# 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_postgres_sqlalchemy_connect_connector]
import os

from google.cloud.sql.connector import Connector, IPTypes
import pg8000

import sqlalchemy


def connect_with_connector() -> sqlalchemy.engine.base.Engine:
    """
    Initializes a connection pool for a Cloud SQL instance of Postgres.

    Uses the Cloud SQL Python Connector package.
    """
    # 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.

    instance_connection_name = os.environ[
        "INSTANCE_CONNECTION_NAME"
    ]  # e.g. 'project:region:instance'
    db_user = os.environ["DB_USER"]  # e.g. 'my-db-user'
    db_pass = os.environ["DB_PASS"]  # e.g. 'my-db-password'
    db_name = os.environ["DB_NAME"]  # e.g. 'my-database'

    ip_type = IPTypes.PRIVATE if os.environ.get("PRIVATE_IP") else IPTypes.PUBLIC

    # initialize Cloud SQL Python Connector object
    connector = Connector()

    def getconn() -> pg8000.dbapi.Connection:
        conn: pg8000.dbapi.Connection = connector.connect(
            instance_connection_name,
            "pg8000",
            user=db_user,
            password=db_pass,
            db=db_name,
            ip_type=ip_type,
        )
        return conn

    # The Cloud SQL Python Connector can be used with SQLAlchemy
    # using the 'creator' argument to 'create_engine'
    pool = sqlalchemy.create_engine(
        "postgresql+pg8000://",
        creator=getconn,
        # [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_postgres_sqlalchemy_connect_connector]