# -*- coding: utf-8 -*-
# Copyright 2014-2016 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.

import logging
import random

from twisted.internet import defer

from synapse.api.constants import EventTypes, Membership
from synapse.api.errors import AuthError, SynapseError
from synapse.events import EventBase
from synapse.types import UserID
from synapse.util.logutils import log_function
from synapse.visibility import filter_events_for_client

from ._base import BaseHandler

logger = logging.getLogger(__name__)


class EventStreamHandler(BaseHandler):

    def __init__(self, hs):
        super(EventStreamHandler, self).__init__(hs)

        # Count of active streams per user
        self._streams_per_user = {}
        # Grace timers per user to delay the "stopped" signal
        self._stop_timer_per_user = {}

        self.distributor = hs.get_distributor()
        self.distributor.declare("started_user_eventstream")
        self.distributor.declare("stopped_user_eventstream")

        self.clock = hs.get_clock()

        self.notifier = hs.get_notifier()
        self.state = hs.get_state_handler()
        self._server_notices_sender = hs.get_server_notices_sender()
        self._event_serializer = hs.get_event_client_serializer()

    @defer.inlineCallbacks
    @log_function
    def get_stream(self, auth_user_id, pagin_config, timeout=0,
                   as_client_event=True, affect_presence=True,
                   only_keys=None, room_id=None, is_guest=False):
        """Fetches the events stream for a given user.

        If `only_keys` is not None, events from keys will be sent down.
        """

        if room_id:
            blocked = yield self.store.is_room_blocked(room_id)
            if blocked:
                raise SynapseError(403, "This room has been blocked on this server")

        # send any outstanding server notices to the user.
        yield self._server_notices_sender.on_user_syncing(auth_user_id)

        auth_user = UserID.from_string(auth_user_id)
        presence_handler = self.hs.get_presence_handler()

        context = yield presence_handler.user_syncing(
            auth_user_id, affect_presence=affect_presence,
        )
        with context:
            if timeout:
                # If they've set a timeout set a minimum limit.
                timeout = max(timeout, 500)

                # Add some randomness to this value to try and mitigate against
                # thundering herds on restart.
                timeout = random.randint(int(timeout * 0.9), int(timeout * 1.1))

            events, tokens = yield self.notifier.get_events_for(
                auth_user, pagin_config, timeout,
                only_keys=only_keys,
                is_guest=is_guest, explicit_room_id=room_id
            )

            # When the user joins a new room, or another user joins a currently
            # joined room, we need to send down presence for those users.
            to_add = []
            for event in events:
                if not isinstance(event, EventBase):
                    continue
                if event.type == EventTypes.Member:
                    if event.membership != Membership.JOIN:
                        continue
                    # Send down presence.
                    if event.state_key == auth_user_id:
                        # Send down presence for everyone in the room.
                        users = yield self.state.get_current_users_in_room(event.room_id)
                        states = yield presence_handler.get_states(
                            users,
                            as_event=True,
                        )
                        to_add.extend(states)
                    else:

                        ev = yield presence_handler.get_state(
                            UserID.from_string(event.state_key),
                            as_event=True,
                        )
                        to_add.append(ev)

            events.extend(to_add)

            time_now = self.clock.time_msec()

            chunks = yield self._event_serializer.serialize_events(
                events, time_now, as_client_event=as_client_event,
            )

            chunk = {
                "chunk": chunks,
                "start": tokens[0].to_string(),
                "end": tokens[1].to_string(),
            }

            defer.returnValue(chunk)


class EventHandler(BaseHandler):

    @defer.inlineCallbacks
    def get_event(self, user, room_id, event_id):
        """Retrieve a single specified event.

        Args:
            user (synapse.types.UserID): The user requesting the event
            room_id (str|None): The expected room id. We'll return None if the
                event's room does not match.
            event_id (str): The event ID to obtain.
        Returns:
            dict: An event, or None if there is no event matching this ID.
        Raises:
            SynapseError if there was a problem retrieving this event, or
            AuthError if the user does not have the rights to inspect this
            event.
        """
        event = yield self.store.get_event(event_id, check_room_id=room_id)

        if not event:
            defer.returnValue(None)
            return

        users = yield self.store.get_users_in_room(event.room_id)
        is_peeking = user.to_string() not in users

        filtered = yield filter_events_for_client(
            self.store,
            user.to_string(),
            [event],
            is_peeking=is_peeking
        )

        if not filtered:
            raise AuthError(
                403,
                "You don't have permission to access that event."
            )

        defer.returnValue(event)
