package lujing;

import java.util.*;

/**
 * 异形草地路径规划 - 围边+全局扫描版 V4.1
 * 优化：围边终点与弓字形起点自动对齐，实现无缝切换，确保路径不越界
 */
public class YixinglujingNoObstacle {

    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：逆时针化
        ensureCounterClockwise(rawPoints);
        
        // 2. 生成内缩多边形
        List<Point> boundary = getInsetPolygon(rawPoints, safeMargin);
        if (boundary.size() < 3) return new ArrayList<>();

        // 3. 确定最优扫描角度并找到弓字形路径的第一个作业起点
        double bestAngle = findOptimalAngle(boundary);
        Point firstScanStart = getFirstScanPoint(boundary, mowWidth, bestAngle);

        // 4. 对齐围边起点：重新排列围边坐标，使最后一个点靠近(或等于)扫描起点
        List<Point> alignedBoundary = alignBoundaryStart(boundary, firstScanStart);

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

        // 5. 【第一步】生成围边路径
        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));
        }

        // 6. 【第二步】从对齐后的终点开始生成内部扫描路径
        Point lastEdgePos = alignedBoundary.get(0); // 围边闭合回到起点
        List<PathSegment> scanPath = generateGlobalScanPath(boundary, mowWidth, bestAngle, lastEdgePos);
        
        finalPath.addAll(scanPath);

        return finalPath;
    }

    /**
     * 计算并获取扫描路径的第一行起点
     */
    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; 
        List<Double> xIntersections = getXIntersections(rotatedPoly, firstY);
        
        if (xIntersections.isEmpty()) return polygon.get(0);
        return rotatePoint(new Point(Collections.min(xIntersections), firstY), angle);
    }

    /**
     * 重新排列多边形顶点，使起始点与扫描起点对接
     */
    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<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;
        // 从 minY + width 开始，避开围边已割区域
        for (double y = minY + width; y <= maxY - width/2; y += width) {
            List<Double> xIntersections = getXIntersections(rotatedPoly, y);
            if (xIntersections.size() < 2) continue;
            Collections.sort(xIntersections);

            List<PathSegment> lineRows = 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);
                lineRows.add(new PathSegment(pS, pE, true));
            }

            if (!leftToRight) {
                Collections.reverse(lineRows);
                for (PathSegment s : lineRows) {
                    Point t = s.start; s.start = s.end; s.end = t;
                }
            }

            for (PathSegment s : lineRows) {
                // 如果间距极小，视为无缝衔接
                if (Math.hypot(currentPos.x - s.start.x, currentPos.y - s.start.y) > 0.05) {
                    segments.add(new PathSegment(currentPos, s.start, false));
                }
                segments.add(s);
                currentPos = s.end;
            }
            leftToRight = !leftToRight;
        }
        return segments;
    }

    private static List<Double> getXIntersections(List<Point> rotatedPoly, double y) {
        List<Double> xIntersections = new ArrayList<>();
        for (int i = 0; i < rotatedPoly.size(); i++) {
            Point p1 = rotatedPoly.get(i);
            Point p2 = rotatedPoly.get((i + 1) % rotatedPoly.size());
            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;
    }

    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;
    }

    private 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;
            double n1x = -d1y / l1, n1y = d1x / l1;
            double n2x = -d2y / l2, n2y = d2x / l2;
            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);
            result.add(new Point(pCurr.x + bisectorX * dist, pCurr.y + bisectorY * dist));
        }
        return result;
    }

    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);
    }

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