/*      $OpenBSD: expand.c,v 1.15 2022/12/04 23:50:48 cheloha Exp $     */
/*      $NetBSD: expand.c,v 1.5 1995/09/02 06:19:46 jtc Exp $   */

/*
 * Copyright (c) 1980, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <unistd.h>
#include <err.h>

/*
 * expand - expand tabs to equivalent spaces
 */
int     nstops;
int     tabstops[100];

static void getstops(char *);
static void usage(void);

int
main(int argc, char *argv[])
{
        int c, column;
        int n;

        if (pledge("stdio rpath", NULL) == -1)
                err(1, "pledge");

        /* handle obsolete syntax */
        while (argc > 1 && argv[1][0] == '-' &&
            isdigit((unsigned char)argv[1][1])) {
                getstops(&argv[1][1]);
                argc--; argv++;
        }

        while ((c = getopt (argc, argv, "t:")) != -1) {
                switch (c) {
                case 't':
                        getstops(optarg);
                        break;
                default:
                        usage();
                        /* NOTREACHED */
                }
        }
        argc -= optind;
        argv += optind;

        do {
                if (argc > 0) {
                        if (freopen(argv[0], "r", stdin) == NULL)
                                err(1, "%s", argv[0]);
                        argc--, argv++;
                }
                column = 0;
                while ((c = getchar()) != EOF) {
                        switch (c) {
                        case '\t':
                                if (nstops == 0) {
                                        do {
                                                putchar(' ');
                                                column++;
                                        } while (column & 07);
                                        continue;
                                }
                                if (nstops == 1) {
                                        do {
                                                putchar(' ');
                                                column++;
                                        } while (((column - 1) %
                                            tabstops[0]) != (tabstops[0] - 1));
                                        continue;
                                }
                                for (n = 0; n < nstops; n++)
                                        if (tabstops[n] > column)
                                                break;
                                if (n == nstops) {
                                        putchar(' ');
                                        column++;
                                        continue;
                                }
                                while (column < tabstops[n]) {
                                        putchar(' ');
                                        column++;
                                }
                                continue;

                        case '\b':
                                if (column)
                                        column--;
                                putchar('\b');
                                continue;

                        default:
                                putchar(c);
                                column++;
                                continue;

                        case '\n':
                                putchar(c);
                                column = 0;
                                continue;
                        }
                }
        } while (argc > 0);
        exit(0);
}

static void
getstops(char *cp)
{
        int i;

        nstops = 0;
        for (;;) {
                i = 0;
                while (*cp >= '0' && *cp <= '9')
                        i = i * 10 + *cp++ - '0';
                if (i <= 0 || i > 256) {
bad:
                        errx(1, "Bad tab stop spec");
                }
                if (nstops > 0 && i <= tabstops[nstops-1])
                        goto bad;
                if (nstops >= sizeof(tabstops) / sizeof(tabstops[0]))
                        errx(1, "Too many tab stops");
                tabstops[nstops++] = i;
                if (*cp == 0)
                        break;
                if (*cp != ',' && *cp != ' ')
                        goto bad;
                cp++;
        }
}

static void
usage(void)
{
        extern char *__progname;
        fprintf (stderr, "usage: %s [-t tablist] [file ...]\n", __progname);
        exit(1);
}