# Copyright 2018 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 functions_sql_postgres]
from os import getenv

from psycopg2 import OperationalError
from psycopg2.pool import SimpleConnectionPool

# TODO(developer): specify SQL connection details
CONNECTION_NAME = getenv(
  'INSTANCE_CONNECTION_NAME',
  '<YOUR INSTANCE CONNECTION NAME>')
DB_USER = getenv('POSTGRES_USER', '<YOUR DB USER>')
DB_PASSWORD = getenv('POSTGRES_PASSWORD', '<YOUR DB PASSWORD>')
DB_NAME = getenv('POSTGRES_DATABASE', '<YOUR DB NAME>')

pg_config = {
  'user': DB_USER,
  'password': DB_PASSWORD,
  'dbname': DB_NAME
}

# Connection pools reuse connections between invocations,
# and handle dropped or expired connections automatically.
pg_pool = None


def __connect(host):
    """
    Helper function to connect to Postgres
    """
    global pg_pool
    pg_config['host'] = host
    pg_pool = SimpleConnectionPool(1, 1, **pg_config)


def postgres_demo(request):
    global pg_pool

    # Initialize the pool lazily, in case SQL access isn't needed for this
    # GCF instance. Doing so minimizes the number of active SQL connections,
    # which helps keep your GCF instances under SQL connection limits.
    if not pg_pool:
        try:
            __connect(f'/cloudsql/{CONNECTION_NAME}')
        except OperationalError:
            # If production settings fail, use local development ones
            __connect('localhost')

    # Remember to close SQL resources declared while running this function.
    # Keep any declared in global scope (e.g. pg_pool) for later reuse.
    with pg_pool.getconn().cursor() as cursor:
        cursor.execute('SELECT NOW() as now')
        results = cursor.fetchone()
        return str(results[0])
# [END functions_sql_postgres]