namespace IStation.Curve
{
    /// <summary>
    /// 样条曲线（二次拟合）：使用Math.Net
    /// </summary>
    public class TwinRelateCurve2M : IFitPoint
    {
        /// <summary>
        /// 
        /// </summary>
        public TwinRelateCurve2M(CurveExpress express)
        {
            _express = express;
        }

        /// <summary>
        /// 
        /// </summary>
        public TwinRelateCurve2M(List<CurvePoint> points)
        {
            if (points == null || points.Count < 3)
            {
                throw new Exception("出现数值计算问题, 无法解出二次拟合曲线！");
            }


            _express = BuildCurveExpress(points);
        }

        //曲线表达式
        private CurveExpress _express = null;

        /// <summary>
        /// 获取拟合点Y
        /// </summary>
        public double GetFitPointY(double x)
        {
            if (_express == null)
                return default;
            return _express.Index2 * x * x + _express.Index1 * x + _express.Index0;
        }

        /// <summary>
        /// 获取拟合点列表
        /// </summary>
        public List<CurvePoint> GetFitPoints(int pointNumber)
        {
            if (_express == null)
            {
                return default;
            }
            return GetFitPointsByXRange(_express.Min, _express.Max, pointNumber);
        }

        /// <summary>
        /// 通过X区间获取拟合点列表
        /// </summary>
        public List<CurvePoint> GetFitPointsByXRange(double minX, double maxX, int pointNumber)
        {
            if (_express == null)
            {
                return default;
            }
            if (pointNumber < 1)
            {
                pointNumber = 12;
            }
            if (pointNumber > 10000)
            {
                pointNumber = 10000;
            }

            double space = (maxX - minX) / (pointNumber - 1);
            if (space < 0.0001)
            {
                return default;
            }
            var points = new List<CurvePoint>();
            for (int i = 0; i < pointNumber; i++)
            {
                double x = space * i + minX;
                double y = GetFitPointY(x);
                points.Add(new CurvePoint(x, y));
            }
            return points;
        }

        /// <summary>
        /// 创建曲线表达式
        /// </summary>
        public static CurveExpress BuildCurveExpress(List<CurvePoint> points)
        {
            if (points == null || points.Count < 3)
            {
                return default;
            }
            points = points.OrderBy(x => x.X).ToList();
            CurveExpress express = new CurveExpress
            {
                FitType = eFitType.ConicCurve,
                DefinePoints = points.Select(x => new CurvePoint(x)).ToList(),
                Min = points.First().X,
                Max = points.Last().X
            };

            var X = (from x in points select x.X).ToArray();
            var Y = (from x in points select x.Y).ToArray();
            var res = Fit.Polynomial(X, Y, 2);

            //0次方
            express.Index0 = res[0];
            //1次方
            express.Index1 = res[1];
            //2次方
            express.Index2 = res[2];
            //3次方
            express.Index3 = 0;// res[3];

            return express;
        }




    }
}