package lujing;

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

/**
 * 异形草地路径规划 - 避障增强版 V8.0
 * 修复说明：
 * 1. 修正了地块内缩和障碍物外扩的正负逻辑。
 * 2. 优化了多边形偏移算法，确保逆时针点序下正值内缩，负值外扩。
 * 3. 增强了障碍物解析的健壮性。
 */
public class YixinglujingHaveObstacel {

    public static List<PathSegment> planPath(String coordinates, String obstaclesStr, String widthStr, String marginStr) {
        List<Point> rawPoints = parseCoordinates(coordinates);
        if (rawPoints.size() < 3) return new ArrayList<>();

        double mowWidth = Double.parseDouble(widthStr);
        double safeMargin = Double.parseDouble(marginStr);

        // 1. 预处理地块（确保逆时针顺序）
        ensureCounterClockwise(rawPoints);
        
        // 【核心修复】：对于逆时针多边形，正数是向内偏移（Inset）
        List<Point> boundary = getOffsetPolygon(rawPoints, safeMargin); 
        if (boundary.size() < 3) return new ArrayList<>();

        // 2. 确定最优角度并规划基础路径
        double bestAngle = findOptimalAngle(boundary);
        Point firstScanStart = getFirstScanPoint(boundary, mowWidth, bestAngle);
        List<Point> alignedBoundary = alignBoundaryStart(boundary, firstScanStart);

        List<PathSegment> baseLines = new ArrayList<>();
        // 第一阶段：围边路径
        for (int i = 0; i < alignedBoundary.size(); i++) {
            baseLines.add(new PathSegment(alignedBoundary.get(i), alignedBoundary.get((i + 1) % alignedBoundary.size()), true));
        }
        // 第二阶段：生成内部扫描路径
        Point lastEdgePos = alignedBoundary.get(0);
        baseLines.addAll(generateGlobalScanPath(boundary, mowWidth, bestAngle, lastEdgePos));

        // 3. 处理障碍物：解析并执行【外扩】
        // 【核心修复】：对于逆时针障碍物，负数是向外偏移（Outset）
        List<Obstacle> obstacles = parseObstacles(obstaclesStr, safeMargin);

        // 4. 路径裁剪与优化连接
        return optimizeAndClipPath(baseLines, obstacles);
    }

    private static List<Obstacle> parseObstacles(String obsStr, double margin) {
        List<Obstacle> obstacles = new ArrayList<>();
        if (obsStr == null || obsStr.trim().isEmpty()) return obstacles;
        
        for (String group : obsStr.split("\\$")) {
            List<Point> pts = parseCoordinates(group);
            if (pts.isEmpty()) continue;
            
            if (pts.size() == 2) {
                // 圆形障碍物：第一个点心，第二个点上一点，半径增加 margin
                double r = Math.hypot(pts.get(0).x - pts.get(1).x, pts.get(0).y - pts.get(1).y);
                obstacles.add(new CircleObstacle(pts.get(0), r + margin));
            } else if (pts.size() > 2) {
                // 多边形障碍物：确保逆时针，然后使用负 margin 进行【外扩】
                ensureCounterClockwise(pts);
                obstacles.add(new PolyObstacle(getOffsetPolygon(pts, -margin)));
            }
        }
        return obstacles;
    }

    /**
     * 多边形偏移算法：基于角平分线偏移
     * 在逆时针顺序下：offset > 0 为内缩，offset < 0 为外扩
     */
    private static List<Point> getOffsetPolygon(List<Point> points, double offset) {
        List<Point> result = new ArrayList<>();
        int n = points.size();
        for (int i = 0; i < n; i++) {
            Point p1 = points.get((i - 1 + n) % n);
            Point p2 = points.get(i);
            Point p3 = points.get((i + 1) % n);
            
            double v1x = p2.x - p1.x, v1y = p2.y - p1.y;
            double v2x = p3.x - p2.x, v2y = p3.y - p2.y;
            double l1 = Math.hypot(v1x, v1y), l2 = Math.hypot(v2x, v2y);
            
            if (l1 < 1e-6 || l2 < 1e-6) continue;

            // 获取两条边的法向量（向左偏移）
            double n1x = -v1y / l1, n1y = v1x / l1;
            double n2x = -v2y / l2, n2y = v2x / l2;

            // 角平分线向量
            double bx = n1x + n2x, by = n1y + n2y;
            double bl = Math.hypot(bx, by);
            if (bl < 1e-6) { 
                bx = n1x; by = n1y; 
            } else { 
                bx /= bl; by /= bl; 
            }

            // 计算偏移长度修正系数：1/sin(theta/2)
            double cosHalf = n1x * bx + n1y * by;
            double d = offset / Math.max(cosHalf, 0.1); // 避免分母过小导致无穷大
            
            // 限制最大位移量，防止极尖角畸变
            d = Math.signum(offset) * Math.min(Math.abs(d), Math.abs(offset) * 5);

            result.add(new Point(p2.x + bx * d, p2.y + by * d));
        }
        return result;
    }

    private static List<PathSegment> optimizeAndClipPath(List<PathSegment> originalPath, List<Obstacle> obstacles) {
        List<PathSegment> result = new ArrayList<>();
        Point currentPos = null;

        for (PathSegment segment : originalPath) {
            List<PathSegment> clipped = new ArrayList<>();
            clipped.add(segment);

            // 用每一个障碍物依次裁剪
            for (Obstacle obs : obstacles) {
                List<PathSegment> nextIter = new ArrayList<>();
                for (PathSegment s : clipped) {
                    nextIter.addAll(obs.clipSegment(s));
                }
                clipped = nextIter;
            }

            for (PathSegment s : clipped) {
                // 剔除微小段
                if (Math.hypot(s.start.x - s.end.x, s.start.y - s.end.y) < 1e-4) continue;

                // 如果新段的起点与上段的终点不连贯，添加空走（非割草）路径
                if (currentPos != null && Math.hypot(currentPos.x - s.start.x, currentPos.y - s.start.y) > 0.01) {
                    result.add(new PathSegment(currentPos, s.start, false));
                }
                result.add(s);
                currentPos = s.end;
            }
        }
        return result;
    }

    // --- 障碍物类定义 ---
    abstract static class Obstacle {
        abstract boolean isInside(Point p);
        abstract List<PathSegment> clipSegment(PathSegment seg);
    }

    static class PolyObstacle extends Obstacle {
        List<Point> points;
        double minX, maxX, minY, maxY;

        public PolyObstacle(List<Point> pts) {
            this.points = pts;
            minX = minY = Double.MAX_VALUE;
            maxX = maxY = -Double.MAX_VALUE;
            for (Point p : pts) {
                minX = Math.min(minX, p.x); maxX = Math.max(maxX, p.x);
                minY = Math.min(minY, p.y); maxY = Math.max(maxY, p.y);
            }
        }

        @Override
        boolean isInside(Point p) {
            if (p.x < minX || p.x > maxX || p.y < minY || p.y > maxY) return false;
            boolean inside = false;
            for (int i = 0, j = points.size() - 1; i < points.size(); j = i++) {
                if (((points.get(i).y > p.y) != (points.get(j).y > p.y)) &&
                    (p.x < (points.get(j).x - points.get(i).x) * (p.y - points.get(i).y) / (points.get(j).y - points.get(i).y) + points.get(i).x)) {
                    inside = !inside;
                }
            }
            return inside;
        }

        @Override
        List<PathSegment> clipSegment(PathSegment seg) {
            List<Double> ts = new ArrayList<>(Arrays.asList(0.0, 1.0));
            for (int i = 0; i < points.size(); i++) {
                double t = getIntersectionT(seg.start, seg.end, points.get(i), points.get((i + 1) % points.size()));
                if (t > 0 && t < 1) ts.add(t);
            }
            Collections.sort(ts);
            List<PathSegment> res = new ArrayList<>();
            for (int i = 0; i < ts.size() - 1; i++) {
                Point s = interpolate(seg.start, seg.end, ts.get(i));
                Point e = interpolate(seg.start, seg.end, ts.get(i + 1));
                // 检查中点是否在障碍物内
                if (!isInside(new Point((s.x + e.x) / 2, (s.y + e.y) / 2))) {
                    res.add(new PathSegment(s, e, seg.isMowing));
                }
            }
            return res;
        }
    }

    static class CircleObstacle extends Obstacle {
        Point center; double radius;
        public CircleObstacle(Point c, double r) { this.center = c; this.radius = r; }

        @Override
        boolean isInside(Point p) { return Math.hypot(p.x - center.x, p.y - center.y) < radius - 1e-4; }

        @Override
        List<PathSegment> clipSegment(PathSegment seg) {
            List<Double> ts = new ArrayList<>(Arrays.asList(0.0, 1.0));
            double dx = seg.end.x - seg.start.x, dy = seg.end.y - seg.start.y;
            double fx = seg.start.x - center.x, fy = seg.start.y - center.y;
            double a = dx * dx + dy * dy;
            double b = 2 * (fx * dx + fy * dy);
            double c = fx * fx + fy * fy - radius * radius;
            double disc = b * b - 4 * a * c;
            if (disc >= 0) {
                disc = Math.sqrt(disc);
                double t1 = (-b - disc) / (2 * a), t2 = (-b + disc) / (2 * a);
                if (t1 > 0 && t1 < 1) ts.add(t1);
                if (t2 > 0 && t2 < 1) ts.add(t2);
            }
            Collections.sort(ts);
            List<PathSegment> res = new ArrayList<>();
            for (int i = 0; i < ts.size() - 1; i++) {
                Point s = interpolate(seg.start, seg.end, ts.get(i));
                Point e = interpolate(seg.start, seg.end, ts.get(i + 1));
                if (!isInside(new Point((s.x + e.x) / 2, (s.y + e.y) / 2))) res.add(new PathSegment(s, e, seg.isMowing));
            }
            return res;
        }
    }

    // --- 内部算法与数学支持 ---

    private static List<PathSegment> generateGlobalScanPath(List<Point> polygon, double width, double angle, Point currentPos) {
        List<PathSegment> segments = new ArrayList<>();
        List<Point> rotated = new ArrayList<>();
        for (Point p : polygon) rotated.add(rotatePoint(p, -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); }

        boolean l2r = true;
        for (double y = minY + width/2; y <= maxY - width/2; y += width) {
            List<Double> xInters = getXIntersections(rotated, y);
            if (xInters.size() < 2) continue;
            Collections.sort(xInters);

            List<PathSegment> row = new ArrayList<>();
            for (int i = 0; i < xInters.size() - 1; i += 2) {
                Point s = rotatePoint(new Point(xInters.get(i), y), angle);
                Point e = rotatePoint(new Point(xInters.get(i + 1), y), angle);
                row.add(new PathSegment(s, e, true));
            }
            if (!l2r) {
                Collections.reverse(row);
                for (PathSegment s : row) { Point t = s.start; s.start = s.end; s.end = t; }
            }
            for (PathSegment s : row) {
                if (Math.hypot(currentPos.x - s.start.x, currentPos.y - s.start.y) > 0.01) {
                    segments.add(new PathSegment(currentPos, s.start, false));
                }
                segments.add(s);
                currentPos = s.end;
            }
            l2r = !l2r;
        }
        return segments;
    }

    private static double getIntersectionT(Point a, Point b, Point c, Point d) {
        double ux = b.x - a.x, uy = b.y - a.y, vx = d.x - c.x, vy = d.y - c.y;
        double det = vx * uy - vy * ux;
        if (Math.abs(det) < 1e-6) return -1;
        return (vx * (c.y - a.y) - vy * (c.x - a.x)) / det;
    }

    private static Point interpolate(Point a, Point b, double t) {
        return new Point(a.x + (b.x - a.x) * t, a.y + (b.y - a.y) * t);
    }

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

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

    private static Point getFirstScanPoint(List<Point> poly, double w, double a) {
        List<Point> rot = new ArrayList<>();
        for (Point p : poly) rot.add(rotatePoint(p, -a));
        double minY = Double.MAX_VALUE;
        for (Point p : rot) minY = Math.min(minY, p.y);
        List<Double> xs = getXIntersections(rot, minY + w/2);
        if (xs.isEmpty()) return poly.get(0);
        Collections.sort(xs);
        return rotatePoint(new Point(xs.get(0), minY + w/2), a);
    }

    private static List<Point> alignBoundaryStart(List<Point> poly, Point target) {
        int idx = 0; double minD = Double.MAX_VALUE;
        for (int i = 0; i < poly.size(); i++) {
            double d = Math.hypot(poly.get(i).x - target.x, poly.get(i).y - target.y);
            if (d < minD) { minD = d; idx = i; }
        }
        List<Point> res = new ArrayList<>();
        for (int i = 0; i < poly.size(); i++) res.add(poly.get((idx + i) % poly.size()));
        return res;
    }

    private static double findOptimalAngle(List<Point> poly) {
        double bestA = 0, minH = Double.MAX_VALUE;
        for (int i = 0; i < poly.size(); i++) {
            Point p1 = poly.get(i), p2 = poly.get((i + 1) % poly.size());
            double a = Math.atan2(p2.y - p1.y, p2.x - p1.x);
            double miY = Double.MAX_VALUE, maY = -Double.MAX_VALUE;
            for (Point p : poly) {
                Point r = rotatePoint(p, -a);
                miY = Math.min(miY, r.y); maY = Math.max(maY, r.y);
            }
            if (maY - miY < minH) { minH = maY - miY; bestA = a; }
        }
        return bestA;
    }

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

    private static List<Point> parseCoordinates(String s) {
        List<Point> pts = new ArrayList<>();
        if (s == null || s.isEmpty()) return pts;
        for (String p : s.split(";")) {
            String[] xy = p.split(",");
            if (xy.length == 2) pts.add(new Point(Double.parseDouble(xy[0]), Double.parseDouble(xy[1])));
        }
        if (pts.size() > 1 && pts.get(0).equals(pts.get(pts.size() - 1))) pts.remove(pts.size() - 1);
        return pts;
    }

    public static class Point {
        public double x, y;
        public Point(double x, double y) { this.x = x; this.y = y; }
        @Override
        public boolean equals(Object o) {
            if (!(o instanceof Point)) return false;
            Point p = (Point) o;
            return Math.abs(x - p.x) < 1e-4 && Math.abs(y - p.y) < 1e-4;
        }
    }

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