# -*- coding: utf-8 -*-
# Copyright 2015 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 ._base import BaseHandler

from synapse.streams.config import PaginationConfig
from synapse.api.constants import Membership, EventTypes

from twisted.internet import defer

import collections
import logging

logger = logging.getLogger(__name__)


SyncConfig = collections.namedtuple("SyncConfig", [
    "user",
    "filter",
])


class TimelineBatch(collections.namedtuple("TimelineBatch", [
    "prev_batch",
    "events",
    "limited",
])):
    __slots__ = []

    def __nonzero__(self):
        """Make the result appear empty if there are no updates. This is used
        to tell if room needs to be part of the sync result.
        """
        return bool(self.events)


class JoinedSyncResult(collections.namedtuple("JoinedSyncResult", [
    "room_id",
    "timeline",
    "state",
    "ephemeral",
])):
    __slots__ = []

    def __nonzero__(self):
        """Make the result appear empty if there are no updates. This is used
        to tell if room needs to be part of the sync result.
        """
        return bool(self.timeline or self.state or self.ephemeral)


class InvitedSyncResult(collections.namedtuple("InvitedSyncResult", [
    "room_id",
    "invite",
])):
    __slots__ = []


class SyncResult(collections.namedtuple("SyncResult", [
    "next_batch",  # Token for the next sync
    "presence",  # List of presence events for the user.
    "joined",  # JoinedSyncResult for each joined room.
    "invited",  # InvitedSyncResult for each invited room.
])):
    __slots__ = []

    def __nonzero__(self):
        """Make the result appear empty if there are no updates. This is used
        to tell if the notifier needs to wait for more events when polling for
        events.
        """
        return bool(
            self.presence or self.joined or self.invited
        )


class SyncHandler(BaseHandler):

    def __init__(self, hs):
        super(SyncHandler, self).__init__(hs)
        self.event_sources = hs.get_event_sources()
        self.clock = hs.get_clock()

    @defer.inlineCallbacks
    def wait_for_sync_for_user(self, sync_config, since_token=None, timeout=0):
        """Get the sync for a client if we have new data for it now. Otherwise
        wait for new data to arrive on the server. If the timeout expires, then
        return an empty sync result.
        Returns:
            A Deferred SyncResult.
        """
        if timeout == 0 or since_token is None:
            result = yield self.current_sync_for_user(sync_config, since_token)
            defer.returnValue(result)
        else:
            def current_sync_callback(before_token, after_token):
                return self.current_sync_for_user(sync_config, since_token)

            rm_handler = self.hs.get_handlers().room_member_handler

            app_service = yield self.store.get_app_service_by_user_id(
                sync_config.user.to_string()
            )
            if app_service:
                rooms = yield self.store.get_app_service_rooms(app_service)
                room_ids = set(r.room_id for r in rooms)
            else:
                room_ids = yield rm_handler.get_joined_rooms_for_user(
                    sync_config.user
                )

            result = yield self.notifier.wait_for_events(
                sync_config.user, room_ids, timeout, current_sync_callback,
                from_token=since_token
            )
            defer.returnValue(result)

    def current_sync_for_user(self, sync_config, since_token=None):
        """Get the sync for client needed to match what the server has now.
        Returns:
            A Deferred SyncResult.
        """
        if since_token is None:
            return self.initial_sync(sync_config)
        else:
            return self.incremental_sync_with_gap(sync_config, since_token)

    @defer.inlineCallbacks
    def initial_sync(self, sync_config):
        """Get a sync for a client which is starting without any state
        Returns:
            A Deferred SyncResult.
        """
        now_token = yield self.event_sources.get_current_token()

        now_token, typing_by_room = yield self.typing_by_room(
            sync_config, now_token
        )

        presence_stream = self.event_sources.sources["presence"]
        # TODO (mjark): This looks wrong, shouldn't we be getting the presence
        # UP to the present rather than after the present?
        pagination_config = PaginationConfig(from_token=now_token)
        presence, _ = yield presence_stream.get_pagination_rows(
            user=sync_config.user,
            pagination_config=pagination_config.get_source_config("presence"),
            key=None
        )
        room_list = yield self.store.get_rooms_for_user_where_membership_is(
            user_id=sync_config.user.to_string(),
            membership_list=[Membership.INVITE, Membership.JOIN]
        )

        joined = []
        invited = []
        for event in room_list:
            if event.membership == Membership.JOIN:
                room_sync = yield self.initial_sync_for_joined_room(
                    event.room_id, sync_config, now_token, typing_by_room
                )
                joined.append(room_sync)
            elif event.membership == Membership.INVITE:
                invite = yield self.store.get_event(event.event_id)
                invited.append(InvitedSyncResult(
                    room_id=event.room_id,
                    invite=invite,
                ))

        defer.returnValue(SyncResult(
            presence=presence,
            joined=joined,
            invited=invited,
            next_batch=now_token,
        ))

    @defer.inlineCallbacks
    def initial_sync_for_joined_room(self, room_id, sync_config, now_token,
                                     typing_by_room):
        """Sync a room for a client which is starting without any state
        Returns:
            A Deferred JoinedSyncResult.
        """

        batch = yield self.load_filtered_recents(
            room_id, sync_config, now_token,
        )

        current_state = yield self.state_handler.get_current_state(
            room_id
        )
        current_state_events = current_state.values()

        defer.returnValue(JoinedSyncResult(
            room_id=room_id,
            timeline=batch,
            state=current_state_events,
            ephemeral=typing_by_room.get(room_id, []),
        ))

    @defer.inlineCallbacks
    def typing_by_room(self, sync_config, now_token, since_token=None):
        """Get the typing events for each room the user is in
        Args:
            sync_config (SyncConfig): The flags, filters and user for the sync.
            now_token (StreamToken): Where the server is currently up to.
            since_token (StreamToken): Where the server was when the client
                last synced.
        Returns:
            A tuple of the now StreamToken, updated to reflect the which typing
            events are included, and a dict mapping from room_id to a list of
            typing events for that room.
        """

        typing_key = since_token.typing_key if since_token else "0"

        typing_source = self.event_sources.sources["typing"]
        typing, typing_key = yield typing_source.get_new_events_for_user(
            user=sync_config.user,
            from_key=typing_key,
            limit=sync_config.filter.ephemeral_limit(),
        )
        now_token = now_token.copy_and_replace("typing_key", typing_key)

        typing_by_room = {event["room_id"]: [event] for event in typing}
        for event in typing:
            event.pop("room_id")
        logger.debug("Typing %r", typing_by_room)

        defer.returnValue((now_token, typing_by_room))

    @defer.inlineCallbacks
    def incremental_sync_with_gap(self, sync_config, since_token):
        """ Get the incremental delta needed to bring the client up to
        date with the server.
        Returns:
            A Deferred SyncResult.
        """
        now_token = yield self.event_sources.get_current_token()

        presence_source = self.event_sources.sources["presence"]
        presence, presence_key = yield presence_source.get_new_events_for_user(
            user=sync_config.user,
            from_key=since_token.presence_key,
            limit=sync_config.filter.presence_limit(),
        )
        now_token = now_token.copy_and_replace("presence_key", presence_key)

        now_token, typing_by_room = yield self.typing_by_room(
            sync_config, now_token, since_token
        )

        rm_handler = self.hs.get_handlers().room_member_handler
        app_service = yield self.store.get_app_service_by_user_id(
            sync_config.user.to_string()
        )
        if app_service:
            rooms = yield self.store.get_app_service_rooms(app_service)
            joined_room_ids = set(r.room_id for r in rooms)
        else:
            joined_room_ids = yield rm_handler.get_joined_rooms_for_user(
                sync_config.user
            )

        timeline_limit = sync_config.filter.timeline_limit()

        room_events, _ = yield self.store.get_room_events_stream(
            sync_config.user.to_string(),
            from_key=since_token.room_key,
            to_key=now_token.room_key,
            room_id=None,
            limit=timeline_limit + 1,
        )

        joined = []
        if len(room_events) <= timeline_limit:
            # There is no gap in any of the rooms. Therefore we can just
            # partition the new events by room and return them.
            invite_events = []
            events_by_room_id = {}
            for event in room_events:
                events_by_room_id.setdefault(event.room_id, []).append(event)
                if event.room_id not in joined_room_ids:
                    if (event.type == EventTypes.Member
                            and event.membership == Membership.INVITE
                            and event.state_key == sync_config.user.to_string()):
                        invite_events.append(event)

            for room_id in joined_room_ids:
                recents = events_by_room_id.get(room_id, [])
                state = [event for event in recents if event.is_state()]
                if recents:
                    prev_batch = now_token.copy_and_replace(
                        "room_key", recents[0].internal_metadata.before
                    )
                else:
                    prev_batch = now_token

                state = yield self.check_joined_room(
                    sync_config, room_id, state
                )

                room_sync = JoinedSyncResult(
                    room_id=room_id,
                    timeline=TimelineBatch(
                        events=recents,
                        prev_batch=prev_batch,
                        limited=False,
                    ),
                    state=state,
                    ephemeral=typing_by_room.get(room_id, [])
                )
                if room_sync:
                    joined.append(room_sync)
        else:
            invite_events = yield self.store.get_invites_for_user(
                sync_config.user.to_string()
            )

            for room_id in joined_room_ids:
                room_sync = yield self.incremental_sync_with_gap_for_room(
                    room_id, sync_config, since_token, now_token,
                    typing_by_room
                )
                if room_sync:
                    joined.append(room_sync)

        invited = [
            InvitedSyncResult(room_id=event.room_id, invite=event)
            for event in invite_events
        ]

        defer.returnValue(SyncResult(
            presence=presence,
            joined=joined,
            invited=invited,
            next_batch=now_token,
        ))

    @defer.inlineCallbacks
    def load_filtered_recents(self, room_id, sync_config, now_token,
                              since_token=None):
        limited = True
        recents = []
        filtering_factor = 2
        timeline_limit = sync_config.filter.timeline_limit()
        load_limit = max(timeline_limit * filtering_factor, 100)
        max_repeat = 3  # Only try a few times per room, otherwise
        room_key = now_token.room_key
        end_key = room_key

        while limited and len(recents) < timeline_limit and max_repeat:
            events, keys = yield self.store.get_recent_events_for_room(
                room_id,
                limit=load_limit + 1,
                from_token=since_token.room_key if since_token else None,
                end_token=end_key,
            )
            (room_key, _) = keys
            end_key = "s" + room_key.split('-')[-1]
            loaded_recents = sync_config.filter.filter_room_timeline(events)
            loaded_recents = yield self._filter_events_for_client(
                sync_config.user.to_string(), loaded_recents,
            )
            loaded_recents.extend(recents)
            recents = loaded_recents
            if len(events) <= load_limit:
                limited = False
            max_repeat -= 1

        if len(recents) > timeline_limit:
            limited = True
            recents = recents[-timeline_limit:]
            room_key = recents[0].internal_metadata.before

        prev_batch_token = now_token.copy_and_replace(
            "room_key", room_key
        )

        defer.returnValue(TimelineBatch(
            events=recents, prev_batch=prev_batch_token, limited=limited
        ))

    @defer.inlineCallbacks
    def incremental_sync_with_gap_for_room(self, room_id, sync_config,
                                           since_token, now_token,
                                           typing_by_room):
        """ Get the incremental delta needed to bring the client up to date for
        the room. Gives the client the most recent events and the changes to
        state.
        Returns:
            A Deferred JoinedSyncResult
        """

        # TODO(mjark): Check for redactions we might have missed.

        batch = yield self.load_filtered_recents(
            room_id, sync_config, now_token, since_token,
        )

        logging.debug("Recents %r", batch)

        # TODO(mjark): This seems racy since this isn't being passed a
        # token to indicate what point in the stream this is
        current_state = yield self.state_handler.get_current_state(
            room_id
        )
        current_state_events = current_state.values()

        state_at_previous_sync = yield self.get_state_at_previous_sync(
            room_id, since_token=since_token
        )

        state_events_delta = yield self.compute_state_delta(
            since_token=since_token,
            previous_state=state_at_previous_sync,
            current_state=current_state_events,
        )

        state_events_delta = yield self.check_joined_room(
            sync_config, room_id, state_events_delta
        )

        room_sync = JoinedSyncResult(
            room_id=room_id,
            timeline=batch,
            state=state_events_delta,
            ephemeral=typing_by_room.get(room_id, [])
        )

        logging.debug("Room sync: %r", room_sync)

        defer.returnValue(room_sync)

    @defer.inlineCallbacks
    def get_state_at_previous_sync(self, room_id, since_token):
        """ Get the room state at the previous sync the client made.
        Returns:
            A Deferred list of Events.
        """
        last_events, token = yield self.store.get_recent_events_for_room(
            room_id, end_token=since_token.room_key, limit=1,
        )

        if last_events:
            last_event = last_events[0]
            last_context = yield self.state_handler.compute_event_context(
                last_event
            )
            if last_event.is_state():
                state = [last_event] + last_context.current_state.values()
            else:
                state = last_context.current_state.values()
        else:
            state = ()
        defer.returnValue(state)

    def compute_state_delta(self, since_token, previous_state, current_state):
        """ Works out the differnce in state between the current state and the
        state the client got when it last performed a sync.
        Returns:
            A list of events.
        """
        # TODO(mjark) Check if the state events were received by the server
        # after the previous sync, since we need to include those state
        # updates even if they occured logically before the previous event.
        # TODO(mjark) Check for new redactions in the state events.
        previous_dict = {event.event_id: event for event in previous_state}
        state_delta = []
        for event in current_state:
            if event.event_id not in previous_dict:
                state_delta.append(event)
        return state_delta

    @defer.inlineCallbacks
    def check_joined_room(self, sync_config, room_id, state_delta):
        joined = False
        for event in state_delta:
            if (
                event.type == EventTypes.Member
                and event.state_key == sync_config.user.to_string()
            ):
                if event.content["membership"] == Membership.JOIN:
                    joined = True

        if joined:
            res = yield self.state_handler.get_current_state(room_id)
            state_delta = res.values()

        defer.returnValue(state_delta)