#include <stdio.h>
#include <getopt.h>
#include <time.h>

void printhelp(char *callname) {
  printf("bintime - show the current time of day in binary format\n");
  printf("Usage: %s [-dsvh]\n\n", callname);
  printf("   -d, --decimal      Show decimal numbers along with the binary ones\n");
  printf("   -s, --seconds      Show seconds along with hours and minutes\n");
  printf("   -v, --version      Print the version of bintime and exit\n");
  printf("   -h, --help         Print this help and exit\n");
}


void dec2binstr(int in, char *out, int outlen) {
/* See http://en.wikipedia.org/wiki/Binary_numeral_system#Decimal for the  *
 * principle of the conversion algorithm used here.                        */

  char *outend = out + outlen;	        /* Initialize a pointer to do the  */
  *outend = '\0';		        /* string from behind and insert   */
                                        /* the ASCII 0 at the end          */

  while (in) {                  /* Fill wih binary digits from LSB to MSB  */
    outend--;
    switch (in % 2) {
      case 0:
        *outend = '0'; break;
      case 1:
        *outend = '1'; break;
    }
    in = in / 2;
  }

  while (outend > out) {	/* Fill with '0's until beginning of out */
    outend--;
    *outend = '0';
  }
}


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

/* --- Declarations for getopt_long.h functionality ------------------- */
  int opt_seconds = 0;
  int opt_decimal = 0;
  struct option longoptions[] = {
    {"decimal", no_argument, 0, 'd'},
    {"seconds", no_argument, 0, 's'},
    {"version", no_argument, 0, 'v'},
    {"help", no_argument, 0, 'h'}
  };
  int longoptions_i = 0;
  signed char c;

/* --- Declarations for time.h functionality ---------------------------*/
  time_t curtime;
  struct tm *timedata;

/* --- My own humble declarations --------------------------------------*/
  int twelve_hour;
  char bin_hour[5];    /* only four digits for the hour */
  char bin_min[7];
  char bin_sec[7];

/* For a better idea of how getopt_long is used, you'd better check out *
 * http://www.gnu.org/software/libc/manual/html_node/Getopt.html along  *
 * with my code here. They do it differently and more intelligible IMHO.*/

  while(1) {
    if ((c = getopt_long(argc, argv, "dsvh",
                         longoptions, &longoptions_i)) == -1) { break; }
    switch (c) {
      case 0: break;
      case 'd':
        opt_decimal = 1;
        break;
      case 's':
        opt_seconds = 1;
        break;
      case 'v':
        printf("bintime 0.0.1\n");
        return 0;
        break;
      case 'h':
        printhelp(argv[0]);
        return 0;
        break;
      case '?':
      default:
        printhelp(argv[0]);
        return 1;
        break;
    }
  }

  curtime = time(0);            /* Getting system time and making it 12h*/
  timedata = localtime(&curtime);
  twelve_hour = timedata->tm_hour;
  if (twelve_hour > 12) { twelve_hour -= 12; }

  dec2binstr(twelve_hour, bin_hour, 4);
  dec2binstr(timedata->tm_min, bin_min, 6);
  if (opt_seconds) { dec2binstr(timedata->tm_sec, bin_sec, 6); }

  /* I thought a lot about how to do this and I've decided to rather go *
   * with a bunch of printf(); lines than to do some kind of smartass   *
   * printf("%s  %s\n", bin_min, dec_min) black voodoo thing, because   *
   * that would involve initializing an empty dec_min string and then   *
   * filling it if needed. And since this is C and not Perl, that would *
   * be Shooting Myself In The Foot(tm) big time.                       */

  if (opt_decimal) {
    if (timedata->tm_hour < 10) {
      printf(" %s   (0%ih)\n", bin_hour, timedata->tm_hour); }
    else {
      printf(" %s   (%ih)\n", bin_hour, timedata->tm_hour); }

    if (timedata->tm_min < 10) {
      printf("%s  (0%im)\n", bin_min, timedata->tm_min); }
    else {
      printf("%s  (%im)\n", bin_min, timedata->tm_min); }

    if (opt_seconds) {
      if (timedata->tm_sec < 10) {
        printf("%s  (0%is)\n", bin_sec, timedata->tm_sec); }
      else {
        printf("%s  (%is)\n", bin_sec, timedata->tm_sec); }
    }
  }
  else {                        /* Life's much easier without decimal! */
    printf(" %s\n%s\n", bin_hour, bin_min);
    if (opt_seconds) {
      printf("%s\n", bin_sec); }
  }

  return 0;
}