# Copyright 2022 Google LLC
#
# 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.

# [START cloud_sql_mysql_sqlalchemy_connect_unix]
import os

import sqlalchemy


def connect_unix_socket() -> sqlalchemy.engine.base.Engine:
    """Initializes a Unix socket connection pool for a Cloud SQL instance of MySQL."""
    # Note: Saving credentials in environment variables is convenient, but not
    # secure - consider a more secure solution such as
    # Cloud Secret Manager (https://cloud.google.com/secret-manager) to help
    # keep secrets safe.
    db_user = os.environ["DB_USER"]  # e.g. 'my-database-user'
    db_pass = os.environ["DB_PASS"]  # e.g. 'my-database-password'
    db_name = os.environ["DB_NAME"]  # e.g. 'my-database'
    unix_socket_path = os.environ[
        "INSTANCE_UNIX_SOCKET"
    ]  # e.g. '/cloudsql/project:region:instance'

    pool = sqlalchemy.create_engine(
        # Equivalent URL:
        # mysql+pymysql://<db_user>:<db_pass>@/<db_name>?unix_socket=<socket_path>/<cloud_sql_instance_name>
        sqlalchemy.engine.url.URL.create(
            drivername="mysql+pymysql",
            username=db_user,
            password=db_pass,
            database=db_name,
            query={"unix_socket": unix_socket_path},
        ),
        # [START_EXCLUDE]
        # Pool size is the maximum number of permanent connections to keep.
        pool_size=5,
        # Temporarily exceeds the set pool_size if no connections are available.
        max_overflow=2,
        # The total number of concurrent connections for your application will be
        # a total of pool_size and max_overflow.
        # 'pool_timeout' is the maximum number of seconds to wait when retrieving a
        # new connection from the pool. After the specified amount of time, an
        # exception will be thrown.
        pool_timeout=30,  # 30 seconds
        # 'pool_recycle' is the maximum number of seconds a connection can persist.
        # Connections that live longer than the specified amount of time will be
        # re-established
        pool_recycle=1800,  # 30 minutes
        # [END_EXCLUDE]
    )
    return pool


# [END cloud_sql_mysql_sqlalchemy_connect_unix]