/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2002 Tim J. Robbins.
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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.
 */

/*
 * tabs -- set terminal tabs
 *
 * This utility displays a series of characters that clears the terminal
 * hardware tab settings, then initialises them to specified values,
 * and optionally sets a soft margin.
 */

#include <sys/types.h>
#include <sys/tty.h>

#include <ctype.h>
#include <err.h>
#include <errno.h>
#include <locale.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <term.h>
#include <unistd.h>

/* Maximum number of tab stops allowed in table. */
#define NSTOPS          20

#define NELEMS(a) (sizeof(a) / sizeof(a[0]))

/* Predefined formats, taken from IEEE Std 1003.1-2001. */
static const struct {
        const char      *name;          /* Format name used on cmd. line */
        long            stops[NSTOPS];  /* Column positions */
} formats[] = {
        { "a",  { 1, 10, 16, 36, 72 } },
        { "a2", { 1, 10, 16, 40, 72 } },
        { "c",  { 1, 8, 12, 16, 20, 55 } },
        { "c2", { 1, 6, 10, 14, 49 } },
        { "c3", { 1, 6, 10, 14, 18, 22, 26, 30, 34, 38, 42, 46, 50, 54, 58,
                62, 67 } },
        { "f",  { 1, 7, 11, 15, 19, 23 } },
        { "p",  { 1, 5, 9, 13, 17, 21, 25, 29, 33, 37, 41, 45, 49, 53, 57,
                61 } },
        { "s",  { 1, 10, 55 } },
        { "u",  { 1, 12, 20, 44 } }
};

static void      gettabs(char *, long *, long *);
static int       ttywidth(void);
static void      usage(void);

int
main(int argc __unused, char *argv[])
{
        long cols, i, inc, j, margin, nstops, stops[NSTOPS];
        const char *cr, *ct, *st, *ML;
        char area[1024], *ap, *arg, *end;

        setlocale(LC_ALL, "");

        inc = 8;
        margin = 0;
        nstops = -1;
        while ((arg = *++argv) != NULL && (*arg == '-' || *arg == '+')) {
                if (*arg == '+') {
                        /* +m[n] or +[n] */
                        if (*++arg == 'm')
                                arg++;
                        if (*arg != '\0') {
                                errno = 0;
                                margin = strtol(arg, &end, 10);
                                if (errno != 0 || *end != '\0' || margin < 0)
                                        errx(1, "%s: invalid margin width",
                                            arg);
                        } else
                                margin = 10;
                } else if (isdigit(arg[1])) {
                        /* -n */
                        errno = 0;
                        inc = strtol(arg + 1, &end, 10);
                        if (errno != 0 || *end != '\0' || inc < 0)
                                errx(1, "%s: invalid increment", arg + 1);
                } else if (arg[1] == 'T') {
                        /* -Ttype or -T type */
                        if (arg[2] != '\0')
                                setenv("TERM", arg + 2, 1);
                        else {
                                if ((arg = *++argv) == NULL)
                                        usage();
                                setenv("TERM", arg, 1);
                        }
                } else if (arg[1] == '-') {
                        arg = *++argv;
                        break;
                } else {
                        /* Predefined format */
                        for (i = 0; i < (int)NELEMS(formats); i++)
                                if (strcmp(formats[i].name, arg + 1) == 0)
                                        break;
                        if (i == NELEMS(formats))
                                usage();
                        for (j = nstops = 0; j < NSTOPS &&
                            formats[i].stops[j] != 0; j++)
                                stops[nstops++] = formats[i].stops[j];
                }
        }       
        
        if (arg != NULL) {
                if (nstops != -1)
                        usage();
                gettabs(arg, stops, &nstops);
        }

        /* Initialise terminal, get the strings we need */
        setupterm(NULL, 1, NULL);
        ap = area;
        if ((ct = tgetstr("ct", &ap)) == NULL)
                errx(1, "terminal cannot clear tabs");
        if ((st = tgetstr("st", &ap)) == NULL)
                errx(1, "terminal cannot set tabs");
        if ((cr = tgetstr("cr", &ap)) == NULL)
                cr = "\r";
        ML = tgetstr("ML", &ap);
        cols = ttywidth();

        /* Clear all tabs. */
        putp(cr);
        putp(ct);

        /*
         * Set soft margin.
         * XXX Does this actually work?
         */
        if (ML != NULL) {
                printf("%*s", (int)margin, "");
                putp(ML);
        } else if (margin != 0)
                warnx("terminal cannot set left margin");

        /* Optionally output new tab stops. */
        if (nstops >= 0) {
                printf("%*s", (int)stops[0] - 1, "");
                putp(st);
                for (i = 1; i < nstops; i++) {
                        printf("%*s", (int)(stops[i] - stops[i - 1]), "");
                        putp(st);
                }
        } else if (inc > 0) {
                for (i = 0; i < cols / inc; i++) {
                        putp(st);
                        printf("%*s", (int)inc, "");
                }
                putp(st);
        }
        putp(cr);

        exit(0);
}

static void
usage(void)
{

        fprintf(stderr,
"usage: tabs [-n|-a|-a2|-c|-c2|-c3|-f|-p|-s|-u] [+m[n]] [-T type]\n");
        fprintf(stderr,
"       tabs [-T type] [+[n]] n1,[n2,...]\n");
        exit(1);
}

static void
gettabs(char *arg, long stops[], long *nstops)
{
        char *tok, *end;
        long last, stop;

        for (last = *nstops = 0, tok = strtok(arg, ","); tok != NULL;
            tok = strtok(NULL, ",")) {
                if (*nstops >= NSTOPS)
                        errx(1, "too many tab stops (limit %d)", NSTOPS);
                errno = 0;
                stop = strtol(tok, &end, 10);
                if (errno != 0 || *end != '\0' || stop <= 0)
                        errx(1, "%s: invalid tab stop", tok);
                if (*tok == '+') {
                        if (tok == arg)
                                errx(1, "%s: first tab may not be relative",
                                    tok);
                        stop += last;
                }
                if (last > stop)
                        errx(1, "cannot go backwards");
                last = stops[(*nstops)++] = stop;
        }
}

static int
ttywidth(void)
{
        struct winsize ws;
        int width;

        if (ioctl(STDOUT_FILENO, TIOCGWINSZ, &ws) != -1)
                width = ws.ws_col;
        else if ((width = tgetnum("co")) == 0) {
                width = 80;
                warnx("cannot find terminal width; defaulted to %d", width);
        }

        return (width);
}