using MathNet.Numerics;
using MathNet.Numerics.IntegralTransforms;

namespace KLHZ.Trader.Core.Math.Declisions.Utils
{
    public static class FFT
    {
        public static void Test()
        {
            var da = new List<float>();
            for (int i = 0; i < 1000; i++)
            {
                da.Add((float)System.Math.Sin(0.01 * i)+ (float)System.Math.Cos(0.01 * i));
            }

            var start = da.ToArray();
            var arrv = da.Select(d => new Complex32(d, 0)).ToArray();
            Fourier.Forward(arrv);

            Fourier.Inverse(arrv);
            var res = arrv.Select(a => a.Real).ToArray();

            for (int i = 0; i < 1000; i++)
            {
                var d = res[i] - start[i];
            }
        }

        public static TimeSpan CaclHarmonycPeriod(TimeSpan signalLength, int signalLengthItems, int harmonyNumber)
        {
            var fdiscretisation = signalLengthItems /signalLength.TotalSeconds ;
            var fharm = harmonyNumber * fdiscretisation / signalLengthItems;
            return TimeSpan.FromSeconds(1/fharm);
        }

        public static double CalcCurrentPhase(Complex32[] spectr, int harmonyNumber)
        {
            var item = spectr[harmonyNumber];
            return System.Math.Atan(item.Imaginary / item.Real);
        }

        public static (double min, double max) CalcPhaseRange(double aSin, double aCos, double initPhase, double maxLevel)
        {
            var x = new List<double>();
            var x2 = new List<double>();
            var y = new List<double>();
            for (double i = 0; i <= 10 * System.Math.PI; i += 0.0001)
            {
                var _2pi = 2 * System.Math.PI;
                var df = ((i / _2pi) % 1) * _2pi;
                x.Add(df);
                y.Add(aSin * System.Math.Sin(i + initPhase) + aCos * System.Math.Cos(i + initPhase));
            }

            var prevI = -1;
            var max = y.Max();
            for (int i = 0; i < y.Count; i++)
            {
                if (y[i] > (1 - maxLevel) * max && (i - prevI == 1 || prevI < 0))
                {
                    x2.Add(x[i]);
                    prevI = i;
                }
            }
            var minPhase = x2.Min();
            var maxPhase = x2.Max();
            return (minPhase, maxPhase);
        }
    }
}