using System;

namespace FftSharp.Windows
{
    public class BlackmanHarris : Window, IWindow
    {
        private readonly double A = 0.35875;
        private readonly double B = 0.48829;
        private readonly double C = 0.14128;
        private readonly double D = 0.01168;

        public override string Name => "Blackman-Harris";
        public override string Description =>
            "The Blackman-Harris window is similar to Hamming and Hanning windows. " +
            "The resulting spectrum has a wide peak, but good side lobe compression.";

        public BlackmanHarris() { }

        public BlackmanHarris(double a, double b, double c, double d) : this()
        {
            (A, B, C, D) = (a, b, c, d);
        }

        protected override double windowValue(int index, int size)
        {
            return A - B * Math.Cos(2 * Math.PI * index / size) + C * Math.Cos(4 * Math.PI * index / size) - D * Math.Cos(6 * Math.PI * index / size);
        }
    }
}