/*
 * Copyright (c) 2023-2024 Ian Marco Moffett and the Osmora Team.
 * 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 Hyra 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 OWNER 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/queue.h>
#include <sys/mount.h>
#include <sys/vfs.h>
#include <sys/errno.h>
#include <vm/dynalloc.h>
#include <assert.h>

/* For caching */
#define MOUNTLIST_SIZE 8

/* Mountlist cache entry */
struct mountlist_entry {
    TAILQ_HEAD(, mount) buckets;
};

static struct mountlist_entry *mountlist = NULL;

/*
 * Cache a mountpoint
 *
 * @mp: Mountpoint to cache
 * @path: Path this mountpoint belongs to
 *
 * If this cache entry already exists, -EEXIST
 * will be returned.
 */
int
vfs_cache_mp(struct mount *mp, const char *path)
{
    size_t hash = vfs_hash_path(path);
    struct mountlist_entry *entry;

    if (hash == 0) {
        /* Something is wrong with the path */
        return -EINVAL;
    }

    if (vfs_cache_fetch_mp(path, NULL) == 0) {
        /* Cache hit, do not duplicate this entry */
        return -EEXIST;
    }

    mp->phash = hash;
    entry = &mountlist[hash % MOUNTLIST_SIZE];
    TAILQ_INSERT_TAIL(&entry->buckets, mp, link);
    return 0;
}

/*
 * Fetch mountpoint from cache
 *
 * @path: Path of target mountpoint
 * @mp: Pointer of variable where mountpoint fetched will
 *      be stored
 *
 * Returns 0 upon a cache hit, on a cache miss this
 * function returns -ENOENT.
 */
int
vfs_cache_fetch_mp(const char *path, struct mount **mp)
{
    size_t hash = vfs_hash_path(path);
    struct mountlist_entry *entry;
    struct mount *mount_iter;

    if (hash == 0) {
        /* Something is wrong with the path */
        return -EINVAL;
    }

    entry = &mountlist[hash % MOUNTLIST_SIZE];
    TAILQ_FOREACH(mount_iter, &entry->buckets, link) {
        if (mount_iter->phash == hash) {
            /* Cache hit */
            if (mp != NULL) *mp = mount_iter;
            return 0;
        }
    }

    /* Cache miss */
    return -ENOENT;
}

/*
 * Init all caches
 */
void
vfs_init_cache(void)
{
    mountlist = dynalloc(sizeof(struct mountlist_entry) * MOUNTLIST_SIZE);
    __assert(mountlist != NULL);

    for (size_t i = 0; i < MOUNTLIST_SIZE; ++i) {
        TAILQ_INIT(&mountlist[i].buckets);
    }
}