/*
  Quick routine to try and make a map in the GrADS format

  byte 0 = 1 (write the data .. don't skip)
  byte 1 = 1 (political boundary)
  byte 2 = number of lon,lat pairs
  byte 3 - n = encoded lon/lat pairs in 3-bytes.  See GrADS Documentation
*/

#include <stdio.h>
//#include <unistd.h>

// Define maximum number of connected line segment possible
// GrADS maximum is only 256 segments
#define    MAXLINESEGMENTS    250
#define    MAXBUFFERSIZE      255
/*unique id changed by user to manipulate map background file with mpt command*/
#define    MPTID        24      	


void printUsage( char *progName );

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

  FILE  *infile, *outfile;
  char  buffer[MAXBUFFERSIZE];

  float flat, flon;      // latitude and longitude read from file
  int   flag;            // LLP flag 0 --> start new line

  int   ncount;          // counter for number of lat/lon pairs to write
  int   ilat,ilon;       // pointers to memory for lat and lon

  unsigned char  *data, *currec;  // output grads data file .. I hope

  int   i,c, INTSIZE = sizeof (int), linenum;

  int overwrite = 0, recordtype, thindata = 0;

  extern char *optarg;
  extern int optind, optopt, opterr;

  // check the arg count
  if ( argc < 3 ) {
    // print usage message
    printUsage( argv[0] );
    return 1;
  }

  // parse the arg options
  while ((c = getopt(argc, argv, "hot:")) != -1) {
    switch(c) {
      case 'o':
        overwrite = 1;
        break;
      case 't':
        if ( (sscanf( optarg,"%d", &thindata)) != 1 ) {
          fprintf( stderr, "-t without valid numeric argument\n", optopt );
          printUsage( argv[0] );
          return 1;
        }
        break;
      case ':':
        fprintf( stderr, "-%c without arg\n", optopt );
        printUsage( argv[0] );
        return 1;
        break;
      case '?':
        fprintf( stderr, "unknown arg %c\n", optopt );
      case 'h':
        printUsage( argv[0] );
        return 1;
        break;
    }
  }

  if ( (argc - optind) != 2 ) {
    printUsage( argv[0] );
    return 1;
  }

  // if overwrite flag not set, check if the outfile exist
  if (!overwrite) {
    outfile = fopen( argv[optind+1], "r" );
    // if file exists do not overwrite, exit.
    if ( outfile != NULL ) {
      close( outfile );
      fprintf( stderr, "Outfile already exists!\n" );
      fprintf( stderr, "Use -o option to force overwrite.\n" );
      return 1;
    }
  }
                                                                                
  outfile = fopen( argv[optind+1], "w" );
  if ( outfile == NULL ) {
    fprintf( stderr, "Cannot open outfile!\n" );
    return 1;
  }

  //  Open the input file
  infile = fopen( argv[optind], "r" );
  if ( infile == NULL ) {
    fprintf( stderr, "Cannot open infile!\n" );
    close(outfile);
    return 1;
  }

  // malloc space for the GrADS map formated data
  data = (unsigned char *) malloc (MAXLINESEGMENTS * 6 * sizeof(char) + 3);

  if ( !data) {
    fprintf( stderr, "Cannot malloc!\n" );
    return 1;
  }

  currec = data + 3;
  ncount = 0;
  i = 0;

  // read the E00 file header and discard
  fgets( buffer, MAXBUFFERSIZE-1, infile );
  fgets( buffer, MAXBUFFERSIZE-1, infile );

  while ( (fgets( buffer, MAXBUFFERSIZE-1, infile ) != NULL) &&
          (sscanf(buffer,"%d%d%*d%*d%*d%*d%d", &linenum, &recordtype, &ncount) == 3) && 
          (linenum != -1) ) {

      recordtype = MPTID;

    if (recordtype == 0) {
      recordtype = MPTID;
    }
    // setup the new record header
    data[0] = 1;       
    data[1] = recordtype;
    currec = data + 3;
    i=0;

    for ( c = 0; c < ncount; c++ ) {

      if ( (fscanf( infile, "%f %f", &flon, &flat)) == EOF) {
        // cleanup and exit
        close( infile );
        close( outfile );
        free(data);
        return 1;
      }

      ilon = (int) ( ( ( flon < 0 ) ? flon + 360 : flon ) * 10000 );
      ilat = (int) ((flat + 90.0) * 10000);

      currec[0] = ( (unsigned char *)(&ilon) )[INTSIZE-2];
      currec[1] = ( (unsigned char *)(&ilon) )[INTSIZE-3];
      currec[2] = ( (unsigned char *)(&ilon) )[INTSIZE-4];

      currec[3] = ( (unsigned char *)(&ilat) )[INTSIZE-2];
      currec[4] = ( (unsigned char *)(&ilat) )[INTSIZE-3];
      currec[5] = ( (unsigned char *)(&ilat) )[INTSIZE-4];

      currec += 6;

      i++;

      if (i == MAXLINESEGMENTS) {
        data[2] =  i;
        fwrite(data, sizeof(char), (3 + i * 6), outfile);
        data[0] = 1;       
        data[1] = recordtype;
        currec = data + 3;
        i = 0;
      }

    }

    // if there is still data in the buffer write it out
    if (i > 0) {
      data[2] =  i;
      fwrite(data, sizeof(char), (3 + i * 6), outfile);
      i = 0;
    }

    //fscanf( infile, "%*s");
    fgets( buffer, MAXBUFFERSIZE-1, infile );
  }

  // if there is still data in the buffer write it out
  if (i > 0) {
    data[2] =  i;
    fwrite(data, sizeof(char), (3 + i * 6), outfile);
  }

  close( infile );
  close( outfile );
  free(data);
  return 0;
}


void printUsage( char *progName ) {

  fprintf( stderr, "Usage: %s [OPTION]... infile outfile\n", progName );
  fprintf( stderr, "Options:\n" );
  fprintf( stderr, "  -o         force overwrite of outfile\n" );
  fprintf( stderr, "  -t:num     thin data; drop every num data record\n" );

  return;
}