package evo.audio.dcf
{
	import evoflash.audio.util.PrecalTableGenerator;
	import evoflash.audio.PCMSoundFormat;
	
	public class LowPassMoog implements IFilter
	{
		/*
		f = 0 .. 0.9*Fs/2
		res = 0 .. 1.05
		comp = 0 .. 1 (0 = moog, 0.5 = cem)
		
		wc = 2*pi*f/Fs
		g = 0.9892*wc - 0.4342*wc^2 + 0.1381*wc^3 - 0.0202*wc^4
		fb = res*(1.0029 + 0.0526*wc^2 - 0.0926*wc^2 + 0.0218*wc^3)
		
		A = 0.769
		B = 0.231
		
		x1 = tanh(in - 4*fb*(y4 - comp*in))
		y1 += g*(A*x1 + B*x1_b - y1)
		x1_b = x1;
		
		y2 += g*(A*y1 + B*x2_b - y2)
		x2_b = y1;
		
		y3 += g*(A*y2 + B*x3_b - y3)
		x3_b = y2;
		
		y4 += g*(A*y3 + B*x4_b - y4)
		x4_b = y3;
		
		*/
		private var tanh:Array;
		private var _res:Number = 0;
		private var _cutoff:Number = 0;
		private var _wc:Number;
		private var _wc2:Number;
		private var _wc3:Number;
		private var _wc4:Number;
		private var _g:Number;
		private var _fb:Number;
		
		private var y1:Number = 0;
		private var y2:Number = 0;
		private var y3:Number = 0;
		private var y4:Number = 0;

		private var x1_b:Number = 0;
		private var x2_b:Number = 0;
		private var x3_b:Number = 0;
		private var x4_b:Number = 0;
		
		private var _fmt:PCMSoundFormat;
		
		public function LowPassMoog(fmt:PCMSoundFormat, cutoff:Number, res:Number)
		{
			_fmt = fmt;
			tanh = PrecalTableGenerator.getTanhTable();
			_cutoff = cutoff;
			_res = res;
			refresh();
		}
		public function getCutoff():Number
		{
			return _cutoff;
		}
		
		public function getResonance():Number
		{			
			return _res;
		}
		
		public function setCutoff(cutoff:Number):void
		{
			_cutoff = Math.min(Math.max(cutoff,0), 0.9*_fmt.sampleRate / 2);
			refresh();	
		}
		
		public function setResonance(res:Number):void
		{
			_res = Math.min(Math.max(res, 0), 1.05);
			refresh();
		}
		
		public function refresh():void
		{
			_wc = Math.PI * 2 * _cutoff /_fmt.sampleRate;
			_wc2 = _wc*_wc;
			_wc3 = _wc*_wc*_wc;
			_wc4 = _wc*_wc*_wc*_wc;
			_g = 0.9892*_wc - 0.4342*_wc2 + 0.1381*_wc3 - 0.0202*_wc4;
			_fb = _res*(1.0029 + 0.0526*_wc - 0.0926*_wc2 + 0.0218*_wc3);
		}
		
		public function filterSample(sample:Number):Number
		{	
			var A:Number = 0.769
			var B:Number = 0.231
			
			var x1:Number = tanh[uint(((sample - 4*_fb*y4)+16)*128)];
			y1 += _g*(A*x1 + B*x1_b - y1)
			x1_b = x1;
			
		 	y2 += _g*(A*y1 + B*x2_b - y2)
			x2_b = y1;
			
			y3 += _g*(A*y2 + B*x3_b - y3)
			x3_b = y2;
			
			y4 += _g*(A*y3 + B*x4_b - y4)
			x4_b = y3;

			return y4;
		}
		
	}
}