package lujing;

import java.util.*;
import java.util.Set;
import java.util.HashSet;

/**
 * 异形草地路径规划 - 凹多边形兼容优化版 V5.0
 * 修复：解决凹多边形扫描线跨越边界的问题，优化路径对齐
 */
public class YixinglujingNoObstacle {
    // 用法说明（无障碍物路径规划）：
    // - 方法用途：根据地块边界、割草宽度与安全边距，生成覆盖全区域的割草路径。
    // - 参数：
    //   coordinates：地块边界坐标字符串，格式 "x1,y1;x2,y2;..."，至少3个点，单位为米。
    //   widthStr：割草宽度（字符串，单位米），用于确定扫描线间距。
    //   marginStr：安全边距（字符串，单位米），用于将地块边界向内收缩，避免贴边作业。
    // - 返回值：List<PathSegment>，其中 PathSegment.start/end 为坐标点，isMowing 为 true 表示割草段，false 表示空走段。
    // - 失败情况：当边界点不足或内缩后区域过小，返回空列表。
    // - 使用示例：
    //   String boundary = "0,0;20,0;20,15;0,15";
    //   String width = "0.3";
    //   String margin = "0.5";
    //   List<YixinglujingNoObstacle.PathSegment> path =
    //       YixinglujingNoObstacle.planPath(boundary, width, margin);
    public static List<PathSegment> planPath(String coordinates, 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：确保逆时针顺序
        ensureCounterClockwise(rawPoints);
        
        // 2. 生成内缩多边形（安全边界）
        List<Point> boundary = getInsetPolygon(rawPoints, safeMargin);
        if (boundary.size() < 3) return new ArrayList<>();

        // 3. 确定最优作业角度
        double bestAngle = findOptimalAngle(boundary);
        
        // 4. 获取首个作业点，用于对齐围边起点
        Point firstScanStart = getFirstScanPoint(boundary, mowWidth, bestAngle);

        // 5. 对齐围边：使围边最后结束于靠近扫描起点的位置
        List<Point> alignedBoundary = alignBoundaryStart(boundary, firstScanStart);

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

        // 6. 第一阶段：围边路径
        for (int i = 0; i < alignedBoundary.size(); i++) {
            Point pStart = alignedBoundary.get(i);
            Point pEnd = alignedBoundary.get((i + 1) % alignedBoundary.size());
            finalPath.add(new PathSegment(pStart, pEnd, true));
        }

        // 7. 第二阶段：生成内部扫描路径（修复凹部空越问题）
        Point lastEdgePos = alignedBoundary.get(0); 
        List<PathSegment> scanPath = generateGlobalScanPath(boundary, mowWidth, bestAngle, lastEdgePos);
        
        finalPath.addAll(scanPath);

        // 8. 格式化坐标：保留两位小数
        for (PathSegment segment : finalPath) {
            segment.start.x = Math.round(segment.start.x * 100.0) / 100.0;
            segment.start.y = Math.round(segment.start.y * 100.0) / 100.0;
            segment.end.x = Math.round(segment.end.x * 100.0) / 100.0;
            segment.end.y = Math.round(segment.end.y * 100.0) / 100.0;
        }

        return finalPath;
    }

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

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

        boolean leftToRight = true;
        // 步长 y 从最小到最大扫描
        for (double y = minY + width/2; y <= maxY - width/2; y += width) {
            List<Double> xIntersections = getXIntersections(rotatedPoly, y);
            if (xIntersections.size() < 2) continue;
            Collections.sort(xIntersections);

            // 处理凹多边形：每两个点组成一个有效作业段
            List<PathSegment> lineSegmentsInRow = new ArrayList<>();
            for (int i = 0; i < xIntersections.size() - 1; i += 2) {
                Point pS = rotatePoint(new Point(xIntersections.get(i), y), angle);
                Point pE = rotatePoint(new Point(xIntersections.get(i + 1), y), angle);
                lineSegmentsInRow.add(new PathSegment(pS, pE, true));
            }

            // 根据当前S型方向排序作业段
            if (!leftToRight) {
                Collections.reverse(lineSegmentsInRow);
                for (PathSegment s : lineSegmentsInRow) {
                    Point temp = s.start; s.start = s.end; s.end = temp;
                }
            }

            // 将作业段连接到总路径
            for (PathSegment s : lineSegmentsInRow) {
                if (Math.hypot(currentPos.x - s.start.x, currentPos.y - s.start.y) > 0.01) {
                    // 如果间距大于1cm，添加空走路径
                    addSafeConnection(segments, currentPos, s.start, polygon);
                }
                segments.add(s);
                currentPos = s.end;
            }
            leftToRight = !leftToRight;
        }
        return segments;
    }

    private static Point getFirstScanPoint(List<Point> polygon, double width, double angle) {
        List<Point> rotatedPoly = new ArrayList<>();
        for (Point p : polygon) rotatedPoly.add(rotatePoint(p, -angle));
        double minY = Double.MAX_VALUE;
        for (Point p : rotatedPoly) minY = Math.min(minY, p.y);
        
        double firstY = minY + width/2;
        List<Double> xInter = getXIntersections(rotatedPoly, firstY);
        if (xInter.isEmpty()) return polygon.get(0);
        Collections.sort(xInter);
        return rotatePoint(new Point(xInter.get(0), firstY), angle);
    }

    private static List<Point> alignBoundaryStart(List<Point> boundary, Point targetStart) {
        int bestIdx = 0;
        double minDist = Double.MAX_VALUE;
        for (int i = 0; i < boundary.size(); i++) {
            double d = Math.hypot(boundary.get(i).x - targetStart.x, boundary.get(i).y - targetStart.y);
            if (d < minDist) { minDist = d; bestIdx = i; }
        }
        List<Point> aligned = new ArrayList<>();
        for (int i = 0; i < boundary.size(); i++) {
            aligned.add(boundary.get((bestIdx + i) % boundary.size()));
        }
        return aligned;
    }

    private static List<Double> getXIntersections(List<Point> rotatedPoly, double y) {
        List<Double> xIntersections = new ArrayList<>();
        double tolerance = 1e-6;
        
        for (int i = 0; i < rotatedPoly.size(); i++) {
            Point p1 = rotatedPoly.get(i);
            Point p2 = rotatedPoly.get((i + 1) % rotatedPoly.size());
            
            // 跳过水平边（避免与扫描线重合时的特殊情况）
            if (Math.abs(p1.y - p2.y) < tolerance) {
                continue;
            }
            
            // 检查是否相交（使用严格不等式避免顶点重复）
            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);
                // 简单去重：检查是否已存在相近的点
                boolean isDuplicate = false;
                for (double existingX : xIntersections) {
                    if (Math.abs(x - existingX) < tolerance) {
                        isDuplicate = true;
                        break;
                    }
                }
                if (!isDuplicate) {
                    xIntersections.add(x);
                }
            }
        }
        return xIntersections;
    }

    private static double findOptimalAngle(List<Point> polygon) {
        double bestAngle = 0;
        double minHeight = Double.MAX_VALUE;
        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 = calculateHeightAtAngle(polygon, angle);
            if (h < minHeight) { minHeight = h; bestAngle = angle; }
        }
        return bestAngle;
    }

    private static double calculateHeightAtAngle(List<Point> poly, double angle) {
        double minY = Double.MAX_VALUE, maxY = -Double.MAX_VALUE;
        for (Point p : poly) {
            Point rp = rotatePoint(p, -angle);
            minY = Math.min(minY, rp.y); maxY = Math.max(maxY, rp.y);
        }
        return maxY - minY;
    }

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

            if (l1 < 1e-6 || l2 < 1e-6) continue;

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

            // 角平分线方向
            double bisectorX = n1x + n2x, bisectorY = n1y + n2y;
            double bLen = Math.hypot(bisectorX, bisectorY);
            if (bLen < 1e-6) { bisectorX = n1x; bisectorY = n1y; } 
            else { bisectorX /= bLen; bisectorY /= bLen; }

            double cosHalfAngle = n1x * bisectorX + n1y * bisectorY;
            double dist = margin / Math.max(cosHalfAngle, 0.1); 
            
            // 限制最大位移量，防止极尖角畸变
            dist = Math.min(dist, margin * 5); 

            result.add(new Point(pCurr.x + bisectorX * dist, pCurr.y + bisectorY * dist));
        }
        return result;
    }

    private static void addSafeConnection(List<PathSegment> segments, Point start, Point end, List<Point> polygon) {
        if (isSegmentSafe(start, end, polygon)) {
            segments.add(new PathSegment(start, end, false));
        } else {
            List<Point> path = getBoundaryPath(start, end, polygon);
            for (int i = 0; i < path.size() - 1; i++) {
                segments.add(new PathSegment(path.get(i), path.get(i+1), false));
            }
        }
    }

    private static boolean isSegmentSafe(Point p1, Point p2, List<Point> polygon) {
        Point mid = new Point((p1.x + p2.x) / 2, (p1.y + p2.y) / 2);
        if (!isPointInPolygon(mid, polygon)) return false;
        
        for (int i = 0; i < polygon.size(); i++) {
            Point a = polygon.get(i);
            Point b = polygon.get((i + 1) % polygon.size());
            if (isSamePoint(p1, a) || isSamePoint(p1, b) || isSamePoint(p2, a) || isSamePoint(p2, b)) continue;
            if (segmentsIntersect(p1, p2, a, b)) return false;
        }
        return true;
    }

    private static boolean isSamePoint(Point a, Point b) {
        return Math.abs(a.x - b.x) < 1e-4 && Math.abs(a.y - b.y) < 1e-4;
    }

    private static boolean segmentsIntersect(Point a, Point b, Point c, Point d) {
        return ccw(a, c, d) != ccw(b, c, d) && ccw(a, b, c) != ccw(a, b, d);
    }

    private static boolean ccw(Point a, Point b, Point c) {
        return (c.y - a.y) * (b.x - a.x) > (b.y - a.y) * (c.x - a.x);
    }

    private static boolean isPointInPolygon(Point p, List<Point> polygon) {
        boolean result = false;
        for (int i = 0, j = polygon.size() - 1; i < polygon.size(); j = i++) {
            if ((polygon.get(i).y > p.y) != (polygon.get(j).y > p.y) &&
                (p.x < (polygon.get(j).x - polygon.get(i).x) * (p.y - polygon.get(i).y) / (polygon.get(j).y - polygon.get(i).y) + polygon.get(i).x)) {
                result = !result;
            }
        }
        return result;
    }

    private static List<Point> getBoundaryPath(Point start, Point end, List<Point> polygon) {
        int idx1 = getEdgeIndex(start, polygon);
        int idx2 = getEdgeIndex(end, polygon);
        
        if (idx1 == -1 || idx2 == -1 || idx1 == idx2) {
            return Arrays.asList(start, end);
        }

        List<Point> path1 = new ArrayList<>();
        path1.add(start);
        int curr = idx1;
        while (curr != idx2) {
            path1.add(polygon.get((curr + 1) % polygon.size()));
            curr = (curr + 1) % polygon.size();
        }
        path1.add(end);

        List<Point> pathRev = new ArrayList<>();
        pathRev.add(start);
        curr = idx1;
        while (curr != idx2) {
            pathRev.add(polygon.get(curr));
            curr = (curr - 1 + polygon.size()) % polygon.size();
        }
        pathRev.add(polygon.get((idx2 + 1) % polygon.size()));
        pathRev.add(end);
        
        return getPathLength(path1) < getPathLength(pathRev) ? path1 : pathRev;
    }

    private static double getPathLength(List<Point> path) {
        double len = 0;
        for (int i = 0; i < path.size() - 1; i++) {
            len += Math.hypot(path.get(i).x - path.get(i+1).x, path.get(i).y - path.get(i+1).y);
        }
        return len;
    }

    private static int getEdgeIndex(Point p, List<Point> poly) {
        for (int i = 0; i < poly.size(); i++) {
            Point p1 = poly.get(i);
            Point p2 = poly.get((i + 1) % poly.size());
            if (distToSegment(p, p1, p2) < 1e-3) return i;
        }
        return -1;
    }
    
    private static double distToSegment(Point p, Point s, Point e) {
        double l2 = (s.x - e.x)*(s.x - e.x) + (s.y - e.y)*(s.y - e.y);
        if (l2 == 0) return Math.hypot(p.x - s.x, p.y - s.y);
        double t = ((p.x - s.x) * (e.x - s.x) + (p.y - s.y) * (e.y - s.y)) / l2;
        t = Math.max(0, Math.min(1, t));
        return Math.hypot(p.x - (s.x + t * (e.x - s.x)), p.y - (s.y + t * (e.y - s.y)));
    }

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

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

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

    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; // true: 割草中, false: 空载移动
        public PathSegment(Point s, Point e, boolean m) { this.start = s; this.end = e; this.isMowing = m; }
    }
}