#include <stdio.h>
#include <stddef.h>
#include <stdarg.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include "geostat.h"
#include "pressure.h"

/* Build_velocity                                       */
/* Build velocity in spectral domain                    */

void build_velocity(int n[3],struct grid_mod grid,struct statistic_mod stat,struct pressure_mod gradient,double *realization,double *ireal,double *xvelocity,double *ixvelocity,int direction)
{
  int i,j,k,maille1;
  int x,y,z;
  double ki,kj,kk;
  double coeff,temp,temp2;
  double grad;

  /* x-direction velocity calculation in the spectral domain*/
  switch(direction)
    {
    case 1:
      grad = gradient.x;
      x=1;
      y=0;
      z=0;
      break;
    case 2:
      grad = gradient.y;
      x=0;
      y=1;
      z=0;
      break;
    case 3:
      grad = gradient.z;
      x=0;
      y=0;
      z=1;
      break;
    default :
      printf("build_velocity.c: wrong velocity direction!!! direction: %d\n",direction);
      break;
    }

  for ( k = 1; k <= n[2]; k++) {
    for (j = 1; j <= n[1]; j++) {
      for (i = 1; i <= n[0]; i++) {
	maille1 = i+(j-1+(k-1)*n[1])*n[0];
/* 	if (i<n[0]/2) { */
/* 	  ki =(double)i/(double)(grid.NX*grid.DX); */
/* 	} else { */
/* 	  ki =-(double)(n[0]-i+1)/(double)(grid.NX*grid.DX); */
/* 	} */
/* 	if (j<n[1]/2) { */
/* 	  kj =(double)j/(double)(grid.NY*grid.DY); */
/* 	} else { */
/* 	  kj =-(double)(n[1]-j+1)/(double)(grid.NY*grid.DY); */
/* 	} */
/* 	if (k<n[2]/2) { */
/* 	  kk =(double)k/(double)(grid.NZ*grid.DZ); */
/* 	} else { */
/* 	  kk =-(double)(n[2]-k+1)/(double)(grid.NZ*grid.DZ); */
/* 	} */
	
	      if (n[0]==1)
		{
		  ki=0;
		}
	      else if (i<n[0]/2)
		{
		  ki =(double)i/(double)(grid.NX*grid.DX);
		}
	      else 
		{
		  ki =-(double)(n[0]-i+1)/(double)(grid.NX*grid.DX);
		}

	      if (n[1]==1)
		{
		  kj=0;
		}
	      else if (j<n[1]/2)
		{
		  kj =(double)j/(double)(grid.NY*grid.DY);
		}
	      else
		{
		  kj =-(double)(n[1]-j+1)/(double)(grid.NY*grid.DY);
		}

	      if (n[2]==1)
		{
		  kk=0;
		}
	      else if (k<n[2]/2)
		{
		  kk =(double)k/(double)(grid.NZ*grid.DZ);
		}
	      else
		{
		  kk =-(double)(n[2]-k+1)/(double)(grid.NZ*grid.DZ);
		}

	coeff = (gradient.x*ki+gradient.y*kj+gradient.z*kk)/(ki*ki+kj*kj+kk*kk);
	temp = realization[maille1];
	temp2= ireal[maille1];
	
	xvelocity[maille1] = stat.mean[0]*(grad-(ki*x+kj*y+kk*z)*coeff)*temp;
	ixvelocity[maille1]= stat.mean[0]*(grad-(ki*x+kj*y+kk*z)*coeff)*temp2;
      }
    }
  }

  return;
}