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#
#    Licensed 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.


import sys

from oslo_config import cfg
from oslo_db.sqlalchemy import enginefacade
from oslo_log import log

CONF = cfg.CONF
LOG = log.getLogger(__name__)


main_context_manager = enginefacade.transaction_context()
api_context_manager = enginefacade.transaction_context()


def _get_db_conf(conf_group, connection=None):
    kw = dict(
        connection=connection or conf_group.connection,
        slave_connection=conf_group.slave_connection,
        sqlite_fk=False,
        __autocommit=True,
        expire_on_commit=False,
        mysql_sql_mode=conf_group.mysql_sql_mode,
        connection_recycle_time=conf_group.connection_recycle_time,
        connection_debug=conf_group.connection_debug,
        max_pool_size=conf_group.max_pool_size,
        max_overflow=conf_group.max_overflow,
        pool_timeout=conf_group.pool_timeout,
        sqlite_synchronous=conf_group.sqlite_synchronous,
        connection_trace=conf_group.connection_trace,
        max_retries=conf_group.max_retries,
        retry_interval=conf_group.retry_interval)
    return kw


def get_backend():
    return sys.modules[__name__]


def create_context_manager(connection=None):
    """Create a database context manager object.
    : param connection: The database connection string
    """
    ctxt_mgr = enginefacade.transaction_context()
    ctxt_mgr.configure(**_get_db_conf(CONF.database, connection=connection))
    return ctxt_mgr


def _context_manager_from_context(context):
    if context:
        try:
            return context.db_connection
        except AttributeError:
            pass


def get_context_manager(context):
    """Get a database context manager object.
    :param context: The request context that can contain a context manager
    """
    return _context_manager_from_context(context) or main_context_manager


def get_engine(use_slave=False, context=None):
    """Get a database engine object.
    :param use_slave: Whether to use the slave connection
    :param context: The request context that can contain a context manager
    """
    ctxt_mgr = get_context_manager(context)
    return ctxt_mgr.get_legacy_facade().get_engine(use_slave=use_slave)


def get_api_engine():
    return api_context_manager.get_legacy_facade().get_engine()