/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 1989, 1993, 1994
 *      The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Case Larsen.
 *
 * 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 <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <wchar.h>
#include <wctype.h>

static int iflag;
static const char *tabs[] = { "", "\t", "\t\t" };

static FILE     *file(const char *);
static wchar_t  *convert(const char *);
static void     show(FILE *, const char *, const char *, char **, size_t *);
static void     usage(void);

int
main(int argc, char *argv[])
{
        int comp, read1, read2;
        int ch, flag1, flag2, flag3;
        FILE *fp1, *fp2;
        const char *col1, *col2, *col3;
        size_t line1len, line2len;
        char *line1, *line2;
        ssize_t n1, n2;
        wchar_t *tline1, *tline2;
        const char **p;

        (void) setlocale(LC_ALL, "");

        flag1 = flag2 = flag3 = 1;

        while ((ch = getopt(argc, argv, "123i")) != -1)
                switch(ch) {
                case '1':
                        flag1 = 0;
                        break;
                case '2':
                        flag2 = 0;
                        break;
                case '3':
                        flag3 = 0;
                        break;
                case 'i':
                        iflag = 1;
                        break;
                case '?':
                default:
                        usage();
                }
        argc -= optind;
        argv += optind;

        if (argc != 2)
                usage();

        fp1 = file(argv[0]);
        fp2 = file(argv[1]);

        /* for each column printed, add another tab offset */
        p = tabs;
        col1 = col2 = col3 = NULL;
        if (flag1)
                col1 = *p++;
        if (flag2)
                col2 = *p++;
        if (flag3)
                col3 = *p;

        line1len = line2len = 0;
        line1 = line2 = NULL;
        n1 = n2 = -1;

        for (read1 = read2 = 1;;) {
                /* read next line, check for EOF */
                if (read1) {
                        n1 = getline(&line1, &line1len, fp1);
                        if (n1 < 0 && ferror(fp1))
                                err(1, "%s", argv[0]);
                        if (n1 > 0 && line1[n1 - 1] == '\n')
                                line1[n1 - 1] = '\0';

                }
                if (read2) {
                        n2 = getline(&line2, &line2len, fp2);
                        if (n2 < 0 && ferror(fp2))
                                err(1, "%s", argv[1]);
                        if (n2 > 0 && line2[n2 - 1] == '\n')
                                line2[n2 - 1] = '\0';
                }

                /* if one file done, display the rest of the other file */
                if (n1 < 0) {
                        if (n2 >= 0)
                                show(fp2, argv[1], col2, &line2, &line2len);
                        break;
                }
                if (n2 < 0) {
                        if (n1 >= 0)
                                show(fp1, argv[0], col1, &line1, &line1len);
                        break;
                }

                tline2 = NULL;
                if ((tline1 = convert(line1)) != NULL)
                        tline2 = convert(line2);
                if (tline1 == NULL || tline2 == NULL)
                        comp = strcmp(line1, line2);
                else
                        comp = wcscoll(tline1, tline2);
                if (tline1 != NULL)
                        free(tline1);
                if (tline2 != NULL)
                        free(tline2);

                /* lines are the same */
                if (!comp) {
                        read1 = read2 = 1;
                        if (col3 != NULL)
                                (void)printf("%s%s\n", col3, line1);
                        continue;
                }

                /* lines are different */
                if (comp < 0) {
                        read1 = 1;
                        read2 = 0;
                        if (col1 != NULL)
                                (void)printf("%s%s\n", col1, line1);
                } else {
                        read1 = 0;
                        read2 = 1;
                        if (col2 != NULL)
                                (void)printf("%s%s\n", col2, line2);
                }
        }
        if (ferror(stdout) != 0 || fflush(stdout) != 0)
                err(1, "stdout");
        exit(0);
}

static wchar_t *
convert(const char *str)
{
        size_t n;
        wchar_t *buf, *p;

        if ((n = mbstowcs(NULL, str, 0)) == (size_t)-1)
                return (NULL);
        if (SIZE_MAX / sizeof(*buf) < n + 1)
                errx(1, "conversion buffer length overflow");
        if ((buf = malloc((n + 1) * sizeof(*buf))) == NULL)
                err(1, "malloc");
        if (mbstowcs(buf, str, n + 1) != n)
                errx(1, "internal mbstowcs() error");

        if (iflag) {
                for (p = buf; *p != L'\0'; p++)
                        *p = towlower(*p);
        }

        return (buf);
}

static void
show(FILE *fp, const char *fn, const char *offset, char **bufp, size_t *buflenp)
{
        ssize_t n;

        do {
                /* offset is NULL when draining fp, not printing */
                if (offset != NULL)
                        (void)printf("%s%s\n", offset, *bufp);
                if ((n = getline(bufp, buflenp, fp)) < 0)
                        break;
                if (n > 0 && offset != NULL && (*bufp)[n - 1] == '\n')
                        (*bufp)[n - 1] = '\0';
        } while (1);
        if (ferror(fp))
                err(1, "%s", fn);
}

static FILE *
file(const char *name)
{
        FILE *fp;

        if (!strcmp(name, "-"))
                return (stdin);
        if ((fp = fopen(name, "r")) == NULL) {
                err(1, "%s", name);
        }
        return (fp);
}

static void
usage(void)
{
        (void)fprintf(stderr, "usage: comm [-123i] file1 file2\n");
        exit(1);
}