/*      $NetBSD: unexpand.c,v 1.18 2019/09/13 17:32:29 dyoung 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 <sys/cdefs.h>
#ifndef lint
__COPYRIGHT("@(#) Copyright (c) 1980, 1993\
 The Regents of the University of California.  All rights reserved.");
#endif /* not lint */

#ifndef lint
#if 0
static char sccsid[] = "@(#)unexpand.c  8.1 (Berkeley) 6/6/93";
#endif
__RCSID("$NetBSD: unexpand.c,v 1.18 2019/09/13 17:32:29 dyoung Exp $");
#endif /* not lint */

/*
 * unexpand - put tabs into a file replacing blanks
 */
#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <err.h>
#include <util.h>


#define DSTOP   8
static int      all;
static size_t   nstops;
static size_t   maxstops;
static size_t   *tabstops;

static void     tabify(const char *, size_t);
static void     usage(void) __attribute__((__noreturn__));

static void
usage(void)
{
        (void)fprintf(stderr, "Usage: %s [-a] [-t tabstop] [file ...]\n",
            getprogname());
        exit(EXIT_FAILURE);
}

int
main(int argc, char **argv)
{
        int c;
        char *ep, *tab;
        char *line;
        size_t len;
        unsigned long i;

        setprogname(argv[0]);

        while ((c = getopt(argc, argv, "at:")) != -1) {
                switch (c) {
                case 'a':
                        all = 1;
                        break;
                case 't':
                        while ((tab = strsep(&optarg, ", \t")) != NULL) {
                                if (*tab == '\0')
                                        continue;
                                errno = 0;
                                i = strtoul(tab, &ep, 0);
                                if (*ep || (errno == ERANGE && i == ULONG_MAX))
                                        errx(EXIT_FAILURE,
                                            "Invalid tabstop `%s'", tab);
                                if (nstops >= maxstops) {
                                        maxstops += 20;
                                        tabstops = erealloc(tabstops, maxstops);
                                }
                                if (nstops && tabstops[nstops - 1] >= (size_t)i)
                                        errx(EXIT_FAILURE,
                                            "Bad tabstop spec `%s', must be "
                                            "greater than the previous `%zu'",
                                            tab, tabstops[nstops - 1]);
                                tabstops[nstops++] = i;
                        }
                        break;
                case '?':
                default:
                        usage();
                }
        }
        argc -= optind;
        argv += optind;

        do {
                if (argc > 0) {
                        if (freopen(argv[0], "r", stdin) == NULL)
                                err(EXIT_FAILURE, "Cannot open `%s'", argv[0]);
                        argc--, argv++;
                }
                while ((line = fgetln(stdin, &len)) != NULL)
                        tabify(line, len);
        } while (argc > 0);
        return EXIT_SUCCESS;
}

static void
tabify(const char *line, size_t len)
{
        const size_t dstop = (nstops == 0) ? DSTOP : tabstops[0];
        const char *e, *p;
        size_t dcol, ocol, limit, n;

        dcol = ocol = 0;
        limit = nstops <= 1 ? UINT_MAX : tabstops[nstops - 1] - 1;
        e = line + len;
        for (p = line; p < e; p++) {
                if (*p == ' ') {
                        dcol++;
                        continue;
                } else if (*p == '\t') {
                        if (nstops <= 1) {
                                dcol = (1 + dcol / dstop) * dstop;
                                continue;
                        }
                        for (n = 0; n < nstops && tabstops[n] <= dcol; n++)
                                continue;
                        if (n < nstops - 1 && tabstops[n] - 1 < limit) {
                                dcol = tabstops[n];
                                continue;
                        }
                }

                /* Output our tabs */
                if (nstops <= 1) {
                        while (((ocol + dstop) / dstop) <= (dcol / dstop)) {
                                if (dcol - ocol < 2)
                                        break;
                                if (putchar('\t') == EOF)
                                        goto out;
                                ocol = (1 + ocol / dstop) * dstop;
                        }
                } else {
                        for (n = 0; n < nstops && tabstops[n] <= ocol; n++)
                                continue;
                        while (n < nstops && tabstops[n] <= dcol && ocol < dcol
                            && ocol < limit) {
                                if (putchar('\t') == EOF)
                                        goto out;
                                ocol = tabstops[n++];
                        }
                }

                /* Output remaining spaces */
                while (ocol < dcol && ocol < limit) {
                        if (putchar(' ') == EOF)
                                goto out;
                        ocol++;
                }

                /* Output our char */
                if (putchar(*p) == EOF)
                        goto out;
                if (*p == '\b') {
                        if (ocol > 0) {
                                ocol--;
                                dcol--;
                        }
                } else {
                        ocol++;
                        dcol++;
                }

                if (all && dcol < limit)
                        continue; /* Collapse the rest of the line. */

                /* Output remainder of line */
                for (p++; p < e; p++) {
                        if (putchar(*p) == EOF)
                                goto out;
                }
                return;
        }
        return;
out:
        err(EXIT_FAILURE, "write failed");
}