namespace IStation.Curve
{
    /// <summary>
    /// 贝塞尔曲线类(三次)
    /// </summary>
    public class Bezier3
    {
        /// <summary>
        /// 
        /// </summary>
        public Bezier3() { }

        /// <summary>
        /// 
        /// </summary>
        public Bezier3(List<CurvePoint> points)
        {
            if (points == null || points.Count < 4)
            {
                throw new Exception("参数错误，无法解出三次贝塞尔曲线！");
            }

            this.Point0 = points[0];
            this.Point1 = points[1];
            this.Point2 = points[2];
            this.Point3 = points[3];
        }

        /// <summary>
        /// 开始点
        /// </summary>
        public CurvePoint Point0 { get; set; }

        /// <summary>
        /// 开始点的控制点
        /// </summary>
        public CurvePoint Point1 { get; set; }

        /// <summary>
        /// 结束点的控制点
        /// </summary>
        public CurvePoint Point2 { get; set; }

        /// <summary>
        /// 结束点
        /// </summary>
        public CurvePoint Point3 { get; set; }

        /// <summary>
        /// 获取 X 用于插值
        /// </summary>
        public double GetX(double uu)
        {
            double u0 = Point3.X * uu * uu * uu;
            double u1 = 3 * Point2.X * uu * uu * (1 - uu);
            double u2 = 3 * Point1.X * uu * (1 - uu) * (1 - uu);
            double u3 = Point0.X * (1 - uu) * (1 - uu) * (1 - uu);

            return u0 + u1 + u2 + u3;
        }

        /// <summary>
        /// 获取 Y 用于插值
        /// </summary>
        public double GetY(double uu)
        {
            double u0 = Point3.Y * uu * uu * uu;
            double u1 = 3 * Point2.Y * uu * uu * (1 - uu);
            double u2 = 3 * Point1.Y * uu * (1 - uu) * (1 - uu);
            double u3 = Point0.Y * (1 - uu) * (1 - uu) * (1 - uu);

            return u0 + u1 + u2 + u3;
        }

        /// <summary>
        /// 距离最近的点
        /// </summary>
        public CurvePoint GetClosePoint(CurvePoint ref_pt)
        {
            double boundary_min_x = Math.Min(Point0.X, Point3.X);
            double boundary_max_x = Math.Max(Point0.X, Point3.X);
            double boundary_min_y = Math.Min(Point0.Y, Point3.Y);
            double boundary_max_y = Math.Max(Point0.Y, Point3.Y);
            //由于流量扬程数量差别特别大, 所以假设他们在一个100*100的方格内,求距离
            double ratio_x = 0;
            if (boundary_max_x == boundary_min_x)
            {
                ratio_x = 100 / (boundary_max_x);
            }
            else
            {
                ratio_x = 100 / (boundary_max_x - boundary_min_x);
            }


            double ratio_y = 0;
            if (boundary_max_y == boundary_min_y)
            {
                ratio_y = 100 / (boundary_max_y);
            }
            else
            {
                ratio_y = 100 / (boundary_max_y - boundary_min_y);
            }

            double chart_ref_x = (ref_pt.X - boundary_min_x) * ratio_x;
            double chart_ref_y = (ref_pt.Y - boundary_min_y) * ratio_y;

            CurvePoint sect = null;
            double min_dist = double.MaxValue;
            for (double uu = 0; uu <= 1; uu = uu + 0.01)
            {
                double chart_x = (GetX(uu) - boundary_min_x) * ratio_x - chart_ref_x;
                double chart_y = (GetY(uu) - boundary_min_y) * ratio_y - chart_ref_y;
                double distance = chart_x * chart_x + chart_y * chart_y;
                if (distance < min_dist)
                {
                    min_dist = distance;
                    sect = new CurvePoint(GetX(uu), GetY(uu));
                }
            }

            return sect;
        }

        /// <summary>
        /// 求与曲线的交点 (可能有多个,但只取第一个点)
        /// </summary>
        public CurvePoint GetCrossPoint(CurveExpress curve)
        {
            if (curve == null)
                return null;

            //第一次迭代
            var index1 = GetCrossPointIndex_不迭代(curve, 0.2, 0, 5);
            if (index1 < 0)
                return null;

            //第二次迭代
            var index2 = GetCrossPointIndex_不迭代(curve, 0.02, 0.2 * index1, 10);
            if (index2 < 0)
                return null;
            double uu = 0.2 * index1 + 0.02 * index2;
            double x_bers = GetX(uu);
            double y_bers = FitHelper.GetFitPointY(curve, x_bers);

            return new CurvePoint(x_bers, y_bers);
        }

        //计算在第几个点相交(可能有多个,但只取第一个点):思路, 不断逼近,一个正数一个负数就表示有交点
        private int GetCrossPointIndex_不迭代(CurveExpress curve, double space, double start, int number)
        {
            double last_dis_y = 0;

            for (int i = 0; i <= number; i++)
            {
                double uu1 = start + space * i;
                double x_bers = GetX(uu1);
                double y_bers = GetY(uu1);
                double y_curve = FitHelper.GetFitPointY(curve, x_bers);
                double current_dis_y = y_bers - y_curve;
                if (uu1 == 0)
                {
                    last_dis_y = current_dis_y;
                    continue;
                }

                if ((current_dis_y > 0 && last_dis_y < 0) || (current_dis_y < 0 && last_dis_y > 0))
                {
                    return i - 1;
                }

                last_dis_y = current_dis_y;
            }

            return -1;
        }

        /// <summary>
        /// 变成一条一条直线段
        /// </summary>
        /// <param name="pointNumber">贝赛尔曲线中间插入的点数量</param>
        public List<CurvePoint> GetApexPoints(int pointNumber)
        {
            var points_sect_list = new List<CurvePoint>();
            for (int i = 0; i <= pointNumber; i++)
            {
                var uu = i * 1.0 / pointNumber;
                var p_x = this.GetX(uu);
                var p_y = this.GetY(uu);
                points_sect_list.Add(new CurvePoint(p_x, p_y));
            }

            return points_sect_list;
        }

        /// <summary>
        /// 获取距离
        /// </summary>
        public double Distance(CurvePoint point)
        {
            var point1 = GetClosePoint(point);
            return point.Distance(point1);
        }

        /// <summary>
        /// 通过 Y 判断是否在其中
        /// </summary>
        public bool IsInnerByY(double y)
        {
            if (y >= this.Point0.Y && y <= this.Point3.Y)
                return true;
            if (y >= this.Point3.Y && y <= this.Point0.Y)
                return true;
            return false;
        }

    }
}