package gecaoji;

import java.awt.geom.Point2D;
import java.util.List;

/**
 * 割草机边界检查工具类。
 *
 * 用法契约：
 * - 输入的地块边界为闭合的多边形点序列（顺序为顺时针或逆时针均可），每个点包含 X（米）、Y（米）坐标。
 * - 若点位于多边形内部或位于边界线上，返回 true；否则返回 false。
 */
public final class MowerBoundaryChecker {

    private MowerBoundaryChecker() { }

    /**
     * 判断给定点是否在边界多边形内部（含边界）。
     *
     * @param polygonPoints 边界点列表，每个元素为 double[2]，索引0为x，索引1为y；至少需要3个点
     * @param x 割草机实时X坐标（米）
     * @param y 割草机实时Y坐标（米）
     * @return 如果点在多边形内部或边界上则返回 true；否则返回 false
     */
    public static boolean isInsideBoundary(List<double[]> polygonPoints, double x, double y) {
        if (polygonPoints == null || polygonPoints.size() < 3) {
            return false;
        }
        int n = polygonPoints.size();
        boolean inside = false;
        for (int i = 0, j = n - 1; i < n; j = i++) {
            double xi = polygonPoints.get(i)[0];
            double yi = polygonPoints.get(i)[1];
            double xj = polygonPoints.get(j)[0];
            double yj = polygonPoints.get(j)[1];

            // 判断点是否在当前边上（考虑浮点容差）
            if (pointOnSegment(xj, yj, xi, yi, x, y)) {
                return true;
            }

            boolean intersect = ((yi > y) != (yj > y)) &&
                    (x < (xj - xi) * (y - yi) / (yj - yi + 0.0) + xi);
            if (intersect) {
                inside = !inside;
            }
        }
        return inside;
    }

    /**
     * 重载：接受 Point2D 列表
     */
    public static boolean isInsideBoundaryPoints(List<Point2D.Double> polygonPoints, double x, double y) {
        if (polygonPoints == null || polygonPoints.size() < 3) {
            return false;
        }
        int n = polygonPoints.size();
        boolean inside = false;
        for (int i = 0, j = n - 1; i < n; j = i++) {
            double xi = polygonPoints.get(i).x;
            double yi = polygonPoints.get(i).y;
            double xj = polygonPoints.get(j).x;
            double yj = polygonPoints.get(j).y;

            if (pointOnSegment(xj, yj, xi, yi, x, y)) {
                return true;
            }

            boolean intersect = ((yi > y) != (yj > y)) &&
                    (x < (xj - xi) * (y - yi) / (yj - yi + 0.0) + xi);
            if (intersect) {
                inside = !inside;
            }
        }
        return inside;
    }

    /**
     * 重载：接受二维数组 double[][]，每行 [x,y]
     */
    public static boolean isInsideBoundary(double[][] polygon, double x, double y) {
        if (polygon == null || polygon.length < 3) {
            return false;
        }
        int n = polygon.length;
        boolean inside = false;
        for (int i = 0, j = n - 1; i < n; j = i++) {
            double xi = polygon[i][0];
            double yi = polygon[i][1];
            double xj = polygon[j][0];
            double yj = polygon[j][1];

            if (pointOnSegment(xj, yj, xi, yi, x, y)) {
                return true;
            }

            boolean intersect = ((yi > y) != (yj > y)) &&
                    (x < (xj - xi) * (y - yi) / (yj - yi + 0.0) + xi);
            if (intersect) {
                inside = !inside;
            }
        }
        return inside;
    }

    // 判断点是否在线段 (x1,y1)-(x2,y2) 上（包括端点），允许小的数值误差
    private static boolean pointOnSegment(double x1, double y1, double x2, double y2, double px, double py) {
        double cross = (px - x1) * (y2 - y1) - (py - y1) * (x2 - x1);
        double eps = 1e-8;
        if (Math.abs(cross) > eps) {
            return false;
        }
        double dot = (px - x1) * (px - x2) + (py - y1) * (py - y2);
        return dot <= eps;
    }
}