email_service.py

import os
import pickle
# Gmail API utils
from googleapiclient.discovery import build
from google_auth_oauthlib.flow import InstalledAppFlow
from google.auth.transport.requests import Request
# for encoding/decoding messages in base64
from mimetypes import guess_type as guess_mime_type
from bs4 import BeautifulSoup
import base64

# Request all access (permission to read/send/receive emails, manage the inbox, and more)
SCOPES = ['https://mail.google.com/']

def gmail_authenticate():
    creds = None
    # the file token.pickle 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.pickle"):
        with open("token.pickle", "rb") as token:
            creds = pickle.load(token)
    # if there are no (valid) credentials availablle, 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.pickle", "wb") as token:
            pickle.dump(creds, token)
    return build('gmail', 'v1', credentials=creds)

# get the Gmail API service "from:yashmeh98@gmail.com"
def get_gmail_service():
    service = gmail_authenticate()
    return service

def get_latest_email(service, q):
    results = service.users().messages().list(userId='me', labelIds=['INBOX'], q=q).execute()
    messages = results.get('messages',[])
    for msg in messages:
        # Get the message from its id
        txt = service.users().messages().get(userId='me', id=msg['id']).execute()
        # Mark the message as read
        service.users().messages().modify(userId='me', id=msg['id'], body={'removeLabelIds': ['UNREAD']}).execute()
        # Use try-except to avoid any Errors
        try:
            # Get value of 'payload' from dictionary 'txt'
            payload = txt['payload']
            headers = payload['headers']

            # Look for Subject and Sender Email in the headers
            for d in headers:
                if d['name'] == 'Subject':
                    subject = d['value']
                if d['name'] == 'From':
                    sender = d['value']

            # The Body of the message is in Encrypted format. So, we have to decode it.
            # Get the data and decode it with base 64 decoder.
            parts = payload.get('parts')[0]
            data = parts['body']['data']
            data = data.replace("-","+").replace("_","/")
            decoded_data = base64.b64decode(data)

            # Now, the data obtained is in lxml. So, we will parse
            # it with BeautifulSoup library
            soup = BeautifulSoup(decoded_data , "lxml")
            body = soup.body()
        except Exception as e:
            print("Error retrieving email ", e)
        #return the last body to ensure that only latest email body is sent back    
        return body