using System;

namespace FftSharp.Windows
{
    public class Tukey : Window, IWindow
    {
        private readonly double Alpha;

        public override string Name => "Tukey";
        public override string Description =>
            "A Tukey window has a flat center and tapers at the edges according to a cosine function. " +
            "The amount of taper is defined by alpha (with low values being less taper). " +
            "Tukey windows are ideal for analyzing transient data since the amplitude of transient signal " +
            "in the time domain is less likely to be altered compared to using Hanning or flat top.";

        public Tukey()
        {
            Alpha = .5;
        }

        public Tukey(double alpha = .5)
        {
            Alpha = alpha;
        }
        protected override double windowValue(int index, int size)
        {
            double m = 2 * Math.PI / (Alpha * size);
            int edgeSizePoints = (int)(size * Alpha / 2);
            bool isEdge = (index < edgeSizePoints) || (index > size - edgeSizePoints);

            return isEdge ? (1 - Math.Cos(index * m)) / 2 : 1;
        }
    }
}