#!/usr/bin/env python2
# -*- coding: utf-8 -*-

# SAT plugin for OMEMO encryption
# Copyright (C) 2009-2018 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/>.

from sat.core.i18n import _
from sat.core.constants import Const as C
from sat.core.log import getLogger
from sat.core import exceptions
from twisted.internet import defer
from twisted.words.xish import domish
from twisted.words.protocols.jabber import jid
from twisted.words.protocols.jabber import error
from sat.memory import persistent
from functools import partial
import logging
import random
import base64
try:
    import omemo
    from omemo.extendedpublicbundle import ExtendedPublicBundle
    from omemo import wireformat
except ImportError:
    raise exceptions.MissingModule(
        u'Missing module omemo, please download/install it. You can use '
        u'"pip install omemo"'
    )

log = getLogger(__name__)

PLUGIN_INFO = {
    C.PI_NAME: u"OMEMO",
    C.PI_IMPORT_NAME: u"OMEMO",
    C.PI_TYPE: u"SEC",
    C.PI_PROTOCOLS: [u"XEP-0384"],
    C.PI_DEPENDENCIES: [u"XEP-0280", u"XEP-0334", u"XEP-0060"],
    C.PI_MAIN: u"OMEMO",
    C.PI_HANDLER: u"no",
    C.PI_DESCRIPTION: _(u"""Implementation of OMEMO"""),
}

NS_OMEMO = "eu.siacs.conversations.axolotl"
NS_OMEMO_DEVICES = NS_OMEMO + ".devicelist"
NS_OMEMO_BUNDLE = NS_OMEMO + ".bundles:{device_id}"
KEY_STATE = "STATE"
KEY_DEVICE_ID = "DEVICE_ID"
KEY_SESSION = "SESSION"
KEY_ACTIVE_DEVICES = "DEVICES"
KEY_INACTIVE_DEVICES = "DEVICES"


# we want to manage log emitted by omemo module ourseves

class SatHandler(logging.Handler):

    def emit(self, record):
        log.log(record.levelname, record.getMessage())

    @staticmethod
    def install():
        omemo_sm_logger = logging.getLogger("omemo.SessionManager")
        omemo_sm_logger.propagate = False
        omemo_sm_logger.addHandler(SatHandler())


SatHandler.install()


def b64enc(data):
    return base64.b64encode(bytes(bytearray(data))).decode("ASCII")


class OmemoStorage(omemo.Storage):

    def __init__(self, client, device_id, persistent_dict):
        """
        @param persistent_dict(persistent.LazyPersistentBinaryDict): object which will
            store data in SàT database
        """
        self.own_bare_jid_s = client.jid.userhost()
        self.device_id = device_id
        self.data = persistent_dict

    @property
    def is_async(self):
        return True

    def setCb(self, deferred, callback):
        """Associate Deferred and callback

        callback of omemo.Storage expect a boolean with success state then result
        Deferred on the other hand use 2 methods for callback and errback
        This method use partial to call callback with boolean then result when
        Deferred is called
        """
        deferred.addCallback(partial(callback, True))
        deferred.addErrback(partial(callback, False))

    def loadOwnData(self, callback):
        callback(True, {'own_bare_jid': self.own_bare_jid_s,
                        'own_device_id': self.device_id})

    def storeOwnData(self, callback, own_bare_jid, own_device_id):
        if own_bare_jid != self.own_bare_jid_s or own_device_id != self.device_id:
            raise exceptions.InternalError('bare jid or device id inconsistency!')
        callback(True, None)

    def loadState(self, callback):
        d = self.data.get(KEY_STATE)
        self.setCb(d, callback)

    def storeState(self, callback, state):
        d = self.data.force(KEY_STATE, state)
        self.setCb(d, callback)

    def loadSession(self, callback, bare_jid, device_id):
        key = u'\n'.join([KEY_SESSION, bare_jid, unicode(device_id)])
        d = self.data.get(key)
        self.setCb(d, callback)

    def storeSession(self, callback, bare_jid, device_id, session):
        key = u'\n'.join([KEY_SESSION, bare_jid, unicode(device_id)])
        d = self.data.force(key, session)
        self.setCb(d, callback)

    def loadActiveDevices(self, callback, bare_jid):
        key = u'\n'.join([KEY_ACTIVE_DEVICES, bare_jid])
        d = self.data.get(key, {})
        self.setCb(d, callback)

    def loadInactiveDevices(self, callback, bare_jid):
        key = u'\n'.join([KEY_INACTIVE_DEVICES, bare_jid])
        d = self.data.get(key, {})
        self.setCb(d, callback)

    def storeActiveDevices(self, callback, bare_jid, devices):
        key = u'\n'.join([KEY_ACTIVE_DEVICES, bare_jid])
        d = self.data.force(key, devices)
        self.setCb(d, callback)

    def storeInactiveDevices(self, callback, bare_jid, devices):
        key = u'\n'.join([KEY_INACTIVE_DEVICES, bare_jid])
        d = self.data.force(key, devices)
        self.setCb(d, callback)

    def isTrusted(self, callback, bare_jid, device):
        trusted = True
        callback(True, trusted)


class SatOTPKPolicy(omemo.OTPKPolicy):

    @staticmethod
    def decideOTPK(preKeyMessages):
        # always delete
        return False


class OmemoSession(object):
    """Wrapper to use omemo.OmemoSession with Deferred"""

    def __init__(self, session):
        self._session = session

    @property
    def state(self):
        return self._session.state

    @staticmethod
    def promise2Deferred(promise_):
        """Create a Deferred and fire it when promise is resolved

        @param promise_(promise.Promise): promise to convert
        @return (defer.Deferred): deferred instance linked to the promise
        """
        d = defer.Deferred()
        promise_.then(d.callback, d.errback)
        return d

    @classmethod
    def create(cls, client, storage, my_device_id = None):
        omemo_session_p = client._xep_0384_session = omemo.SessionManager.create(
            storage,
            SatOTPKPolicy,
            client.jid.userhost(),
            my_device_id)
        d = cls.promise2Deferred(omemo_session_p)
        d.addCallback(lambda session: cls(session))
        return d

    def newDeviceList(self, devices, jid):
        jid = jid.userhost()
        new_device_p = self._session.newDeviceList(devices, jid)
        return self.promise2Deferred(new_device_p)

    def getDevices(self, bare_jid=None):
        get_devices_p = self._session.getDevices(bare_jid=bare_jid)
        return self.promise2Deferred(get_devices_p)

    def buildSession(self, bare_jid, device, bundle):
        bare_jid = bare_jid.userhost()
        build_session_p = self._session.buildSession(bare_jid, device, bundle)
        return self.promise2Deferred(build_session_p)

    def encryptMessage(self, bare_jids, message, bundles=None, devices=None,
            always_trust = False):
        """Encrypt a message

        @param bare_jids(iterable[jid.JID]): destinees of the message
        @param message(unicode): message to encode
        @param bundles(dict[jid.JID, dict[int, ExtendedPublicBundle]):
            entities => devices => bundles map
        @param devices(iterable[int], None): devices to encode for
        @param always_trust(bool): TODO
        @return D(dict): encryption data
        """
        if isinstance(bare_jids, jid.JID):
            bare_jids = bare_jids.userhost()
        else:
            bare_jids = [e.userhost() for e in bare_jids]
        if bundles is not None:
            bundles = {e.userhost(): v for e, v in bundles.iteritems()}
        encrypt_mess_p = self._session.encryptMessage(
            bare_jids=bare_jids,
            plaintext=message.encode('utf-8'),
            bundles=bundles,
            devices=devices,
            always_trust=always_trust)
        return self.promise2Deferred(encrypt_mess_p)

    def decryptMessage(self, bare_jid, device, iv, message, is_pre_key_message,
                       payload=None, from_storage=False):
        bare_jid = bare_jid.userhost()
        decrypt_mess_p = self._session.decryptMessage(
            bare_jid=bare_jid,
            device=device,
            iv=iv,
            message=message,
            is_pre_key_message=is_pre_key_message,
            payload=payload,
            from_storage=from_storage)
        return self.promise2Deferred(decrypt_mess_p)


class OMEMO(object):
    def __init__(self, host):
        log.info(_(u"OMEMO plugin initialization"))
        self.host = host
        self._p_hints = host.plugins[u"XEP-0334"]
        self._p_carbons = host.plugins[u"XEP-0280"]
        self._p = host.plugins[u"XEP-0060"]
        host.trigger.add("MessageReceived", self._messageReceivedTrigger, priority=100050)
        host.trigger.add("sendMessageData", self._sendMessageDataTrigger)
        self.host.registerEncryptionPlugin(self, u"OMEMO", NS_OMEMO, 100)

    @defer.inlineCallbacks
    def profileConnected(self, client):
        # we first need to get devices ids (including our own)
        persistent_dict = persistent.LazyPersistentBinaryDict("XEP-0384", client.profile)
        # all known devices of profile
        devices = yield self.getDevices(client)
        # and our own device id
        device_id = yield persistent_dict.get(KEY_DEVICE_ID)
        if device_id is None:
            # we have a new device, we create device_id
            device_id = random.randint(1, 2**31-1)
            # we check that it's really unique
            while device_id in devices:
                device_id = random.randint(1, 2**31-1)
            # and we save it
            persistent_dict[KEY_DEVICE_ID] = device_id

        if device_id not in devices:
            devices.add(device_id)
            yield self.setDevices(client, devices)

        omemo_storage = OmemoStorage(client, device_id, persistent_dict)
        omemo_session = yield OmemoSession.create(client, omemo_storage, device_id)
        client._xep_0384_session = omemo_session
        client._xep_0384_device_id = device_id
        yield omemo_session.newDeviceList(devices, client.jid)
        if omemo_session.state.changed:
            log.info(_(u"Saving public bundle for this device ({device_id})").format(
                device_id=device_id))
            bundle = omemo_session.state.getPublicBundle()
            yield self.setBundle(client, bundle, device_id)

    ## XMPP PEP nodes manipulation

    # devices

    @defer.inlineCallbacks
    def getDevices(self, client, entity_jid=None):
        """Retrieve list of registered OMEMO devices

        @param entity_jid(jid.JID, None): get devices from this entity
            None to get our own devices
        @return (set(int)): list of devices
        """
        if entity_jid is not None:
            assert not entity_jid.resource
        devices = set()
        try:
            items, metadata = yield self._p.getItems(client, entity_jid, NS_OMEMO_DEVICES)
        except error.StanzaError as e:
            if e.condition == 'item-not-found':
                log.info(_(u"there is no node to handle OMEMO devices"))
                defer.returnValue(devices)

        if len(items) > 1:
            log.warning(_(u"OMEMO devices list is stored in more that one items, "
                          u"this is not expected"))
        if items:
            try:
                list_elt = next(items[0].elements(NS_OMEMO, 'list'))
            except StopIteration:
                log.warning(_(u"no list element found in OMEMO devices list"))
                return
            for device_elt in list_elt.elements(NS_OMEMO, 'device'):
                try:
                    device_id = int(device_elt['id'])
                except KeyError:
                    log.warning(_(u'device element is missing "id" attribute: {elt}')
                                .format(elt=device_elt.toXml()))
                except ValueError:
                    log.warning(_(u'invalid device id: {device_id}').format(
                        device_id=device_elt['id']))
                else:
                    devices.add(device_id)
        defer.returnValue(devices)

    def setDevicesEb(self, failure_):
        log.warning(_(u"Can't set devices: {reason}").format(reason=failure_))

    def setDevices(self, client, devices):
        list_elt = domish.Element((NS_OMEMO, 'list'))
        for device in devices:
            device_elt = list_elt.addElement('device')
            device_elt['id'] = unicode(device)
        d = self._p.sendItem(
            client, None, NS_OMEMO_DEVICES, list_elt, item_id=self._p.ID_SINGLETON)
        d.addErrback(self.setDevicesEb)
        return d

    # bundles

    @defer.inlineCallbacks
    def getBundles(self, client, entity_jid, devices_ids):
        """Retrieve public bundles of an entity devices

        @param entity_jid(jid.JID): bare jid of entity
        @param devices_id(iterable[int]): ids of the devices bundles to retrieve
        @return (dict[int, ExtendedPublicBundle]): bundles collection
            key is device_id
            value is parsed bundle
        """
        assert not entity_jid.resource
        bundles = {}
        for device_id in devices_ids:
            node = NS_OMEMO_BUNDLE.format(device_id=device_id)
            try:
                items, metadata = yield self._p.getItems(client, entity_jid, node)
            except Exception as e:
                log.warning(_(u"Can't get bundle for device {device_id}: {reason}")
                            .format(device_id=device_id, reason=e))
                continue
            if not items:
                log.warning(_(u"no item found in node {node}, can't get public bundle "
                              u"for device {device_id}").format(node=node,
                                                                device_id=device_id))
                continue
            if len(items) > 1:
                log.warning(_(u"more than one item found in {node}, "
                              u"this is not expected").format(node=node))
            item = items[0]
            try:
                bundle_elt = next(item.elements(NS_OMEMO, 'bundle'))
                signedPreKeyPublic_elt = next(bundle_elt.elements(
                    NS_OMEMO, 'signedPreKeyPublic'))
                signedPreKeySignature_elt = next(bundle_elt.elements(
                    NS_OMEMO, 'signedPreKeySignature'))
                identityKey_elt = next(bundle_elt.elements(
                    NS_OMEMO, 'identityKey'))
                prekeys_elt =  next(bundle_elt.elements(
                    NS_OMEMO, 'prekeys'))
            except StopIteration:
                log.warning(_(u"invalid bundle for device {device_id}, ignoring").format(
                    device_id=device_id))
                continue

            try:
                spkPublic = base64.b64decode(unicode(signedPreKeyPublic_elt))
                spkSignature = base64.b64decode(
                    unicode(signedPreKeySignature_elt))

                identityKey = base64.b64decode(unicode(identityKey_elt))
                spk = {
                    "key": wireformat.decodePublicKey(spkPublic),
                    "id": int(signedPreKeyPublic_elt['signedPreKeyId'])
                }
                ik = wireformat.decodePublicKey(identityKey)
                otpks = []
                for preKeyPublic_elt in prekeys_elt.elements(NS_OMEMO, 'preKeyPublic'):
                    preKeyPublic = base64.b64decode(unicode(preKeyPublic_elt))
                    otpk = {
                        "key": wireformat.decodePublicKey(preKeyPublic),
                        "id": int(preKeyPublic_elt['preKeyId'])
                    }
                    otpks.append(otpk)

            except Exception as e:
                log.warning(_(u"error while decoding key for device {device_id}: {msg}")
                            .format(device_id=device_id, msg=e))
                continue

            bundles[device_id] = ExtendedPublicBundle(ik, spk, spkSignature, otpks)

        defer.returnValue(bundles)

    def setBundleEb(self, failure_):
        log.warning(_(u"Can't set bundle: {reason}").format(reason=failure_))

    def setBundle(self, client, bundle, device_id):
        """Set public bundle for this device.

        @param bundle(ExtendedPublicBundle): bundle to publish
        """
        log.debug(_(u"updating bundle for {device_id}").format(device_id=device_id))
        bundle_elt = domish.Element((NS_OMEMO, 'bundle'))
        signedPreKeyPublic_elt = bundle_elt.addElement(
            "signedPreKeyPublic",
            content=b64enc(wireformat.encodePublicKey(bundle.spk['key'])))
        signedPreKeyPublic_elt['signedPreKeyId'] = unicode(bundle.spk['id'])

        bundle_elt.addElement(
            "signedPreKeySignature",
            content=b64enc(bundle.spk_signature))

        bundle_elt.addElement(
            "identityKey",
            content=b64enc(wireformat.encodePublicKey(bundle.ik)))

        prekeys_elt = bundle_elt.addElement('prekeys')
        for otpk in bundle.otpks:
            preKeyPublic_elt = prekeys_elt.addElement(
                'preKeyPublic',
                content=b64enc(wireformat.encodePublicKey(otpk["key"])))
            preKeyPublic_elt['preKeyId'] = unicode(otpk['id'])

        node = NS_OMEMO_BUNDLE.format(device_id=device_id)
        d = self._p.sendItem(client, None, node, bundle_elt, item_id=self._p.ID_SINGLETON)
        d.addErrback(self.setBundleEb)
        return d

    ## triggers

    @defer.inlineCallbacks
    def encryptMessage(self, client, entity_bare_jid, message):
        omemo_session = client._xep_0384_session
        devices = yield self.getDevices(client, entity_bare_jid)
        omemo_session.newDeviceList(devices, entity_bare_jid)
        bundles = yield self.getBundles(client, entity_bare_jid, devices)
        encrypted = yield omemo_session.encryptMessage(
            entity_bare_jid,
            message,
            {entity_bare_jid: bundles})
        defer.returnValue(encrypted)

    @defer.inlineCallbacks
    def _messageReceivedTrigger(self, client, message_elt, post_treat):
        if message_elt.getAttribute("type") == C.MESS_TYPE_GROUPCHAT:
            defer.returnValue(True)
        try:
            encrypted_elt = next(message_elt.elements(NS_OMEMO, u"encrypted"))
        except StopIteration:
            # no OMEMO message here
            defer.returnValue(True)

        # we have an encrypted message let's decrypt it
        from_jid = jid.JID(message_elt['from'])
        omemo_session = client._xep_0384_session
        device_id = client._xep_0384_device_id
        try:
            header_elt = next(encrypted_elt.elements(NS_OMEMO, u'header'))
            iv_elt = next(header_elt.elements(NS_OMEMO, u'iv'))
        except StopIteration:
            log.warning(_(u"Invalid OMEMO encrypted stanza, ignoring: {xml}")
                .format(xml=message_elt.toXml()))
            defer.returnValue(False)
        try:
            s_device_id = header_elt['sid']
        except KeyError:
            log.warning(_(u"Invalid OMEMO encrypted stanza, missing sender device ID, "
                          u"ignoring: {xml}")
                .format(xml=message_elt.toXml()))
            defer.returnValue(False)
        try:
            key_elt = next((e for e in header_elt.elements(NS_OMEMO, u'key')
                            if int(e[u'rid']) == device_id))
        except StopIteration:
            log.warning(_(u"This OMEMO encrypted stanza has not been encrypted"
                          u"for our device ({device_id}): {xml}").format(
                          device_id=device_id, xml=encrypted_elt.toXml()))
            defer.returnValue(False)
        except ValueError as e:
            log.warning(_(u"Invalid recipient ID: {msg}".format(msg=e)))
            defer.returnValue(False)
        is_pre_key = C.bool(key_elt.getAttribute('prekey', 'false'))
        payload_elt = next(encrypted_elt.elements(NS_OMEMO, u'payload'), None)

        try:
            cipher, plaintext = yield omemo_session.decryptMessage(
                bare_jid=from_jid.userhostJID(),
                device=s_device_id,
                iv=base64.b64decode(bytes(iv_elt)),
                message=base64.b64decode(bytes(key_elt)),
                is_pre_key_message=is_pre_key,
                payload=base64.b64decode(bytes(payload_elt))
                    if payload_elt is not None else None,
                from_storage=False
            )
        except Exception as e:
            log.error(_(u"Can't decrypt message: {reason}\n{xml}").format(
                reason=e, xml=message_elt.toXml()))
            defer.returnValue(False)
        if omemo_session.state.changed:
            bundle = omemo_session.state.getPublicBundle()
            # we don't wait for the Deferred (i.e. no yield) on purpose
            # there is no need to block the whole message workflow while
            # updating the bundle
            self.setBundle(client, bundle, device_id)

        message_elt.children.remove(encrypted_elt)
        if plaintext:
            message_elt.addElement("body", content=plaintext.decode('utf-8'))
        defer.returnValue(True)

    @defer.inlineCallbacks
    def _sendMessageDataTrigger(self, client, mess_data):
        encryption = mess_data.get(C.MESS_KEY_ENCRYPTION)
        if encryption is None or encryption['plugin'].namespace != NS_OMEMO:
            return
        message_elt = mess_data["xml"]
        to_jid = mess_data["to"].userhostJID()
        log.debug(u"encrypting message")
        body = None
        for child in list(message_elt.children):
            if child.name == "body":
                # we remove all unencrypted body,
                # and will only encrypt the first one
                if body is None:
                    body = child
                message_elt.children.remove(child)
            elif child.name == "html":
                # we don't want any XHTML-IM element
                message_elt.children.remove(child)

        if body is None:
            log.warning(u"No message found")
            return

        encryption_data = yield self.encryptMessage(client, to_jid, unicode(body))

        encrypted_elt = message_elt.addElement((NS_OMEMO, 'encrypted'))
        header_elt = encrypted_elt.addElement('header')
        header_elt['sid'] = unicode(encryption_data['sid'])
        bare_jid_s = to_jid.userhost()

        for message in (m for m in encryption_data['messages']
                        if m['bare_jid'] == bare_jid_s):
            key_elt = header_elt.addElement(
                'key',
                content=b64enc(message['message']))
            key_elt['rid'] = unicode(message['rid'])
            if message['pre_key']:
                key_elt['prekey'] = 'true'

        header_elt.addElement(
            'iv',
            content=b64enc(encryption_data['iv']))
        try:
            encrypted_elt.addElement(
                'payload',
                content=b64enc(encryption_data['payload']))
        except KeyError:
            pass