# 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_mysql]
from os import getenv

import pymysql
from pymysql.err import OperationalError

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

mysql_config = {
  'user': DB_USER,
  'password': DB_PASSWORD,
  'db': DB_NAME,
  'charset': 'utf8mb4',
  'cursorclass': pymysql.cursors.DictCursor,
  'autocommit': True
}

# Create SQL connection globally to enable reuse
# PyMySQL does not include support for connection pooling
mysql_conn = None


def __get_cursor():
    """
    Helper function to get a cursor
      PyMySQL does NOT automatically reconnect,
      so we must reconnect explicitly using ping()
    """
    try:
        return mysql_conn.cursor()
    except OperationalError:
        mysql_conn.ping(reconnect=True)
        return mysql_conn.cursor()


def mysql_demo(request):
    global mysql_conn

    # Initialize connections 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 mysql_conn:
        try:
            mysql_conn = pymysql.connect(**mysql_config)
        except OperationalError:
            # If production settings fail, use local development ones
            mysql_config['unix_socket'] = f'/cloudsql/{CONNECTION_NAME}'
            mysql_conn = pymysql.connect(**mysql_config)

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