/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 1990, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Kevin Ruddy.
 *
 * 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 <err.h>
#include <limits.h>
#include <locale.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <wchar.h>
#include <wctype.h>

#define DEFLINEWIDTH    80

void fold(int);
static int newpos(int, wint_t);
static void usage(void) __dead2;

static int bflag;               /* Count bytes, not columns */
static int sflag;               /* Split on word boundaries */

int
main(int argc, char **argv)
{
        int ch, previous_ch;
        int rval, width;

        (void) setlocale(LC_CTYPE, "");

        width = -1;
        previous_ch = 0;
        while ((ch = getopt(argc, argv, "0123456789bsw:")) != -1) {
                switch (ch) {
                case 'b':
                        bflag = 1;
                        break;
                case 's':
                        sflag = 1;
                        break;
                case 'w':
                        if ((width = atoi(optarg)) <= 0) {
                                errx(1, "illegal width value");
                        }
                        break;
                case '0': case '1': case '2': case '3': case '4':
                case '5': case '6': case '7': case '8': case '9':
                        /* Accept a width as eg. -30. Note that a width
                         * specified using the -w option is always used prior
                         * to this undocumented option. */
                        switch (previous_ch) {
                        case '0': case '1': case '2': case '3': case '4':
                        case '5': case '6': case '7': case '8': case '9':
                                /* The width is a number with multiple digits:
                                 * add the last one. */
                                width = width * 10 + (ch - '0');
                                break;
                        default:
                                /* Set the width, unless it was previously
                                 * set. For instance, the following options
                                 * would all give a width of 5 and not 10:
                                 *   -10 -w5
                                 *   -5b10
                                 *   -5 -10b */
                                if (width == -1)
                                        width = ch - '0';
                                break;
                        }
                        break;
                default:
                        usage();
                }
                previous_ch = ch;
        }
        argv += optind;
        argc -= optind;

        if (width == -1)
                width = DEFLINEWIDTH;
        rval = 0;
        if (!*argv)
                fold(width);
        else for (; *argv; ++argv)
                if (!freopen(*argv, "r", stdin)) {
                        warn("%s", *argv);
                        rval = 1;
                } else
                        fold(width);
        exit(rval);
}

static void
usage(void)
{
        (void)fprintf(stderr, "usage: fold [-bs] [-w width] [file ...]\n");
        exit(1);
}

/*
 * Fold the contents of standard input to fit within WIDTH columns (or bytes)
 * and write to standard output.
 *
 * If sflag is set, split the line at the last space character on the line.
 * This flag necessitates storing the line in a buffer until the current
 * column > width, or a newline or EOF is read.
 *
 * The buffer can grow larger than WIDTH due to backspaces and carriage
 * returns embedded in the input stream.
 */
void
fold(int width)
{
        static wchar_t *buf;
        static int buf_max;
        int col, i, indx, space;
        wint_t ch;

        col = indx = 0;
        while ((ch = getwchar()) != WEOF) {
                if (ch == '\n') {
                        wprintf(L"%.*ls\n", indx, buf);
                        col = indx = 0;
                        continue;
                }
                if ((col = newpos(col, ch)) > width) {
                        if (sflag) {
                                i = indx;
                                while (--i >= 0 && !iswblank(buf[i]))
                                        ;
                                space = i;
                        }
                        if (sflag && space != -1) {
                                space++;
                                wprintf(L"%.*ls\n", space, buf);
                                wmemmove(buf, buf + space, indx - space);
                                indx -= space;
                                col = 0;
                                for (i = 0; i < indx; i++)
                                        col = newpos(col, buf[i]);
                        } else {
                                wprintf(L"%.*ls\n", indx, buf);
                                col = indx = 0;
                        }
                        col = newpos(col, ch);
                }
                if (indx + 1 > buf_max) {
                        buf_max += LINE_MAX;
                        buf = realloc(buf, sizeof(*buf) * buf_max);
                        if (buf == NULL)
                                err(1, "realloc()");
                }
                buf[indx++] = ch;
        }

        if (indx != 0)
                wprintf(L"%.*ls", indx, buf);
}

/*
 * Update the current column position for a character.
 */
static int
newpos(int col, wint_t ch)
{
        char buf[MB_LEN_MAX];
        size_t len;
        int w;

        if (bflag) {
                len = wcrtomb(buf, ch, NULL);
                col += len;
        } else
                switch (ch) {
                case '\b':
                        if (col > 0)
                                --col;
                        break;
                case '\r':
                        col = 0;
                        break;
                case '\t':
                        col = (col + 8) & ~7;
                        break;
                default:
                        if ((w = wcwidth(ch)) > 0)
                                col += w;
                        break;
                }

        return (col);
}