#define _GNU_SOURCE
#include <getopt.h>
#include <stddef.h>
#include <stdio.h>
#include <string.h>

extern int __optpos, __optreset;

static void permute(char* const* argv, int dest, int src) {
  char** av = (char**)argv;
  char* tmp = av[src];
  int i;
  for (i = src; i > dest; i--)
    av[i] = av[i - 1];
  av[dest] = tmp;
}

void __getopt_msg(const char*, const char*, const char*, size_t);

static int __getopt_long_core(int argc, char* const* argv, const char* optstring,
                              const struct option* longopts, int* idx, int longonly);

static int __getopt_long(int argc, char* const* argv, const char* optstring,
                         const struct option* longopts, int* idx, int longonly) {
  int ret, skipped, resumed;
  if (!optind || __optreset) {
    __optreset = 0;
    __optpos = 0;
    optind = 1;
  }
  if (optind >= argc || !argv[optind])
    return -1;
  skipped = optind;
  if (optstring[0] != '+' && optstring[0] != '-') {
    int i;
    for (i = optind;; i++) {
      if (i >= argc || !argv[i])
        return -1;
      if (argv[i][0] == '-' && argv[i][1])
        break;
    }
    optind = i;
  }
  resumed = optind;
  ret = __getopt_long_core(argc, argv, optstring, longopts, idx, longonly);
  if (resumed > skipped) {
    int i, cnt = optind - resumed;
    for (i = 0; i < cnt; i++)
      permute(argv, skipped, optind - 1);
    optind = skipped + cnt;
  }
  return ret;
}

static int __getopt_long_core(int argc, char* const* argv, const char* optstring,
                              const struct option* longopts, int* idx, int longonly) {
  optarg = 0;
  if (longopts && argv[optind][0] == '-' &&
      ((longonly && argv[optind][1]) || (argv[optind][1] == '-' && argv[optind][2]))) {
    int colon = optstring[optstring[0] == '+' || optstring[0] == '-'] == ':';
    int i, cnt, match;
    char* opt;
    for (cnt = i = 0; longopts[i].name; i++) {
      const char* name = longopts[i].name;
      opt = argv[optind] + 1;
      if (*opt == '-')
        opt++;
      for (; *name && *name == *opt; name++, opt++)
        ;
      if (*opt && *opt != '=')
        continue;
      match = i;
      if (!*name) {
        cnt = 1;
        break;
      }
      cnt++;
    }
    if (cnt == 1) {
      i = match;
      optind++;
      optopt = longopts[i].val;
      if (*opt == '=') {
        if (!longopts[i].has_arg) {
          if (colon || !opterr)
            return '?';
          __getopt_msg(argv[0], ": option does not take an argument: ", longopts[i].name,
                       strlen(longopts[i].name));
          return '?';
        }
        optarg = opt + 1;
      } else if (longopts[i].has_arg == required_argument) {
        if (!(optarg = argv[optind])) {
          if (colon)
            return ':';
          if (!opterr)
            return '?';
          __getopt_msg(argv[0], ": option requires an argument: ", longopts[i].name,
                       strlen(longopts[i].name));
          return '?';
        }
        optind++;
      }
      if (idx)
        *idx = i;
      if (longopts[i].flag) {
        *longopts[i].flag = longopts[i].val;
        return 0;
      }
      return longopts[i].val;
    }
    if (argv[optind][1] == '-') {
      if (!colon && opterr)
        __getopt_msg(argv[0],
                     cnt ? ": option is ambiguous: " : ": unrecognized option: ", argv[optind] + 2,
                     strlen(argv[optind] + 2));
      optind++;
      return '?';
    }
  }
  return getopt(argc, argv, optstring);
}

int getopt_long(int argc, char* const* argv, const char* optstring, const struct option* longopts,
                int* idx) {
  return __getopt_long(argc, argv, optstring, longopts, idx, 0);
}

int getopt_long_only(int argc, char* const* argv, const char* optstring,
                     const struct option* longopts, int* idx) {
  return __getopt_long(argc, argv, optstring, longopts, idx, 1);
}