using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

#pragma warning disable CS8601 // 引用类型赋值可能为 null。

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

        //double[] _res = null;
        private CurveExpress _express = null;

        /// <summary>
        /// 创建曲线表达式
        /// </summary>
        public static Model.CurveExpress? BuildCurveExpress(List<CurvePoint> points)
        {
            if (points == null || points.Count() < 3)
                return default;
            points = points.OrderBy(x => x.X).ToList();
            CurveExpress express = new CurveExpress();
            express.FitPow = 2;
            express.FitType = eCurveFitType.ConicCurve;
            express.DefinePoints = points.Select(x => new CurvePoint(x)).ToList();
            express.Min = points.First().X;
            express.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 = IStation.Numerics.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;
        }

        /// <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 GetFitPointsByRange(_express.Min, _express.Max, pointNumber);
        }

        /// <summary>
        /// 通过区间获取拟合点列表
        /// </summary>
        public List<CurvePoint> GetFitPointsByRange(double x_min, double x_max, int pointNumber)
        {
            if (_express == null)
                return default;
            if (pointNumber < 1)
                pointNumber = 12;
            if (pointNumber > 10000)
                pointNumber = 10000;

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

        /// <summary>
        /// 通过区间获取拟合点列表
        /// </summary>
        public static List<CurvePoint> GetFitPointsByRange(CurveExpress express, double x_min, double x_max, int pointNumber)
        {
            if (express == null)
                return default;
            return new TwinRelateCurve2M(express).GetFitPointsByRange(x_min, x_max, pointNumber);
        }

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

        /// <summary>
        /// 获取拟合点Y
        /// </summary>
        public static double GetFitPointY(CurveExpress express, double x)
        {
            if (express == null)
                return default;
            if (express.IsNull)
                return default;
            var s = new TwinRelateCurve2M(express);
            return s.GetFitPointY(x);
        }

        /// <summary>
        /// 获取拟合点Y
        /// </summary>
        public static double GetFitPointY(List<CurvePoint> points, double x)
        {
            if (points == null || points.Count < 3)
                return default;
            var s = new TwinRelateCurve2M(points);
            return s.GetFitPointY(x);
        }


    }
}