/**
 * Copyright (c) 2000 Dan Papasian.  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. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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>

__FBSDID("$FreeBSD: releng/10.0/usr.bin/which/which.c 227245 2011-11-06 18:50:26Z ed $");

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

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

#ifdef __OS2__
#define DOS
#endif

#ifdef DOS
#define PATH_SEP ";"
#else
#define PATH_SEP ":"
#endif

static void	 usage(void);
static int	 print_matches(char *, char *);
	
static int 	 silent;
static int 	 allpaths;

#ifdef DOS
static void  unixify_slashes(char *);
static int   ends_with(char *, char **, int);
#endif

int
main(int argc, char **argv)
{
	char *p, *path;
	ssize_t pathlen;
	int opt, status;

	status = EXIT_SUCCESS;

	while ((opt = getopt(argc, argv, "as")) != -1) {
		switch (opt) {
		case 'a':
			allpaths = 1;
			break;
		case 's':
			silent = 1;
			break;
		default:
			usage();
			break;
		}
	}

	argv += optind;
	argc -= optind;

	if (argc == 0)
		usage();

	if ((p = getenv("PATH")) == NULL)
		exit(EXIT_FAILURE);
	pathlen = strlen(p) + 1;
	path = malloc(pathlen);
	if (path == NULL)
		err(EXIT_FAILURE, NULL);

	while (argc > 0) {
		memcpy(path, p, pathlen);
#ifdef DOS
		unixify_slashes(path);
#endif
	
		if (strlen(*argv) >= FILENAME_MAX ||
		    print_matches(path, *argv) == -1)
			status = EXIT_FAILURE;

		argv++;
		argc--;
	}

	exit(status);
}

static void
usage(void)
{

	(void)fprintf(stderr, "usage: which [-as] program ...\n");
	exit(EXIT_FAILURE);
}

static int
is_there(char *candidate)
{
	struct stat fin;

#ifdef  DOS
	int i, len, found;
	char *exts[] = { ".exe", ".cmd", ".bat" };
	char candidate2[PATH_MAX];

	found = 0;
	len = strlen(candidate);
	for (i = 0; i <= sizeof(exts)/sizeof(exts[0]); ++i) {
		if (i > 0) {
			if (len + strlen(exts[i-1]) >= PATH_MAX)
				continue;
			if (i == 1) {
				strcpy(candidate2, candidate);
				candidate = candidate2;
			}
			strcpy(candidate+len, exts[i-1]);
		}
#endif
	/* XXX work around access(2) false positives for superuser */
	if (access(candidate, X_OK) == 0 &&
	    stat(candidate, &fin) == 0 &&
	    S_ISREG(fin.st_mode) &&
#ifdef DOS
		(
#endif
	    (getuid() != 0 ||
	    (fin.st_mode & (S_IXUSR | S_IXGRP | S_IXOTH)) != 0)
#ifdef DOS
		|| i > 0 || ends_with(candidate, exts, sizeof(exts)/sizeof(exts[0])))
#endif
		) {
		if (!silent) {
			printf("%s\n", candidate);
		}
#ifdef  DOS
        found = 1;
        if (!allpaths)
            break;
	}
	}
	return found;
#else
		return (1);
	}
	return (0);
#endif
}

static int
print_matches(char *path, char *filename)
{
	char candidate[PATH_MAX];
	const char *d;
	int found;

#ifdef DOS
	if (strpbrk(filename, "/:\\") != NULL)
#else
	if (strchr(filename, '/') != NULL)
#endif
		return (is_there(filename) ? 0 : -1);
	found = 0;
#ifdef DOS
	if (is_there(filename)) {
		found = 1;
		if (!allpaths)
			return (0);
	}
#endif
	while ((d = strsep(&path, PATH_SEP)) != NULL) {
		if (*d == '\0')
#ifdef DOS
			continue;
#else
			d = ".";
#endif
		if (snprintf(candidate, sizeof(candidate), "%s/%s", d,
		    filename) >= (int)sizeof(candidate))
			continue;
		if (is_there(candidate)) {
			found = 1;
			if (!allpaths)
				break;
		}
	}
	return (found ? 0 : -1);
}

#ifdef DOS
static void
unixify_slashes(char *path)
{
	while (*path) {
		if (*path == '\\')
			*path = '/';
		++path;
	}
}

static int
ends_with(char *path, char **exts, int extnum)
{
	int found;
	int i, len, l;

	found = 0;
	len = strlen(path);
	for (i = 0; i < extnum; ++i) {
		l = strlen(exts[i]);
		if (len < l)
			continue;
		if (stricmp(path+len-l, exts[i]) == 0) {
			found = 1;
			break;
		}
	}

	return found;
}
#endif