using System;

using System.Collections.Generic;

using System.Text;

namespace Spectrogram

{

class Settings

{

public readonly double SampleRate;

// vertical information

public readonly int FftSize;

public readonly double FftLengthSec;

public readonly double FreqNyquist;

public readonly double HzPerPixel;

public readonly double PxPerHz;

public readonly int FftIndex1;

public readonly int FftIndex2;

public readonly double FreqMin;

public readonly double FreqMax;

public readonly double FreqSpan;

public readonly int Height;

public int OffsetHz;

// horizontal information

public readonly double[] Window;

public readonly int StepSize;

public readonly double StepLengthSec;

public readonly double StepOverlapFrac;

public readonly double StepOverlapSec;

public Settings(double sampleRate, int fftSize, int stepSize, double minFreq, double maxFreq, int offsetHz)

{

static bool IsPowerOfTwo(int x) => ((x & (x - 1)) == 0) && (x > 0);

if (IsPowerOfTwo(fftSize) == false)

throw new ArgumentException("FFT size must be a power of 2");

// FFT info

SampleRate = sampleRate;

FftSize = fftSize;

StepSize = stepSize;

FftLengthSec = (double)fftSize / sampleRate;

// vertical

minFreq = Math.Max(minFreq, 0);

FreqNyquist = sampleRate / 2;

HzPerPixel = sampleRate / fftSize;

PxPerHz = (double)fftSize / sampleRate;

FftIndex1 = (minFreq == 0) ? 0 : (int)(minFreq / HzPerPixel);

FftIndex2 = (maxFreq >= FreqNyquist) ? fftSize / 2 : (int)(maxFreq / HzPerPixel);

Height = FftIndex2 - FftIndex1;

FreqMin = FftIndex1 * HzPerPixel;

FreqMax = FftIndex2 * HzPerPixel;

FreqSpan = FreqMax - FreqMin;

OffsetHz = offsetHz;

// horizontal

StepLengthSec = (double)StepSize / sampleRate;

var window = new FftSharp.Windows.Hanning();

Window = window.Create(fftSize);

StepOverlapSec = FftLengthSec - StepLengthSec;

StepOverlapFrac = StepOverlapSec / FftLengthSec;

}

public int PixelY(double freq)

{

return (int)(Height - (freq - FreqMin + HzPerPixel) * PxPerHz - 1);

}

}

}