/* record2gridpt.c */

/* -----------------------
 *  INPUT FILE:  geog3.nc 
 *      OUTPUT:  STDOUT  
 * ----------------------- */

 /* nanr 26May98 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

/* VEMAP users:  customize Netcdf path here */
#include "/contrib/netcdf-3.4/include/netcdf.h"

void background(int *row,int *col,int *gridpt,int record);
void grid(int gridpt, float *olat, float *olon);

int main(argc, argv)
int argc;
char *argv[];
{

/* misc ids */
  int i=0;
  char BUFFER[512];

  int gridpt;		/* For VEMAP US Grid 1 thru 5520 */
  int record;		/* Gridpt record position */
  int row;		/* Row number */
  int col;		/* Column number */
  float olat;           /* cell center latitude */
  float olon;           /* cell center longitude */
       
/* --- Command line instructions --- */
  if(argc != 2) {
	printf("\n  syntax is <exe> <record_number_(1->3261)>\n");
        printf("  example: a.out 3261 \n\n");
        printf("  Note that although records number from 1->3261, record \n");
        printf("  number does not necessarily equal netCDF position index:\n\n");
        printf("  e.g. netCDF position index for record 1:\n");
	printf("        	C = 0 \n");
        printf("  	  Fortran = 1\n\n");
        return(0);
  }

  record = atoi(argv[1]);
  if(record > 3261 || record <= 0) {
     printf("\n  Record %d is out of range. \n",record);
     printf("  Records number from 1->3261. Note that record \n");
     printf("  number does not necessarily equal netCDF position index.\n\n");
     printf("  e.g. netCDF position index for record 1:\n");
     printf("                C = 0 \n");
     printf("          Fortran = 1\n\n");
     exit(1);
  }
  /* account for 0-based file positioning in C */
  record -= 1;

/* translate record number to gridpt & screen for background point */

   background(&row,&col,&gridpt,record);

/* translate record to row/col, lat/lon */

   grid(gridpt,&olat,&olon);

/* --- Print gridpoint information --- */
        printf("-----------------------------------------\n\n");
        printf("\n NOTE:  Records number from 1->3261.\n");
        printf(" Therefore record number does not \n");
        printf(" necessarily equal netCDF position index:\n\n");
        printf(" record number = %d\n", record+1);
        printf("           row = %d\n", row);
        printf("        column = %d\n", col);
        printf("      latitude = %6.2f\n", olat);
        printf("     longitude = %6.2f\n", olon);
        printf("      gridcell = %d\n\n", gridpt);
        printf("-----------------------------------------\n");
}


/*------------------------------------------------------------*/
void grid(int gridpt, float *olat, float *olon)
{
/* Program converts gridpoint to 2D matrix (row and col) */
/*  and returns gridcell center latitude and longitude.  */
/*  nanr 12-4-95 	           		         */

      int z;
      int row, col;

      for (z=0; z<48; z++) {
            if ((gridpt > z*115) && (gridpt <= (z+1)*115)) {
                   row = z+1;
                   col = gridpt-z*115;
            }
      }

      *olat =  49.0 + (0.5 * (1 - row)) - 0.25;
      *olon = 124.5 + (0.5 * (1 - col)) - 0.25;

      return;
}

void background(int *row,int *col,int *gridpt,int record)
{
         int backgrpt=0, datapt=0, sum=0;
         int varid, ncid;
         int nrows=48, ncols=115;
         int irow=0, i=0;
         long int count[2] = {1, 115};
         long int start[2];
         short var[115];
         FILE *fopen(), *fp_in;
 
         if(!(ncid = ncopen("geog3.nc",NC_NOWRITE))) {
                printf("ERROR:  Can't find 'geog3.nc' file. \n");
                exit(0);
         }
 
        varid = ncvarid(ncid, "mask");
        while(irow < nrows) {
                start[0] = irow;
                start[1] = 0;
                count[0] = 1;
                count[1] = ncols;
                ncvarget(ncid, varid, start, count, var);
                for(i=0; i<ncols; i++) {
                    if(var[i]) datapt++;
                    else       backgrpt++;
		    if(datapt == record+1) {
			*row = irow+1;
			*col = i+1;
			*gridpt = datapt+backgrpt;
			return;
		    }
                }
                irow++;
         }
         return;
}