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

/* @author Geir K. Nilsen (geir.kjetil.nilsen@gmail.com) 2017 */

namespace ParametricEqualizer
{
    public class Section
    {
        private Filter filter;
        private double G0;
        private double G;
        private double GB;
        private double f0;
        private double Bf;
        private double fs;

        private double[][] coeffs;

        public Section(double f0, double Bf, double GB, double G0, double G, double fs)
        {
            this.f0 = f0;
            this.Bf = Bf;
            this.GB = GB;
            this.G0 = G0;
            this.G = G;
            this.fs = fs;

            this.coeffs = new double[2][];
            this.coeffs[0] = new double[3];
            this.coeffs[1] = new double[3];

            double beta = Math.Tan(Bf / 2.0 * Math.PI / (fs / 2.0)) * Math.Sqrt(Math.Abs(Math.Pow(Math.Pow(10, GB / 20.0), 2.0) - Math.Pow(Math.Pow(10.0, G0 / 20.0), 2.0))) / Math.Sqrt(Math.Abs(Math.Pow(Math.Pow(10.0, G / 20.0), 2.0) - Math.Pow(Math.Pow(10.0, GB/20.0), 2.0)));

            coeffs[0][0] = (Math.Pow(10.0, G0 / 20.0) + Math.Pow(10.0, G/20.0) * beta) / (1 + beta);
            coeffs[0][1] = (-2 * Math.Pow(10.0, G0/20.0) * Math.Cos(f0 * Math.PI / (fs / 2.0))) / (1 + beta);
            coeffs[0][2] = (Math.Pow(10.0, G0/20) - Math.Pow(10.0, G/20.0) * beta) / (1 + beta);

            coeffs[1][0] = 1.0;
            coeffs[1][1] = -2 * Math.Cos(f0 * Math.PI / (fs / 2.0)) / (1 + beta);
            coeffs[1][2] = (1 - beta) / (1 + beta);

            filter = new Filter(coeffs[1].ToList(), coeffs[0].ToList());
        }

        public List<double> run(List<double> x, out List<double> y)
        {
            filter.apply(x, out y);
            return y;
        }
    }


}