p.x * s + p.y * c);
    }

    private static List<Point> rotatePolygon(List<Point> poly, double angle) {
        List<Point> res = new ArrayList<>();
        for (Point p : poly) res.add(rotatePoint(p, angle));
        return res;
    }

    private static void ensureCCW(List<Point> poly) {
        double s = 0;
        for (int i = 0; i < poly.size(); i++) {
            Point p1 = poly.get(i), p2 = poly.get((i + 1) % poly.size());
            s += (p2.x - p1.x) * (p2.y + p1.y);
        }
        if (s > 0) Collections.reverse(poly);
    }

    private static List<Point> parseCoords(String s) {
        List<Point> list = new ArrayList<>();
        for (String p : s.split(";")) {
            String[] xy = p.split(",");
            if (xy.length >= 2) list.add(new Point(Double.parseDouble(xy[0]), Double.parseDouble(xy[1])));
        }
        return list;
    }
}