# Copyright 2020 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.

import datetime
import logging
import os

from flask import Flask, render_template, request, Response
import sqlalchemy
from sqlalchemy import Column
from sqlalchemy import DateTime
from sqlalchemy import Integer
from sqlalchemy import String
from sqlalchemy import Table


app = Flask(__name__)

logger = logging.getLogger()


def init_connection_engine():
    db_config = {
        # [START cloud_sql_server_sqlalchemy_limit]
        # [START cloud_sql_sqlserver_sqlalchemy_limit]
        # 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.
        # [END cloud_sql_sqlserver_sqlalchemy_limit]
        # [END cloud_sql_server_sqlalchemy_limit]
        # [START cloud_sql_server_sqlalchemy_backoff]
        # [START cloud_sql_sqlserver_sqlalchemy_backoff]
        # SQLAlchemy automatically uses delays between failed connection attempts,
        # but provides no arguments for configuration.
        # [END cloud_sql_sqlserver_sqlalchemy_backoff]
        # [END cloud_sql_server_sqlalchemy_backoff]
        # [START cloud_sql_server_sqlalchemy_timeout]
        # [START cloud_sql_sqlserver_sqlalchemy_timeout]
        # '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
        # [END cloud_sql_sqlserver_sqlalchemy_timeout]
        # [END cloud_sql_server_sqlalchemy_timeout]
        # [START cloud_sql_server_sqlalchemy_lifetime]
        # [START cloud_sql_sqlserver_sqlalchemy_lifetime]
        # 'pool_recycle' is the maximum number of seconds a connection can persist.
        # Connections that live longer than the specified amount of time will be
        # reestablished
        "pool_recycle": 1800,  # 30 minutes
        # [END cloud_sql_sqlserver_sqlalchemy_lifetime]
        # [END cloud_sql_server_sqlalchemy_lifetime]
    }

    return init_tcp_connection_engine(db_config)


def init_tcp_connection_engine(db_config):
    # [START cloud_sql_server_sqlalchemy_create_tcp]
    # [START cloud_sql_sqlserver_sqlalchemy_create_tcp]
    # Remember - storing secrets in plaintext is potentially unsafe. Consider using
    # something like https://cloud.google.com/secret-manager/docs/overview to help keep
    # secrets secret.
    db_user = os.environ["DB_USER"]
    db_pass = os.environ["DB_PASS"]
    db_name = os.environ["DB_NAME"]
    db_host = os.environ["DB_HOST"]

    # Extract host and port from environment variable DB_HOST
    host_args = db_host.split(":")
    db_hostname, db_port = host_args[0], int(host_args[1])

    # SQL Server drivers don't account for this
    if db_hostname == "localhost":
        db_hostname = "127.0.0.1"

    # The SQLAlchemy engine will help manage interactions, including automatically
    # managing a pool of connections to your database
    pool = sqlalchemy.create_engine(
        # Equivalent URL:
        # mssql+pytds://<db_user>:<db_pass>@/<host>:<port>/<db_name>?driver=ODBC+Driver+17+for+SQL+Server
        sqlalchemy.engine.url.URL.create(
            "mssql+pytds",
            username=db_user,
            password=db_pass,
            database=db_name,
            host=db_hostname,
            port=db_port,
        ),
        **db_config
    )
    # [END cloud_sql_sqlserver_sqlalchemy_create_tcp]
    # [END cloud_sql_server_sqlalchemy_create_tcp]

    return pool


# This global variable is declared with a value of `None`, instead of calling
# `init_connection_engine()` immediately, to simplify testing. In general, it
# is safe to initialize your database connection pool when your script starts
# -- there is no need to wait for the first request.
db = None


@app.before_first_request
def create_tables():
    global db
    db = db or init_connection_engine()
    # Create tables (if they don't already exist)
    if not db.has_table("votes"):
        metadata = sqlalchemy.MetaData(db)
        Table(
            "votes",
            metadata,
            Column("vote_id", Integer, primary_key=True, nullable=False),
            Column("time_cast", DateTime, nullable=False),
            Column("candidate", String(6), nullable=False),
        )
        metadata.create_all()


@app.route("/", methods=["GET"])
def index():
    context = get_index_context()
    return render_template("index.html", **context)


def get_index_context():
    votes = []
    with db.connect() as conn:
        # Execute the query and fetch all results
        recent_votes = conn.execute(
            "SELECT TOP(5) candidate, time_cast FROM votes " "ORDER BY time_cast DESC"
        ).fetchall()
        # Convert the results into a list of dicts representing votes
        for row in recent_votes:
            votes.append({"candidate": row[0], "time_cast": row[1]})

        stmt = sqlalchemy.text(
            "SELECT COUNT(vote_id) FROM votes WHERE candidate=:candidate"
        )
        # Count number of votes for tabs
        tab_result = conn.execute(stmt, candidate="TABS").fetchone()
        tab_count = tab_result[0]
        # Count number of votes for spaces
        space_result = conn.execute(stmt, candidate="SPACES").fetchone()
        space_count = space_result[0]
    return {
        "recent_votes": votes,
        "space_count": space_count,
        "tab_count": tab_count,
    }


@app.route("/", methods=["POST"])
def save_vote():
    # Get the team and time the vote was cast.
    team = request.form["team"]
    time_cast = datetime.datetime.now(tz=datetime.timezone.utc)
    # Verify that the team is one of the allowed options
    if team != "TABS" and team != "SPACES":
        logger.warning(team)
        return Response(response="Invalid team specified.", status=400)

    # [START cloud_sql_server_sqlalchemy_connection]
    # [START cloud_sql_sqlserver_sqlalchemy_connection]
    # Preparing a statement before hand can help protect against injections.
    stmt = sqlalchemy.text(
        "INSERT INTO votes (time_cast, candidate)" " VALUES (:time_cast, :candidate)"
    )
    try:
        # Using a with statement ensures that the connection is always released
        # back into the pool at the end of statement (even if an error occurs)
        with db.connect() as conn:
            conn.execute(stmt, time_cast=time_cast, candidate=team)
    except Exception as e:
        # If something goes wrong, handle the error in this section. This might
        # involve retrying or adjusting parameters depending on the situation.
        # [START_EXCLUDE]
        logger.exception(e)
        return Response(
            status=500,
            response="Unable to successfully cast vote! Please check the "
            "application logs for more details.",
        )
        # [END_EXCLUDE]
    # [END cloud_sql_sqlserver_sqlalchemy_connection]
    # [END cloud_sql_server_sqlalchemy_connection]

    return Response(
        status=200,
        response="Vote successfully cast for '{}' at time {}!".format(team, time_cast),
    )


if __name__ == "__main__":
    app.run(host="127.0.0.1", port=8080, debug=True)