#
#    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 itertools
import uuid

import migrate.changeset.constraint as constraint
from oslo_utils import timeutils
import sqlalchemy


def upgrade(migrate_engine):
    if migrate_engine.name == 'sqlite':
        upgrade_sqlite(migrate_engine)
        return

    meta = sqlalchemy.MetaData(bind=migrate_engine)

    event_table = sqlalchemy.Table('event', meta, autoload=True)
    event_uuid_column_kwargs = {}
    if migrate_engine.name == 'ibm_db_sa':
        # NOTE(mriedem): DB2 10.5 doesn't support unique constraints over
        # nullable columns, it creates a unique index instead, so we have
        # to make the uuid column non-nullable in the DB2 case.
        event_uuid_column_kwargs['nullable'] = False
    event_uuid = sqlalchemy.Column('uuid', sqlalchemy.String(length=36),
                                   default=lambda: str(uuid.uuid4),
                                   **event_uuid_column_kwargs)
    event_table.create_column(event_uuid)

    if migrate_engine.name == 'postgresql':
        sequence = sqlalchemy.Sequence('evt')
        sqlalchemy.schema.CreateSequence(sequence,
                                         bind=migrate_engine).execute()
        event_id = sqlalchemy.Column('tmp_id', sqlalchemy.Integer,
                                     server_default=sqlalchemy.text(
                                         "nextval('evt')"))
    else:
        event_id_column_kwargs = {}
        if migrate_engine.name == 'ibm_db_sa':
            # NOTE(mriedem): This is turned into a primary key constraint
            # later so it must be non-nullable.
            event_id_column_kwargs['nullable'] = False
        event_id = sqlalchemy.Column('tmp_id', sqlalchemy.Integer,
                                     **event_id_column_kwargs)
    event_table.create_column(event_id)

    fake_autoincrement = itertools.count(1)

    event_list = event_table.select().order_by(
        sqlalchemy.sql.expression.asc(
            event_table.c.created_at)).execute().fetchall()
    for event in event_list:
        values = {'tmp_id': fake_autoincrement.next(), 'uuid': event.id}
        update = event_table.update().where(
            event_table.c.id == event.id).values(values)
        migrate_engine.execute(update)

    constraint_kwargs = {'table': event_table}
    if migrate_engine.name == 'ibm_db_sa':
        # NOTE(mriedem): DB2 gives a random name to the unique constraint
        # if one is not provided so let's set the standard name ourselves.
        constraint_kwargs['name'] = 'uniq_event0uuid0'
    cons = constraint.UniqueConstraint('uuid', **constraint_kwargs)
    cons.create()

    event_table.c.id.drop()

    alter_kwargs = {}
    if migrate_engine.name == 'ibm_db_sa':
        alter_kwargs['nullable'] = False
    event_table.c.tmp_id.alter('id', sqlalchemy.Integer, **alter_kwargs)

    cons = constraint.PrimaryKeyConstraint('tmp_id', table=event_table)
    cons.create()

    if migrate_engine.name == 'ibm_db_sa':
        # NOTE(chenxiao): For DB2, setting "ID" column "autoincrement=True"
        # can't make sense after above "tmp_id=>id" transformation,
        # so should work around it.
        sql = ("ALTER TABLE EVENT ALTER COLUMN ID SET GENERATED BY "
               "DEFAULT AS IDENTITY (START WITH 1, INCREMENT BY 1)")
        migrate_engine.execute(sql)
    else:
        event_table.c.tmp_id.alter(sqlalchemy.Integer, autoincrement=True)


def upgrade_sqlite(migrate_engine):
    meta = sqlalchemy.MetaData(bind=migrate_engine)

    # (pafuent) Here it isn't recommended to import the table from the models,
    # because in future migrations the model could change and this migration
    # could fail.
    # I know it is ugly but it's the only way that I found to 'freeze'
    # the model state for this migration.
    stack_table = sqlalchemy.Table('stack', meta, autoload=True)
    event_table = sqlalchemy.Table(
        'new_event', meta,
        sqlalchemy.Column('id', sqlalchemy.Integer, primary_key=True),
        sqlalchemy.Column('stack_id', sqlalchemy.String(36),
                          sqlalchemy.ForeignKey(stack_table.c.id),
                          nullable=False),
        sqlalchemy.Column('uuid', sqlalchemy.String(36),
                          default=lambda: str(uuid.uuid4()),
                          unique=True),
        sqlalchemy.Column('resource_action', sqlalchemy.String(255)),
        sqlalchemy.Column('resource_status', sqlalchemy.String(255)),
        sqlalchemy.Column('resource_name', sqlalchemy.String(255)),
        sqlalchemy.Column('physical_resource_id', sqlalchemy.String(255)),
        sqlalchemy.Column('resource_status_reason', sqlalchemy.String(255)),
        sqlalchemy.Column('resource_type', sqlalchemy.String(255)),
        sqlalchemy.Column('resource_properties', sqlalchemy.PickleType),
        sqlalchemy.Column('created_at', sqlalchemy.DateTime,
                          default=timeutils.utcnow),
        sqlalchemy.Column('updated_at', sqlalchemy.DateTime,
                          onupdate=timeutils.utcnow))
    event_table.create()

    prev_event_table = sqlalchemy.Table('event', meta, autoload=True)
    event_list = list(prev_event_table.select().order_by(
        sqlalchemy.sql.expression.asc(prev_event_table.c.created_at))
        .execute())
    for event in event_list:
        values = {
            'stack_id': event.stack_id,
            'uuid': event.id,
            'resource_action': event.resource_action,
            'resource_status': event.resource_status,
            'resource_name': event.resource_name,
            'physical_resource_id': event.physical_resource_id,
            'resource_status_reason': event.resource_status_reason,
            'resource_type': event.resource_type,
            'resource_properties': event.resource_properties}
        migrate_engine.execute(event_table.insert(values))

    prev_event_table.drop()
    event_table.rename('event')


def downgrade(migrate_engine):
    if migrate_engine.name == 'sqlite':
        downgrade_sqlite(migrate_engine)
        return

    meta = sqlalchemy.MetaData(bind=migrate_engine)

    event_table = sqlalchemy.Table('event', meta, autoload=True)

    event_id_column_kwargs = {}
    if migrate_engine.name == 'ibm_db_sa':
        event_id_column_kwargs['nullable'] = False

    event_id = sqlalchemy.Column('tmp_id', sqlalchemy.String(length=36),
                                 default=lambda: str(uuid.uuid4),
                                 **event_id_column_kwargs)
    event_id.create(event_table)

    event_list = event_table.select().execute()
    for event in event_list:
        values = {'tmp_id': event.uuid}
        update = event_table.update().where(
            event_table.c.uuid == event.uuid).values(values)
        migrate_engine.execute(update)

    event_table.c.id.drop()
    event_table.c.uuid.drop()

    cons = constraint.PrimaryKeyConstraint('tmp_id', table=event_table)
    cons.create()

    alter_kwargs = {}
    # NOTE(mriedem): DB2 won't allow a primary key on a nullable column so
    # we have to make it non-nullable.
    if migrate_engine.name == 'ibm_db_sa':
        alter_kwargs['nullable'] = False
    event_table.c.tmp_id.alter('id', default=lambda: str(uuid.uuid4),
                               **alter_kwargs)
    if migrate_engine.name == 'postgresql':
        sequence = sqlalchemy.Sequence('evt')
        sqlalchemy.schema.DropSequence(sequence, bind=migrate_engine).execute()


def downgrade_sqlite(migrate_engine):
    meta = sqlalchemy.MetaData(bind=migrate_engine)

    # (pafuent) Here it isn't recommended to import the table from the models,
    # because in future migrations the model could change and this migration
    # could fail.
    # I know it is ugly but it's the only way that I found to 'freeze'
    # the model state for this migration.
    stack_table = sqlalchemy.Table('stack', meta, autoload=True)
    event_table = sqlalchemy.Table(
        'new_event', meta,
        sqlalchemy.Column('id', sqlalchemy.String(36),
                          default=lambda: str(uuid.uuid4())),
        sqlalchemy.Column('stack_id', sqlalchemy.String(36),
                          sqlalchemy.ForeignKey(stack_table.c.id),
                          nullable=False),
        sqlalchemy.Column('resource_action', sqlalchemy.String(255)),
        sqlalchemy.Column('resource_status', sqlalchemy.String(255)),
        sqlalchemy.Column('resource_name', sqlalchemy.String(255)),
        sqlalchemy.Column('physical_resource_id', sqlalchemy.String(255)),
        sqlalchemy.Column('resource_status_reason', sqlalchemy.String(255)),
        sqlalchemy.Column('resource_type', sqlalchemy.String(255)),
        sqlalchemy.Column('resource_properties', sqlalchemy.PickleType),
        sqlalchemy.Column('created_at', sqlalchemy.DateTime,
                          default=timeutils.utcnow),
        sqlalchemy.Column('updated_at', sqlalchemy.DateTime,
                          onupdate=timeutils.utcnow))
    event_table.create()

    prev_event_table = sqlalchemy.Table('event', meta, autoload=True)
    event_list = prev_event_table.select().execute().fetchall()
    for event in event_list:
        values = {
            'id': event.uuid,
            'stack_id': event.stack_id,
            'resource_action': event.resource_action,
            'resource_status': event.resource_status,
            'resource_name': event.resource_name,
            'physical_resource_id': event.physical_resource_id,
            'resource_status_reason': event.resource_status_reason,
            'resource_type': event.resource_type,
            'resource_properties': event.resource_properties}
        migrate_engine.execute(event_table.insert(values))

    prev_event_table.drop()
    event_table.rename('event')
