#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);
}