#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <err.h>

/* list of records of who's logged-in */
typedef struct _urecord_t {
   char *name;
   int   idle;
   int   count;

   struct _urecord_t *next;
} urecord;

void
add_urecord(urecord **list, char *n, int i) {
   if (*list == NULL) {
      *list = malloc(sizeof(urecord));
      asprintf(&((*list)->name), "%s", n);
      (*list)->idle = i;
      (*list)->count = 1;
      (*list)->next = NULL;
   } else
      add_urecord(&((*list)->next), n, i);
}

urecord*
find_urecord(urecord *list, char *name) {
   if (list == NULL)
      return NULL;
   else if (strcmp(name, list->name) == 0)
      return list;
   else
      return find_urecord(list->next, name);
}

const char *getcolor(int i) {
   static char *green = "00ff00";
   static char *lgreen = "00cc00";
   static char *yellow = "ffff00";
   static char *lyellow = "cccc00";
   static char *red1 = "ff0000";
   static char *red2 = "cc0000";
   static char *red3 = "990000";
   static char *red4 = "660000";

   if (i == 0)
      return green;
   else if (i < 10)
      return lgreen;
   else if (i < 20)
      return yellow;
   else if (i < 30)
      return lyellow;
   else if (i < 40)
      return red1;
   else if (i < 50)
      return red2;
   else if (i < 60)
      return red3;
   else
      return red4;
}

void
print_urecords(urecord *list) {
   if (list != NULL) {
      printf("#%s#%s##%d", getcolor(list->idle), list->name, list->count);

      if (list->next != NULL)
         printf(",");

      print_urecords(list->next);
   }
}

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

   char *finger_command;
   char *buf, *lbuf = NULL;
   FILE *p;
   size_t len;
   int time, hours, minutes, days;

   char username[255];
   char idle[255];
   char dummy[255];

   urecord *list = NULL;

   /* ensure proper usage */
   if (argc != 2)
      errx(1, "usage: %s hostname", argv[0]);

   /* build finger command from provided hostname */
   if (asprintf(&finger_command, "/usr/bin/finger @%s", argv[1]) == -1)
      errx(1, "asprintf fail");

   /* fork command and read output */
   p = popen(finger_command, "r");
   free(finger_command);
   if (p == NULL)
      errx(1, "finger failure");

   /* start parsing output */

   /* discard first two lines */
   fgetln(p, &len);
   fgetln(p, &len);

   /* start reading user data, if any.  note that if the host was invalid, or
    * there are no users logged in, this simply skips.
    */
   while ((buf = fgetln(p, &len))) {

      /* zero-end buff (see fgetln(3)) */
      if ((buf[len - 1] = '\n'))
         buf[len - 1] = '\0';
      else {
         if ((lbuf = malloc(len + 1)) == NULL)
            err(1, NULL);
         memcpy(lbuf, buf, len);
         lbuf[len] = '\0';
         buf = lbuf;
      }

      /* get username */
      int offset;
      if (sscanf(buf, "%s %*20c %*s %n ", username, &offset) != 1) {
         err(1, "parse fail (username)");
      }
      buf += offset;

      /* begin long campaign to decipher finger(1) idle format... */
      sscanf(buf, "%s", idle);
      if (idle[0] == '-') {
         time = 0;
      } else if (sscanf(buf, "%d%2[ ]", &time, dummy) == 2) {
      } else if (sscanf(buf, "%dd%2[ ]", &days, dummy) == 2) {
         time = days * 60 * 24;
      } else if (sscanf(buf, "%d:%d%*2[ ]", &hours, &minutes) == 2) {
         time = hours * 60 + minutes;
      } else if (sscanf(buf, "%d day%d:%d%*2[ ]", &days, &hours, &minutes) == 2) {
         time = days * 24 * 60 + hours * 60 + minutes;
      } else if (sscanf(buf, "%d days%d:%d%*2[ ]", &days, &hours, &minutes) == 2) {
         time = days * 24 * 60 + hours * 60 + minutes;
      }

      /* insert/update record */
      urecord *location = find_urecord(list, username);
      if (location == NULL)
         add_urecord(&list, username, time);
      else {
         location->count++;
         if (time < location->idle)
            location->idle = time;
      }

      if (lbuf != NULL) {
         free(lbuf);
         lbuf = NULL;
      }
   }

   print_urecords(list);
   pclose(p);
   return 0;
}