# -*- coding: utf-8 -*-
# Copyright 2010-2013 Kolab Systems AG (http://www.kolabsys.com)
#
# Jeroen van Meeuwen (Kolab Systems) <vanmeeuwen a kolabsys.com>
#
# 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; version 3 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 Library 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.
#

import os
import tempfile
import time

from email import message_from_string
from email.MIMEBase import MIMEBase
from email.MIMEText import MIMEText
from email.parser import Parser
from email.utils import formataddr
from email.utils import getaddresses

import email.mime.application
import email.mime.multipart
import email.mime.text
import email.encoders
import gnupg

import modules

import pykolab

from pykolab.translate import _

log = pykolab.getLogger('pykolab.wallace')
conf = pykolab.getConf()

mybasepath = '/var/spool/pykolab/wallace/gpgencrypt/'

def __init__():
    modules.register('gpgencrypt', execute, description=description())

def description():
    return """Encrypt messages to the recipient(s)."""

def pgp_mime(msg, recepients):
    gpg = gnupg.GPG(gnupghome='/var/lib/kolab/.gnupg', verbose=conf.debuglevel > 8)
    gpg.encoding = 'utf-8'

    msg = msg

    msg_boundary = str(msg.get_boundary())
    msg_content_type = str(msg.get_content_type())
    payload = msg.get_payload()

    content = "Content-Type: " + msg_content_type + ";" + "\n boundary=\"" + msg_boundary + "\"\n\n" + payload
    encrypted_content = gpg.encrypt(content, recepients, always_trust=True)
    msg.set_type("multipart/encrypted")
    msg.set_param("protocol","application/pgp-encrypted")

    msg_boundary_gpg = "--boundary-gpg-encryption-42"

    msg_preamble = "This is an OpenPGP/MIME encrypted message (RFC 4880 and 3156)\n\
" + msg_boundary_gpg + "\n\
Content-Type: application/pgp-encrypted\n\
Content-Description: PGP/MIME version identification\n\
\n\
Version: 1\n\
\n\
" + msg_boundary_gpg + "\n\
Content-Type: application/octet-stream; name=\"encrypted.asc\"\n\
Content-Description: OpenPGP encrypted message\n\
Content-Disposition: inline; filename=\"encrypted.asc\"\n\n"

    msg.set_boundary(msg_boundary_gpg)
    msg.set_payload(msg_preamble + str(encrypted_content) + "\n" + msg_boundary_gpg)

    return msg

def execute(*args, **kw):
    if not os.path.isdir(mybasepath):
        os.makedirs(mybasepath)

    for stage in ['incoming', 'ACCEPT' ]:
        if not os.path.isdir(os.path.join(mybasepath, stage)):
            os.makedirs(os.path.join(mybasepath, stage))

    # TODO: Test for correct call.
    filepath = args[0]

    if kw.has_key('stage'):
        log.debug(_("Issuing callback after processing to stage %s") % (kw['stage']), level=8)
        log.debug(_("Testing cb_action_%s()") % (kw['stage']), level=8)
        if hasattr(modules, 'cb_action_%s' % (kw['stage'])):
            log.debug(_("Attempting to execute cb_action_%s()") % (kw['stage']), level=8)
            exec('modules.cb_action_%s(%r, %r)' % (kw['stage'],'gpgencrypt',filepath))

    log.debug(_("Executing module gpgencrypt for %r, %r") % (args, kw), level=8)

    new_filepath = os.path.join('/var/spool/pykolab/wallace/gpgencrypt/incoming', os.path.basename(filepath))

    if not filepath == new_filepath:
        log.debug("Renaming %r to %r" % (filepath, new_filepath))
        os.rename(filepath, new_filepath)
        filepath = new_filepath

    # parse message headers
    # @TODO: make sure we can use True as the 2nd argument here
    message = Parser().parse(open(filepath, 'r'), True)

    # Possible gpgencrypt answers are limited to ACCEPT only
    answers = [ 'ACCEPT' ]

# from Mail::GnuPG.is_encrypted
# 
#sub is_encrypted {
#  my ($self,$entity) = @_;
#  return 1
#    if (($entity->effective_type =~ m!multipart/encrypted!)
#    ||
#    ($entity->as_string =~ m!^-----BEGIN PGP MESSAGE-----!m));
#  return 0;
#}

    message_already_encrypted = False

    for part in message.walk():
        if part.get_content_type() in [ "application/pgp-encrypted" ]:
            message_already_encrypted = True
            log.debug(_("Message is already encrypted (app/pgp-enc content-type)"), level=8)

    if message.get_content_type() in [ "multipart/encrypted" ]:
        message_already_encrypted = True
        log.debug(_("Message already encrypted by main content-type header"), level=8)

    if message_already_encrypted:
        return filepath

    try:
        # What are recipient addresses to encrypt to (bitmask)?
        # 1 - organization key
        # 2 - envelope to
        # 4 - to
        # 8 - cc
        # 16 - resent-to
        # 32 - resent-cc
        encrypt_to_rcpts = conf.get('wallace', 'gpgencrypt_to_rcpts')
        if encrypt_to_rcpts == None:
            encrypt_to_rcpts = 14
        else:
            encrypt_to_rcpts = (int)(encrypt_to_rcpts)

        # Only encrypt to keys that are trusted
        strict_crypt = conf.get('wallace', 'gpgencrypt_strict')
        if strict_crypt == None:
            strict_crypt = False

        # Organization key ID
        if encrypt_to_rcpts & 1:
            encrypt_to_org = conf.get('wallace', 'gpgencrypt_to_org_key')
            if encrypt_to_org == None and encrypt_to_rcpts & 1:
                if strict_crypt:
                    log.error(_("Configured to encrypt to a key not configured, and strict policy enabled. Bailing out."))
                    modules.cb_action_REJECT('gpgencrypt',filepath)
                else:
                    log.error(_("Configured to encrypt to a key not configured, but continuing anyway (see 'gpgencrypt_strict')."))
        else:
            encrypt_to_org = []

        # Bounce the message if encryption fails?
        force_crypt = conf.get('wallace', 'gpgencrypt_force')
        if force_crypt == None:
            force_crypt = False

        # Retrieve keys from remote server(s) automatically?
        retrieve_keys = conf.get('wallace', 'gpgencrypt_retrieve_keys')
        if retrieve_keys == None:
            retrieve_keys = False

        if retrieve_keys:
            gpgserver = conf.get('wallace', 'gpgencrypt_server')
            if gpgserver == None:
                gpgserver = 'pgp.mit.edu'

        encrypt_to = []
        if encrypt_to_rcpts & 2:
            encrypt_to.extend(message.get_all('X-Kolab-To', []))

        if encrypt_to_rcpts & 4:
            encrypt_to.extend(message.get_all('to', []))

        if encrypt_to_rcpts & 8:
            encrypt_to.extend(message.get_all('cc', []))

        if encrypt_to_rcpts & 16:
            encrypt_to.extend(message.get_all('resent-to', []))

        if encrypt_to_rcpts & 32:
            encrypt_to.extend(message.get_all('resent-cc', []))

        recipients = [address for displayname,address in getaddresses(encrypt_to)]

        log.debug(_("Recipients: %r") % (recipients))

        # Split between recipients we can encrypt for/to, and ones we can not
        encrypt_rcpts = []
        nocrypt_rcpts = []


        gpg = gnupg.GPG(gnupghome='/var/lib/kolab/.gnupg', verbose=conf.debuglevel > 8)
        gpg.encoding = 'utf-8'

        local_keys = gpg.list_keys()
        log.debug(_("Current keys: %r") % (local_keys), level=8)

        for recipient in recipients:
            key_local = False

            log.debug(_("Retrieving key for recipient: %r") % (recipient))

            for key in local_keys:
                for address in [x for x in [address for displayname,address in getaddresses(key['uids'])] if x == recipient]:
                    log.debug(_("Found matching address %r") % (address))
                    key_local = key['keyid']

            if key_local == False:
                if retrieve_keys:
                    remote_keys = gpg.search_keys(recipient, gpgserver)
                    if len(remote_keys) == 1:
                        for address in [x for x in [address for displayname,address in getaddresses(remote_keys[0]['uids'])] if x == recipient]:
                            log.debug(_("Found matching address %r in remote keys") % (address))
                            gpg.recv_keys(gpgserver, remote_keys[0]['keyid'])
                            local_keys = gpg.list_keys()
                    else:
                        nocrypt_rcpts.append(recipient)

            for key in local_keys:
                for address in [x for x in [address for displayname,address in getaddresses(key['uids'])] if x == recipient]:
                    log.debug(_("Found matching address %r") % (address))
                    key_local = key['keyid']
            if not key_local == False:
                encrypt_rcpts.append(key_local)

        payload = message.get_payload()
        #print "payload:", payload
        if len(encrypt_rcpts) < 1:
            return filepath

        if "multipart" in message.get_content_type():

            log.debug(_("Mime Message - we need to build multipart/encrypted structure"), level=8)

            msg = message
            enc_mime_message = pgp_mime(msg, encrypt_rcpts)

            message = enc_mime_message

        else:

            log.debug(_("No Mime Message - encypt plain"), level=8)

            encrypted_data = gpg.encrypt(payload, encrypt_rcpts, always_trust=True)
            encrypted_string = str(encrypted_data)

            message.set_payload(encrypted_string)

            message.add_header('X-wallace-gpg-encrypted', 'true')

        (fp, new_filepath) = tempfile.mkstemp(dir="/var/spool/pykolab/wallace/gpgencrypt/ACCEPT")
        os.write(fp, message.as_string())
        os.close(fp)
        os.unlink(filepath)

        exec('modules.cb_action_%s(%r, %r)' % ('ACCEPT','gpgencrypt', new_filepath))
    except Exception, errmsg:
        log.error(_("An error occurred: %r") % (errmsg))
        if conf.debuglevel > 8:
            import traceback
            traceback.print_exc()