root/python/ml/ml.py

#!/usr/bin/python
#vim:fileencoding=utf-8

'''
ml.py -- simple mailing list to just distribute messages in a group.

Copyright (c) 2007,2010 Shigeru KANEMOTO
All rights reserved.
'''

LIST_ADDRESS = 'list@example.com'
LIST_SUBSCRIBERS = {
  # 'email address (lower case)': u'real name',
  'somebody@example.com': u'なまえ',
}

import sys
import re
import email.FeedParser
import email.Header
import email.Utils
import smtplib

BUFFER_SIZE = 1024


class MLError(RuntimeError):
  pass


def message_from_fileobj(fileobj):
  parser = email.FeedParser.FeedParser()
  while True:
    buffer = fileobj.read(BUFFER_SIZE)
    if not buffer:
      return parser.close()
    parser.feed(buffer)


def alter_message_for_forwarding(message):
  # Check the destination
  recipients = message.get_all('to', [])
  recipients += message.get_all('cc', [])
  recipients += message.get_all('resent-to', [])
  recipients += message.get_all('resent-cc', [])
  recipients = email.Utils.getaddresses(recipients)
  for (realname, address) in recipients:
    if address.lower() == LIST_ADDRESS:
      break
  else:
    raise MLError, 'Not sent to this list.'

  # Get nickname of the sender
  sender = message['from']
  if not sender:
    raise MLError, 'No "from" header found.'
  (realname, sender) = email.Utils.parseaddr(sender)
  if not sender:
    raise MLError, '"from" header not recognized.'
  sender = sender.lower()
  try:
    nickname = LIST_SUBSCRIBERS[sender]
  except KeyError:
    raise MLError, 'Sender "%s" not allowed.' % sender

  # Get the subject
  subject = message.get('subject', '')
  subject = email.Header.decode_header(subject)
  (s, charset) = subject[0]
  s = re.sub(r'^(Re|RE|re)(\d*|\[\d+\])[:>]\s*(Bcc:\s*|)', '', s, 1)
  subject[0] = (s, charset)
  subject = email.Header.make_header(subject)

  # Prepare the new message
  del message['to']
  del message['cc']
  del message['resent-to']
  del message['resent-cc']
  del message['from']
  del message['reply-to']
  del message['subject']
  message['To'] = LIST_ADDRESS
  message['From'] = LIST_ADDRESS
  message['Subject'] = subject

  def insert_nickname(m):
    if m.get_content_maintype() != 'text':
      return
    charset = m.get_content_charset().lower()
    body = m.get_payload(i=None, decode=True)

    # Decode
    if charset == 'iso-2022-jp':
      #XXX 「㍑」対応
      body = body.replace('\x1b$B', '\x1b$(Q').decode('iso-2022-jp-2004')
    else:
      body = body.decode(charset)

    # Insert
    if m.get_content_subtype() == 'html':
      body = re.sub(r'^(.*<(body|BODY).*>|)', r'\1[%s]<br />' % nickname, body, 1)
    else:
      body = ('[%s]\r\n' % nickname) + body

    # Encode
    #XXX 「㍑」対応
    body = body.encode('iso-2022-jp-2004').replace('\033$(Q', '\033$B')
    del m['content-transfer-encoding']
    m.set_payload(body, 'iso-2022-jp')

  if message.is_multipart():
    for m in message.get_payload():
      insert_nickname(m)
  else:
    insert_nickname(message)

  return sender


def deliver_message(sender, message):
  recipients = LIST_SUBSCRIBERS.keys()
  recipients.remove(sender)
  smtp = smtplib.SMTP('localhost')
  smtp.sendmail(LIST_ADDRESS, recipients, message.as_string())
  smtp.close()


if __name__ == '__main__':
  try:
    message = message_from_fileobj(sys.stdin)
    sender = alter_message_for_forwarding(message)
    deliver_message(sender, message)
  except MLError, e:
    print >>sys.stderr, str(e)
    # Courier suspends delivery to same address for a while after exiting
    # with exit code except zero.
    sys.exit(0)