#include <math.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>

typedef struct Person {
  char *name;
  struct Person *opponent;
} Person;

static void
die(const char *fmt, ...)
{
  va_list ap;

  va_start(ap, fmt);
  vfprintf(stderr, fmt, ap);
  va_end(ap);

  if (fmt[0] && fmt[strlen(fmt)-1] == ':') {
    fputc(' ', stderr);
    perror(NULL);
  } else
    fputc('\n', stderr);
  exit(1);
}

/**
 * @brief get number of substr in str
 *
 * @param haystack str to search
 * @param needle substr
 * @return number of substr in str
 */
static inline int
numsubstr(const char *haystack, const char *needle)
{
  int i = 0;
  const char *tmp = haystack;

  while((tmp = strstr(tmp, needle))) {
    i++;
    tmp++;
  }

  return i;
}

/**
 * @brief cleanup people ptrs
 *
 * @param p pointer to person
 * @param len number of people in p
 */
void
destroypeopleptr(Person *p, size_t num)
{
  int i;

  for (i = 0; i < num; i++)
    if (p[i].name && p[i].name == NULL)
      free(p[i].name);
  free(p);
}

int
main(int argc, char *argv[])
{
  int j, i, l, t, c, a, r, min, numteams, numpeople, peopleperteam;
  Person *people, **teams;

  /* seed random number generator */
  srand(time(NULL));

  /* get number of people declared and allocate enough space for them */
  for (i = numpeople = 0; i < argc; i++)
    numpeople += numsubstr(argv[i], "-p");

  /* allocate space for all people */
  people = calloc(numpeople, sizeof(Person));

  /* collect people and team numbers */
  i = 0;
  while ((c = getopt(argc, argv, "p:t:")) != -1) {
    switch (c) {
      case 'p':
        people[i++] = (Person){
          .name = optarg,
          .opponent = NULL
        };
        break;
      case 't':
          numteams = atoi(optarg);
        break;
    }
  }

  /* exit if there aren't enough people for the number of teams */
  if (floor((double)numpeople / (double)numteams) < 1)
    die("%d people is not enough for %d teams", numpeople, numteams);

  /* allocate space for teams */
  teams = calloc(numteams, sizeof(Person *));

  /* calculate maximum number of people per team */
  peopleperteam = floor(((double)numpeople / (double)numteams) + 0.5);

  /* allocate space for people in each team */
  for (i = 0; i < numteams; i++)
    teams[i] = calloc(peopleperteam, sizeof(Person));

  /* randomize array */
  for (i = 0; i < numpeople; i++) {
    r = rand() / (RAND_MAX / numpeople);
    Person tmp = people[r];
    people[r] = people[i];
    people[i] = tmp;
  }

  /* sort people into teams */
  for (i = j = l = min = 0; i < numpeople; i++) {
    if (l == peopleperteam) {
      if (j < numteams - 1) {
        j++;
        l = min;
      } else {
        /* resize arrays */
        for (t = 0; t < numteams; t++) {
          Person *b = calloc(peopleperteam + 1, sizeof(Person));

          for (a = 0; a < peopleperteam; a++) {
            b[a].name = teams[t][a].name;
            b[a].opponent = teams[t][a].opponent;
          }

          destroypeopleptr(teams[t], numpeople);
          teams[t] = b;
          b = NULL;
        }

        j = 0;
        l = min = peopleperteam++;
      }
    }

    /* assign person to team */
    teams[j][l++] = people[i];
  }

  /* print out teams */
  for (i = 0; i < numteams; i++) {
    printf("team #%d:\n", i + 1);
    for (j = 0; j < peopleperteam; j++)
      if (teams[i][j].name)
        puts(teams[i][j].name);
  }

  /* cleanup */
  destroypeopleptr(people, numpeople);

  for (i = 0; i < numteams; i++)
    free(teams[i]);
  free(teams);

  return 0;
}