# Copyright (C) 2008-2014 by the Free Software Foundation, Inc.
#
# This file is part of GNU Mailman.
#
# GNU Mailman 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 3 of the License, or (at your option)
# any later version.
#
# GNU Mailman 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
# GNU Mailman.  If not, see <http://www.gnu.org/licenses/>.

"""Prototypical permalinking archiver."""

__all__ = [
    'Prototype',
    ]


import os
import errno
import logging

from datetime import timedelta
from flufl.lock import Lock, TimeOutError
from mailbox import Maildir
from mailman.config import config
from mailman.interfaces.archiver import IArchiver
from six.moves.urllib_parse import urljoin
from zope.interface import implementer


log = logging.getLogger('mailman.error')



@implementer(IArchiver)
class Prototype:
    """A prototype of a third party archiver.

    Mailman proposes a draft specification for interoperability between list
    servers and archivers: <http://wiki.list.org/display/DEV/Stable+URLs>.
    """

    name = 'prototype'
    is_enabled = False

    @staticmethod
    def list_url(mlist):
        """See `IArchiver`."""
        return mlist.domain.base_url

    @staticmethod
    def permalink(mlist, msg):
        """See `IArchiver`."""
        # It is the LMTP server's responsibility to ensure that the message
        # has a X-Message-ID-Hash header.  If it doesn't then there's no
        # permalink.
        message_id_hash = msg.get('x-message-id-hash')
        if message_id_hash is None:
            return None
        if isinstance(message_id_hash, bytes):
            message_id_hash = message_id_hash.decode('ascii')
        return urljoin(Prototype.list_url(mlist), message_id_hash)

    @staticmethod
    def archive_message(mlist, message):
        """See `IArchiver`.

        This archiver saves messages into a maildir.
        """
        archive_dir = os.path.join(config.ARCHIVE_DIR, 'prototype')
        try:
            os.makedirs(archive_dir, 0o775)
        except OSError as error:
            # If this already exists, then we're fine
            if error.errno != errno.EEXIST:
                raise

        # Maildir will throw an error if the directories are partially created
        # (for instance the toplevel exists but cur, new, or tmp do not)
        # therefore we don't create the toplevel as we did above.
        list_dir = os.path.join(archive_dir, mlist.fqdn_listname)
        mailbox = Maildir(list_dir, create=True, factory=None)
        lock_file = os.path.join(
            config.LOCK_DIR, '{0}-maildir.lock'.format(mlist.fqdn_listname))
        # Lock the maildir as Maildir.add() is not threadsafe.  Don't use the
        # context manager because it's not an error if we can't acquire the
        # archiver lock.  We'll just log the problem and continue.
        #
        # XXX 2012-03-14 BAW: When we extend the chain/pipeline architecture
        # to other runners, e.g. the archive runner, it would be better to let
        # any TimeOutError propagate up.  That would cause the message to be
        # re-queued and tried again later, rather than being discarded as
        # happens now below.
        lock = Lock(lock_file)
        try:
            lock.lock(timeout=timedelta(seconds=1))
            # Add the message to the maildir.  The return value could be used
            # to construct the file path if necessary.  E.g.
            #
            # os.path.join(archive_dir, mlist.fqdn_listname, 'new',
            #              message_key)
            mailbox.add(message)
        except TimeOutError:
            # Log the error and go on.
            log.error('Unable to acquire prototype archiver lock for {0}, '
                      'discarding: {1}'.format(
                          mlist.fqdn_listname,
                          message.get('message-id', 'n/a')))
        finally:
            lock.unlock(unconditionally=True)
