using System;
using System.Collections.Generic;
using System.Text;
using AP;

namespace _27corrector
{
    class Misc
    {

        //Сдвиг сигнала на произвольную величину
        //x - сигнал
        //offs - сдвиг выраженный в отсчетах
        public static double[] ShiftSignal(double[] x, double offs)
        {
            int N = x.Length;
            Complex[] s = new Complex[N];
            for (int n = 0; n < N; n++) s[n].real = x[n];
            s = Misc.DFT(s);
            //
            int j = N - 1;
            for (int k = 1; k < N / 2 + 1; k++)
            {
                double fi = System.Math.Atan2(s[k].image, s[k].real);
                double mod = AP.Math.AbsComplex(s[k]);
                fi += k * offs * 2 * System.Math.PI / N;
                s[k].real = mod * System.Math.Cos(fi);
                s[k].image = mod * System.Math.Sin(fi);
                //
                if (j != 0)
                {
                    s[j].real = s[k].real;
                    s[j].image = -s[k].image;
                }
                j--;
            }
            s = Misc.IDFT(s);
            double[] result = new double[N];
            for (int n = 0; n < N; n++) result[n] = s[n].real;
            return result;
        }

        //Прямое преобразование Фурье
        public static Complex[] DFT(Complex[] x)
        {
            int N = x.Length;
            Complex[] X = new Complex[N];
            for (int k = 0; k < N; k++)
            {
                for (int n = 0; n < N; n++)
                {
                    double fi = -2 * System.Math.PI * k * n / N;
                    Complex e = new Complex(System.Math.Cos(fi), System.Math.Sin(fi));
                    X[k] += x[n] * e;
                }
            }
            return X;
        }

        //Обратное преобразование Фурье
        public static Complex[] IDFT(Complex[] X)
        {
            int N = X.Length;
            Complex[] x = new Complex[N];
            for (int n = 0; n < N; n++)
            {
                for (int k = 0; k < N; k++)
                {
                    double fi = 2 * System.Math.PI * k * n / N;
                    Complex e = new Complex(System.Math.Cos(fi), System.Math.Sin(fi));
                    x[n] += X[k] * e;
                }
                x[n] /= N;
            }
            return x;
        }
    }
}