# 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.

"""Extend mailbox.UnixMailbox.
"""

import sys
import mailbox

import email
from email.parser import Parser
from email.errors import MessageParseError
from email.generator import Generator

from Mailman import mm_cfg
from Mailman.Message import Message
from Mailman import Utils


def _safeparser(fp):
    try:
        return email.message_from_binary_file(fp, Message)
    except MessageParseError:
        # Don't return None since that will stop a mailbox iterator
        return ''



class Mailbox(mailbox.mbox):
    def __init__(self, fp):
        if not isinstance( fp, str ):
            fp = fp.name
        self.filepath = fp
        mailbox.mbox.__init__(self, fp, _safeparser)

    # msg should be an rfc822 message or a subclass.
    def AppendMessage(self, msg):
        # Check the last character of the file and write a newline if it isn't
        # a newline (but not at the beginning of an empty file).
        with open(self.filepath, 'r+') as fileh:
            try:
                fileh.seek(-1, 2)
            except IOError as e:
                # Assume the file is empty.  We can't portably test the error code
                # returned, since it differs per platform.
                pass
            else:
                if fileh.read(1) != '\n':
                    fileh.write('\n')
            # Seek to the last char of the mailbox
            fileh.seek(0, 2)
            # Create a Generator instance to write the message to the file
            g = Generator(fileh)
            Utils.set_cte_if_missing(msg)
            g.flatten(msg, unixfrom=True)
            # Add one more trailing newline for separation with the next message
            # to be appended to the mbox.
            print('\n', fileh)


# This stuff is used by pipermail.py:processUnixMailbox().  It provides an
# opportunity for the built-in archiver to scrub archived messages of nasty
# things like attachments and such...
def _archfactory(mailbox):
    # The factory gets a file object, but it also needs to have a MailList
    # object, so the clearest <wink> way to do this is to build a factory
    # function that has a reference to the mailbox object, which in turn holds
    # a reference to the mailing list.  Nested scopes would help here, BTW,
    # but we can't rely on them being around (e.g. Python 2.0).
    def scrubber(fp, mailbox=mailbox):
        msg = _safeparser(fp)
        if msg == '':
            return msg
        return mailbox.scrub(msg)
    return scrubber


class ArchiverMailbox(Mailbox):
    # This is a derived class which is instantiated with a reference to the
    # MailList object.  It is build such that the factory calls back into its
    # scrub() method, giving the scrubber module a chance to do its thing
    # before the message is archived.
    def __init__(self, fp, mlist):
        if mm_cfg.ARCHIVE_SCRUBBER:
            __import__(mm_cfg.ARCHIVE_SCRUBBER)
            self._scrubber = sys.modules[mm_cfg.ARCHIVE_SCRUBBER].process
        else:
            self._scrubber = None
        self._mlist = mlist
        if not isinstance(fp, str):
            fp = fp.name
        mailbox.mbox.__init__(self, fp, _archfactory(self))

    def scrub(self, msg):
        if self._scrubber:
            return self._scrubber(self._mlist, msg)
        else:
            return msg

    def skipping(self, flag):
        """ This method allows the archiver to skip over messages without
        scrubbing attachments into the attachments directory."""
        if flag:
            self.factory = _safeparser
        else:
            self.factory = _archfactory(self)