/*-*- mode: C; c-basic-offset:2 ; tab-width: 2; -*-
Simple hack to loop through a shapefile and extract only those shapes
  that have a specified value of a specified field

*/
#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <string.h>
#include <math.h>
#include <shapefil.h>

int main(int argc, char **argv)
{

  char inshape[120] = "";
  char outshape[120] = "";
  char attribute_name[120] = "";
  char attribute_value[120] = "";
  int field_index;

  SHPHandle InShape=NULL, OutShape=NULL;
  DBFHandle InDBF=NULL, OutDBF=NULL;
  int nShapeType, nEntities, nVertices, *panParts, i, iPart,j;
  SHPObject	*psCShape;
  char	*DBFRow = NULL;

  if (argc < 5)
    {
      fprintf(stderr,"Usage: %s inshape outshape attribute_name attribute_value\n",
              argv[0]);
      exit(0);
    }

  strncpy( inshape, *++argv, sizeof(inshape));
  --argc;
  strncpy( outshape, *++argv, sizeof(outshape));
  --argc; 
  printf("In: %s, out: %s\n",inshape,outshape);
  
  
  strncpy( attribute_name, *++argv, sizeof(attribute_name));
  --argc; 
  strncpy( attribute_value, *++argv, sizeof(attribute_value));
  --argc; 
  
  if (argc != 1)
    {
      fprintf(stderr,"Usage: %s inshape outshape attribute_name attribute_value\n",
              argv[0]);
      fprintf(stderr,"Ignoring %d extra arguments.\n",argc-1);
    }
  


  InShape = SHPOpen(inshape, "rb");
  InDBF = DBFOpen( inshape, "rb");

  if (InShape == NULL || InDBF == NULL)
    {
      fprintf (stderr,"Unable to open source shapefiles: %s\n", inshape);
      exit(1);
    }
  
  field_index = DBFGetFieldIndex( InDBF, attribute_name );
  if (field_index == -1)
    {
      fprintf(stderr,"Unable to locate field %s in %s\n",attribute_name,
              inshape);
      exit(1);
    }

  SHPGetInfo(InShape, &nEntities, &nShapeType, NULL, NULL);
  OutShape = SHPCreate( outshape, nShapeType);
  OutDBF = DBFCloneEmpty(InDBF, outshape);
  if (OutShape == NULL || OutDBF == NULL)
    {
      fprintf (stderr,"Unable to open destination shapefiles: %s\n", outshape);
      exit(1);
    }
  DBFRow = (char *) malloc ( (InDBF->nRecordLength) + 15 );

  for( i = 0; i < nEntities; i++ )
    {
      psCShape = SHPReadObject ( InShape, i );
      
      // This is meant to match the way xastir selects bounding boxes
      // as compared to its view region
      if (strncmp(attribute_value,DBFReadStringAttribute( InDBF, i, field_index),strlen(attribute_value))==0)
        {
          SHPWriteObject ( OutShape, -1, psCShape );   
          SHPDestroyObject ( psCShape );
          
          memcpy ( DBFRow, DBFReadTuple ( InDBF, i ), InDBF->nRecordLength );
          DBFWriteTuple ( OutDBF, OutDBF->nRecords, DBFRow );
        }
    }
  SHPClose(InShape);
  SHPClose(OutShape);
  DBFClose(InDBF);
  DBFClose(OutDBF);

}