# Copyright (C) 1998,1999,2000,2001,2002 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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.

"""Parse RFC 1894 (i.e. DSN) bounce formats."""

from email.Iterators import typed_subpart_iterator
from email.Utils import parseaddr
from cStringIO import StringIO



def check(msg):
    # Iterate over each message/delivery-status subpart
    addrs = []
    for part in typed_subpart_iterator(msg, 'message', 'delivery-status'):
        if not part.is_multipart():
            # Huh?
            continue
        # Each message/delivery-status contains a list of Message objects
        # which are the header blocks.  Iterate over those too.
        for msgblock in part.get_payload():
            # We try to dig out the Original-Recipient (which is optional) and
            # Final-Recipient (which is mandatory, but may not exactly match
            # an address on our list).  Some MTA's also use X-Actual-Recipient
            # as a synonym for Original-Recipient, but some apparently use
            # that for other purposes :(
            #
            # Also grok out Action so we can do something with that too.
            action = msgblock.get('action', '')
            # BAW: Should we treat delayed bounces the same?  Yes, because if
            # the transient problem clears up, they should get unbounced.  The
            # other problem is what to do about a DSN that has both delayed
            # and failed actions in multiple header blocks?  We're not
            # architected to handle that. ;/
            if action.lower() not in ('failed', 'failure', 'delayed'):
                # Some non-permanent failure, so ignore this block
                continue
            params = []
            foundp = 0
            for header in ('original-recipient', 'final-recipient'):
                for k, v in msgblock.get_params([], header):
                    if k.lower() == 'rfc822':
                        foundp = 1
                    else:
                        params.append(k)
                if foundp:
                    # Note that params should already be unquoted.
                    addrs.extend(params)
                    break
    # Uniquify
    rtnaddrs = {}
    for a in addrs:
        if a is not None:
            realname, a = parseaddr(a)
            rtnaddrs[a] = 1
    return rtnaddrs.keys()



def process(msg):
    # The report-type parameter should be "delivery-status", but it seems that
    # some DSN generating MTAs don't include this on the Content-Type: header,
    # so let's relax the test a bit.
    if not msg.is_multipart() or msg.get_subtype() <> 'report':
        return None
    return check(msg)