ical-reply

#!/usr/bin/env python

from __future__ import print_function

import datetime
import email
import email.utils
import optparse
import os
import re
import smtplib
import sys

import icalendar  # https://pypi.python.org/pypi/icalendar

from email.mime.text import MIMEText


ICALENDAR_PRODID = '-//net.aperiodic.mutt-ical//1.0'
ICALENDAR_CONTENT_TYPES = ['text/calendar', 'application/ics']
ICALENDAR_REPLY_STATUSES = {
    'yes': 'ACCEPTED',
    'no': 'DECLINED',
    'maybe': 'TENTATIVE',
}

parser = optparse.OptionParser(usage='Usage: %prog [opts] {-r <response> | --refresh} email-address')
parser.add_option('-r', '--reply', type='choice',
                  choices=ICALENDAR_REPLY_STATUSES.keys(),
                  help='Give your reply to a request for attendance.')
parser.add_option('--refresh', action='store_true',
                  help='Request an updated copy of the given event.')
parser.add_option('-d', '--debug', action='store_true',
                  help='Enable debugging; do not actually send email.')
parser.add_option('-s', '--smtp', default='localhost',
                  help='SMTP server to use when sending email.  Defaults to localhost.')

(options, args) = parser.parse_args()
if not (options.reply or options.refresh):
    print('You must specify an action.', file=sys.stderr)
    exit(1)
if options.reply and options.refresh:
    print('You annot give more than one action.', file=sys.stderr)
    exit(1)
if len(args) == 0:
    print('You must give your email address.', file=sys.stderr)
    exit(1)
if len(args) > 1:
    print('You can only give one email address.', file=sys.stderr)
    exit(1)
email_address = 'mailto:' + args[0]

def copy_prop(prop, source, dest):
    if prop in source:
        dest.add(prop, source[prop])

def find_icalendar(email):
    global ICALENDAR_CONTENT_TYPES
    for part in email.walk():
        if part.get_content_type() in ICALENDAR_CONTENT_TYPES:
            return part
    return None


###
# Find the iCalendar in the source email and parse it.

source_email = email.message_from_file(sys.stdin)
source_icalendar = find_icalendar(source_email)
if not source_email:
    print('No iCalendar found to reply to.', file=sys.stderr)
    exit(1)
request = icalendar.Calendar.from_ical(source_icalendar.get_payload(decode=True))


###
# Verification of the validity of the requestion action relative to the supplied
# iCalendar.

if options.reply and not ('METHOD' in request and request['METHOD'] == 'REQUEST'):
    print('Cannot generate reply; source calendar was not a REQUEST.',
          file=sys.stderr)
    exit(1)

source_event = None
for component in request.subcomponents:
    if component.name == 'VEVENT':
        if source_event:
            print('Cannot generate reply; more than one event in source calendar.',
                  file=sys.stderr)
            exit(1)
        source_event = component
if not source_event:
    print('Cannot generate reply; no events in source calendar.',
          file=sys.stderr)
    exit(1)

attendee = None
if isinstance(source_event['ATTENDEE'], list):
    for a in source_event['ATTENDEE']:
        if a.lower() == email_address.lower():
            attendee = a
elif source_event['ATTENDEE'].lower() == email_address.lower():
    attendee = source_event['ATTENDEE']
if not attendee:
    print('Email "%s" is not listed as an attendee.' % email_address.replace('mailto:', ''),
          file=sys.stderr)
    exit(1)

###
# Build response calendar.

response_icalendar = icalendar.Calendar()
if options.reply:
    response_icalendar['METHOD'] = 'REPLY'
elif options.refresh:
    response_icalendar['METHOD'] = 'REFRESH'
response_icalendar['VERSION'] = '2.0'
response_icalendar['PRODID'] = ICALENDAR_PRODID
response_icalendar['CALSCALE'] = 'GREGORIAN'

reply_event = icalendar.Event()
reply_event['ATTENDEE'] = attendee
if options.reply:
    reply_event['ATTENDEE'].params['PARTSTAT'] = ICALENDAR_REPLY_STATUSES[options.reply]
    reply_event['ATTENDEE'].params['X-NUM-GUESTS'] = '1'
reply_event.add('DTSTAMP', datetime.datetime.now())
copy_prop('ORGANIZER', source_event, reply_event)
copy_prop('RECURRENCE-ID', source_event, reply_event)
copy_prop('UID', source_event, reply_event)
if options.reply:
    copy_prop('SEQUENCE', source_event, reply_event)

response_icalendar.add_component(reply_event)

###
# Build response email.

response_email = MIMEText(response_icalendar.to_ical(), 'calendar')#, 'UTF-8')
response_email.set_param('method', response_icalendar['METHOD'])
response_email['From'] = email_address.replace('mailto:', '')
organizer_address = source_event['ORGANIZER'].replace('mailto:', '')
organizer_address = source_event['ORGANIZER'].replace('Mailto:', '')
organizer_address = source_event['ORGANIZER'].replace('MAILTO:', '')
if 'CN' in source_event['ORGANIZER'].params:
    reply_to = email.utils.formataddr((source_event['ORGANIZER'].params['CN'], organizer_address))
else:
    reply_to = organizer_address
response_email['To'] = reply_to

if 'SUMMARY' in source_event:
    response_email['Subject'] = 'Re: ' + source_event['SUMMARY']
else:
    response_email['Subject'] = 'Re: ' + source_event['UID']
response_email['Date'] = email.utils.formatdate(localtime=True)

if options.debug:
    print(response_email.as_string(), end='')
else:
    parsed_reply_to = email.utils.parseaddr(reply_to)
    if parsed_reply_to == ('', ''):
        destination = reply_to
    else:
        destination = parsed_reply_to[1]
    s = smtplib.SMTP(options.smtp)
    s.sendmail(email_address.replace('mailto:', ''), [destination],
               response_email.as_string())
    s.quit()