# -*- coding: utf-8 -*-
# Copyright 2017 Vector Creations 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.

import logging

from twisted.internet import defer

from synapse.util.async_helpers import Linearizer

from ._base import BaseHandler

logger = logging.getLogger(__name__)


class ReadMarkerHandler(BaseHandler):
    def __init__(self, hs):
        super(ReadMarkerHandler, self).__init__(hs)
        self.server_name = hs.config.server_name
        self.store = hs.get_datastore()
        self.read_marker_linearizer = Linearizer(name="read_marker")
        self.notifier = hs.get_notifier()

    @defer.inlineCallbacks
    def received_client_read_marker(self, room_id, user_id, event_id):
        """Updates the read marker for a given user in a given room if the event ID given
        is ahead in the stream relative to the current read marker.

        This uses a notifier to indicate that account data should be sent down /sync if
        the read marker has changed.
        """

        with (yield self.read_marker_linearizer.queue((room_id, user_id))):
            existing_read_marker = yield self.store.get_account_data_for_room_and_type(
                user_id, room_id, "m.fully_read",
            )

            should_update = True

            if existing_read_marker:
                # Only update if the new marker is ahead in the stream
                should_update = yield self.store.is_event_after(
                    event_id,
                    existing_read_marker['event_id']
                )

            if should_update:
                content = {
                    "event_id": event_id
                }
                max_id = yield self.store.add_account_data_to_room(
                    user_id, room_id, "m.fully_read", content
                )
                self.notifier.on_new_event("account_data_key", max_id, users=[user_id])
