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

namespace IStation.Model
{
    /// <summary>
    /// 直线
    /// </summary>
    public class TwinRelateCurve1 : IFitCurvePoint
    {
        public TwinRelateCurve1(CurveExpress express)
        {
            _express = express;
        }
        public TwinRelateCurve1(List<Model.CurvePoint> points)
        {
            if (points == null || points.Count < 2)
            {
                throw new Exception("出现数值计算问题, 无法解出直线！");
            }

            _express = BuildCurveExpress(points);
        }

        private CurveExpress _express = null;

        /// <summary>
        /// 创建曲线表达式
        /// </summary>
        public static CurveExpress BuildCurveExpress(List<CurvePoint> points)
        {
            if (points == null || points.Count < 2)
            {
                return default;
            }
            points = points.OrderBy(x => x.X).ToList();
            if (!CurveLineHelper.GetKandB(points.First(), points.Last(), out double k, out double b))
            {
                return default;
            }
            var express = new CurveExpress();
            express.FitPow = 1;
            express.FitType = eCurveFitType.LinearCurve;
            express.DefinePoints = points.Select(x => new CurvePoint(x)).ToList();
            express.Min = points.First().X;
            express.Max = points.Last().X;
            express.Index0 = b;
            express.Index1 = k;

            return express;
        }

        /// <summary>
        /// 获取拟合点Y
        /// </summary>
        public double GetFitPointY(double x)
        {
            if (_express == null)
                return default;
            return _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 < 2)
                pointNumber = 2;
            if (pointNumber > 100)
                pointNumber = 100;

            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;
        }
    }
}