/*
  Copyright (c) 2008-2010 Gluster, Inc. <http://www.gluster.com>
  This file is part of GlusterFS.

  GlusterFS is free software; you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published
  by the Free Software Foundation; either version 3 of the License,
  or (at your option) any later version.

  GlusterFS is distributed in the hope that it will be useful, but
  WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with this program.  If not, see
  <http://www.gnu.org/licenses/>.
*/

#include <list.h>
#include <bdb.h>
#include <libgen.h> /* for dirname */

static void
__destroy_bctx (bctx_t *bctx)
{
        if (bctx->directory)
                GF_FREE (bctx->directory);

        if (bctx->db_path)
                GF_FREE (bctx->db_path);

        GF_FREE (bctx);
}

static void
__unhash_bctx (bctx_t *bctx)
{
        list_del_init (&bctx->b_hash);
}

static int32_t
bctx_table_prune (bctx_table_t *table)
{
        int32_t ret = 0;
        struct list_head purge = {0,};
        struct list_head *next = NULL;
        bctx_t *entry = NULL;
        bctx_t *del = NULL, *tmp = NULL;

        if (!table)
                return 0;

        INIT_LIST_HEAD (&purge);

        LOCK (&table->lock);
        {
                if ((table->lru_limit) &&
                    (table->lru_size > table->lru_limit)) {
                        while (table->lru_size > table->lru_limit) {
                                next = table->b_lru.next;
                                entry = list_entry (next, bctx_t, list);

                                list_move_tail (next, &table->purge);
                                __unhash_bctx (entry);

                                table->lru_size--;
                                ret++;
                        }
                }
                list_move_tail (&purge, &table->purge);
                list_del_init (&table->purge);
        }
        UNLOCK (&table->lock);

        list_for_each_entry_safe (del, tmp, &purge, list) {
                list_del_init (&del->list);
                if (del->primary) {
                        ret = del->primary->close (del->primary, 0);
                        if (ret != 0) {
                                gf_log (table->this->name, GF_LOG_DEBUG,
                                        "_BCTX_TABLE_PRUNE %s: %s "
                                        "(failed to close primary database)",
                                        del->directory, db_strerror (ret));
                        } else {
                                gf_log (table->this->name, GF_LOG_DEBUG,
                                        "_BCTX_TABLE_PRUNE %s (lru=%d)"
                                        "(closed primary database)",
                                        del->directory, table->lru_size);
                        }
                }
                if (del->secondary) {
                        ret = del->secondary->close (del->secondary, 0);
                        if (ret != 0) {
                                gf_log (table->this->name, GF_LOG_DEBUG,
                                        "_BCTX_TABLE_PRUNE %s: %s "
                                        "(failed to close secondary database)",
                                        del->directory, db_strerror (ret));
                        } else {
                                gf_log (table->this->name, GF_LOG_DEBUG,
                                        "_BCTX_TABLE_PRUNE %s (lru=%d)"
                                        "(closed secondary database)",
                                        del->directory, table->lru_size);
                        }
                }
                __destroy_bctx (del);
        }

        return ret;
}


/* struct bdb_ctx related */
static inline uint32_t
bdb_key_hash (char *key, uint32_t hash_size)
{
        uint32_t hash = 0;

        hash = *key;

        if (hash) {
                for (key += 1; *key != '\0'; key++) {
                        hash = (hash << 5) - hash + *key;
                }
        }

        return (hash + *key) % hash_size;
}

static void
__hash_bctx (bctx_t *bctx)
{
        bctx_table_t *table = NULL;
        char *key = NULL;

        table = bctx->table;

        MAKE_KEY_FROM_PATH (key, bctx->directory);
        bctx->key_hash = bdb_key_hash (key, table->hash_size);

        list_del_init (&bctx->b_hash);
        list_add (&bctx->b_hash, &table->b_hash[bctx->key_hash]);
}

static inline bctx_t *
__bctx_passivate (bctx_t *bctx)
{
        if (bctx->primary) {
                list_move_tail (&bctx->list, &(bctx->table->b_lru));
                bctx->table->lru_size++;
        } else {
                list_move_tail (&bctx->list, &bctx->table->purge);
                __unhash_bctx (bctx);
        }
        return bctx;
}

static inline bctx_t *
__bctx_activate (bctx_t *bctx)
{
        list_move (&bctx->list, &bctx->table->active);
        bctx->table->lru_size--;

        return bctx;
}

static bctx_t *
__bdb_ctx_unref (bctx_t *bctx)
{
        GF_ASSERT (bctx->ref);

        --bctx->ref;

        if (!bctx->ref)
                bctx = __bctx_passivate (bctx);

        return bctx;
}


bctx_t *
bctx_unref (bctx_t *bctx)
{
        bctx_table_t *table = NULL;

        if (!bctx && !bctx->table)
                return NULL;

        table = bctx->table;

        LOCK (&table->lock);
        {
                bctx = __bdb_ctx_unref (bctx);
        }
        UNLOCK (&table->lock);

        bctx_table_prune (table);

        return bctx;
}

/*
 * NOTE: __bdb_ctx_ref() is called only after holding table->lock and
 * bctx->lock, in that order
 */
static inline bctx_t *
__bctx_ref (bctx_t *bctx)
{
        if (!bctx->ref)
                __bctx_activate (bctx);

        bctx->ref++;

        return bctx;
}

bctx_t *
bctx_ref (bctx_t *bctx)
{
        LOCK (&(bctx->table->lock));
        {
                __bctx_ref (bctx);
        }
        UNLOCK (&(bctx->table->lock));

        return bctx;
}


#define BDB_THIS(table) (table->this)

static inline bctx_t *
__create_bctx (bctx_table_t *table,
               const char *path)
{
        bctx_t *bctx = NULL;
        char *db_path = NULL;

        bctx = GF_CALLOC (1, sizeof (*bctx), gf_bdb_mt_bctx_t);
        GF_VALIDATE_OR_GOTO ("bctx", bctx, out);

        bctx->table = table;
        bctx->directory = gf_strdup (path);
        GF_VALIDATE_OR_GOTO ("bctx", bctx->directory, out);

        MAKE_REAL_PATH_TO_STORAGE_DB (db_path, BDB_THIS (table), path);

        bctx->db_path = gf_strdup (db_path);
        GF_VALIDATE_OR_GOTO ("bctx", bctx->directory, out);

        INIT_LIST_HEAD (&bctx->c_list);
        INIT_LIST_HEAD (&bctx->list);
        INIT_LIST_HEAD (&bctx->b_hash);

        LOCK_INIT (&bctx->lock);

        __hash_bctx (bctx);

        list_add (&bctx->list, &table->b_lru);
        table->lru_size++;

out:
        return bctx;
}

/* bctx_lookup - lookup bctx_t for the directory @directory.
 *               (see description of bctx_t in bdb.h)
 *
 * @table:     bctx_table_t for this instance of bdb.
 * @directory: directory for which bctx_t is being looked up.
 */
bctx_t *
bctx_lookup (bctx_table_t *table,
             const char *directory)
{
        char    *key = NULL;
        uint32_t key_hash = 0;
        bctx_t  *trav = NULL, *bctx = NULL, *tmp = NULL;
        int32_t  need_break = 0;

        GF_VALIDATE_OR_GOTO ("bctx", table, out);
        GF_VALIDATE_OR_GOTO ("bctx", directory, out);

        MAKE_KEY_FROM_PATH (key, directory);
        key_hash = bdb_key_hash (key, table->hash_size);

        LOCK (&table->lock);
        {
                if (list_empty (&table->b_hash[key_hash])) {
                        goto creat_bctx;
                }

                list_for_each_entry_safe (trav, tmp, &table->b_hash[key_hash],
                                          b_hash) {
                        LOCK(&trav->lock);
                        {
                                if (!strcmp(trav->directory, directory)) {
                                        bctx = __bctx_ref (trav);
                                        need_break = 1;
                                }
                        }
                        UNLOCK(&trav->lock);

                        if (need_break)
                                break;
                }

        creat_bctx:
                if (!bctx) {
                        bctx = __create_bctx (table, directory);
                        bctx = __bctx_ref (bctx);
                }
        }
        UNLOCK (&table->lock);
out:
        return bctx;
}


bctx_t *
bctx_parent (bctx_table_t *table,
             const char *path)
{
        char   *pathname = NULL, *directory = NULL;
        bctx_t *bctx = NULL;

        GF_VALIDATE_OR_GOTO ("bctx", table, out);
        GF_VALIDATE_OR_GOTO ("bctx", path, out);

        pathname = gf_strdup (path);
        GF_VALIDATE_OR_GOTO ("bctx", pathname, out);
        directory = dirname (pathname);

        bctx = bctx_lookup (table, directory);
        GF_VALIDATE_OR_GOTO ("bctx", bctx, out);

out:
        if (pathname)
                free (pathname);
        return bctx;
}