#include <mex.h>
#include <math.h>
void mexFunction (int nlhs, mxArray *plhs[],
             int nrhs, const mxArray *prhs[])
{
	const char *funcName = mexFunctionName ();
	mexPrintf ("You called function: %s\n", funcName);
	mexPrintf ("I have %d inputs and %d outputs\n", nrhs, nlhs);

	if (nrhs < 3)
		mexErrMsgTxt ("Too few arguments");

	const mxArray *array_x = prhs[0];
	const mxArray *scalar_alpha_attack = prhs[1];
	const mxArray *scalar_alpha_release = prhs[2];

	
	plhs[0] = mxCreateNumericArray (mxGetNumberOfDimensions (array_x),
								  mxGetDimensions (array_x),
								  mxGetClassID (array_x),
								  mxIsComplex (array_x));

	mwIndex channelsDim = 1;
	double alpha_a = *mxGetPr(scalar_alpha_attack);
	double alpha_r = *mxGetPr(scalar_alpha_release);

	double *vri = mxGetPr (array_x);
	double *vro = mxGetPr (plhs[0]);
	
	mwSize M = mxGetM (array_x);
	mwSize N = mxGetN (array_x);
	if (channelsDim == 1)
	{
		M = mxGetN (array_x);
		N = mxGetM (array_x);
	}

	mexPrintf ("Number of channels = %u\n", M);
	mexPrintf ("Number of samples per channel = %u\n", N);
	mexPrintf ("alpha_a = %f\n", alpha_a);
	mexPrintf ("alpha_r = %f\n", alpha_r);
	
	double level[M];
	for (mwIndex m=0; m < M; m++)
	{
		level[m] = 0;
	}	
	
	for (mwIndex n=0; n < N; n++)
	{
		for (mwIndex m=0; m < M; m++)
		{
			double x = vri[n*M + m];
			double xmag = fabs(x);
				
			if (xmag > level[m])
			{
				level[m] = (1.0-alpha_a)*level[m] + alpha_a*xmag;
			}
			else
			{
				level[m] = (1.0-alpha_r)*level[m];
			}
			vro[n*M + m] = level[m];
		}	
	}
}