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

/* prebuild_gwn      */
/* Produce a first construction in real space of the Gaussian white noise */
/* grid:  structure defining the grid          */
/*n: vector with the number of cells along the */
/*   X, Y and Z axes for the underlying grid   */
/*   i = [0 1 2]                               */
/*   --> 0 0 0        : n will be computed and */
/*   updated as output                         */
/*   --> nx ny nz: these dimensions are used   */
/*realin: structure defining a realization -   */
/*        must be a Gaussian white noise       */
/*realization: structure defining a realization*/

void prebuild_gwn(struct grid_mod grid, int n[3], struct realization_mod* realin, double* realization, int solver)

{
    int i, j, k, maille0, maille1;
    int ntot;

    ntot = n[0] * n[1] * n[2];
    realization[0] = 0.;
    if (solver == 1) {
        for (i = 0; i < ntot; i++) {
            realization[i + 1] = (*realin).vector[i];
        }
    } else {
        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 <= grid.NX && j <= grid.NY && k <= grid.NZ) {
                        maille0 = i - 1 + (j - 1 + (k - 1) * grid.NY) * grid.NX;
                        realization[maille1] = (*realin).vector[maille0];
                    } else {
                        realization[maille1] = 0.;
                    }
                }
            }
        }
    }
    return;
}