/* txn-table.c : operations on the `transactions' table
 *
 * ====================================================================
 *    Licensed to the Apache Software Foundation (ASF) under one
 *    or more contributor license agreements.  See the NOTICE file
 *    distributed with this work for additional information
 *    regarding copyright ownership.  The ASF licenses this file
 *    to you under the Apache License, Version 2.0 (the
 *    "License"); you may not use this file except in compliance
 *    with the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *    Unless required by applicable law or agreed to in writing,
 *    software distributed under the License is distributed on an
 *    "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 *    KIND, either express or implied.  See the License for the
 *    specific language governing permissions and limitations
 *    under the License.
 * ====================================================================
 */

#include <string.h>
#include <assert.h>

#include "bdb_compat.h"

#include "svn_pools.h"
#include "private/svn_skel.h"

#include "dbt.h"
#include "../err.h"
#include "../fs.h"
#include "../key-gen.h"
#include "../util/fs_skels.h"
#include "../trail.h"
#include "../../libsvn_fs/fs-loader.h"
#include "bdb-err.h"
#include "txn-table.h"

#include "svn_private_config.h"


static svn_boolean_t
is_committed(transaction_t *txn)
{
  return (txn->kind == transaction_kind_committed);
}


int
svn_fs_bdb__open_transactions_table(DB **transactions_p,
                                    DB_ENV *env,
                                    svn_boolean_t create)
{
  const u_int32_t open_flags = (create ? (DB_CREATE | DB_EXCL) : 0);
  DB *txns;

  BDB_ERR(svn_fs_bdb__check_version());
  BDB_ERR(db_create(&txns, env, 0));
  BDB_ERR((txns->open)(SVN_BDB_OPEN_PARAMS(txns, NULL),
                       "transactions", 0, DB_BTREE,
                       open_flags, 0666));

  /* Create the `next-key' table entry.  */
  if (create)
  {
    DBT key, value;

    BDB_ERR(txns->put(txns, 0,
                      svn_fs_base__str_to_dbt(&key, NEXT_KEY_KEY),
                      svn_fs_base__str_to_dbt(&value, "0"), 0));
  }

  *transactions_p = txns;
  return 0;
}


svn_error_t *
svn_fs_bdb__put_txn(svn_fs_t *fs,
                    const transaction_t *txn,
                    const char *txn_name,
                    trail_t *trail,
                    apr_pool_t *pool)
{
  base_fs_data_t *bfd = fs->fsap_data;
  svn_skel_t *txn_skel;
  DBT key, value;

  /* Convert native type to skel. */
  SVN_ERR(svn_fs_base__unparse_transaction_skel(&txn_skel, txn, pool));

  /* Only in the context of this function do we know that the DB call
     will not attempt to modify txn_name, so the cast belongs here.  */
  svn_fs_base__str_to_dbt(&key, txn_name);
  svn_fs_base__skel_to_dbt(&value, txn_skel, pool);
  svn_fs_base__trail_debug(trail, "transactions", "put");
  return BDB_WRAP(fs, _("storing transaction record"),
                  bfd->transactions->put(bfd->transactions, trail->db_txn,
                                         &key, &value, 0));
}


/* Allocate a Subversion transaction ID in FS, as part of TRAIL.  Set
   *ID_P to the new transaction ID, allocated in POOL.  */
static svn_error_t *
allocate_txn_id(const char **id_p,
                svn_fs_t *fs,
                trail_t *trail,
                apr_pool_t *pool)
{
  base_fs_data_t *bfd = fs->fsap_data;
  DBT query, result;
  apr_size_t len;
  char next_key[MAX_KEY_SIZE];
  int db_err;

  svn_fs_base__str_to_dbt(&query, NEXT_KEY_KEY);

  /* Get the current value associated with the `next-key' key in the table.  */
  svn_fs_base__trail_debug(trail, "transactions", "get");
  SVN_ERR(BDB_WRAP(fs, "allocating new transaction ID (getting 'next-key')",
                   bfd->transactions->get(bfd->transactions, trail->db_txn,
                                          &query,
                                          svn_fs_base__result_dbt(&result),
                                          0)));
  svn_fs_base__track_dbt(&result, pool);

  /* Set our return value. */
  *id_p = apr_pstrmemdup(pool, result.data, result.size);

  /* Bump to future key. */
  len = result.size;
  svn_fs_base__next_key(result.data, &len, next_key);
  svn_fs_base__str_to_dbt(&query, NEXT_KEY_KEY);
  svn_fs_base__str_to_dbt(&result, next_key);
  svn_fs_base__trail_debug(trail, "transactions", "put");
  db_err = bfd->transactions->put(bfd->transactions, trail->db_txn,
                                  &query, &result, 0);

  return BDB_WRAP(fs, "bumping next transaction key", db_err);
}


svn_error_t *
svn_fs_bdb__create_txn(const char **txn_name_p,
                       svn_fs_t *fs,
                       const svn_fs_id_t *root_id,
                       trail_t *trail,
                       apr_pool_t *pool)
{
  const char *txn_name;
  transaction_t txn;

  SVN_ERR(allocate_txn_id(&txn_name, fs, trail, pool));
  txn.kind = transaction_kind_normal;
  txn.root_id = root_id;
  txn.base_id = root_id;
  txn.proplist = NULL;
  txn.copies = NULL;
  txn.revision = SVN_INVALID_REVNUM;
  SVN_ERR(svn_fs_bdb__put_txn(fs, &txn, txn_name, trail, pool));

  *txn_name_p = txn_name;
  return SVN_NO_ERROR;
}


svn_error_t *
svn_fs_bdb__delete_txn(svn_fs_t *fs,
                       const char *txn_name,
                       trail_t *trail,
                       apr_pool_t *pool)
{
  base_fs_data_t *bfd = fs->fsap_data;
  DBT key;
  transaction_t *txn;

  /* Make sure TXN is dead. */
  SVN_ERR(svn_fs_bdb__get_txn(&txn, fs, txn_name, trail, pool));
  if (is_committed(txn))
    return svn_fs_base__err_txn_not_mutable(fs, txn_name);

  /* Delete the transaction from the `transactions' table. */
  svn_fs_base__str_to_dbt(&key, txn_name);
  svn_fs_base__trail_debug(trail, "transactions", "del");
  return BDB_WRAP(fs, "deleting entry from 'transactions' table",
                  bfd->transactions->del(bfd->transactions,
                                         trail->db_txn, &key, 0));
}


svn_error_t *
svn_fs_bdb__get_txn(transaction_t **txn_p,
                    svn_fs_t *fs,
                    const char *txn_name,
                    trail_t *trail,
                    apr_pool_t *pool)
{
  base_fs_data_t *bfd = fs->fsap_data;
  DBT key, value;
  int db_err;
  svn_skel_t *skel;
  transaction_t *transaction;

  /* Only in the context of this function do we know that the DB call
     will not attempt to modify txn_name, so the cast belongs here.  */
  svn_fs_base__trail_debug(trail, "transactions", "get");
  db_err = bfd->transactions->get(bfd->transactions, trail->db_txn,
                                  svn_fs_base__str_to_dbt(&key, txn_name),
                                  svn_fs_base__result_dbt(&value),
                                  0);
  svn_fs_base__track_dbt(&value, pool);

  if (db_err == DB_NOTFOUND)
    return svn_fs_base__err_no_such_txn(fs, txn_name);
  SVN_ERR(BDB_WRAP(fs, "reading transaction", db_err));

  /* Parse TRANSACTION skel */
  skel = svn_skel__parse(value.data, value.size, pool);
  if (! skel)
    return svn_fs_base__err_corrupt_txn(fs, txn_name);

  /* Convert skel to native type. */
  SVN_ERR(svn_fs_base__parse_transaction_skel(&transaction, skel, pool));
  *txn_p = transaction;
  return SVN_NO_ERROR;
}


svn_error_t *
svn_fs_bdb__get_txn_list(apr_array_header_t **names_p,
                         svn_fs_t *fs,
                         trail_t *trail,
                         apr_pool_t *pool)
{
  base_fs_data_t *bfd = fs->fsap_data;
  apr_size_t const next_key_key_len = strlen(NEXT_KEY_KEY);
  apr_pool_t *subpool = svn_pool_create(pool);
  apr_array_header_t *names;
  DBC *cursor;
  DBT key, value;
  int db_err, db_c_err;

  /* Allocate the initial names array */
  names = apr_array_make(pool, 4, sizeof(const char *));

  /* Create a database cursor to list the transaction names. */
  svn_fs_base__trail_debug(trail, "transactions", "cursor");
  SVN_ERR(BDB_WRAP(fs, "reading transaction list (opening cursor)",
                   bfd->transactions->cursor(bfd->transactions,
                                             trail->db_txn, &cursor, 0)));

  /* Build a null-terminated array of keys in the transactions table. */
  for (db_err = svn_bdb_dbc_get(cursor,
                                svn_fs_base__result_dbt(&key),
                                svn_fs_base__result_dbt(&value),
                                DB_FIRST);
       db_err == 0;
       db_err = svn_bdb_dbc_get(cursor,
                                svn_fs_base__result_dbt(&key),
                                svn_fs_base__result_dbt(&value),
                                DB_NEXT))
    {
      transaction_t *txn;
      svn_skel_t *txn_skel;
      svn_error_t *err;

      /* Clear the per-iteration subpool */
      svn_pool_clear(subpool);

      /* Track the memory alloc'd for fetching the key and value here
         so that when the containing pool is cleared, this memory is
         freed. */
      svn_fs_base__track_dbt(&key, subpool);
      svn_fs_base__track_dbt(&value, subpool);

      /* Ignore the "next-key" key. */
      if (key.size == next_key_key_len
          && 0 == memcmp(key.data, NEXT_KEY_KEY, next_key_key_len))
        continue;

      /* Parse TRANSACTION skel */
      txn_skel = svn_skel__parse(value.data, value.size, subpool);
      if (! txn_skel)
        {
          svn_bdb_dbc_close(cursor);
          return svn_fs_base__err_corrupt_txn
            (fs, apr_pstrmemdup(pool, key.data, key.size));
        }

      /* Convert skel to native type. */
      if ((err = svn_fs_base__parse_transaction_skel(&txn, txn_skel,
                                                     subpool)))
        {
          svn_bdb_dbc_close(cursor);
          return svn_error_trace(err);
        }

      /* If this is an immutable "committed" transaction, ignore it. */
      if (is_committed(txn))
        continue;

      /* Add the transaction name to the NAMES array, duping it into POOL. */
      APR_ARRAY_PUSH(names, const char *) = apr_pstrmemdup(pool, key.data,
                                                           key.size);
    }

  /* Check for errors, but close the cursor first. */
  db_c_err = svn_bdb_dbc_close(cursor);
  if (db_err != DB_NOTFOUND)
    {
      SVN_ERR(BDB_WRAP(fs, "reading transaction list (listing keys)",
                       db_err));
    }
  SVN_ERR(BDB_WRAP(fs, "reading transaction list (closing cursor)",
                   db_c_err));

  /* Destroy the per-iteration subpool */
  svn_pool_destroy(subpool);

  *names_p = names;
  return SVN_NO_ERROR;
}