// SPDX-License-Identifier: MIT

// This implementation was taken from musl and modified for RGBDS.

#include "extern/getopt.hpp"

#include <limits.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <wchar.h>

char *musl_optarg;
int musl_optind = 1, musl_opterr = 1, musl_optopt;
int musl_optreset = 0;
static int musl_optpos;

static void musl_getopt_msg(char const *a, char const *b, char const *c, size_t l) {
	FILE *f = stderr;

	if (fputs(a, f) >= 0 && fwrite(b, strlen(b), 1, f) && fwrite(c, 1, l, f) == l) {
		putc('\n', f);
	}
}

static int getopt(int argc, char *argv[], char const *optstring) {
	int i;
	wchar_t c, d;
	int k, l;
	char *optchar;

	if (!musl_optind || musl_optreset) {
		musl_optreset = 0;
		musl_optpos = 0;
		musl_optind = 1;
	}

	if (musl_optind >= argc || !argv[musl_optind]) {
		return -1;
	}

	if (argv[musl_optind][0] != '-') {
		if (optstring[0] == '-') {
			musl_optarg = argv[musl_optind++];
			return 1;
		}
		return -1;
	}

	if (!argv[musl_optind][1]) {
		return -1;
	}

	if (argv[musl_optind][1] == '-' && !argv[musl_optind][2]) {
		return musl_optind++, -1;
	}

	if (!musl_optpos) {
		++musl_optpos;
	}
	k = mbtowc(&c, argv[musl_optind] + musl_optpos, MB_LEN_MAX);
	if (k < 0) {
		k = 1;
		c = 0xFFFD; // replacement char
	}
	optchar = argv[musl_optind] + musl_optpos;
	musl_optpos += k;

	if (!argv[musl_optind][musl_optpos]) {
		++musl_optind;
		musl_optpos = 0;
	}

	if (optstring[0] == '-' || optstring[0] == '+') {
		++optstring;
	}

	i = 0;
	d = 0;
	do {
		l = mbtowc(&d, optstring + i, MB_LEN_MAX);
		if (l > 0) {
			i += l;
		} else {
			++i;
		}
	} while (l && d != c);

	if (d != c || c == ':') {
		musl_optopt = c;
		if (optstring[0] != ':' && musl_opterr) {
			musl_getopt_msg(argv[0], ": unrecognized option: ", optchar, k);
		}
		return '?';
	}
	if (optstring[i] == ':') {
		musl_optarg = 0;
		if (optstring[i + 1] != ':' || musl_optpos) {
			musl_optarg = argv[musl_optind++] + musl_optpos;
			musl_optpos = 0;
		}
		if (musl_optind > argc) {
			musl_optopt = c;
			if (optstring[0] == ':') {
				return ':';
			}
			if (musl_opterr) {
				musl_getopt_msg(argv[0], ": option requires an argument: ", optchar, k);
			}
			return '?';
		}
	}
	return c;
}

static void permute(char **argv, int dest, int src) {
	char *tmp = argv[src];
	int i;

	for (i = src; i > dest; --i) {
		argv[i] = argv[i - 1];
	}
	argv[dest] = tmp;
}

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

static int musl_getopt_long(
    int argc, char **argv, char const *optstring, option const *longopts, int *idx, int longonly
) {
	int ret, skipped, resumed;

	if (!musl_optind || musl_optreset) {
		musl_optreset = 0;
		musl_optpos = 0;
		musl_optind = 1;
	}

	if (musl_optind >= argc || !argv[musl_optind]) {
		return -1;
	}

	skipped = musl_optind;
	if (optstring[0] != '+' && optstring[0] != '-') {
		int i;
		for (i = musl_optind;; ++i) {
			if (i >= argc || !argv[i]) {
				return -1;
			}
			if (argv[i][0] == '-' && argv[i][1]) {
				break;
			}
		}
		musl_optind = i;
	}
	resumed = musl_optind;
	ret = musl_getopt_long_core(argc, argv, optstring, longopts, idx, longonly);
	if (resumed > skipped) {
		int i, cnt = musl_optind - resumed;

		for (i = 0; i < cnt; ++i) {
			permute(argv, skipped, musl_optind - 1);
		}
		musl_optind = skipped + cnt;
	}
	return ret;
}

static int musl_getopt_long_core(
    int argc, char **argv, char const *optstring, option const *longopts, int *idx, int longonly
) {
	musl_optarg = 0;
	if (longopts && argv[musl_optind][0] == '-'
	    && ((longonly && argv[musl_optind][1] && argv[musl_optind][1] != '-')
	        || (argv[musl_optind][1] == '-' && argv[musl_optind][2]))) {
		int colon = optstring[optstring[0] == '+' || optstring[0] == '-'] == ':';
		int i, cnt, match = 0;
		char *arg = 0, *opt, *start = argv[musl_optind] + 1;

		for (cnt = i = 0; longopts[i].name; ++i) {
			char const *name = longopts[i].name;

			opt = start;
			if (*opt == '-') {
				++opt;
			}
			while (*opt && *opt != '=' && *opt == *name) {
				++name;
				++opt;
			}
			if (*opt && *opt != '=') {
				continue;
			}
			arg = opt;
			match = i;
			if (!*name) {
				cnt = 1;
				break;
			}
			++cnt;
		}
		if (cnt == 1 && longonly && arg - start == mblen(start, MB_LEN_MAX)) {
			int l = arg - start;

			for (i = 0; optstring[i]; ++i) {
				int j = 0;

				while (j < l && start[j] == optstring[i + j]) {
					++j;
				}
				if (j == l) {
					++cnt;
					break;
				}
			}
		}
		if (cnt == 1) {
			i = match;
			opt = arg;
			++musl_optind;
			if (*opt == '=') {
				if (!longopts[i].has_arg) {
					musl_optopt = longopts[i].val;
					if (colon || !musl_opterr) {
						return '?';
					}
					musl_getopt_msg(
					    argv[0],
					    ": option does not take an argument: ",
					    longopts[i].name,
					    strlen(longopts[i].name)
					);
					return '?';
				}
				musl_optarg = opt + 1;
			} else if (longopts[i].has_arg == required_argument) {
				musl_optarg = argv[musl_optind];
				if (!musl_optarg) {
					musl_optopt = longopts[i].val;
					if (colon) {
						return ':';
					}
					if (!musl_opterr) {
						return '?';
					}
					musl_getopt_msg(
					    argv[0],
					    ": option requires an argument: ",
					    longopts[i].name,
					    strlen(longopts[i].name)
					);
					return '?';
				}
				++musl_optind;
			}
			if (idx) {
				*idx = i;
			}
			if (longopts[i].flag) {
				*longopts[i].flag = longopts[i].val;
				return 0;
			}
			return longopts[i].val;
		}
		if (argv[musl_optind][1] == '-') {
			musl_optopt = 0;
			if (!colon && musl_opterr) {
				musl_getopt_msg(
				    argv[0],
				    cnt ? ": option is ambiguous: " : ": unrecognized option: ",
				    argv[musl_optind] + 2,
				    strlen(argv[musl_optind] + 2)
				);
			}
			++musl_optind;
			return '?';
		}
	}
	return getopt(argc, argv, optstring);
}

int musl_getopt_long_only(
    int argc, char **argv, char const *optstring, option const *longopts, int *idx
) {
	return musl_getopt_long(argc, argv, optstring, longopts, idx, 1);
}