/*      $OpenBSD: colrm.c,v 1.14 2022/12/04 23:50:47 cheloha Exp $      */
/*      $NetBSD: colrm.c,v 1.4 1995/09/02 05:51:37 jtc Exp $    */

/*-
 * Copyright (c) 1991, 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/types.h>

#include <err.h>
#include <errno.h>
#include <limits.h>
#include <locale.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <wchar.h>

#define TAB     8

void usage(void);

int
main(int argc, char *argv[])
{
        char     *line, *p;
        ssize_t   linesz;
        wchar_t   wc;
        u_long    column, newcol, start, stop;
        int       ch, len, width;

        setlocale(LC_CTYPE, "");

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

        while ((ch = getopt(argc, argv, "")) != -1)
                switch(ch) {
                default:
                        usage();
                }
        argc -= optind;
        argv += optind;

        start = stop = 0;
        switch(argc) {
        case 2:
                stop = strtol(argv[1], &p, 10);
                if (stop <= 0 || *p)
                        errx(1, "illegal column -- %s", argv[1]);
                /* FALLTHROUGH */
        case 1:
                start = strtol(argv[0], &p, 10);
                if (start <= 0 || *p)
                        errx(1, "illegal column -- %s", argv[0]);
                break;
        case 0:
                break;
        default:
                usage();
        }

        if (stop && start > stop)
                err(1, "illegal start and stop columns");

        line = NULL;
        while (getline(&line, &linesz, stdin) != -1) {
                column = 0;
                width = 0;
                for (p = line; *p != '\0'; p += len) {
                        len = 1;
                        switch (*p) {
                        case '\n':
                                putchar('\n');
                                continue;
                        case '\b':
                                /*
                                 * Pass it through if the previous character
                                 * was in scope, still represented by the
                                 * current value of "column".
                                 * Allow an optional second backspace
                                 * after a double-width character.
                                 */
                                if (start == 0 || column < start ||
                                    (stop > 0 &&
                                     column > stop + (width > 1))) {
                                        putchar('\b');
                                        if (width > 1 && p[1] == '\b')
                                                putchar('\b');
                                } 
                                if (width > 1 && p[1] == '\b')
                                        p++;
                                column -= width;
                                continue;
                        case '\t':
                                newcol = (column + TAB) & ~(TAB - 1);
                                if (start == 0 || newcol < start) {
                                        putchar('\t');
                                        column = newcol;
                                } else
                                        /*
                                         * Expand tabs that intersect or
                                         * follow deleted columns.
                                         */
                                        while (column < newcol)
                                                if (++column < start ||
                                                    (stop > 0 &&
                                                     column > stop))
                                                        putchar(' ');
                                continue;
                        default:
                                break;
                        }

                        /*
                         * Handle the three cases of invalid bytes,
                         * non-printable, and printable characters.
                         */

                        if ((len = mbtowc(&wc, p, MB_CUR_MAX)) == -1) {
                                (void)mbtowc(NULL, NULL, MB_CUR_MAX);
                                len = 1;
                                width = 1;
                        } else if ((width = wcwidth(wc)) == -1)
                                width = 1;

                        /*
                         * If the character completely fits before or
                         * after the cut, keep it; otherwise, skip it.
                         */

                        if ((start == 0 || column + width < start ||
                            (stop > 0 && column + (width > 0) > stop)))
                                fwrite(p, 1, len, stdout);

                        /*
                         * If the cut cuts the character in half
                         * and no backspace follows,
                         * print a blank for correct columnation.
                         */

                        else if (width > 1 && p[len] != '\b' &&
                            (start == 0 || column + 1 < start ||
                            (stop > 0 && column + width > stop)))
                                putchar(' ');

                        column += width;
                }
        }
        if (ferror(stdin))
                err(1, "stdin");
        if (ferror(stdout))
                err(1, "stdout");
        return 0;
}

void
usage(void)
{
        (void)fprintf(stderr, "usage: colrm [start [stop]]\n");
        exit(1);
}