text: import json
  import jinja2
  from datetime import datetime, timedelta
  from collections import defaultdict
  from dateutil.parser import parse
  from flask import current_app
  
  from email.mime.text import MIMEText
  from email.mime.multipart import MIMEMultipart
  
  from .smtp_server import LoggedInServer
  
  
  class EmailReminder():
  
      def __init__(self):
          self.day_of_the_week = datetime.now().weekday()
          self.day_in_question = 'Monday' if self.day_of_the_week == 4 else 'tomorrow'
          self.logged_in_server = LoggedInServer()
          self.admin = current_app.config['ADMIN_EMAIL']
  
      def send_reminders(self):
          calendar = current_app.config['CALENDAR']
          room_list = self._load_room_ids()
          rooms = [room for room in room_list if 'all' in room['lists']]
          days_until_next_working_day = 3 if self.day_of_the_week == 4 else 1
          next_working_day_events = self._get_all_days_events(
              calendar,
              rooms,
              datetime.now() + timedelta(days=days_until_next_working_day)
          )
          user_events = self._parse_events(next_working_day_events)
          self._send_the_emails(user_events)
  
      def _load_room_ids(self):
          with open('./app/data/room_ids.json') as file:
              return json.load(file)
  
      def _get_all_days_events(self, calendar, rooms, date):
          start = date.replace(hour=0, minute=0, second=0).isoformat() + 'Z'
          end = date.replace(hour=23, minute=59, second=59).isoformat() + 'Z'
          all_events = []
          for room_id in rooms:
              page_token = None
              while True:
                  room_events = calendar.events().list(calendarId=room_id,
                                                       timeMin=start,
                                                       timeMax=end,
                                                       pageToken=page_token,
                                                       showDeleted=False,
                                                       singleEvents=True).execute()
                  all_events = all_events + room_events['items']
                  page_token = room_events.get('nextPageToken')
                  if not page_token:
                      break
  
          return all_events
  
      def _parse_events(self, events):
          output = defaultdict(list)
          for event in events:
              organizer = event['organizer']['email']
  
              if organizer[0:29] == 'digital.cabinet-office.gov.uk':
                  continue
  
              output[organizer].append(
                  {
                      'summary': event.get('summary'),
                      'location': event.get('location', 'Check your calendar'),
                      'start': parse(event.get('start').get('dateTime')).strftime('%H:%M'),
                      'end': parse(event.get('end').get('dateTime')).strftime('%H:%M')
                  }
              )
  
          for email, event_list in output.items():
              output[email] = sorted(event_list, key=lambda k: k['start'])
  
          return output
  
      def _send_the_emails(self, all_events):
          for email_address, events in all_events.items():
              sender = self.admin
              receiver = current_app.config['TEST_MAIL_ADDRESS'] if current_app.config.get('TESTING') \
                  else email_address
              subject = 'Your meeting room booking{} for {}'.format('s' if len(events) > 1 else '', self.day_in_question)
              message = self._create_message(sender, receiver, subject)
  
              part1, part2 = self._render_content(events)
  
              message.attach(part1)
              message.attach(part2)
              if not current_app.config.get('TESTING'):
                  try:
                      self.logged_in_server.sendmail(sender, [receiver], message.as_string())
                  except Exception as e:
                      subject = 'Error sending email to {}'.format(receiver)
                      message = 'A wild error appeared! $$$ {}'.format(e)
                      self._email_admin(subject, message)
  
          self._email_admin(
              'Reminder emails sent.',
              '{} emails sent at {}'.format(
                  len(all_events.items()),
                  datetime.now().strftime('%d/%m/%y @ %H:%M')
              )
          )
  
      def _email_admin(self, subject, content):
          message = MIMEText(content)
          message['Subject'] = subject
          message['From'] = self.admin
          message['To'] = self.admin
          self.logged_in_server.sendmail(self.admin, [self.admin], message.as_string())
  
      def _create_message(self, sender, receiver, subject):
          msg = MIMEMultipart('alternative')
          msg['From'] = sender
          msg['To'] = receiver
          msg['Subject'] = subject
          return msg
  
      def _render_content(self, events):
          env = jinja2.Environment(
              loader=jinja2.PackageLoader('app', 'templates')
          )
          text_body = env.get_template('reminder.txt')
          html_body = env.get_template('reminder.html')
  
          text = text_body.render(events=events, day=self.day_in_question)
          html = html_body.render(events=events, day=self.day_in_question)
  
          part1 = MIMEText(text, 'plain')
          part2 = MIMEText(html, 'html')
  
          return part1, part2
  