from __future__ import print_function
from flask import current_app
from googleapiclient.discovery import build
from apiclient import errors
import os
from email.mime.multipart import MIMEMultipart
from email.mime.text import MIMEText
import base64
from google.oauth2 import service_account
from exceptions import EmailFailedException


def _login():
    """Logs in to the google API for emails"""
    scopes = ['https://www.googleapis.com/auth/gmail.send']
    service_account_file = os.path.abspath(os.path.join(os.path.dirname(__file__), 'service-key.json'))
    creds = service_account.Credentials.from_service_account_file(service_account_file, scopes=scopes)
    delegated_creds = creds.with_subject(current_app.config['MAIL_USERNAME'])
    service = build('gmail', 'v1', credentials=delegated_creds)
    return service


def _create_message(subject, sender, recipient, txt_body, html_body):
    message = MIMEMultipart('alternative')
    message['To'] = recipient
    message['From'] = sender
    message['Subject'] = subject
    message.attach(MIMEText(txt_body, 'plain'))
    message.attach(MIMEText(html_body, 'html'))
    return {'raw': base64.urlsafe_b64encode(message.as_bytes()).decode('utf-8')}


def send_email(subject, sender, recipient, txt_body, html_body):
    """
    Sends an email using the google email API.

    Arguments:
        subject (`str`): The subject text for the email.
        sender (`str`): The email address of the sender.
        recipient (`str`): The email address to send the email to.
        txt_body (`str`): The plain text of the email.
        html_body (`str`): The HTML of the email.
    """
    service = _login()
    message = _create_message(subject, sender, recipient, txt_body, html_body)

    try:
        msg = (service.users().messages().send(userId='me', body=message).execute())
        print(f'Message ID: {msg["id"]}')
        return msg
    except errors.HttpError as error:
        raise EmailFailedException(message=f'Failed to send message: {str(error)}')