# -*- 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.api.constants import EventTypes, JoinRules, Membership
from synapse.storage.roommember import ProfileInfo
from synapse.util.metrics import Measure


logger = logging.getLogger(__name__)


class UserDirectoyHandler(object):
    """Handles querying of and keeping updated the user_directory.

    N.B.: ASSUMES IT IS THE ONLY THING THAT MODIFIES THE USER DIRECTORY

    The user directory is filled with users who this server can see are joined to a
    world_readable or publically joinable room. We keep a database table up to date
    by streaming changes of the current state and recalculating whether users should
    be in the directory or not when necessary.

    For each user in the directory we also store a room_id which is public and that the
    user is joined to. This allows us to ignore history_visibility and join_rules changes
    for that user in all other public rooms, as we know they'll still be in at least
    one public room.
    """

    def __init__(self, hs):
        self.store = hs.get_datastore()
        self.state = hs.get_state_handler()
        self.server_name = hs.hostname
        self.clock = hs.get_clock()

        # When start up for the first time we need to populate the user_directory.
        # This is a set of user_id's we've inserted already
        self.initially_handled_users = set()

        # The current position in the current_state_delta stream
        self.pos = None

        # Guard to ensure we only process deltas one at a time
        self._is_processing = False

        # We kick this off so that we don't have to wait for a change before
        # we start populating the user directory
        self.clock.call_later(0, self.notify_new_event)

    def search_users(self, search_term, limit):
        """Searches for users in directory

        Returns:
            dict of the form::

                {
                    "limited": <bool>,  # whether there were more results or not
                    "results": [  # Ordered by best match first
                        {
                            "user_id": <user_id>,
                            "display_name": <display_name>,
                            "avatar_url": <avatar_url>
                        }
                    ]
                }
        """
        return self.store.search_user_dir(search_term, limit)

    @defer.inlineCallbacks
    def notify_new_event(self):
        """Called when there may be more deltas to process
        """
        if self._is_processing:
            return

        self._is_processing = True
        try:
            yield self._unsafe_process()
        finally:
            self._is_processing = False

    @defer.inlineCallbacks
    def _unsafe_process(self):
        # If self.pos is None then means we haven't fetched it from DB
        if self.pos is None:
            self.pos = yield self.store.get_user_directory_stream_pos()

        # If still None then we need to do the initial fill of directory
        if self.pos is None:
            yield self._do_initial_spam()
            self.pos = yield self.store.get_user_directory_stream_pos()

        # Loop round handling deltas until we're up to date
        while True:
            with Measure(self.clock, "user_dir_delta"):
                deltas = yield self.store.get_current_state_deltas(self.pos)
                if not deltas:
                    return

                yield self._handle_deltas(deltas)

                self.pos = deltas[-1]["stream_id"]
                yield self.store.update_user_directory_stream_pos(self.pos)

    @defer.inlineCallbacks
    def _do_initial_spam(self):
        """Populates the user_directory from the current state of the DB, used
        when synapse first starts with user_directory support
        """
        new_pos = yield self.store.get_max_stream_id_in_current_state_deltas()

        # Delete any existing entries just in case there are any
        yield self.store.delete_all_from_user_dir()

        # We process by going through each existing room at a time.
        room_ids = yield self.store.get_all_rooms()

        for room_id in room_ids:
            yield self._handle_intial_room(room_id)

        self.initially_handled_users = None

        yield self.store.update_user_directory_stream_pos(new_pos)

    @defer.inlineCallbacks
    def _handle_intial_room(self, room_id):
        """Called when we initially fill out user_directory one room at a time
        """
        is_in_room = yield self.state.get_is_host_in_room(room_id, self.server_name)
        if not is_in_room:
            return

        is_public = yield self.store.is_room_world_readable_or_publicly_joinable(room_id)
        if not is_public:
            return

        users_with_profile = yield self.state.get_current_user_in_room(room_id)
        unhandled_users = set(users_with_profile) - self.initially_handled_users

        yield self.store.add_profiles_to_user_dir(
            room_id, {
                user_id: users_with_profile[user_id] for user_id in unhandled_users
            }
        )

        self.initially_handled_users |= unhandled_users

    @defer.inlineCallbacks
    def _handle_deltas(self, deltas):
        """Called with the state deltas to process
        """
        for delta in deltas:
            typ = delta["type"]
            state_key = delta["state_key"]
            room_id = delta["room_id"]
            event_id = delta["event_id"]
            prev_event_id = delta["prev_event_id"]

            logger.debug("Handling: %r %r, %s", typ, state_key, event_id)

            # For join rule and visibility changes we need to check if the room
            # may have become public or not and add/remove the users in said room
            if typ in (EventTypes.RoomHistoryVisibility, EventTypes.JoinRules):
                yield self._handle_room_publicity_change(
                    room_id, prev_event_id, event_id, typ,
                )
            elif typ == EventTypes.Member:
                change = yield self._get_key_change(
                    prev_event_id, event_id,
                    key_name="membership",
                    public_value=Membership.JOIN,
                )

                if change is None:
                    continue

                if not change:
                    # Need to check if the server left the room entirely, if so
                    # we might need to remove all the users in that room
                    is_in_room = yield self.state.get_is_host_in_room(
                        room_id, self.server_name,
                    )
                    if not is_in_room:
                        # Fetch all the users that we marked as being in user
                        # directory due to being in the room and then check if
                        # need to remove those users or not
                        user_ids = yield self.store.get_users_in_dir_due_to_room(room_id)
                        for user_id in user_ids:
                            yield self._handle_remove_user(room_id, user_id)
                        return

                is_public = yield self.store.is_room_world_readable_or_publicly_joinable(
                    room_id
                )

                if change:  # The user joined
                    if not is_public:
                        return

                    event = yield self.store.get_event(event_id)
                    profile = ProfileInfo(
                        avatar_url=event.content.get("avatar_url"),
                        display_name=event.content.get("displayname"),
                    )

                    yield self._handle_new_user(room_id, state_key, profile)
                else:  # The user left
                    yield self._handle_remove_user(room_id, state_key)
            else:
                logger.debug("Ignoring irrelevant type: %r", typ)

    @defer.inlineCallbacks
    def _handle_room_publicity_change(self, room_id, prev_event_id, event_id, typ):
        """Handle a room having potentially changed from/to world_readable/publically
        joinable.

        Args:
            room_id (str)
            prev_event_id (str|None): The previous event before the state change
            event_id (str|None): The new event after the state change
            typ (str): Type of the event
        """
        logger.debug("Handling change for %s", typ)

        if typ == EventTypes.RoomHistoryVisibility:
            change = yield self._get_key_change(
                prev_event_id, event_id,
                key_name="history_visibility",
                public_value="world_readable",
            )
        elif typ == EventTypes.JoinRules:
            change = yield self._get_key_change(
                prev_event_id, event_id,
                key_name="join_rule",
                public_value=JoinRules.PUBLIC,
            )
        else:
            raise Exception("Invalid event type")
        # If change is None, no change. True => become world_readable/public,
        # False => was world_readable/public
        if change is None:
            logger.debug("No change")
            return

        # There's been a change to or from being world readable.

        is_public = yield self.store.is_room_world_readable_or_publicly_joinable(
            room_id
        )

        logger.debug("Change: %r, is_public: %r", change, is_public)

        if change and not is_public:
            # If we became world readable but room isn't currently public then
            # we ignore the change
            return
        elif not change and is_public:
            # If we stopped being world readable but are still public,
            # ignore the change
            return

        users_with_profile = yield self.state.get_current_user_in_room(room_id)
        for user_id, profile in users_with_profile.iteritems():
            if change:
                yield self._handle_new_user(room_id, user_id, profile)
            else:
                yield self._handle_remove_user(room_id, user_id)

    @defer.inlineCallbacks
    def _handle_new_user(self, room_id, user_id, profile):
        """Called when we might need to add user to directory

        Args:
            room_id (str): room_id that user joined or started being public that
            user_id (str)
        """
        row = yield self.store.get_user_in_directory(user_id)
        if row:
            return

        yield self.store.add_profiles_to_user_dir(room_id, {user_id: profile})

    @defer.inlineCallbacks
    def _handle_remove_user(self, room_id, user_id):
        """Called when we might need to remove user to directory

        Args:
            room_id (str): room_id that user left or stopped being public that
            user_id (str)
        """
        logger.debug("Maybe removing user %r", user_id)

        row = yield self.store.get_user_in_directory(user_id)
        if not row or row["room_id"] != room_id:
            # Either the user wasn't in directory or we're still in a room that
            # is public (i.e. the room_id in the database)
            logger.debug("Not removing as row: %r", row)
            return

        # XXX: Make this faster?
        rooms = yield self.store.get_rooms_for_user(user_id)
        for j_room_id in rooms:
            is_public = yield self.store.is_room_world_readable_or_publicly_joinable(
                j_room_id
            )

            if is_public:
                yield self.store.update_user_in_user_dir(user_id, j_room_id)
                logger.debug("Not removing as found other public room: %r", j_room_id)
                return

        yield self.store.remove_from_user_dir(user_id)

    @defer.inlineCallbacks
    def _get_key_change(self, prev_event_id, event_id, key_name, public_value):
        """Given two events check if the `key_name` field in content changed
        from not matching `public_value` to doing so.

        For example, check if `history_visibility` (`key_name`) changed from
        `shared` to `world_readable` (`public_value`).

        Returns:
            None if the field in the events either both match `public_value`
            neither do, i.e. there has been no change.
            True if it didnt match `public_value` but now does
            False if it did match `public_value` but now doesn't
        """
        prev_event = None
        event = None
        if prev_event_id:
            prev_event = yield self.store.get_event(prev_event_id, allow_none=True)

        if event_id:
            event = yield self.store.get_event(event_id, allow_none=True)

        if not event and not prev_event:
            logger.debug("Neither event exists: %r %r", prev_event_id, event_id)
            defer.returnValue(None)

        prev_value = None
        value = None

        if prev_event:
            prev_value = prev_event.content.get(key_name, None)

        if event:
            value = event.content.get(key_name, None)

        logger.debug("prev_value: %r -> value: %r", prev_value, value)

        if value == public_value and prev_value != public_value:
            defer.returnValue(True)
        elif value != public_value and prev_value == public_value:
            defer.returnValue(False)
        else:
            defer.returnValue(None)