/*
 * Copyright (c) 2011, Norma Kuehn
 * All rights reserved.
 *
 */

// Pseudo random number generator 'ran1' used in the stimulation program.

#include <mex.h>
#include <memory.h>
#include <matrix.h>
#include <math.h>

#define IA 16807
#define IM 2147483647
#define AM (1.0/IM)
#define IQ 127773
#define IR 2836
#define NTAB 32
#define NDIV (1+(IM-1)/NTAB)
#define EPS 1.2e-7
#define RNMX (1.0-EPS)

int iset = 0;
double gset = 0;


// function declarations
double gauss(long &idum);

void mexFunction(int nlhs, mxArray *plhs[], int nrhs, const mxArray *prhs[])
{
    if (nrhs < 3) mexErrMsgTxt("Input arguments are stixel width, stixel height, number of frames [and seed].");
    if (nrhs > 4) mexErrMsgTxt("Input arguments are stixel width, stixel height, number of frames [and seed].");
    if (nlhs != 1) mexErrMsgTxt("Wrong number of output arguments.");
    
    // required input arguments
    int xstixels, ystixels, nframes;
    
    long seed = -1000;
    
    float meanintensity = 0.5;
    float contrast = 1; // 0.3;

    //get input data
	if (mxIsDouble(prhs[0])) xstixels = (int)mxGetScalar(prhs[0]);
	else mexErrMsgTxt("Invalid class of input argument 'xpixels'.");
    
	if (mxIsDouble(prhs[1])) ystixels = (int)mxGetScalar(prhs[1]);
	else mexErrMsgTxt("Invalid class of input argument 'ypixels'.");

	if (mxIsDouble(prhs[2])) nframes = (int)mxGetScalar(prhs[2]);
	else mexErrMsgTxt("Invalid class of input argument 'nframes'.");
    
    if (nrhs == 4) {
	  if (mxIsDouble(prhs[3])) {
          seed = (int)mxGetScalar(prhs[3]);
          if (seed > 0) seed = -seed;
      }
	  else mexErrMsgTxt("Invalid class of input argument 'nframes'.");
    }

    // create pointer array
    double *stimulus = new double[xstixels*ystixels*nframes];
    
	// generate array of random numbers
    for (int n=0; n<nframes; n++) {
        for (int x=0; x<xstixels; x++) {
			for (int y=0; y<ystixels; y++) {
                stimulus[n*xstixels*ystixels + x*ystixels + y] = meanintensity*(1 + contrast*gauss( seed ));
            }
        }
    }
        
    // allocate space for output mxArray
    
    int dims[3] = {ystixels, xstixels, nframes};
	plhs[0] = mxCreateNumericArray(3, dims, mxDOUBLE_CLASS, mxREAL);
    // plhs[0] = mxCreateDoubleMatrix(xstixels*ystixels*nframes, 1, mxREAL);

    memcpy(mxGetPr(plhs[0]), stimulus, xstixels*ystixels*nframes*sizeof(double));
    
    // delete pointer array
    delete [] stimulus;
}


double ran1(long &idum)
{
	int j;
	long k;
	static long iy=0;
	static long iv[NTAB];
	double temp;

	if (idum <= 0 || !iy) {
		if (-(idum) < 1) idum=1;
		else idum = -(idum);
		for (j=NTAB+7;j>=0;j--) {
			k=(idum)/IQ;
			idum=IA*(idum-k*IQ)-IR*k;
			if (idum < 0) idum += IM;
			if (j < NTAB) iv[j] = idum;
		}
		iy=iv[0];
	}
	k=(idum)/IQ;
	idum=IA*(idum-k*IQ)-IR*k;
	if (idum < 0) idum += IM;
	j=iy/NDIV;
	iy=iv[j];
	iv[j] = idum;
	if ((temp=AM*iy) > RNMX) return RNMX;
	else return temp;
}

double gauss(long &idum)
{
	double fac,rsq,v1,v2;

	if (idum < 0) iset=0;
	if  (iset == 0) {
		do {
			v1=2.0*ran1(idum)-1.0;
			v2=2.0*ran1(idum)-1.0;
			rsq=v1*v1+v2*v2;
		} while (rsq >= 1.0 || rsq == 0.0);
		fac=sqrt(-2.0*log(rsq)/rsq);
		gset=v1*fac;
		iset=1;
		return v2*fac;
	} 
    else {
		iset=0;
		return gset;
	}
}