# Copyright (C) 1998-2018 by the Free Software Foundation, Inc.
#
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License
# as published by the Free Software Foundation; either version 2
# of the License, or (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
# USA.

"""Parse bounce messages generated by qmail.

Qmail actually has a standard, called QSBMF (qmail-send bounce message
format), as described in

    http://cr.yp.to/proto/qsbmf.txt

This module should be conformant.

"""

import re
import email.Iterators

# Other (non-standard?) intros have been observed in the wild.
introtags = [
    'Hi. This is the',
    'Hi. The MTA program at',
    "We're sorry. There's a problem",
    'Check your send e-mail address.',
    'This is the mail delivery agent at',
    'Unfortunately, your mail was not delivered',
    'Your mail message to the following',
    ]
acre = re.compile(r'<(?P<addr>[^>]*)>:')



def process(msg):
    addrs = []
    # simple state machine
    #    0 = nothing seen yet
    #    1 = intro paragraph seen
    #    2 = recip paragraphs seen
    state = 0
    for line in email.Iterators.body_line_iterator(msg):
        line = line.strip()
        if state == 0:
            for introtag in introtags:
                if line.startswith(introtag):
                    state = 1
                    break
        elif state == 1 and not line:
            # Looking for the end of the intro paragraph
            state = 2
        elif state == 2:
            if line.startswith('-'):
                # We're looking at the break paragraph, so we're done
                break
            # At this point we know we must be looking at a recipient
            # paragraph
            mo = acre.match(line)
            if mo:
                addrs.append(mo.group('addr'))
            # Otherwise, it must be a continuation line, so just ignore it
        # Not looking at anything in particular
    return addrs