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

#include "nmea.h"

int nmea_check_sentence(char *s)
{
  char *c;
  int c1 = 0, c2 = 0;
  int err = 0;

  c = s;
  if ( *c++ != '$' ) {
    err = 1;
  }
  else {

    for (; *c && *c != '*'; c++) {
      c1 ^= *c;
    }

    if ( *c && *(c+1) && *(c+2) ) {
      c2 = (*++c - '0') * 16;
      c2 += (*++c - '0');

      if ( *++c || c1 != c2 )
        err = 1;
    }
    else {
      err = 1;
    }
  }

  return err;
}

double nmea_to_double(char *n)
{
  double t1, t2;

  t1 = atof(n);
  t2 = floor(t1 / 100);
  t2 += (t1 - t2*100)/60;

  return t2;
}

char *latitude_to_nmea(char *b, double latitude)
{
  int whole_lat;
  double lat_min;
  char d;

  if (b == NULL)
    b = (char *) malloc (16);

  if (latitude > 0)
    d='N';
  else {
    latitude = -latitude;
    d='S';
  }

  whole_lat = floor(latitude);
  lat_min = (latitude - whole_lat) * 60;

  sprintf(b,"%02d%05.2f,%c",whole_lat,lat_min,d);

  return b;
}
char *longitude_to_nmea(char *b, double longitude)
{
  int whole_long;
  double long_min;
  char d;

  if (b == NULL)
    b = (char *) malloc (16);

  if (longitude > 0)
    d='E';
  else {
    longitude = -longitude;
    d='W';
  }

  whole_long = floor(longitude);
  long_min = (longitude - whole_long) * 60;

  sprintf(b,"%03d%05.2f,%c",whole_long,long_min,d);

  return b;
}