#!/usr/bin/env python3
import os
from typing import Optional

from oauth2client import client, tools
from oauth2client.file import Storage

try:
    import argparse

    flags = argparse.ArgumentParser(
        parents=[tools.argparser]
    ).parse_args()  # type: Optional[argparse.Namespace]
except ImportError:
    flags = None

# If modifying these scopes, delete your previously saved credentials
# at zulip/bots/gcal/
# NOTE: When adding more scopes, add them after the previous one in the same field, with a space
# seperating them.
SCOPES = 'https://www.googleapis.com/auth/calendar.readonly'
# This file contains the information that google uses to figure out which application is requesting
# this client's data.
CLIENT_SECRET_FILE = 'client_secret.json'
APPLICATION_NAME = 'Zulip Calendar Bot'
HOME_DIR = os.path.expanduser('~')


def get_credentials() -> client.Credentials:
    """Gets valid user credentials from storage.

    If nothing has been stored, or if the stored credentials are invalid,
    the OAuth2 flow is completed to obtain the new credentials.

    Returns:
        Credentials, the obtained credential.
    """

    credential_path = os.path.join(HOME_DIR, 'google-credentials.json')

    store = Storage(credential_path)
    credentials = store.get()
    if not credentials or credentials.invalid:
        flow = client.flow_from_clientsecrets(os.path.join(HOME_DIR, CLIENT_SECRET_FILE), SCOPES)
        flow.user_agent = APPLICATION_NAME
        if flags:
            # This attempts to open an authorization page in the default web browser, and asks the user
            # to grant the bot access to their data. If the user grants permission, the run_flow()
            # function returns new credentials.
            credentials = tools.run_flow(flow, store, flags)
        else:  # Needed only for compatibility with Python 2.6
            credentials = tools.run(flow, store)
        print('Storing credentials to ' + credential_path)


get_credentials()