# -*- coding: utf-8 -*-
# Copyright 2016 OpenMarket Ltd
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

from synapse.util.caches import cache_counter, caches_by_name


from blist import sorteddict
import logging


logger = logging.getLogger(__name__)


class RoomStreamChangeCache(object):
    """Keeps track of the stream_id of the latest change in rooms.

    Given a list of rooms and stream key, it will give a subset of rooms that
    may have changed since that key. If the key is too old then the cache
    will simply return all rooms.
    """
    def __init__(self, name, current_key, size_of_cache=10000):
        self._size_of_cache = size_of_cache
        self._room_to_key = {}
        self._cache = sorteddict()
        self._earliest_known_key = current_key
        self.name = name
        caches_by_name[self.name] = self._cache

    def get_room_has_changed(self, room_id, key):
        assert type(key) is int

        if key <= self._earliest_known_key:
            return True

        room_key = self._room_to_key.get(room_id, None)
        if room_key is None:
            return True

        if key < room_key:
            return True

        return False

    def get_rooms_changed(self, room_ids, key):
        """Returns subset of room ids that have had new things since the
        given key. If the key is too old it will just return the given list.
        """
        assert type(key) is int

        if key > self._earliest_known_key:
            keys = self._cache.keys()
            i = keys.bisect_right(key)

            result = set(
                self._cache[k] for k in keys[i:]
            ).intersection(room_ids)

            cache_counter.inc_hits(self.name)
        else:
            result = room_ids
            cache_counter.inc_misses(self.name)

        return result

    def room_has_changed(self, room_id, key):
        """Informs the cache that the room has been changed at the given key.
        """
        assert type(key) is int

        if key > self._earliest_known_key:
            old_key = self._room_to_key.get(room_id, None)
            if old_key:
                key = max(key, old_key)
                self._cache.pop(old_key, None)
            self._cache[key] = room_id

            while len(self._cache) > self._size_of_cache:
                k, r = self._cache.popitem()
                self._earliest_key = max(k, self._earliest_key)
                self._room_to_key.pop(r, None)