/*      $OpenBSD: comm.c,v 1.11 2022/12/04 23:50:47 cheloha Exp $       */
/*      $NetBSD: comm.c,v 1.10 1995/09/05 19:57:43 jtc Exp $    */

/*
 * 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 <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#define MAXLINELEN      (LINE_MAX + 1)

char *tabs[] = { "", "\t", "\t\t" };

FILE   *file(const char *);
void    show(FILE *, char *, char *);
void    usage(void);

int
main(int argc, char *argv[])
{
        int comp, file1done, file2done, read1, read2;
        int ch, flag1, flag2, flag3;
        FILE *fp1, *fp2;
        char *col1, *col2, *col3;
        char **p, line1[MAXLINELEN], line2[MAXLINELEN];
        int (*compare)(const char * ,const char *);

        setlocale(LC_ALL, "");

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

        flag1 = flag2 = flag3 = 1;
        compare = strcoll;
        while ((ch = getopt(argc, argv, "123f")) != -1)
                switch(ch) {
                case '1':
                        flag1 = 0;
                        break;
                case '2':
                        flag2 = 0;
                        break;
                case '3':
                        flag3 = 0;
                        break;
                case 'f':
                        compare = strcasecmp;
                        break;
                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;

        for (read1 = read2 = 1;;) {
                /* read next line, check for EOF */
                if (read1)
                        file1done = !fgets(line1, MAXLINELEN, fp1);
                if (read2)
                        file2done = !fgets(line2, MAXLINELEN, fp2);

                /* if one file done, display the rest of the other file */
                if (file1done) {
                        if (!file2done && col2)
                                show(fp2, col2, line2);
                        break;
                }
                if (file2done) {
                        if (!file1done && col1)
                                show(fp1, col1, line1);
                        break;
                }

                /* lines are the same */
                if (!(comp = compare(line1, line2))) {
                        read1 = read2 = 1;
                        if (col3)
                                if (printf("%s%s", col3, line1) < 0)
                                        break;
                        continue;
                }

                /* lines are different */
                if (comp < 0) {
                        read1 = 1;
                        read2 = 0;
                        if (col1)
                                if (printf("%s%s", col1, line1) < 0)
                                        break;
                } else {
                        read1 = 0;
                        read2 = 1;
                        if (col2)
                                if (printf("%s%s", col2, line2) < 0)
                                        break;
                }
        }

        if (ferror (stdout) || fclose (stdout) == EOF)
                err(1, "stdout");

        exit(0);
}

void
show(FILE *fp, char *offset, char *buf)
{
        while (printf("%s%s", offset, buf) >= 0 && fgets(buf, MAXLINELEN, fp))
                ;
}

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

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

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