namespace Yw.Curve
{
    /// <summary>
    /// 直线辅助类
    /// </summary>
    public static class CurveLineHelper
    {
        /// <summary>
        /// 是否垂直
        /// </summary>
        /// <param name="k"></param>
        /// <returns></returns>
        public static bool IsVerticalK(double k)
        {
            if (k >= _verticalK - 1)
                return true;
            else
                return false;
        }
        private const double _verticalK = 100000000;//垂直时K的值

        /// <summary>
        /// 获取插值Y
        /// </summary>
        public static double GetInsertY(double x1, double y1, double x2, double y2, double x)
        {
            return new CurveLine(x1, y1, x2, y2).GetInsertY(x);
        }

        /// <summary>
        /// 是否一个点向x轴的射线穿透线段,有交点且在线的左边
        /// </summary>
        public static bool IsIntersectLeft(CurvePoint pt1, CurvePoint pt2, CurvePoint pt)
        {
            return new CurveLine(pt1, pt2).IsIntersectLeft(pt);
        }

        /// <summary>
        /// 是否一个点向x轴的射线穿透线段,有交点且在线的左边
        /// </summary>
        public static bool IsIntersectLeft(double x1, double y1, double x2, double y2, double x, double y)
        {
            return new CurveLine(x1, y1, x2, y2).IsIntersectLeft(new CurvePoint(x, y));
        }

        /// <summary>
        /// X1和X2之间连一条线, 在比率ratio处点的坐标
        /// </summary>
        public static double GetInnerX(double x1, double x2, double ratio)
        {
            double x = x1 + ratio * (x2 - x1);
            return x;
        }

        /// <summary>
        /// X1,Y1和X2 Y2之间连一条线,在X处点的Y坐标
        /// </summary>
        public static double GetYbyX(double x1, double y1, double x2, double y2, double x)
        {
            return new CurveLine(x1, y1, x2, y2).GetYByX(x);
        }

        /// <summary>
        /// X1,Y1和X2 Y2之间连一条线,在Y处点的X坐标
        /// </summary>
        public static double GetXbyY(double x1, double y1, double x2, double y2, double y)
        {
            return new CurveLine(x1, y1, x2, y2).GetXByY(y);
        }

        /// <summary>
        /// 输入(X1,Y1),(X1,Y1)生成直线,返回直线的k和b y=kx+b
        /// </summary>
        public static bool GetKandB(double x1, double y1, double x2, double y2, out double k, out double b, double ignore = 0.000001)
        {
            return new CurveLine(x1, y1, x2, y2).GetKandB(out k, out b, ignore);
        }

        /// <summary>
        /// 通过2点,得到通过这2点的直线的k,b  线的形式是 y=k*x+b,竖直返回false
        /// </summary>
        public static bool GetKandB(CurvePoint pt1, CurvePoint pt2, out double k, out double b, double ignore = 0.000001)
        {
            return new CurveLine(pt1, pt2).GetKandB(out k, out b, ignore);
        }

        /// <summary>
        /// 取中间点
        /// </summary>
        public static CurvePoint GetMiddlePoint(CurvePoint pt1, CurvePoint pt2)
        {
            return new CurveLine(pt1, pt2).GetMiddlePoint();
        }

        /// <summary>
        /// 取内部点
        /// </summary>
        public static CurvePoint GetInnerPoint(CurvePoint startPt, CurvePoint endPt, double ratio)
        {
            return new CurveLine(startPt, endPt).GetInnerPoint(ratio);
        }

        /// <summary>
        /// 是否是内部点
        /// </summary>
        public static bool IsInnerByX(CurvePoint startPt, CurvePoint endPt, double x)
        {
            return new CurveLine(startPt, endPt).IsInnerByX(x);
        }

        /// <summary>
        /// 三个点在同一条直线上,输入(X1,Y1),(X2,Y2)以及沿(X2,Y2)侧延长Length,得到的点(X3,Y3)
        /// </summary>
        public static CurvePoint GetExtendPoint(CurvePoint startPt, CurvePoint endPt, double length)
        {
            return new CurveLine(startPt, endPt).GetExtendPoint(length);
        }

        /// <summary>
        /// 求直线外一点到该直线的投影点
        /// </summary>
        /// <param name="pl">线上任一点</param>
        /// <param name="k">直线斜率</param>
        /// <param name="pout">线外指定点</param>
        public static CurvePoint GetProjectivePoint(CurvePoint pl, double k, CurvePoint pout)
        {
            CurvePoint pProject = new CurvePoint();
            if (k == 0) //垂线斜率不存在情况
            {
                pProject.X = pout.X;
                pProject.Y = pl.Y;
            }
            else
            {
                pProject.X = (float)((k * pl.X + pout.X / k + pout.Y - pl.Y) / (1 / k + k));
                pProject.Y = (float)(-1 / k * (pProject.X - pout.X) + pout.Y);
            }
            return pProject;
        }

        /// <summary>
        /// 求直线外一点到该直线的投影点
        /// </summary>
        /// <param name="pLine1"></param>
        /// <param name="pLine2"></param>
        /// <param name="pOut"></param>
        /// <returns></returns>
        public static CurvePoint GetProjectivePoint(CurvePoint pLine1, CurvePoint pLine2, CurvePoint pOut)
        {
            if (!GetKandB(pLine1, pLine2, out double k, out double b))
                return default;
            return GetProjectivePoint(pLine1, k, pOut);
        }

        /// <summary>
        /// 点到线的距离, 注意不一定是垂直距离,点只在(line_start和line_end之间
        /// </summary>
        public static double Distance(CurvePoint line_start, CurvePoint line_end, CurvePoint point)
        {
            return new CurveLine(line_start, line_end).Distance(point);
        }

        /// <summary>
        /// 计算交点(没有 就返回null)
        /// </summary>
        public static Yw.Curve.CurvePoint GetCrossPoint(Yw.Curve.CurvePoint startPt1, Yw.Curve.CurvePoint endPt1, Yw.Curve.CurvePoint startPt2, Yw.Curve.CurvePoint endPt2)
        {
            if (startPt1 == null || endPt1 == null)
                return null;
            if (startPt2 == null || endPt2 == null)
                return null;

            double k1, b1;
            GetKandB(startPt1, endPt1, out k1, out b1);

            double k2, b2;
            GetKandB(startPt2, endPt2, out k2, out b2);

            if (Math.Abs(k1 - k2) < 0.000001)
                return null;

            if (k1 == _verticalK)
            {//垂直 
                return new Yw.Curve.CurvePoint(startPt1.X, startPt1.X * k2 + b2);
            }
            if (k2 == _verticalK)
            {//垂直 
                return new Yw.Curve.CurvePoint(startPt2.X, startPt2.X * k1 + b1);
            }

            double sect_x = (b2 - b1) / (k1 - k2);
            return new Yw.Curve.CurvePoint(sect_x, sect_x * k1 + b1);
        }


        /// <summary>
        /// 是否平行
        /// </summary>
        /// <param name="startPt1"></param>
        /// <param name="endPt1"></param>
        /// <param name="startPt2"></param>
        /// <param name="endPt2"></param>
        /// <returns></returns>
        public static bool IsParallel(Yw.Curve.CurvePoint startPt1, Yw.Curve.CurvePoint endPt1, Yw.Curve.CurvePoint startPt2, Yw.Curve.CurvePoint endPt2)
        {
            if (startPt1 == null || endPt1 == null)
                return false;
            if (startPt2 == null || endPt2 == null)
                return false;

            double k1, b1;
            GetKandB(startPt1, endPt1, out k1, out b1);

            double k2, b2;
            GetKandB(startPt2, endPt2, out k2, out b2);

            if (Math.Abs(k1 - k2) < 0.000001)
                return true;
            else
                return false;
        }


    }
}