/*
 * Copyright (c) 2023 DTB <trinity@trinity.moe>
 * 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 <errno.h> /* errno */
#include <stdio.h> /* fprintf(3), stderr */
#include <stdlib.h> /* strtol(3), size_t */
#ifndef EX_USAGE
#	include <sysexits.h> /* EX_USAGE */
#endif
#include <unistd.h> /* getopt(3), optind */

/* 0b00? */		/*                     Equal | -e  | 0b001 | 1 */
#define EQUAL	0x01	/*                   Greater | -g  | 0b010 | 2 */
/* 0b0?0 */		/*          Greater or Equal | -ge | 0b011 | 3 */
#define GREATER	0x02	/*                      Less | -l  | 0b100 | 4 */
/* 0b?00 */		/*             Less or Equal | -le | 0b101 | 5 */
#define LESS	0x04	/* Inequal (Greater or Less) | -gl | 0b110 | 6 */

static char *program_name = "intcmp";

int main(int argc, char *argv[]){
	int c;
	size_t i;
	unsigned char mode;
	int r; /* reference integer */

	mode = 0;

	if(argc < 3)
		goto usage;

	while((c = getopt(argc, argv, "egl")) != -1)
		switch(c){
		case 'e': mode |= EQUAL;   break;
		case 'g': mode |= GREATER; break;
		case 'l': mode |= LESS;	   break;
		default:  goto usage;
		}

	if(optind + 2 /* ref cmp */ > argc){
usage:		fprintf(stderr,
			"Usage: %s (-eghl) [integer] [integer...]\n",
			argv[0] == NULL ? program_name : argv[0]);
		return EX_USAGE;
	}

	i = optind;

	do{	r = c;
		c = strtol(argv[i], &argv[i], 10);
		if(*argv[i] != '\0' || errno != 0){
			fprintf(stderr, "%s: argument #%d: Invalid integer\n",
				argv[0], (int)i);
			return EX_USAGE;
		}

		if(i == optind)
			continue;

		/* rule enforcement; if a mode isn't permitted and the numbers
		 * correspond to it, return 1 */
		if(		(!(mode & EQUAL) && r == c)
				|| (!(mode & GREATER) && r > c)
				|| (!(mode & LESS) && r < c))
			return 1;
	}while(++i < argc);
	
	return 0;
}