/*
 * Copyright (c) 2009 The DragonFly Project.  All rights reserved.
 *
 * This code is derived from software contributed to The DragonFly Project
 * by Matthew Dillon <dillon@backplane.com>
 *
 * 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 DragonFly Project 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 COPYRIGHT HOLDERS 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
 * COPYRIGHT HOLDERS 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/types.h>
#include <sys/stat.h>

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <paths.h>
#include <limits.h>
#include <fstab.h>

static void finddevlabel(char **pathp, const char *devname);
static int xlatedevpath(char **pathp, struct stat *st);
static char *dodequote(char *base);

/*
 * Acquire device path.
 *
 */
char *
getdevpath(const char *devname, int flags)
{
        struct stat st;
        char *path = NULL;
        int stgood = 0;

        if (devname[0] == '/' || devname[0] == '.') {
                asprintf(&path, "%s", devname);
        } else {
                asprintf(&path, "/dev/%s", devname);
                if (lstat(path, &st) < 0) {
                        free(path);
                        path = NULL;
                        finddevlabel(&path, devname);
                        if (path == NULL)
                                asprintf(&path, "%s", devname);
                } else {
                        stgood = 1;
                }
        }

        /*
         * Translate softlinks if requested.  If the lstat() of the
         * pre-translated path fails NULL is expected to be returned.
         * lstat() is not called on the post-translated path.
         */
        if ((flags & GETDEVPATH_RAWDEV) && path) {
                if (stgood == 0 && lstat(path, &st) == 0)
                        stgood = 1;
                if (stgood)
                        stgood = xlatedevpath(&path, &st);
                if (stgood == 0) {
                        free(path);
                        path = NULL;
                }

        }
        if (path == NULL)
                errno = ENOENT;
        return(path);
}

static void
finddevlabel(char **pathp, const char *devname)
{
        const char *prefix = _PATH_DEVTAB_PATHS;
        const char *ptr1;
        const char *trailer;
        char *label;
        char *ptr2;
        char *ptr3;
        char *dtpath;
        char *bufp;
        char buf[256];
        FILE *fp;
        size_t len;     /* directory prefix length */
        size_t tlen;    /* devname length without trailer */

        if ((trailer = strrchr(devname, '.')) != NULL)
                tlen = trailer - devname;
        else
                tlen = 0;

        while (*prefix && *pathp == NULL) {
                /*
                 * Directory search path
                 */
                ptr1 = strchr(prefix, ':');
                len = (ptr1) ? (size_t)(ptr1 - prefix) : strlen(prefix);
                asprintf(&dtpath, "%*.*s/devtab", (int)len, (int)len, prefix);

                /*
                 * Each devtab file
                 */
                if ((fp = fopen(dtpath, "r")) != NULL) {
                        while (fgets(buf, sizeof(buf), fp) != NULL) {
                                /*
                                 * Extract label field, check degenerate
                                 * cases.
                                 */
                                label = strtok_r(buf, " \t\r\n", &bufp);
                                if (label == NULL || *label == 0 ||
                                    *label == '#') {
                                        continue;
                                }

                                /*
                                 * Match label, with or without the
                                 * trailer (aka ".s1a").  The trailer
                                 * is tacked on if the match is without
                                 * the trailer.
                                 */
                                if (strcmp(devname, label) == 0) {
                                        trailer = "";
                                } else if (tlen && strlen(label) == tlen &&
                                           strncmp(devname, label, tlen) == 0) {
                                        trailer = devname + tlen;
                                } else {
                                        continue;
                                }

                                /*
                                 * Match, extract and process remaining fields.
                                 */
                                ptr2 = strtok_r(NULL, " \t\r\n", &bufp);
                                ptr3 = strtok_r(NULL, " \t\r\n", &bufp);
                                if (ptr2 == NULL || ptr3 == NULL)
                                        continue;
                                if (*ptr2 == 0 || *ptr3 == 0)
                                        continue;
                                ptr3 = dodequote(ptr3);
                                if (strcmp(ptr2, "path") == 0) {
                                        asprintf(pathp, "%s%s", ptr3, trailer);
                                } else {
                                        asprintf(pathp, "/dev/%s/%s%s",
                                                 ptr2, ptr3, trailer);
                                }
                                break;
                        }
                        fclose(fp);
                }
                free(dtpath);
                prefix += len;
                if (*prefix == ':')
                        ++prefix;
        }
}

static int
xlatedevpath(char **pathp, struct stat *st)
{
        char *path;
        int n;
        int len;

        /*
         * If not a softlink return unchanged.
         */
        if (!S_ISLNK(st->st_mode))
                return(1);

        /*
         * If the softlink isn't reasonable return bad (0)
         */
        len = (int)st->st_size;
        if (len < 0 || len > PATH_MAX)
                return(0);

        /*
         * Read the link, return if the result is not what we expected.
         */
        path = malloc(len + 1);
        n = readlink(*pathp, path, len);
        if (n < 0 || n > len) {
                free(path);
                return(0);
        }

        /*
         * Success, replace (*pathp).
         */
        path[n] = 0;
        free(*pathp);
        *pathp = path;
        return(1);
}

static char *
dodequote(char *base)
{
        int len = strlen(base);

        if (len && base[0] == '\"' && base[len-1] == '\"') {
                base[len - 1] = 0;
                ++base;
        }
        return(base);
}