# Copyright 2015 Futurewei. All rights reserved.
#
#    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.

from alembic import context
from neutron_lib.db import model_base
from oslo_config import cfg
import sqlalchemy as sa
from sqlalchemy import event

from neutron.db.migration.alembic_migrations import external
from neutron.db.migration import autogen
from neutron.db.migration.connection import DBConnection

from networking_sfc.db.migration.models import head  # noqa


try:
    # NOTE(mriedem): This is to register the DB2 alembic code which
    # is an optional runtime dependency.
    from ibm_db_alembic.ibm_db import IbmDbImpl  # noqa # pylint: disable=unused-import
except ImportError:
    pass


MYSQL_ENGINE = None
SFC_VERSION_TABLE = 'alembic_version_sfc'
config = context.config
neutron_config = config.neutron_config
target_metadata = model_base.BASEV2.metadata


def set_mysql_engine():
    try:
        mysql_engine = neutron_config.command.mysql_engine
    except cfg.NoSuchOptError:
        mysql_engine = None

    global MYSQL_ENGINE
    MYSQL_ENGINE = (mysql_engine or
                    model_base.BASEV2.__table_args__['mysql_engine'])


def include_object(object_, name, type_, reflected, compare_to):
    if type_ == 'table' and name in external.TABLES:
        return False
    elif type_ == 'index' and reflected and name.startswith("idx_autoinc_"):
        # skip indexes created by SQLAlchemy autoincrement=True
        # on composite PK integer columns
        return False
    return True


def run_migrations_offline():
    """Run migrations in 'offline' mode.

    This configures the context with either a URL
    or an Engine.

    Calls to context.execute() here emit the given string to the
    script output.

    """
    set_mysql_engine()

    kwargs = dict()
    if neutron_config.database.connection:
        kwargs['url'] = neutron_config.database.connection
    else:
        kwargs['dialect_name'] = neutron_config.database.engine
    kwargs['include_object'] = include_object
    kwargs['version_table'] = SFC_VERSION_TABLE
    context.configure(**kwargs)

    with context.begin_transaction():
        context.run_migrations()


@event.listens_for(sa.Table, 'after_parent_attach')
def set_storage_engine(target, parent):
    if MYSQL_ENGINE:
        target.kwargs['mysql_engine'] = MYSQL_ENGINE


def run_migrations_online():
    """Run migrations in 'online' mode.

    In this scenario we need to create an Engine
    and associate a connection with the context.

    """
    set_mysql_engine()
    connection = config.attributes.get('connection')
    with DBConnection(neutron_config.database.connection, connection) as conn:
        context.configure(
            connection=conn,
            target_metadata=target_metadata,
            version_table=SFC_VERSION_TABLE,
            include_object=include_object,
            process_revision_directives=autogen.process_revision_directives
        )
        with context.begin_transaction():
            context.run_migrations()


if context.is_offline_mode():
    run_migrations_offline()
else:
    run_migrations_online()
