/*
 * Copyright (c) 2023–2024 DTB <trinity@trinity.moe>
 * Copyright (c) 2024 Emma Tebibyte <emma@tebibyte.media>
 * SPDX-License-Identifier: AGPL-3.0-or-later
 *
 * This program is free software: you can redistribute it and/or modify it under
 * the terms of the GNU Affero General Public License as published by the Free
 * Software Foundation, either version 3 of the License, or (at your option) any
 * later version.
 * 
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 * FOR A PARTICULAR PURPOSE. See the GNU Affero General Public License for more
 * details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program. If not, see https://www.gnu.org/licenses/.
 */

#include <stdio.h> /* fprintf(3), stderr, NULL */
#include <stdlib.h> /* EXIT_FAILURE, EXIT_SUCCESS */
#include <string.h> /* memset(3), strchr(3) */
#ifndef EX_USAGE
#	include <sysexits.h>
#endif
#include <unistd.h> /* access(3), getopt(3), F_OK, R_OK, W_OK, X_OK */
#include <sys/stat.h> /* lstat(3), stat struct, S_ISBLK, S_ISCHR, S_ISDIR,
                       * S_ISFIFO, S_ISGID, S_ISREG, S_ISLNK, S_ISSOCK,
                       * S_ISUID, S_ISVTX */

static char args[] = "bcdefghkprsuwxLS";
static char ops[(sizeof args) / (sizeof *args)];
static char *program_name = "scrut";

int main(int argc, char *argv[]){
	struct stat buf;
	int c;
	size_t i;
	char *p;

	if(argc < 2)
		goto usage;

	memset(ops, '\0', sizeof ops);
	while((c = getopt(argc, argv, args)) != -1)
		if((p = strchr(args, c)) == NULL)
			goto usage;
		else
			ops[p - args] = c;
	/* straighten out ops */
	for(i = 0, p = ops; i < (sizeof ops) / (sizeof *ops); ++i)
		if(ops[i] != '\0'){
			*p = ops[i];
			if(&ops[i] != p++)
				ops[i] = '\0';
		}

	if(optind == argc)
		goto usage;

	argv += optind;
	do{	if(access(*argv, F_OK) != 0 || lstat(*argv, &buf) == -1)
			return EXIT_FAILURE; /* doesn't exist or isn't stattable */

		for(i = 0; ops[i] != '\0'; ++i)
			if(ops[i] == 'e')
				continue;
			else if(ops[i] == 'h'){
usage:				fprintf(stderr, "Usage: %s [-%s] file...\n",
					argv[0] == NULL
						? program_name
						: argv[0],
					args);

				return EX_USAGE;
			}else if(
					(ops[i] == 'b'
						&& !S_ISBLK(buf.st_mode))
					|| (ops[i] == 'c'
						&& !S_ISCHR(buf.st_mode))
					|| (ops[i] == 'd'
						&& !S_ISDIR(buf.st_mode))
					|| (ops[i] == 'f'
						&& !S_ISREG(buf.st_mode))
					|| (ops[i] == 'g'
						&& !(buf.st_mode & S_ISGID))
					|| (ops[i] == 'k'
						&& !(buf.st_mode & S_ISVTX))
					|| (ops[i] == 'p'
						&& !S_ISFIFO(buf.st_mode))
					|| (ops[i] == 'r'
						&& access(*argv, R_OK) != 0)
					|| (ops[i] == 'u'
						&& !(buf.st_mode & S_ISUID))
					|| (ops[i] == 'w'
						&& access(*argv, W_OK) != 0)
					|| (ops[i] == 'x'
						&& access(*argv, X_OK) != 0)
					|| (ops[i] == 'L'
						&& !S_ISLNK(buf.st_mode))
					|| (ops[i] == 'S'
						&& !S_ISSOCK(buf.st_mode)))
				return EXIT_FAILURE;
	}while(*++argv != NULL);

	return EXIT_SUCCESS;
}