/*      $NetBSD: realpath.c,v 1.3 2023/05/25 17:24:17 kre Exp $ */
/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 1991, 1993, 1994
 *      The Regents of the University of California.  All rights reserved.
 *
 * 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/cdefs.h>
#if !defined(lint)
#if 0
__FBSDID("$FreeBSD: head/bin/realpath/realpath.c 326025 2017-11-20 19:49:47Z pfg $");
#else
__RCSID("$NetBSD: realpath.c,v 1.3 2023/05/25 17:24:17 kre Exp $");
#endif
#endif /* not lint */

#include <sys/param.h>
#include <sys/stat.h>

#include <err.h>
#include <errno.h>
#include <stdio.h>
#include <stdbool.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

static bool process(char *path);
static void usage(void) __dead;

static const char options[] = "Eeq";

char dot[] = ".";

bool eflag = false;             /* default to -E mode */
bool qflag = false;

int
main(int argc, char *argv[])
{
        char *path;
        int ch, rval;

        setprogname(argv[0]);

        while ((ch = getopt(argc, argv, options)) != -1) {
                switch (ch) {
                case 'e':
                        eflag = true;
                        break;
                case 'E':
                        eflag = false;
                        break;
                case 'q':
                        qflag = true;
                        break;
                case '?':
                default:
                        usage();
                }
        }
        argc -= optind;
        argv += optind;

        path = *argv != NULL ? *argv++ : dot;
        rval = 0;
        do {
                if (path[0] == '\0') {
                        /* ignore -q for this one */
                        warnx("Invalid path ''");
                        rval = 1;
                        continue;
                }
                if (!process(path))
                        rval = 1;;
        } while ((path = *argv++) != NULL);
        exit(rval);
}

static bool
process(char *path)
{
        char buf[PATH_MAX];
        char buf2[sizeof buf];
        char lbuf[PATH_MAX];
        char *pp, *p, *q, *r, *s;
        struct stat sb;
        bool dir_reqd = false;

        if ((p = realpath(path, buf)) != NULL) {
                (void)printf("%s\n", p);
                return true;
        }

        if (eflag || errno != ENOENT) {
                if (!qflag)
                        warn("%s", path);
                return false;
        }

        p = strrchr(path, '/');
        while (p != NULL && p > &path[1] && p[1] == '\0') {
                dir_reqd = true;
                *p = '\0';
                p = strrchr(path, '/');
        }

        if (p == NULL) {
                p = realpath(".", buf);
                if (p == NULL) {
                        warnx("relative path; current location unknown");
                        return false;
                }
                if ((size_t)snprintf(buf2, sizeof buf2, "%s/%s", buf, path)
                    >= sizeof buf2) {
                        if (!qflag)
                                warnx("%s/%s: path too long", p, path);
                        return false;
                }
                path = buf2;
                p = strrchr(path, '/');
                if (p == NULL)
                        abort();
        }

        *p = '\0';
        pp = ++p;

        q = path; r = buf; s = buf2;
        while (realpath(*q ? q : "/", r) != NULL) {
                ssize_t llen;

                if (strcmp(r, "/") == 0 || strcmp(r, "//") == 0)
                        r++;
                if ((size_t)snprintf(s, sizeof buf, "%s/%s", r, pp)
                    >= sizeof buf)
                        return false;

                if (lstat(s, &sb) == -1 || !S_ISLNK(sb.st_mode)) {
                        (void)printf("%s\n", s);
                        return true;
                }

                q = strchr(r, '\0');
                if (q >= &r[sizeof buf - 3]) {
                        *p = '/';
                        if (!qflag)
                                warnx("Expanded path for %s too long\n", path);
                        return false;
                }

                if ((llen = readlink(s, lbuf, sizeof lbuf - 2)) == -1) {
                        *p = '/';
                        if (!qflag)
                                warn("%s", path);
                        return false;
                }
                lbuf[llen] = '\0';

                if (lbuf[0] == '/') {
                        q = lbuf;
                        if (dir_reqd) {
                                lbuf[llen++] = '/';
                                lbuf[llen] = '\0';
                        }
                } else {
                        if (q != buf2) {
                                q = buf2;
                                r = buf;
                        } else {
                                q = buf;
                                r = buf2;
                        }

                        if ((size_t)snprintf(q, sizeof buf, "%s/%s%s", r, lbuf,
                            (dir_reqd ? "/" : "")) >= sizeof buf) {
                                *p = '/';
                                if (!qflag)
                                        warnx("Expanded path for %s too long\n",
                                            path);
                                return false;
                        }
                }

                s = realpath(q, r);
                if (s != NULL) {
                        /* this case should almost never happen (race) */
                        (void)printf("%s\n", s);
                        return true;
                }
                if (errno != ENOENT) {
                        *p = '/';
                        if (!qflag)
                                warn("%s", path);
                        return false;
                }

                pp = strrchr(q, '/');
                if (pp == NULL) {
                        /* we just put one there, where did it go? */
                        abort();
                }
                if (dir_reqd) {
                        *pp = '\0';
                        pp = strrchr(q, '/');
                        if (pp == NULL)
                                abort();
                }
                *pp++ = '\0';

                s = q;
        }

        *p = '/';

        if (!qflag)
                warn("%s", path);
        return false;
}

static void
usage(void)
{

        (void)fprintf(stderr, "usage: %s [-%s] [path ...]\n",
            getprogname(), options);
        exit(1);
}