# Copyright (C) 2007 Tomasz Melcer <liori AT exroot.org>
#                    Travis Shirk <travis AT pobox.com>
# Copyright (C) 2007-2014 Yann Leboulanger <asterix AT lagaule.org>
# Copyright (C) 2008 Brendan Taylor <whateley AT gmail.com>
#                    Jonathan Schleifer <js-gajim AT webkeks.org>
# Copyright (C) 2008-2009 Stephan Erb <steve-e AT h3c.de>
#
# This file is part of Gajim.
#
# Gajim 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 only.
#
# Gajim 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 Gajim. If not, see <http://www.gnu.org/licenses/>.

"""
Module containing all XEP-115 (Entity Capabilities) related classes

Basic Idea:
CapsCache caches features to hash relationships. The cache is queried
through ClientCaps objects which are hold by contact instances.
"""

import base64
import hashlib
import logging
from collections import namedtuple

import nbxmpp
from nbxmpp.const import Affiliation
from nbxmpp import (NS_XHTML_IM, NS_ESESSION, NS_CHATSTATES,
    NS_JINGLE_ICE_UDP, NS_JINGLE_RTP_AUDIO, NS_JINGLE_RTP_VIDEO,
    NS_JINGLE_FILE_TRANSFER_5)
# Features where we cannot safely assume that the other side supports them
FEATURE_BLACKLIST = [NS_CHATSTATES, NS_XHTML_IM, NS_ESESSION,
    NS_JINGLE_ICE_UDP, NS_JINGLE_RTP_AUDIO, NS_JINGLE_RTP_VIDEO,
    NS_JINGLE_FILE_TRANSFER_5]

log = logging.getLogger('gajim.c.caps_cache')

# Query entry status codes
NEW = 0
QUERIED = 1
CACHED = 2 # got the answer
FAKED = 3 # allow NullClientCaps to behave as it has a cached item

################################################################################
### Public API of this module
################################################################################

capscache = None
muc_caps_cache = None
def initialize(logger):
    """
    Initialize this module
    """
    global capscache
    global muc_caps_cache
    capscache = CapsCache(logger)
    muc_caps_cache = MucCapsCache()

def client_supports(client_caps, requested_feature):
    lookup_item = client_caps.get_cache_lookup_strategy()
    cache_item = lookup_item(capscache)

    supported_features = cache_item.features
    if requested_feature in supported_features:
        return True
    if not supported_features and cache_item.status in (NEW, QUERIED, FAKED):
        # assume feature is supported, if we don't know yet, what the client
        # is capable of
        return requested_feature not in FEATURE_BLACKLIST
    return False

def get_client_identity(client_caps):
    lookup_item = client_caps.get_cache_lookup_strategy()
    cache_item = lookup_item(capscache)

    for identity in cache_item.identities:
        if identity.get('category') == 'client':
            return identity.get('type')

def create_suitable_client_caps(node, caps_hash, hash_method, fjid=None):
    """
    Create and return a suitable ClientCaps object for the given node,
    caps_hash, hash_method combination.
    """
    if not node or not caps_hash:
        if fjid:
            client_caps = NoClientCaps(fjid)
        else:
            # improper caps, ignore client capabilities.
            client_caps = NullClientCaps()
    elif not hash_method:
        client_caps = OldClientCaps(caps_hash, node)
    else:
        client_caps = ClientCaps(caps_hash, node, hash_method)
    return client_caps

def compute_caps_hash(identities, features, dataforms=None, hash_method='sha-1'):
    """
    Compute caps hash according to XEP-0115, V1.5

    dataforms are nbxmpp.DataForms objects as common.dataforms don't allow several
    values without a field type list-multi
    """
    if dataforms is None:
        dataforms = []

    def sort_identities_key(i):
        return (i['category'], i.get('type', ''), i.get('xml:lang', ''))

    def sort_dataforms_key(dataform):
        f = dataform.getField('FORM_TYPE')
        return (bool(f), f.getValue())

    S = ''
    identities.sort(key=sort_identities_key)
    for i in identities:
        c = i['category']
        type_ = i.get('type', '')
        lang = i.get('xml:lang', '')
        name = i.get('name', '')
        S += '%s/%s/%s/%s<' % (c, type_, lang, name)
    features.sort()
    for f in features:
        S += '%s<' % f
    dataforms.sort(key=sort_dataforms_key)
    for dataform in dataforms:
        # fields indexed by var
        fields = {}
        for f in dataform.getChildren():
            fields[f.getVar()] = f
        form_type = fields.get('FORM_TYPE')
        if form_type:
            S += form_type.getValue() + '<'
            del fields['FORM_TYPE']
        for var in sorted(fields.keys()):
            S += '%s<' % var
            values = sorted(fields[var].getValues())
            for value in values:
                S += '%s<' % value

    if hash_method == 'sha-1':
        hash_ = hashlib.sha1(S.encode('utf-8'))
    elif hash_method == 'md5':
        hash_ = hashlib.md5(S.encode('utf-8'))
    else:
        return ''
    return base64.b64encode(hash_.digest()).decode('utf-8')


################################################################################
### Internal classes of this module
################################################################################

class AbstractClientCaps:
    """
    Base class representing a client and its capabilities as advertised by a
    caps tag in a presence
    """
    def __init__(self, caps_hash, node):
        self._hash = caps_hash
        self._node = node
        self._hash_method = None

    def get_discover_strategy(self):
        return self._discover

    def _discover(self, connection, jid):
        """
        To be implemented by subclasses
        """
        raise NotImplementedError

    def get_cache_lookup_strategy(self):
        return self._lookup_in_cache

    def _lookup_in_cache(self, caps_cache):
        """
        To be implemented by subclasses
        """
        raise NotImplementedError

    def get_hash_validation_strategy(self):
        return self._is_hash_valid

    def _is_hash_valid(self, identities, features, dataforms):
        """
        To be implemented by subclasses
        """
        raise NotImplementedError


class ClientCaps(AbstractClientCaps):
    """
    The current XEP-115 implementation
    """
    def __init__(self, caps_hash, node, hash_method):
        AbstractClientCaps.__init__(self, caps_hash, node)
        assert hash_method != 'old'
        self._hash_method = hash_method

    def _lookup_in_cache(self, caps_cache):
        return caps_cache[(self._hash_method, self._hash)]

    def _discover(self, connection, jid):
        connection.get_module('Discovery').disco_contact(
            jid, '%s#%s' % (self._node, self._hash))

    def _is_hash_valid(self, identities, features, dataforms):
        computed_hash = compute_caps_hash(
            identities, features, dataforms=dataforms,
            hash_method=self._hash_method)
        return computed_hash == self._hash


class OldClientCaps(AbstractClientCaps):
    """
    Old XEP-115 implementation. Kept around for background compatibility
    """
    def __init__(self, caps_hash, node):
        AbstractClientCaps.__init__(self, caps_hash, node)
        self._hash_method = 'old'

    def _lookup_in_cache(self, caps_cache):
        return caps_cache[('old', self._node + '#' + self._hash)]

    def _discover(self, connection, jid):
        connection.get_module('Discovery').disco_contact(jid)

    def _is_hash_valid(self, identities, features, dataforms):
        return True

class NoClientCaps(AbstractClientCaps):
    """
    For clients that don't support XEP-0115
    """
    def __init__(self, fjid):
        AbstractClientCaps.__init__(self, fjid, fjid)
        self._hash_method = 'no'

    def _lookup_in_cache(self, caps_cache):
        return caps_cache[('no', self._node)]

    def _discover(self, connection, jid):
        connection.get_module('Discovery').disco_contact(jid)

    def _is_hash_valid(self, identities, features, dataforms):
        return True

class NullClientCaps(AbstractClientCaps):
    """
    This is a NULL-Object to streamline caps handling if a client has not
    advertised any caps or has advertised them in an improper way

    Assumes (almost) everything is supported.
    """
    _instance = None
    def __new__(cls, *args, **kwargs):
        """
        Make it a singleton.
        """
        if not cls._instance:
            cls._instance = super(NullClientCaps, cls).__new__(
                    cls, *args, **kwargs)
        return cls._instance

    def __init__(self):
        AbstractClientCaps.__init__(self, None, None)
        self._hash_method = 'dummy'

    def _lookup_in_cache(self, caps_cache):
        # lookup something which does not exist to get a new CacheItem created
        cache_item = caps_cache[('dummy', '')]
        # Mark the item as cached so that protocol/caps.py does not update it
        cache_item.status = FAKED
        return cache_item

    def _discover(self, connection, jid):
        pass

    def _is_hash_valid(self, identities, features, dataforms):
        return False


class CapsCache:
    """
    This object keeps the mapping between caps data and real disco features they
    represent, and provides simple way to query that info
    """
    def __init__(self, logger=None):
        # our containers:
        # __cache is a dictionary mapping: pair of hash method and hash maps
        #   to CapsCacheItem object
        # __CacheItem is a class that stores data about particular
        #   client (hash method/hash pair)
        self.__cache = {}

        class CacheItem:
            # __names is a string cache; every string long enough is given
            #   another object, and we will have plenty of identical long
            #   strings. therefore we can cache them
            __names = {}

            def __init__(self, hash_method, hash_, logger):
                # cached into db
                self.hash_method = hash_method
                self.hash = hash_
                self._features = []
                self._identities = []
                self._logger = logger

                self.status = NEW
                self._recently_seen = False

            def _get_features(self):
                return self._features

            def _set_features(self, value):
                self._features = []
                for feature in value:
                    self._features.append(self.__names.setdefault(feature, feature))

            features = property(_get_features, _set_features)

            def _get_identities(self):
                list_ = []
                for i in self._identities:
                    # transforms it back in a dict
                    d = dict()
                    d['category'] = i[0]
                    if i[1]:
                        d['type'] = i[1]
                    if i[2]:
                        d['xml:lang'] = i[2]
                    if i[3]:
                        d['name'] = i[3]
                    list_.append(d)
                return list_

            def _set_identities(self, value):
                self._identities = []
                for identity in value:
                    # dict are not hashable, so transform it into a tuple
                    t = (identity['category'], identity.get('type'),
                            identity.get('xml:lang'), identity.get('name'))
                    self._identities.append(self.__names.setdefault(t, t))

            identities = property(_get_identities, _set_identities)

            def set_and_store(self, identities, features):
                self.identities = identities
                self.features = features
                if self.hash_method != 'no':
                    self._logger.add_caps_entry(self.hash_method, self.hash,
                        identities, features)
                self.status = CACHED

            def update_last_seen(self):
                if not self._recently_seen:
                    self._recently_seen = True
                    if self.hash_method != 'no':
                        self._logger.update_caps_time(self.hash_method,
                            self.hash)

            def is_valid(self):
                """
                Returns True if identities and features for this cache item
                are known.
                """
                return self.status in (CACHED, FAKED)

        self.__CacheItem = CacheItem
        self.logger = logger

    def initialize_from_db(self):
        self._remove_outdated_caps()
        for hash_method, hash_, identities, features in \
        self.logger.iter_caps_data():
            x = self[(hash_method, hash_)]
            x.identities = identities
            x.features = features
            x.status = CACHED

    def _remove_outdated_caps(self):
        """
        Remove outdated values from the db
        """
        self.logger.clean_caps_table()

    def __getitem__(self, caps):
        if caps in self.__cache:
            return self.__cache[caps]

        hash_method, hash_ = caps

        x = self.__CacheItem(hash_method, hash_, self.logger)
        self.__cache[(hash_method, hash_)] = x
        return x

    def query_client_of_jid_if_unknown(self, connection, jid, client_caps):
        """
        Start a disco query to determine caps (node, ver, exts). Won't query if
        the data is already in cache
        """
        lookup_cache_item = client_caps.get_cache_lookup_strategy()
        q = lookup_cache_item(self)

        if q.status == NEW:
            # do query for bare node+hash pair
            # this will create proper object
            q.status = QUERIED
            discover = client_caps.get_discover_strategy()
            discover(connection, jid)
        else:
            q.update_last_seen()

    def forget_caps(self, client_caps):
        hash_method = client_caps._hash_method
        hash_ = client_caps._hash
        key = (hash_method, hash_)
        if key in self.__cache:
            del self.__cache[key]


class MucCapsCache:

    DiscoInfo = namedtuple('DiscoInfo', ['identities', 'features', 'data'])

    def __init__(self):
        self.cache = {}

    def append(self, stanza):
        jid = stanza.getFrom()
        identities, features, data = [], [], []
        query_childs = stanza.getQueryChildren()
        if not query_childs:
            log.warning('%s returned empty disco info', jid)
            return

        for child in query_childs:
            if child.getName() == 'identity':
                attr = {}
                for key in child.getAttrs().keys():
                    attr[key] = child.getAttr(key)
                identities.append(attr)
            elif child.getName() == 'feature':
                features.append(child.getAttr('var'))
            elif child.getName() == 'x':
                if child.getNamespace() == nbxmpp.NS_DATA:
                    from gajim.common.modules import dataforms
                    data.append(dataforms.extend_form(node=child))

        if nbxmpp.NS_MUC not in features:
            # Not a MUC, don't cache info
            return

        self.cache[jid] = self.DiscoInfo(identities, features, data)

    def is_cached(self, jid):
        return jid in self.cache

    def supports(self, jid, feature):
        if jid in self.cache:
            if feature in self.cache[jid].features:
                return True
        return False

    def has_mam(self, jid):
        try:
            if nbxmpp.NS_MAM_2 in self.cache[jid].features:
                return True
            if nbxmpp.NS_MAM_1 in self.cache[jid].features:
                return True
            return False
        except (KeyError, AttributeError):
            return False

    def get_mam_namespace(self, jid):
        try:
            if nbxmpp.NS_MAM_2 in self.cache[jid].features:
                return nbxmpp.NS_MAM_2
            if nbxmpp.NS_MAM_1 in self.cache[jid].features:
                return nbxmpp.NS_MAM_1
        except (KeyError, AttributeError):
            return

    def is_subject_change_allowed(self, jid, affiliation):
        allowed = True
        if affiliation in (Affiliation.OWNER, Affiliation.ADMIN):
            return allowed

        if jid in self.cache:
            for form in self.cache[jid].data:
                try:
                    allowed = form['muc#roominfo_changesubject'].value
                except KeyError:
                    pass
        return allowed