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

# SAT: a jabber client
# 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/>.

from sat.core.i18n import _
from sat.core import exceptions
from logging import debug, info, warning, error
from twisted.words.protocols.jabber import jid
from twisted.internet import defer
from sat.core.constants import Const as C
from wokkel import disco
from base64 import b64encode
from hashlib import sha1


PRESENCE = '/presence'
NS_ENTITY_CAPABILITY = 'http://jabber.org/protocol/caps'
CAPABILITY_UPDATE = PRESENCE + '/c[@xmlns="' + NS_ENTITY_CAPABILITY + '"]'

class HashGenerationError(Exception):
    pass


class ByteIdentity(object):
    """This class manage identity as bytes (needed for i;octet sort), it is used for the hash generation"""

    def __init__(self, identity, lang=None):
        assert isinstance(identity, disco.DiscoIdentity)
        self.category = identity.category.encode('utf-8')
        self.idType = identity.type.encode('utf-8')
        self.name = identity.name.encode('utf-8') if identity.name else ''
        self.lang = lang.encode('utf-8') if lang is not None else ''

    def __str__(self):
        return "%s/%s/%s/%s" % (self.category, self.idType, self.lang, self.name)


class Discovery(object):
    """ Manage capabilities of entities """

    def __init__(self, host):
        self.host = host
        self.hashes = {} # key: capability hash, value: disco features/identities
        # TODO: save hashes in databse, remove legacy hashes

    @defer.inlineCallbacks
    def hasFeature(self, feature, jid_=None, profile_key=C.PROF_KEY_NONE):
        """Tell if an entity has the required feature

        @param feature: feature namespace
        @param jid_: jid of the target, or None for profile's server
        @param profile_key: %(doc_profile_key)s
        @return: a Deferred which fire a boolean (True if feature is available)
        """
        disco_info = yield self.getInfos(jid_, profile_key)
        defer.returnValue(feature in disco_info.features)

    @defer.inlineCallbacks
    def checkFeature(self, feature, jid_=None, profile_key=C.PROF_KEY_NONE):
        """Like hasFeature, but raise an exception is feature is not Found

        @param feature: feature namespace
        @param jid_: jid of the target, or None for profile's server
        @param profile_key: %(doc_profile_key)s
        @return: None if feature is found

        @raise: exceptions.FeatureNotFound
        """
        disco_info = yield self.getInfos(jid_, profile_key)
        if not feature in disco_info.features:
            raise exceptions.FeatureNotFound
        defer.returnValue(feature in disco_info)

    @defer.inlineCallbacks
    def getInfos(self, jid_=None, profile_key=C.PROF_KEY_NONE):
        """get disco infos from jid_, filling capability hash if needed

        @param jid_: jid of the target, or None for profile's server
        @param profile_key: %(doc_profile_key)s
        @return: a Deferred which fire disco.DiscoInfo
        """
        client = self.host.getClient(profile_key)
        if jid_ is None:
            jid_ = jid.JID(client.jid.host)
        try:
            cap_hash = self.host.memory.getEntityData(jid_, [C.ENTITY_CAP_HASH], client.profile)[C.ENTITY_CAP_HASH]
            disco_info = self.hashes[cap_hash]
        except KeyError:
            # capability hash is not available, we'll compute one
            disco_info = yield client.disco.requestInfo(jid_)
            cap_hash = self.generateHash(disco_info)
            self.hashes[cap_hash] = disco_info
            yield self.host.memory.updateEntityData(jid_, C.ENTITY_CAP_HASH, cap_hash, client.profile)
        defer.returnValue(disco_info)

    @defer.inlineCallbacks
    def getItems(self, jid_=None, profile_key=C.PROF_KEY_NONE):
        """get disco items from jid_, cache them for our own server

        @param jid_: jid of the target, or None for profile's server
        @param profile_key: %(doc_profile_key)s
        @return: a Deferred which fire disco.DiscoInfo
        """
        client = self.host.getClient(profile_key)
        if jid_ is None:
            jid_ = jid.JID(client.jid.host)
            # we cache items only for our own server
            try:
                items = self.host.memory.getEntityData(jid_, ["DISCO_ITEMS"], client.profile)["DISCO_ITEMS"]
                debug("[%s] disco items are in cache" % jid_.full())
            except KeyError:
                debug("Caching [%s] disco items" % jid_.full())
                items = yield client.disco.requestItems(jid_)
                self.host.memory.updateEntityData(jid_, "DISCO_ITEMS", items, client.profile)
        else:
            items = yield client.disco.requestItems(jid_)

        defer.returnValue(items)


    @defer.inlineCallbacks
    def findServiceEntities(self, category, type_, jid_=None, profile_key=C.PROF_KEY_NONE):
        """Return all available items of an entity which correspond to (category, type_)

        @param category: identity's category
        @param type_: identitiy's type
        @param jid_: the jid of the target server (None for profile's server)
        @param profile_key: %(doc_profile_key)s
        @return: a set of entities or None if no cached data were found
        """
        found_identities = set()
        items = yield self.getItems(jid_, profile_key)
        for item in items:
            infos = yield self.getInfos(item.entity, profile_key)
            if (category, type_) in infos.identities:
                found_identities.add(item.entity)

        defer.returnValue(found_identities)

    @defer.inlineCallbacks
    def findFeaturesSet(self, features, category=None, type_=None, jid_=None, profile_key=C.PROF_KEY_NONE):
        """Return entities (including jid_ and its items) offering features

        @param features: iterable of features which must be present
        @param category: if not None, accept only this category
        @param type_: if not None, accept only this type
        @param jid_: the jid of the target server (None for profile's server)
        @param profile_key: %(doc_profile_key)s
        @return: a set of found entities
        """
        client = self.host.getClient(profile_key)
        if jid_ is None:
            jid_ = jid.JID(client.jid.host)
        features = set(features)
        found_entities = set()

        items = yield self.getItems(jid_, profile_key)
        for entity in [jid_] + items:
            infos = yield self.getInfos(entity, profile_key)
            if category is not None or type_ is not None:
                categories = set()
                types = set()
                for identity in infos.identities:
                    id_cat, id_type = identity
                    categories.add(id_cat)
                    types.add(id_type)
                if category is not None and category not in categories:
                    continue
                if type_ is not None and type_ not in types:
                    continue
            if features.issubset(infos.features):
                found_entities.add(entity)

        defer.returnValue(found_entities)

    def generateHash(self, services):
        """ Generate a unique hash for given service

        hash algorithm is the one described in XEP-0115
        @param services: iterable of disco.DiscoIdentity/disco.DiscoFeature, as returned by discoHandler.info

        """
        s = []
        byte_identities = [ByteIdentity(service) for service in services if isinstance(service, disco.DiscoIdentity)]  # FIXME: lang must be managed here
        byte_identities.sort(key=lambda i: i.lang)
        byte_identities.sort(key=lambda i: i.idType)
        byte_identities.sort(key=lambda i: i.category)
        for identity in byte_identities:
            s.append(str(identity))
            s.append('<')
        byte_features = [service.encode('utf-8') for service in services if isinstance(service, disco.DiscoFeature)]
        byte_features.sort()  # XXX: the default sort has the same behaviour as the requested RFC 4790 i;octet sort
        for feature in byte_features:
            s.append(feature)
            s.append('<')
        #TODO: manage XEP-0128 data form here
        cap_hash = b64encode(sha1(''.join(s)).digest())
        debug(_('Capability hash generated: [%s]') % cap_hash)
        return cap_hash