/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License, Version 1.0 only
 * (the "License").  You may not use this file except in compliance
 * with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */

/*
 * Copyright 2005 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

/*      Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T */
/*        All Rights Reserved   */

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <ctype.h>
#include <locale.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <limits.h>
#include <stdarg.h>

#define C               3
#define RANGE           30
#define LEN             255
#define INF             16384

char *text[2][RANGE];
long lineno[2] = {1, 1};        /* no. of 1st stored line in each file */
int ntext[2];           /* number of stored lines in each */
long n0, n1;            /* scan pointer in each */
int bflag;
int debug = 0;
FILE *file[2];
static int diffFound = 0;

static char *getl(int f, long n);
static void clrl(int f, long n);
static void movstr(char *s, char *t);
static int easysynch(void);
static int output(int a, int b);
static void change(long a, int b, long c, int d, char *s);
static void range(long a, int b);
static int cmp(char *s, char *t);
static FILE *dopen(char *f1, char *f2);
static void progerr(char *s);
static void error(char *err, ...);
static int hardsynch(void);

        /* return pointer to line n of file f */
static char *
getl(int f, long n)
{
        char *t;
        int delta, nt;

again:
        delta = n - lineno[f];
        nt = ntext[f];
        if (delta < 0)
                progerr("1");
        if (delta < nt)
                return (text[f][delta]);
        if (delta > nt)
                progerr("2");
        if (nt >= RANGE)
                progerr("3");
        if (feof(file[f]))
                return (NULL);
        t = text[f][nt];
        if (t == 0) {
                t = text[f][nt] = (char *)malloc(LEN+1);
                if (t == NULL)
                        if (hardsynch())
                                goto again;
                        else
                                progerr("5");
        }
        t = fgets(t, LEN, file[f]);
        if (t != NULL)
                ntext[f]++;
        return (t);
}

        /* remove thru line n of file f from storage */
static void
clrl(int f, long n)
{
        int i, j;

        j = n-lineno[f]+1;
        for (i = 0; i+j < ntext[f]; i++)
                movstr(text[f][i+j], text[f][i]);
        lineno[f] = n+1;
        ntext[f] -= j;
}

static void
movstr(char *s, char *t)
{
        while (*t++ = *s++)
                continue;
}

int
main(int argc, char **argv)
{
        char *s0, *s1;

        if ((argc > 1) && (*argv[1] == '-')) {
                argc--;
                argv++;
                while (*++argv[0])
                        if (*argv[0] == 'b')
                                bflag++;
        }

        (void) setlocale(LC_ALL, "");
#if !defined(TEXT_DOMAIN)               /* Should be defined by cc -D */
#define TEXT_DOMAIN     "SYS_TEST"      /* Use this only if it weren't */
#endif
        (void) textdomain(TEXT_DOMAIN);

        if (argc != 3)
                error(gettext("must have 2 file arguments"));
        file[0] = dopen(argv[1], argv[2]);
        file[1] = dopen(argv[2], argv[1]);
        for (;;) {
                s0 = getl(0, ++n0);
                s1 = getl(1, ++n1);
                if (s0 == NULL || s1 == NULL)
                        break;
                if (cmp(s0, s1) != 0) {
                        if (!easysynch() && !hardsynch())
                                progerr("5");
                } else {
                        clrl(0, n0);
                        clrl(1, n1);
                }
        }
        /* diff is expected to return 1 if the files differ */
        if (s0 == NULL && s1 == NULL)
                return (diffFound);
        if (s0 == NULL) {
                (void) output(-1, INF);
                return (1);
        }
        if (s1 == NULL) {
                (void) output(INF, -1);
                return (1);
        }
        /* NOTREACHED */
        return (0);
}

        /* synch on C successive matches */
static int
easysynch()
{
        int i, j;
        int k, m;
        char *s0, *s1;

        for (i = j = 1; i < RANGE && j < RANGE; i++, j++) {
                s0 = getl(0, n0+i);
                if (s0 == NULL)
                        return (output(INF, INF));
                for (k = C-1; k < j; k++) {
                        for (m = 0; m < C; m++)
                                if (cmp(getl(0, n0+i-m),
                                        getl(1, n1+k-m)) != 0)
                                        goto cont1;
                        return (output(i-C, k-C));
cont1:
                        ;
                }
                s1 = getl(1, n1+j);
                if (s1 == NULL)
                        return (output(INF, INF));
                for (k = C-1; k <= i; k++) {
                        for (m = 0; m < C; m++)
                                if (cmp(getl(0, n0+k-m),
                                        getl(1, n1+j-m)) != 0)
                                        goto cont2;
                        return (output(k-C, j-C));
cont2:
                        ;
                }
        }
        return (0);
}

static int
output(int a, int b)
{
        int i;
        char *s;

        if (a < 0)
                change(n0-1, 0, n1, b, "a");
        else if (b < 0)
                change(n0, a, n1-1, 0, "d");
        else
                change(n0, a, n1, b, "c");
        for (i = 0; i <= a; i++) {
                s = getl(0, n0+i);
                if (s == NULL)
                        break;
                (void) printf("< %s", s);
                clrl(0, n0+i);
        }
        n0 += i-1;
        if (a >= 0 && b >= 0)
                (void) printf("---\n");
        for (i = 0; i <= b; i++) {
                s = getl(1, n1+i);
                if (s == NULL)
                        break;
                (void) printf("> %s", s);
                clrl(1, n1+i);
        }
        diffFound = 1;
        n1 += i-1;
        return (1);
}

static void
change(long a, int b, long c, int d, char *s)
{
        range(a, b);
        (void) printf("%s", s);
        range(c, d);
        (void) printf("\n");
}

static void
range(long a, int b)
{
        if (b == INF)
                (void) printf("%ld,$", a);
        else if (b == 0)
                (void) printf("%ld", a);
        else
                (void) printf("%ld,%ld", a, a+b);
}

static int
cmp(char *s, char *t)
{
        if (debug)
                (void) printf("%s:%s\n", s, t);
        for (;;) {
                if (bflag && isspace(*s) && isspace(*t)) {
                        while (isspace(*++s))
                                ;
                        while (isspace(*++t))
                                ;
                }
                if (*s != *t || *s == 0)
                        break;
                s++;
                t++;
        }
        return (*s-*t);
}

static FILE *
dopen(char *f1, char *f2)
{
        FILE *f;
        char b[PATH_MAX], *bptr, *eptr;
        struct stat statbuf;

        if (cmp(f1, "-") == 0) {
                if (cmp(f2, "-") == 0)
                        error(gettext("can't do - -"));
                else {
                        if (fstat(fileno(stdin), &statbuf) == -1)
                                error(gettext("can't access stdin"));
                        else
                                return (stdin);
                }
        }
        if (stat(f1, &statbuf) == -1)
                error(gettext("can't access %s"), f1);
        if ((statbuf.st_mode & S_IFMT) == S_IFDIR) {
                for (bptr = b; *bptr = *f1++; bptr++)
                        ;
                *bptr++ = '/';
                for (eptr = f2; *eptr; eptr++)
                        if (*eptr == '/' && eptr[1] != 0 && eptr[1] != '/')
                                f2 = eptr+1;
                while (*bptr++ = *f2++)
                        ;
                f1 = b;
        }
        f = fopen(f1, "r");
        if (f == NULL)
                error(gettext("can't open %s"), f1);
        return (f);
}


static void
progerr(char *s)
{
        error(gettext("program error %s"), s);
}

static void
error(char *err, ...)
{
        va_list ap;

        va_start(ap, err);
        (void) fprintf(stderr, "diffh: ");
        (void) vfprintf(stderr, err, ap);
        (void) fprintf(stderr, "\n");
        va_end(ap);
        exit(2);
}

        /* stub for resychronization beyond limits of text buf */
static int
hardsynch()
{
        change(n0, INF, n1, INF, "c");
        (void) printf(gettext("---change record omitted\n"));
        error(gettext("can't resynchronize"));
        return (0);
}