# -*- coding: utf-8 -*-
# __init__.py
# Copyright (C) 2013 LEAP
#
# 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 3 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, see <http://www.gnu.org/licenses/>.

"""
SMTP relay helper function.
"""
import logging

from twisted.internet import reactor
from twisted.internet.error import CannotListenError

logger = logging.getLogger(__name__)

from leap.common.events import proto, signal
from leap.mail.smtp.smtprelay import SMTPFactory


def setup_smtp_relay(port, keymanager, smtp_host, smtp_port,
                     smtp_cert, smtp_key, encrypted_only):
    """
    Setup SMTP relay to run with Twisted.

    This function sets up the SMTP relay configuration and the Twisted
    reactor.

    :param port: The port in which to run the server.
    :type port: int
    :param keymanager: A Key Manager from where to get recipients' public
                       keys.
    :type keymanager: leap.common.keymanager.KeyManager
    :param smtp_host: The hostname of the remote SMTP server.
    :type smtp_host: str
    :param smtp_port:  The port of the remote SMTP server.
    :type smtp_port: int
    :param smtp_cert: The client certificate for authentication.
    :type smtp_cert: str
    :param smtp_key: The client key for authentication.
    :type smtp_key: str
    :param encrypted_only: Whether the SMTP relay should send unencrypted mail
                           or not.
    :type encrypted_only: bool

    :returns: tuple of SMTPFactory, twisted.internet.tcp.Port
    """
    # The configuration for the SMTP relay is a dict with the following
    # format:
    #
    # {
    #     'host': '<host>',
    #     'port': <int>,
    #     'cert': '<cert path>',
    #     'key': '<key path>',
    #     'encrypted_only': <True/False>
    # }
    config = {
        'host': smtp_host,
        'port': smtp_port,
        'cert': smtp_cert,
        'key': smtp_key,
        'encrypted_only': encrypted_only
    }

    # configure the use of this service with twistd
    factory = SMTPFactory(keymanager, config)
    try:
        tport = reactor.listenTCP(port, factory,
                                  interface="localhost")
        signal(proto.SMTP_SERVICE_STARTED, str(smtp_port))
        return factory, tport
    except CannotListenError:
        logger.error("STMP Service failed to start: "
                     "cannot listen in port %s" % (
                         smtp_port,))
        signal(proto.SMTP_SERVICE_FAILED_TO_START, str(smtp_port))
    except Exception as exc:
        logger.error("Unhandled error while launching smtp relay service")
        logger.exception(exc)