#
# 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.

#
# Setup : https://developers.google.com/gmail/api/quickstart/python
# Need to have credentials.json were you call main script
#
# File imported from https://github.com/googleworkspace/python-samples/blob/main/gmail/quickstart/quickstart.py
#

from __future__ import print_function

import os.path

from google.auth.transport.requests import Request
from google.oauth2.credentials import Credentials
from google_auth_oauthlib.flow import InstalledAppFlow
from googleapiclient.discovery import build

# If modifying these scopes, delete the file token.json.
SCOPES = ['https://www.googleapis.com/auth/gmail.readonly']

creds = None

def _initCreds():
    global creds
    if creds: return
    
    # The file token.json stores the user's access and refresh tokens, and is
    # created automatically when the authorization flow completes for the first
    # time.
    if os.path.exists('token.json'):
        creds = Credentials.from_authorized_user_file('./token.json', SCOPES)
    # If there are no (valid) credentials available, let the user log in.
    if not creds or not creds.valid:
        if creds and creds.expired and creds.refresh_token:
            creds.refresh(Request())
        else:
            flow = InstalledAppFlow.from_client_secrets_file(
                'credentials.json', SCOPES)
            creds = flow.run_local_server(port=0)
        # Save the credentials for the next run
        with open('token.json', 'w') as token:
            token.write(creds.to_json())
    
def getUnreadMails():
    """
    Get number of unread threads (that may contain multiple messages)
    """

    _initCreds()
    
    service = build('gmail', 'v1', credentials=creds)
    pageToken = ''
    threads = set()
    while True:
        results = service.users().messages().list(userId='me', labelIds=['UNREAD'],\
                                                  includeSpamTrash=False, pageToken=pageToken)\
                                            .execute()
        threads = threads.union(set([k['threadId'] for k in results['messages']]))
        # Loop over all result pages (100 results per page by default)
        pageToken = results.get('nextPageToken', '')
        if not pageToken: break

    return len(threads)