/* ------------------- */
/* conv_fn.cc          */
/* H. M. Stauss, 2001  */
/* ------------------- */

#include <ctype.h>
#include <math.h>
#include <string.h>

int GPStoLOCATOR(float gps_long, float gps_lat, char *locator) {
  /* gps_long and gps_lat are the longitutes (-180 to +180) and   */
  /* latitues (-90 to +90) of the GPS coordinates in degree       */
  /* locator is a string and memory must be allocated for 7 chars */
 
  int   is_err, field_l, field_b, square_l, square_b;
  float ssquare_l, ssquare_b;

  /* Initialization */
  is_err=0;
  if (gps_long < -180 || gps_long > 180) is_err=1;
  if (gps_lat  < -90 || gps_lat > 90) is_err=1;

  /* Mainroutine */
  if (is_err) {
    return(-1);
  }
  else {
    gps_long+=180; gps_lat+=90;
    /* fields */
    field_l=(int)(gps_long/20.0);
    field_b=(int)(gps_lat/10.0);
    /* squares */
    square_l=(int)(fmod(gps_long, 20.0)/2.0);
    square_b=(int)(fmod(gps_lat, 10.0));
    /* subsquares */
    ssquare_l=12.5*(gps_long-(field_l*20)-(square_l*2));
    ssquare_b=24.5*(gps_lat -(field_b*10)-(square_b));

    strcpy(locator,"ZZZZZZ");
    locator[0]=((char)field_l+65); locator[1]=((char)field_b+65);
    locator[2]=((char)square_l+48); locator[3]=((char)square_b+48);
    locator[4]=((char)(((int)ssquare_l)+65));
    locator[5]=((char)(((int)ssquare_b)+65));
  }
  return(0);
}

int LOCATORtoGPS(char *locator, float *gps_long, float *gps_lat) {
  /* gps_long and gps_lat are the longitutes (-180 to +180) and   */
  /* latitues (-90 to +90) of the GPS coordinates in degree       */

  int i, is_err, field_l, field_b, square_l, square_b;
  float ssquare_l, ssquare_b;

  /* Initialization */
  is_err=0;
  locator[6]='\0';
  for (i=0; i<2; i++) {
    locator[i]=toupper(locator[i]);
    if (locator[i]<'A' || locator[i]>'R') is_err=1;
  }
  for (i=4; i<6; i++) {
    locator[i]=toupper(locator[i]);
    if (locator[i]<'A' || locator[i]>'X') is_err=1;
  }

  /* field */
  field_l=20*((int)locator[0]-65);
  field_b=10*((int)locator[1]-65);
  /* square */
  square_l=(int)locator[2]-48;
  square_b=(int)locator[3]-48;
  if (square_l<0 || square_l>9) is_err=1;
  if (square_b<0 || square_b>9) is_err=1;
  square_l=2*square_l;
  /* subsquare */
  ssquare_l=(int)locator[4]-65;
  ssquare_b=(int)locator[5]-65;
  ssquare_l=2.0*(float)ssquare_l/24;
  ssquare_b=1.0*(float)ssquare_b/24;

  if (is_err) {
    return(-1);
  }
  else {
    *gps_long= (float)field_l + (float)square_l + ssquare_l - 180.0;
    *gps_lat = (float)field_b + (float)square_b + ssquare_b - 90.0;
  }
  return(0);
}