# 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 logging.config import fileConfig

from alembic import context
from sqlalchemy import engine_from_config
from sqlalchemy import pool

from heat.db.sqlalchemy import models

# this is the Alembic Config object, which provides
# access to the values within the .ini file in use.
config = context.config

# Interpret the config file for Python logging.
# This line sets up loggers basically.
if config.attributes.get('configure_logger', True):
    fileConfig(config.config_file_name)

# this is the MetaData object for the various models in the database
target_metadata = models.BASE.metadata


def run_migrations_offline() -> None:
    """Run migrations in 'offline' mode.

    This configures the context with just a URL and not an Engine, though an
    Engine is acceptable here as well.  By skipping the Engine creation we
    don't even need a DBAPI to be available.

    Calls to context.execute() here emit the given string to the
    script output.
    """
    url = config.get_main_option("sqlalchemy.url")
    context.configure(
        url=url,
        target_metadata=target_metadata,
        literal_binds=True,
        dialect_opts={"paramstyle": "named"},
    )

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


def run_migrations_online() -> None:
    """Run migrations in 'online' mode.

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

    This is modified from the default based on the below, since we want to
    share an engine when unit testing so in-memory database testing actually
    works.

    https://alembic.sqlalchemy.org/en/latest/cookbook.html#connection-sharing
    """
    connectable = config.attributes.get('connection', None)

    if connectable is None:
        # only create Engine if we don't have a Connection from the outside
        connectable = engine_from_config(
            config.get_section(config.config_ini_section, {}),
            prefix="sqlalchemy.",
            poolclass=pool.NullPool,
        )

    # when connectable is already a Connection object, calling connect() gives
    # us a *branched connection*

    with connectable.connect() as connection:
        context.configure(
            connection=connection,
            target_metadata=target_metadata,
        )

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


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