/*      $OpenBSD: fold.c,v 1.18 2016/05/23 10:31:42 schwarze Exp $      */
/*      $NetBSD: fold.c,v 1.6 1995/09/01 01:42:44 jtc Exp $     */

/*-
 * 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 <ctype.h>
#include <err.h>
#include <limits.h>
#include <locale.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <wchar.h>

#define DEFLINEWIDTH    80

static void fold(unsigned int);
static int isu8cont(unsigned char);
static __dead void usage(void);

int count_bytes = 0;
int split_words = 0;

int
main(int argc, char *argv[])
{
        int ch, lastch, newarg, prevoptind;
        unsigned int width;
        const char *errstr;

        setlocale(LC_CTYPE, "");

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

        width = 0;
        lastch = '\0';
        prevoptind = 1;
        newarg = 1;
        while ((ch = getopt(argc, argv, "0123456789bsw:")) != -1) {
                switch (ch) {
                case 'b':
                        count_bytes = 1;
                        break;
                case 's':
                        split_words = 1;
                        break;
                case 'w':
                        width = strtonum(optarg, 1, UINT_MAX, &errstr);
                        if (errstr != NULL)
                                errx(1, "illegal width value, %s: %s", errstr, 
                                        optarg);
                        break;
                case '0': case '1': case '2': case '3': case '4':
                case '5': case '6': case '7': case '8': case '9':
                        if (newarg)
                                width = 0;
                        else if (!isdigit(lastch))
                                usage();
                        if (width > UINT_MAX / 10 - 1)
                                errx(1, "illegal width value, too large");
                        width = (width * 10) + (ch - '0');
                        if (width < 1)
                                errx(1, "illegal width value, too small");
                        break;
                default:
                        usage();
                }
                lastch = ch;
                newarg = optind != prevoptind;
                prevoptind = optind;
        }
        argv += optind;
        argc -= optind;

        if (width == 0)
                width = DEFLINEWIDTH;

        if (!*argv) {
                if (pledge("stdio", NULL) == -1)
                        err(1, "pledge");
                fold(width);
        } else {
                for (; *argv; ++argv) {
                        if (!freopen(*argv, "r", stdin))
                                err(1, "%s", *argv);
                        else
                                fold(width);
                }
        }
        return 0;
}

/*
 * Fold the contents of standard input to fit within WIDTH columns
 * (or bytes) and write to standard output.
 *
 * If split_words 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.
 */
static void
fold(unsigned int max_width)
{
        static char     *buf = NULL;
        static size_t    bufsz = 2048;
        char            *cp;    /* Current mb character. */
        char            *np;    /* Next mb character. */
        char            *sp;    /* To search for the last space. */
        char            *nbuf;  /* For buffer reallocation. */
        wchar_t          wc;    /* Current wide character. */
        int              ch;    /* Last byte read. */
        int              len;   /* Bytes in the current mb character. */
        unsigned int     col;   /* Current display position. */
        int              width; /* Display width of wc. */

        if (buf == NULL && (buf = malloc(bufsz)) == NULL)
                err(1, NULL);

        np = cp = buf;
        ch = 0;
        col = 0;

        while (ch != EOF) {  /* Loop on input characters. */
                while ((ch = getchar()) != EOF) {  /* Loop on input bytes. */
                        if (np + 1 == buf + bufsz) {
                                nbuf = reallocarray(buf, 2, bufsz);
                                if (nbuf == NULL)
                                        err(1, NULL);
                                bufsz *= 2;
                                cp = nbuf + (cp - buf);
                                np = nbuf + (np - buf);
                                buf = nbuf;
                        }
                        *np++ = ch;

                        /*
                         * Read up to and including the first byte of
                         * the next character, such that we are sure
                         * to have a complete character in the buffer.
                         * There is no need to read more than five bytes
                         * ahead, since UTF-8 characters are four bytes
                         * long at most.
                         */

                        if (np - cp > 4 || (np - cp > 1 && !isu8cont(ch)))
                                break;
                }

                while (cp < np) {  /* Loop on output characters. */

                        /* Handle end of line and backspace. */

                        if (*cp == '\n' || (*cp == '\r' && !count_bytes)) {
                                fwrite(buf, 1, ++cp - buf, stdout);
                                memmove(buf, cp, np - cp);
                                np = buf + (np - cp);
                                cp = buf;
                                col = 0;
                                continue;
                        }
                        if (*cp == '\b' && !count_bytes) {
                                if (col)
                                        col--;
                                cp++;
                                continue;
                        }

                        /*
                         * Measure display width.
                         * Process the last byte only if
                         * end of file was reached.
                         */

                        if (np - cp > (ch != EOF)) {
                                len = 1;
                                width = 1;

                                if (*cp == '\t') {
                                        if (count_bytes == 0)
                                                width = 8 - (col & 7);
                                } else if ((len = mbtowc(&wc, cp,
                                    np - cp)) < 1)
                                        len = 1;
                                else if (count_bytes)
                                        width = len;
                                else if ((width = wcwidth(wc)) < 0)
                                        width = 1;

                                col += width;
                                if (col <= max_width || cp == buf) {
                                        cp += len;
                                        continue;
                                }
                        }

                        /* Line break required. */

                        if (col > max_width) {
                                if (split_words) {
                                        for (sp = cp; sp > buf; sp--) {
                                                if (sp[-1] == ' ') {
                                                        cp = sp;
                                                        break;
                                                }
                                        }
                                }
                                fwrite(buf, 1, cp - buf, stdout);
                                putchar('\n');
                                memmove(buf, cp, np - cp);
                                np = buf + (np - cp);
                                cp = buf;
                                col = 0;
                                continue;
                        }

                        /* Need more input. */

                        break;
                }
        }
        fwrite(buf, 1, np - buf, stdout);

        if (ferror(stdin))
                err(1, NULL);
}

static int
isu8cont(unsigned char c)
{
        return MB_CUR_MAX > 1 && (c & (0x80 | 0x40)) == 0x80;
}

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