/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 1990, 1993, 1994
 *      The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Michael Rendell of the Memorial University of Newfoundland.
 *
 * 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/capsicum.h>

#include <capsicum_helpers.h>
#include <err.h>
#include <errno.h>
#include <locale.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <termios.h>
#include <unistd.h>
#include <wchar.h>
#include <wctype.h>

#define BS      '\b'            /* backspace */
#define TAB     '\t'            /* tab */
#define SPACE   ' '             /* space */
#define NL      '\n'            /* newline */
#define CR      '\r'            /* carriage return */
#define ESC     '\033'          /* escape */
#define SI      '\017'          /* shift in to normal character set */
#define SO      '\016'          /* shift out to alternate character set */
#define VT      '\013'          /* vertical tab (aka reverse line feed) */
#define RLF     '7'             /* ESC-7 reverse line feed */
#define RHLF    '8'             /* ESC-8 reverse half-line feed */
#define FHLF    '9'             /* ESC-9 forward half-line feed */

/* build up at least this many lines before flushing them out */
#define BUFFER_MARGIN           32

typedef char CSET;

typedef struct char_str {
#define CS_NORMAL       1
#define CS_ALTERNATE    2
        short           c_column;       /* column character is in */
        CSET            c_set;          /* character set (currently only 2) */
        wchar_t         c_char;         /* character in question */
        int             c_width;        /* character width */
} CHAR;

typedef struct line_str LINE;
struct line_str {
        CHAR    *l_line;                /* characters on the line */
        LINE    *l_prev;                /* previous line */
        LINE    *l_next;                /* next line */
        int     l_lsize;                /* allocated sizeof l_line */
        int     l_line_len;             /* strlen(l_line) */
        int     l_needs_sort;           /* set if chars went in out of order */
        int     l_max_col;              /* max column in the line */
};

static void     addto_lineno(int *, int);
static LINE     *alloc_line(void);
static void     dowarn(int);
static void     flush_line(LINE *);
static void     flush_lines(int);
static void     flush_blanks(void);
static void     free_line(LINE *);
static void     usage(void);

static CSET     last_set;               /* char_set of last char printed */
static LINE     *lines;
static int      compress_spaces;        /* if doing space -> tab conversion */
static int      fine;                   /* if `fine' resolution (half lines) */
static int      max_bufd_lines;         /* max # of half lines to keep in memory */
static int      nblank_lines;           /* # blanks after last flushed line */
static int      no_backspaces;          /* if not to output any backspaces */
static int      pass_unknown_seqs;      /* pass unknown control sequences */

#define PUTC(ch) \
        do {                                    \
                if (putwchar(ch) == WEOF)       \
                        errx(1, "write error"); \
        } while (0)

int
main(int argc, char **argv)
{
        wint_t ch;
        CHAR *c;
        CSET cur_set;                   /* current character set */
        LINE *l;                        /* current line */
        int extra_lines;                /* # of lines above first line */
        int cur_col;                    /* current column */
        int cur_line;                   /* line number of current position */
        int max_line;                   /* max value of cur_line */
        int this_line;                  /* line l points to */
        int nflushd_lines;              /* number of lines that were flushed */
        int adjust, opt, warned, width;
        const char *errstr;

        (void)setlocale(LC_CTYPE, "");

        if (caph_limit_stdio() == -1)
                err(1, "unable to limit stdio");

        if (caph_enter() < 0)
                err(1, "unable to enter capability mode");

        max_bufd_lines = 256;
        compress_spaces = 1;            /* compress spaces into tabs */
        while ((opt = getopt(argc, argv, "bfhl:px")) != -1)
                switch (opt) {
                case 'b':               /* do not output backspaces */
                        no_backspaces = 1;
                        break;
                case 'f':               /* allow half forward line feeds */
                        fine = 1;
                        break;
                case 'h':               /* compress spaces into tabs */
                        compress_spaces = 1;
                        break;
                case 'l':               /* buffered line count */
                        max_bufd_lines = strtonum(optarg, 1,
                            (INT_MAX - BUFFER_MARGIN) / 2, &errstr) * 2;
                        if (errstr != NULL)
                                errx(1, "bad -l argument, %s: %s", errstr, 
                                        optarg);
                        break;
                case 'p':               /* pass unknown control sequences */
                        pass_unknown_seqs = 1;
                        break;
                case 'x':               /* do not compress spaces into tabs */
                        compress_spaces = 0;
                        break;
                case '?':
                default:
                        usage();
                }

        if (optind != argc)
                usage();

        adjust = cur_col = extra_lines = warned = 0;
        cur_line = max_line = nflushd_lines = this_line = 0;
        cur_set = last_set = CS_NORMAL;
        lines = l = alloc_line();

        while ((ch = getwchar()) != WEOF) {
                if (!iswgraph(ch)) {
                        switch (ch) {
                        case BS:                /* can't go back further */
                                if (cur_col == 0)
                                        continue;
                                --cur_col;
                                continue;
                        case CR:
                                cur_col = 0;
                                continue;
                        case ESC:               /* just ignore EOF */
                                switch(getwchar()) {
                                /*
                                 * In the input stream, accept both the
                                 * XPG5 sequences ESC-digit and the
                                 * traditional BSD sequences ESC-ctrl.
                                 */
                                case '\007':
                                        /* FALLTHROUGH */
                                case RLF:
                                        addto_lineno(&cur_line, -2);
                                        break;
                                case '\010':
                                        /* FALLTHROUGH */
                                case RHLF:
                                        addto_lineno(&cur_line, -1);
                                        break;
                                case '\011':
                                        /* FALLTHROUGH */
                                case FHLF:
                                        addto_lineno(&cur_line, 1);
                                        if (cur_line > max_line)
                                                max_line = cur_line;
                                }
                                continue;
                        case NL:
                                addto_lineno(&cur_line, 2);
                                if (cur_line > max_line)
                                        max_line = cur_line;
                                cur_col = 0;
                                continue;
                        case SPACE:
                                ++cur_col;
                                continue;
                        case SI:
                                cur_set = CS_NORMAL;
                                continue;
                        case SO:
                                cur_set = CS_ALTERNATE;
                                continue;
                        case TAB:               /* adjust column */
                                cur_col |= 7;
                                ++cur_col;
                                continue;
                        case VT:
                                addto_lineno(&cur_line, -2);
                                continue;
                        }
                        if (iswspace(ch)) {
                                if ((width = wcwidth(ch)) > 0)
                                        cur_col += width;
                                continue;
                        }
                        if (!pass_unknown_seqs)
                                continue;
                }

                /* Must stuff ch in a line - are we at the right one? */
                if (cur_line + adjust != this_line) {
                        LINE *lnew;

                        /* round up to next line */
                        adjust = !fine && (cur_line & 1);

                        if (cur_line + adjust < this_line) {
                                while (cur_line + adjust < this_line &&
                                    l->l_prev != NULL) {
                                        l = l->l_prev;
                                        this_line--;
                                }
                                if (cur_line + adjust < this_line) {
                                        if (nflushd_lines == 0) {
                                                /*
                                                 * Allow backup past first
                                                 * line if nothing has been
                                                 * flushed yet.
                                                 */
                                                while (cur_line + adjust
                                                    < this_line) {
                                                        lnew = alloc_line();
                                                        l->l_prev = lnew;
                                                        lnew->l_next = l;
                                                        l = lines = lnew;
                                                        extra_lines++;
                                                        this_line--;
                                                }
                                        } else {
                                                if (!warned++)
                                                        dowarn(cur_line);
                                                cur_line = this_line - adjust;
                                        }
                                }
                        } else {
                                /* may need to allocate here */
                                while (cur_line + adjust > this_line) {
                                        if (l->l_next == NULL) {
                                                l->l_next = alloc_line();
                                                l->l_next->l_prev = l;
                                        }
                                        l = l->l_next;
                                        this_line++;
                                }
                        }
                        if (this_line > nflushd_lines &&
                            this_line - nflushd_lines >=
                            max_bufd_lines + BUFFER_MARGIN) {
                                if (extra_lines) {
                                        flush_lines(extra_lines);
                                        extra_lines = 0;
                                }
                                flush_lines(this_line - nflushd_lines -
                                    max_bufd_lines);
                                nflushd_lines = this_line - max_bufd_lines;
                        }
                }
                /* grow line's buffer? */
                if (l->l_line_len + 1 >= l->l_lsize) {
                        int need;

                        need = l->l_lsize ? l->l_lsize * 2 : 90;
                        if ((l->l_line = realloc(l->l_line,
                            (unsigned)need * sizeof(CHAR))) == NULL)
                                err(1, NULL);
                        l->l_lsize = need;
                }
                c = &l->l_line[l->l_line_len++];
                c->c_char = ch;
                c->c_set = cur_set;
                c->c_column = cur_col;
                c->c_width = wcwidth(ch);
                /*
                 * If things are put in out of order, they will need sorting
                 * when it is flushed.
                 */
                if (cur_col < l->l_max_col)
                        l->l_needs_sort = 1;
                else
                        l->l_max_col = cur_col;
                if (c->c_width > 0)
                        cur_col += c->c_width;
        }
        if (ferror(stdin))
                err(1, NULL);
        if (extra_lines) {
                /*
                 * Extra lines only exist if no lines have been flushed
                 * yet. This means that 'lines' must point to line zero
                 * after we flush the extra lines.
                 */
                flush_lines(extra_lines);
                l = lines;
                this_line = 0;
        }

        /* goto the last line that had a character on it */
        for (; l->l_next; l = l->l_next)
                this_line++;
        flush_lines(this_line - nflushd_lines + 1);

        /* make sure we leave things in a sane state */
        if (last_set != CS_NORMAL)
                PUTC(SI);

        /* flush out the last few blank lines */
        if (max_line >= this_line)
                nblank_lines = max_line - this_line + (max_line & 1);
        if (nblank_lines == 0)
                /* end with a newline even if the source doesn't */
                nblank_lines = 2;
        flush_blanks();
        exit(0);
}

/*
 * Prints the first 'nflush' lines. Printed lines are freed.
 * After this function returns, 'lines' points to the first
 * of the remaining lines, and 'nblank_lines' will have the
 * number of half line feeds between the final flushed line
 * and the first remaining line.
 */
static void
flush_lines(int nflush)
{
        LINE *l;

        while (--nflush >= 0) {
                l = lines;
                lines = l->l_next;
                if (l->l_line) {
                        flush_blanks();
                        flush_line(l);
                        free(l->l_line);
                }
                if (l->l_next)
                        nblank_lines++;
                free_line(l);
        }
        if (lines)
                lines->l_prev = NULL;
}

/*
 * Print a number of newline/half newlines.
 * nblank_lines is the number of half line feeds.
 */
static void
flush_blanks(void)
{
        int half, i, nb;

        half = 0;
        nb = nblank_lines;
        if (nb & 1) {
                if (fine)
                        half = 1;
                else
                        nb++;
        }
        nb /= 2;
        for (i = nb; --i >= 0;)
                PUTC('\n');
        if (half) {
                PUTC(ESC);
                PUTC(FHLF);
                if (!nb)
                        PUTC('\r');
        }
        nblank_lines = 0;
}

/*
 * Write a line to stdout taking care of space to tab conversion (-h flag)
 * and character set shifts.
 */
static void
flush_line(LINE *l)
{
        CHAR *c, *endc;
        int i, j, nchars, last_col, save, this_col, tot;

        last_col = 0;
        nchars = l->l_line_len;

        if (l->l_needs_sort) {
                static CHAR *sorted;
                static int count_size, *count, sorted_size;

                /*
                 * Do an O(n) sort on l->l_line by column being careful to
                 * preserve the order of characters in the same column.
                 */
                if (l->l_lsize > sorted_size) {
                        sorted_size = l->l_lsize;
                        if ((sorted = realloc(sorted,
                            (unsigned)sizeof(CHAR) * sorted_size)) == NULL)
                                err(1, NULL);
                }
                if (l->l_max_col >= count_size) {
                        count_size = l->l_max_col + 1;
                        if ((count = realloc(count,
                            (unsigned)sizeof(int) * count_size)) == NULL)
                                err(1, NULL);
                }
                memset(count, 0, sizeof(int) * l->l_max_col + 1);
                for (i = nchars, c = l->l_line; --i >= 0; c++)
                        count[c->c_column]++;

                /*
                 * calculate running total (shifted down by 1) to use as
                 * indices into new line.
                 */
                for (tot = 0, i = 0; i <= l->l_max_col; i++) {
                        save = count[i];
                        count[i] = tot;
                        tot += save;
                }

                for (i = nchars, c = l->l_line; --i >= 0; c++)
                        sorted[count[c->c_column]++] = *c;
                c = sorted;
        } else
                c = l->l_line;
        while (nchars > 0) {
                this_col = c->c_column;
                endc = c;
                do {
                        ++endc;
                } while (--nchars > 0 && this_col == endc->c_column);

                /* if -b only print last character */
                if (no_backspaces) {
                        c = endc - 1;
                        if (nchars > 0 &&
                            this_col + c->c_width > endc->c_column)
                                continue;
                }

                if (this_col > last_col) {
                        int nspace = this_col - last_col;

                        if (compress_spaces && nspace > 1) {
                                while (1) {
                                        int tab_col, tab_size;

                                        tab_col = (last_col + 8) & ~7;
                                        if (tab_col > this_col)
                                                break;
                                        tab_size = tab_col - last_col;
                                        if (tab_size == 1)
                                                PUTC(' ');
                                        else
                                                PUTC('\t');
                                        nspace -= tab_size;
                                        last_col = tab_col;
                                }
                        }
                        while (--nspace >= 0)
                                PUTC(' ');
                        last_col = this_col;
                }

                for (;;) {
                        if (c->c_set != last_set) {
                                switch (c->c_set) {
                                case CS_NORMAL:
                                        PUTC(SI);
                                        break;
                                case CS_ALTERNATE:
                                        PUTC(SO);
                                }
                                last_set = c->c_set;
                        }
                        PUTC(c->c_char);
                        if ((c + 1) < endc)
                                for (j = 0; j < c->c_width; j++)
                                        PUTC('\b');
                        if (++c >= endc)
                                break;
                }
                last_col += (c - 1)->c_width;
        }
}

/*
 * Increment or decrement a line number, checking for overflow.
 * Stop one below INT_MAX such that the adjust variable is safe.
 */
void
addto_lineno(int *lno, int offset)
{
        if (offset > 0) {
                if (*lno >= INT_MAX - offset)
                        errx(1, "too many lines");
        } else {
                if (*lno < INT_MIN - offset)
                        errx(1, "too many reverse line feeds");
        }
        *lno += offset;
}

#define NALLOC 64

static LINE *line_freelist;

static LINE *
alloc_line(void)
{
        LINE *l;
        int i;

        if (!line_freelist) {
                if ((l = realloc(NULL, sizeof(LINE) * NALLOC)) == NULL)
                        err(1, NULL);
                line_freelist = l;
                for (i = 1; i < NALLOC; i++, l++)
                        l->l_next = l + 1;
                l->l_next = NULL;
        }
        l = line_freelist;
        line_freelist = l->l_next;

        memset(l, 0, sizeof(LINE));
        return (l);
}

static void
free_line(LINE *l)
{

        l->l_next = line_freelist;
        line_freelist = l;
}

static void
usage(void)
{

        (void)fprintf(stderr, "usage: col [-bfhpx] [-l nline]\n");
        exit(1);
}

static void
dowarn(int line)
{

        warnx("warning: can't back up %s",
                line < 0 ? "past first line" : "-- line already flushed");
}