#!/usr/bin/python
# -*- coding: utf-8 -*-

# SAT plugin for OTR encryption
# Copyright (C) 2009, 2010, 2011, 2012, 2013, 2014 Jérôme Poisson (goffi@goffi.org)

# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero 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 Affero General Public License for more details.

# You should have received a copy of the GNU Affero General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

# XXX: thanks to Darrik L Mazey for his documentation (https://blog.darmasoft.net/2013/06/30/using-pure-python-otr.html)
#      this implentation is based on it

from sat.core.i18n import _
from sat.core.log import getLogger
from sat.core import exceptions
log = getLogger(__name__)
from twisted.words.protocols.jabber import jid
from twisted.python import failure
from twisted.internet import defer
import potr
from sat.memory import persistent

NS_OTR = "otr_plugin"
PRIVATE_KEY = "PRIVATE KEY"

DEFAULT_POLICY_FLAGS = {
  'ALLOW_V1':False,
  'ALLOW_V2':True,
  'REQUIRE_ENCRYPTION':True,
}

PLUGIN_INFO = {
    "name": "OTR",
    "import_name": "OTR",
    "type": "SEC",
    "protocols": [],
    "dependencies": [],
    "main": "OTR",
    "handler": "no",
    "description": _("""Implementation of OTR""")
}


class Context(potr.context.Context):

    def __init__(self, host, account, other_jid):
        super(Context, self).__init__(account, other_jid)
        self.host = host

    def getPolicy(self, key):
        if key in DEFAULT_POLICY_FLAGS:
            return DEFAULT_POLICY_FLAGS[key]
        else:
            return False

    def inject(self, msg_str, appdata=None):
        assert isinstance(self.peer, jid.JID)
        msg = msg_str.decode('utf-8')
        client = self.user.client
        log.debug(u'inject(%s, appdata=%s, to=%s)' % (msg, appdata, self.peer))
        mess_data = {'message': msg,
                     'type': 'chat',
                     'from': client.jid,
                      'to': self.peer,
                      'subject': None,
                    }
        self.host.generateMessageXML(mess_data)
        client.xmlstream.send(mess_data['xml'])

    def setState(self, state):
        old_state = self.state
        super(Context, self).setState(state)
        log.debug(u"setState: %s (old_state=%s) " % (state, old_state))

        if state == potr.context.STATE_PLAINTEXT:
            feedback = _(u"/!\\ conversation with %(other_jid)s is now UNENCRYPTED") % {'other_jid': self.peer.full()}
        elif state == potr.context.STATE_ENCRYPTED:
            try:
                fingerprint, trusted = self.getCurrentTrust()
            except TypeError:
                trusted = False
            trusted_str = _(u"trusted") if trusted else _(u"untrusted")

            if old_state == potr.context.STATE_ENCRYPTED:
                feedback = _(u"%(trusted)s OTR conversation with %(other_jid)s REFRESHED") % {'trusted': trusted_str, 'other_jid': self.peer.full()}
            else:
                feedback = _(u"%(trusted)s Encrypted OTR conversation started with %(other_jid)s") % {'trusted': trusted_str, 'other_jid': self.peer.full()}
        elif state == potr.context.STATE_FINISHED:
            feedback = _(u"OTR conversation with %(other_jid)s is FINISHED") % {'other_jid': self.peer.full()}
        else:
            log.error(_(u"Unknown OTR state"))
            return

        client = self.user.client
        # FIXME: newMessage should manage system message, so they don't appear as coming from the contact
        self.host.bridge.newMessage(client.jid.full(),
                                    feedback,
                                    mess_type="headline",
                                    to_jid=self.peer.full(),
                                    extra={},
                                    profile=client.profile)
        # TODO: send signal to frontends


class Account(potr.context.Account):

    def __init__(self, host, client):
        log.debug(u"new account: %s" % client.jid)
        super(Account, self).__init__(client.jid, "xmpp", 1024)
        self.host = host
        self.client = client

    def loadPrivkey(self):
        log.debug(u"loadPrivkey")
        return self.client.otr_priv_key

    def savePrivkey(self):
        log.debug(u"savePrivkey")
        priv_key = self.getPrivkey().serializePrivateKey()
        d = self.host.memory.encryptValue(priv_key, self.client.profile)
        def save_encrypted_key(encrypted_priv_key):
            self.client.otr_data[PRIVATE_KEY] = encrypted_priv_key
        d.addCallback(save_encrypted_key)


class ContextManager(object):

    def __init__(self, host, client):
        self.host = host
        self.account = Account(host, client)
        self.contexts = {}

    def startContext(self, other_jid):
        assert isinstance(other_jid, jid.JID)
        context = self.contexts.setdefault(other_jid, Context(self.host, self.account, other_jid))
        return context

    def getContextForUser(self, other):
        log.debug(u"getContextForUser [%s]" % other)
        return self.startContext(other)


class OTR(object):

    def __init__(self, host):
        log.info(_(u"OTR plugin initialization"))
        self.host = host
        self.context_managers = {}
        host.trigger.add("MessageReceived", self.MessageReceivedTrigger, priority=100000)
        host.trigger.add("sendMessage", self.sendMessageTrigger, priority=100000)

    @defer.inlineCallbacks
    def profileConnected(self, profile):
        client = self.host.getClient(profile)
        self.context_managers[profile] = ContextManager(self.host, client)
        client.otr_data = persistent.PersistentBinaryDict(NS_OTR, profile)
        yield client.otr_data.load()
        encrypted_priv_key = client.otr_data.get(PRIVATE_KEY, None)
        if encrypted_priv_key is not None:
            priv_key = yield self.host.memory.decryptValue(encrypted_priv_key, profile)
            client.otr_priv_key = potr.crypt.PK.parsePrivateKey(priv_key)[0]
        else:
            client.otr_priv_key = None

    def _receivedTreatment(self, data, profile):
        from_jid = jid.JID(data['from'])
        log.debug(u"_receivedTreatment [from_jid = %s]" % from_jid)
        otrctx = self.context_managers[profile].getContextForUser(from_jid)
        encrypted = True

        try:
            res = otrctx.receiveMessage(data['body'].encode('utf-8'))
        except potr.context.UnencryptedMessage:
            if otrctx.state == potr.context.STATE_ENCRYPTED:
                log.warning(u"Received unencrypted message in an encrypted context (from %(jid)s)" % {'jid': from_jid.full()})
                client = self.host.getClient(profile)
                self.host.bridge.newMessage(from_jid.full(),
                                            _(u"WARNING: received unencrypted data in a supposedly encrypted context"),
                                            mess_type="headline", # FIXME: add message type for internal informations
                                            to_jid=client.jid.full(),
                                            extra={},
                                            profile=client.profile)
            encrypted = False

        if not encrypted:
            return data
        else:
            if res[0] != None:
                # decrypted messages handling.
                # receiveMessage() will return a tuple, the first part of which will be the decrypted message
                data['body'] = res[0].decode('utf-8')
                raise failure.Failure(exceptions.SkipHistory()) # we send the decrypted message to frontends, but we don't want it in history
            else:
                raise failure.Failure(exceptions.CancelError()) # no message at all (no history, no signal)

    def MessageReceivedTrigger(self, message, post_treat, profile):
        post_treat.addCallback(self._receivedTreatment, profile)
        return True

    def sendMessageTrigger(self, mess_data, pre_xml_treatments, post_xml_treatments, profile):
        to_jid = mess_data['to']
        if mess_data['type'] != 'groupchat' and not to_jid.resource:
            to_jid.resource = self.host.memory.getLastResource(to_jid, profile) # FIXME: it's dirty, but frontends don't manage resources correctly now, refactoring is planed
        otrctx = self.context_managers[profile].getContextForUser(to_jid)
        if mess_data['type'] != 'groupchat' and otrctx.state == potr.context.STATE_ENCRYPTED:
            log.debug(u"encrypting message")
            otrctx.sendMessage(0, mess_data['message'].encode('utf-8'))
            client = self.host.getClient(profile)
            self.host.sendMessageToBridge(mess_data, client)
            return False
        else:
            log.debug(u"sending message unencrypted")
            return True