def by_stream(self, query, operand, maybe_negate):
        # type: (Query, str, ConditionTransform) -> Query
        stream = get_stream(operand, self.user_profile.realm)
        if stream is None:
            raise BadNarrowOperator('unknown stream ' + operand)

        if self.user_profile.realm.is_zephyr_mirror_realm:
            # MIT users expect narrowing to "social" to also show messages to /^(un)*social(.d)*$/
            # (unsocial, ununsocial, social.d, etc)
            m = re.search(r'^(?:un)*(.+?)(?:\.d)*$', stream.name, re.IGNORECASE)
            # Since the regex has a `.+` in it and "" is invalid as a
            # stream name, this will always match
            assert(m is not None)
            base_stream_name = m.group(1)

            matching_streams = get_active_streams(self.user_profile.realm).filter(
                name__iregex=r'^(un)*%s(\.d)*$' % (self._pg_re_escape(base_stream_name),))
            matching_stream_ids = [matching_stream.id for matching_stream in matching_streams]
            recipients_map = bulk_get_recipients(Recipient.STREAM, matching_stream_ids)
            cond = column("recipient_id").in_([recipient.id for recipient in recipients_map.values()])
            return query.where(maybe_negate(cond))

        recipient = get_recipient(Recipient.STREAM, type_id=stream.id)
        cond = column("recipient_id") == recipient.id
        return query.where(maybe_negate(cond))

def filter_stream_authorization(user_profile, streams):
    # type: (UserProfile, Iterable[Stream]) -> Tuple[List[Stream], List[Stream]]
    streams_subscribed = set()  # type: Set[int]
    recipients_map = bulk_get_recipients(Recipient.STREAM, [stream.id for stream in streams])
    subs = Subscription.objects.filter(
        user_profile=user_profile, recipient__in=list(recipients_map.values()), active=True
    )

    for sub in subs:
        streams_subscribed.add(sub.recipient.type_id)

    unauthorized_streams = []  # type: List[Stream]
    for stream in streams:
        # The user is authorized for his own streams
        if stream.id in streams_subscribed:
            continue

        # The user is not authorized for invite_only streams
        if stream.invite_only:
            unauthorized_streams.append(stream)

    authorized_streams = [
        stream for stream in streams if stream.id not in set(stream.id for stream in unauthorized_streams)
    ]
    return authorized_streams, unauthorized_streams

def exclude_muting_conditions(user_profile, narrow):
    # type: (UserProfile, Optional[Iterable[Dict[str, Any]]]) -> List[Selectable]
    conditions = []
    stream_name = get_stream_name_from_narrow(narrow)

    if stream_name is None:
        rows = Subscription.objects.filter(
            user_profile=user_profile,
            active=True,
            in_home_view=False,
            recipient__type=Recipient.STREAM
        ).values('recipient_id')
        muted_recipient_ids = [row['recipient_id'] for row in rows]
        if len(muted_recipient_ids) > 0:
            # Only add the condition if we have muted streams to simplify/avoid warnings.
            condition = not_(column("recipient_id").in_(muted_recipient_ids))
            conditions.append(condition)

    muted_topics = ujson.loads(user_profile.muted_topics)
    if muted_topics:
        if stream_name is not None:
            muted_topics = [m for m in muted_topics if m[0].lower() == stream_name]
            if not muted_topics:
                return conditions

        muted_streams = bulk_get_streams(user_profile.realm,
                                         [muted[0] for muted in muted_topics])
        muted_recipients = bulk_get_recipients(Recipient.STREAM,
                                               [stream.id for stream in six.itervalues(muted_streams)])
        recipient_map = dict((s.name.lower(), muted_recipients[s.id].id)
                             for s in six.itervalues(muted_streams))

        muted_topics = [m for m in muted_topics if m[0].lower() in recipient_map]

        if muted_topics:
            def mute_cond(muted):
                # type: (Tuple[str, str]) -> Selectable
                stream_cond = column("recipient_id") == recipient_map[muted[0].lower()]
                topic_cond = func.upper(column("subject")) == func.upper(muted[1])
                return and_(stream_cond, topic_cond)

            condition = not_(or_(*list(map(mute_cond, muted_topics))))
            return conditions + [condition]

    return conditions

def exclude_muting_conditions(user_profile, narrow):
    conditions = []
    stream_name = get_stream_name_from_narrow(narrow)

    if stream_name is None:
        rows = Subscription.objects.filter(
            user_profile=user_profile,
            active=True,
            in_home_view=False,
            recipient__type=Recipient.STREAM
        ).values('recipient_id')
        muted_recipient_ids = [row['recipient_id'] for row in rows]
        condition = not_(column("recipient_id").in_(muted_recipient_ids))
        conditions.append(condition)

    muted_topics = ujson.loads(user_profile.muted_topics)
    if muted_topics:
        if stream_name is not None:
            muted_topics = [m for m in muted_topics if m[0].lower() == stream_name]
            if not muted_topics:
                return conditions

        muted_streams = bulk_get_streams(user_profile.realm,
                                         [muted[0] for muted in muted_topics])
        muted_recipients = bulk_get_recipients(Recipient.STREAM,
                                               [stream.id for stream in six.itervalues(muted_streams)])
        recipient_map = dict((s.name.lower(), muted_recipients[s.id].id)
                             for s in six.itervalues(muted_streams))

        muted_topics = [m for m in muted_topics if m[0].lower() in recipient_map]

        if muted_topics:
            def mute_cond(muted):
                stream_cond = column("recipient_id") == recipient_map[muted[0].lower()]
                topic_cond = func.upper(column("subject")) == func.upper(muted[1])
                return and_(stream_cond, topic_cond)

            condition = not_(or_(*list(map(mute_cond, muted_topics))))
            return conditions + [condition]

    return conditions

def filter_stream_authorization(user_profile, streams):
    streams_subscribed = set()
    recipients_map = bulk_get_recipients(Recipient.STREAM, [stream.id for stream in streams])
    subs = Subscription.objects.filter(user_profile=user_profile,
                                       recipient__in=recipients_map.values(),
                                       active=True)

    for sub in subs:
        streams_subscribed.add(sub.recipient.type_id)

    unauthorized_streams = []
    for stream in streams:
        # The user is authorized for his own streams
        if stream.id in streams_subscribed:
            continue

        # The user is not authorized for invite_only streams
        if stream.invite_only:
            unauthorized_streams.append(stream)

    streams = [stream for stream in streams if
               stream.id not in set(stream.id for stream in unauthorized_streams)]
    return streams, unauthorized_streams

    def by_stream(self, query, operand, maybe_negate):
        stream = get_stream(operand, self.user_profile.realm)
        if stream is None:
            raise BadNarrowOperator('unknown stream ' + operand)

        if self.user_profile.realm.domain == "mit.edu":
            # MIT users expect narrowing to "social" to also show messages to /^(un)*social(.d)*$/
            # (unsocial, ununsocial, social.d, etc)
            m = re.search(r'^(?:un)*(.+?)(?:\.d)*$', stream.name, re.IGNORECASE)
            if m:
                base_stream_name = m.group(1)
            else:
                base_stream_name = stream.name

            matching_streams = get_active_streams(self.user_profile.realm).filter(
                name__iregex=r'^(un)*%s(\.d)*$' % (self._pg_re_escape(base_stream_name),))
            matching_stream_ids = [matching_stream.id for matching_stream in matching_streams]
            recipients_map = bulk_get_recipients(Recipient.STREAM, matching_stream_ids)
            cond = column("recipient_id").in_([recipient.id for recipient in recipients_map.values()])
            return query.where(maybe_negate(cond))

        recipient = get_recipient(Recipient.STREAM, type_id=stream.id)
        cond = column("recipient_id") == recipient.id
        return query.where(maybe_negate(cond))