# Copyright 2014-2016 OpenMarket Ltd
# Copyright 2020 The Matrix.org Foundation C.I.C.
#
# 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 collections.abc
import logging
from typing import TYPE_CHECKING, Collection, Dict, Iterable, Optional, Set, Tuple

import attr

from synapse.api.constants import EventTypes, Membership
from synapse.api.errors import NotFoundError, UnsupportedRoomVersionError
from synapse.api.room_versions import KNOWN_ROOM_VERSIONS, RoomVersion
from synapse.events import EventBase
from synapse.events.snapshot import EventContext
from synapse.storage._base import SQLBaseStore
from synapse.storage.database import (
    DatabasePool,
    LoggingDatabaseConnection,
    LoggingTransaction,
    make_in_list_sql_clause,
)
from synapse.storage.databases.main.events_worker import EventsWorkerStore
from synapse.storage.databases.main.roommember import RoomMemberWorkerStore
from synapse.storage.state import StateFilter
from synapse.types import JsonDict, JsonMapping, StateMap
from synapse.util.caches import intern_string
from synapse.util.caches.descriptors import cached, cachedList
from synapse.util.iterutils import batch_iter

if TYPE_CHECKING:
    from synapse.server import HomeServer

logger = logging.getLogger(__name__)


MAX_STATE_DELTA_HOPS = 100


@attr.s(slots=True, frozen=True, auto_attribs=True)
class EventMetadata:
    """Returned by `get_metadata_for_events`"""

    room_id: str
    event_type: str
    state_key: Optional[str]
    rejection_reason: Optional[str]


def _retrieve_and_check_room_version(room_id: str, room_version_id: str) -> RoomVersion:
    v = KNOWN_ROOM_VERSIONS.get(room_version_id)
    if not v:
        raise UnsupportedRoomVersionError(
            "Room %s uses a room version %s which is no longer supported"
            % (room_id, room_version_id)
        )
    return v


# this inherits from EventsWorkerStore because it calls self.get_events
class StateGroupWorkerStore(EventsWorkerStore, SQLBaseStore):
    """The parts of StateGroupStore that can be called from workers."""

    def __init__(
        self,
        database: DatabasePool,
        db_conn: LoggingDatabaseConnection,
        hs: "HomeServer",
    ):
        super().__init__(database, db_conn, hs)

    async def get_room_version(self, room_id: str) -> RoomVersion:
        """Get the room_version of a given room
        Raises:
            NotFoundError: if the room is unknown
            UnsupportedRoomVersionError: if the room uses an unknown room version.
                Typically this happens if support for the room's version has been
                removed from Synapse.
        """
        room_version_id = await self.get_room_version_id(room_id)
        return _retrieve_and_check_room_version(room_id, room_version_id)

    def get_room_version_txn(
        self, txn: LoggingTransaction, room_id: str
    ) -> RoomVersion:
        """Get the room_version of a given room
        Args:
            txn: Transaction object
            room_id: The room_id of the room you are trying to get the version for
        Raises:
            NotFoundError: if the room is unknown
            UnsupportedRoomVersionError: if the room uses an unknown room version.
                Typically this happens if support for the room's version has been
                removed from Synapse.
        """
        room_version_id = self.get_room_version_id_txn(txn, room_id)
        return _retrieve_and_check_room_version(room_id, room_version_id)

    @cached(max_entries=10000)
    async def get_room_version_id(self, room_id: str) -> str:
        """Get the room_version of a given room
        Raises:
            NotFoundError: if the room is unknown
        """
        return await self.db_pool.runInteraction(
            "get_room_version_id_txn",
            self.get_room_version_id_txn,
            room_id,
        )

    def get_room_version_id_txn(self, txn: LoggingTransaction, room_id: str) -> str:
        """Get the room_version of a given room
        Args:
            txn: Transaction object
            room_id: The room_id of the room you are trying to get the version for
        Raises:
            NotFoundError: if the room is unknown
        """

        # First we try looking up room version from the database, but for old
        # rooms we might not have added the room version to it yet so we fall
        # back to previous behaviour and look in current state events.
        #
        # We really should have an entry in the rooms table for every room we
        # care about, but let's be a bit paranoid (at least while the background
        # update is happening) to avoid breaking existing rooms.
        room_version = self.db_pool.simple_select_one_onecol_txn(
            txn,
            table="rooms",
            keyvalues={"room_id": room_id},
            retcol="room_version",
            allow_none=True,
        )

        if room_version is None:
            raise NotFoundError("Could not find room_version for %s" % (room_id,))

        return room_version

    async def get_metadata_for_events(
        self, event_ids: Collection[str]
    ) -> Dict[str, EventMetadata]:
        """Get some metadata (room_id, type, state_key) for the given events.

        This method is a faster alternative than fetching the full events from
        the DB, and should be used when the full event is not needed.

        Returns metadata for rejected and redacted events. Events that have not
        been persisted are omitted from the returned dict.
        """

        def get_metadata_for_events_txn(
            txn: LoggingTransaction,
            batch_ids: Collection[str],
        ) -> Dict[str, EventMetadata]:
            clause, args = make_in_list_sql_clause(
                self.database_engine, "e.event_id", batch_ids
            )

            sql = f"""
                SELECT e.event_id, e.room_id, e.type, se.state_key, r.reason
                FROM events AS e
                LEFT JOIN state_events se USING (event_id)
                LEFT JOIN rejections r USING (event_id)
                WHERE {clause}
            """

            txn.execute(sql, args)
            return {
                event_id: EventMetadata(
                    room_id=room_id,
                    event_type=event_type,
                    state_key=state_key,
                    rejection_reason=rejection_reason,
                )
                for event_id, room_id, event_type, state_key, rejection_reason in txn
            }

        result_map: Dict[str, EventMetadata] = {}
        for batch_ids in batch_iter(event_ids, 1000):
            result_map.update(
                await self.db_pool.runInteraction(
                    "get_metadata_for_events",
                    get_metadata_for_events_txn,
                    batch_ids=batch_ids,
                )
            )

        return result_map

    async def get_room_predecessor(self, room_id: str) -> Optional[JsonMapping]:
        """Get the predecessor of an upgraded room if it exists.
        Otherwise return None.

        Args:
            room_id: The room ID.

        Returns:
            A dictionary containing the structure of the predecessor
            field from the room's create event. The structure is subject to other servers,
            but it is expected to be:
                * room_id (str): The room ID of the predecessor room
                * event_id (str): The ID of the tombstone event in the predecessor room

            None if a predecessor key is not found, or is not a dictionary.

        Raises:
            NotFoundError if the given room is unknown
        """
        # Retrieve the room's create event
        create_event = await self.get_create_event_for_room(room_id)

        # Retrieve the predecessor key of the create event
        predecessor = create_event.content.get("predecessor", None)

        # Ensure the key is a dictionary
        if not isinstance(predecessor, collections.abc.Mapping):
            return None

        # The keys must be strings since the data is JSON.
        return predecessor

    async def get_create_event_for_room(self, room_id: str) -> EventBase:
        """Get the create state event for a room.

        Args:
            room_id: The room ID.

        Returns:
            The room creation event.

        Raises:
            NotFoundError if the room is unknown
        """
        state_ids = await self.get_partial_current_state_ids(room_id)

        if not state_ids:
            raise NotFoundError(f"Current state for room {room_id} is empty")

        create_id = state_ids.get((EventTypes.Create, ""))

        # If we can't find the create event, assume we've hit a dead end
        if not create_id:
            raise NotFoundError(f"No create event in current state for room {room_id}")

        # Retrieve the room's create event and return
        create_event = await self.get_event(create_id)
        return create_event

    @cached(max_entries=100000, iterable=True)
    async def get_partial_current_state_ids(self, room_id: str) -> StateMap[str]:
        """Get the current state event ids for a room based on the
        current_state_events table.

        This may be the partial state if we're lazy joining the room.

        Args:
            room_id: The room to get the state IDs of.

        Returns:
            The current state of the room.
        """

        def _get_current_state_ids_txn(txn: LoggingTransaction) -> StateMap[str]:
            txn.execute(
                """SELECT type, state_key, event_id FROM current_state_events
                WHERE room_id = ?
                """,
                (room_id,),
            )

            return {(intern_string(r[0]), intern_string(r[1])): r[2] for r in txn}

        return await self.db_pool.runInteraction(
            "get_partial_current_state_ids", _get_current_state_ids_txn
        )

    # FIXME: how should this be cached?
    async def get_partial_filtered_current_state_ids(
        self, room_id: str, state_filter: Optional[StateFilter] = None
    ) -> StateMap[str]:
        """Get the current state event of a given type for a room based on the
        current_state_events table.  This may not be as up-to-date as the result
        of doing a fresh state resolution as per state_handler.get_current_state

        This may be the partial state if we're lazy joining the room.

        Args:
            room_id
            state_filter: The state filter used to fetch state
                from the database.

        Returns:
            Map from type/state_key to event ID.
        """

        where_clause, where_args = (
            state_filter or StateFilter.all()
        ).make_sql_filter_clause()

        if not where_clause:
            # We delegate to the cached version
            return await self.get_partial_current_state_ids(room_id)

        def _get_filtered_current_state_ids_txn(
            txn: LoggingTransaction,
        ) -> StateMap[str]:
            results = {}
            sql = """
                SELECT type, state_key, event_id FROM current_state_events
                WHERE room_id = ?
            """

            if where_clause:
                sql += " AND (%s)" % (where_clause,)

            args = [room_id]
            args.extend(where_args)
            txn.execute(sql, args)
            for row in txn:
                typ, state_key, event_id = row
                key = (intern_string(typ), intern_string(state_key))
                results[key] = event_id

            return results

        return await self.db_pool.runInteraction(
            "get_filtered_current_state_ids", _get_filtered_current_state_ids_txn
        )

    @cached(max_entries=50000)
    async def _get_state_group_for_event(self, event_id: str) -> Optional[int]:
        return await self.db_pool.simple_select_one_onecol(
            table="event_to_state_groups",
            keyvalues={"event_id": event_id},
            retcol="state_group",
            allow_none=True,
            desc="_get_state_group_for_event",
        )

    @cachedList(
        cached_method_name="_get_state_group_for_event",
        list_name="event_ids",
        num_args=1,
    )
    async def _get_state_group_for_events(
        self, event_ids: Collection[str]
    ) -> Dict[str, int]:
        """Returns mapping event_id -> state_group.

        Raises:
             RuntimeError if the state is unknown at any of the given events
        """
        rows = await self.db_pool.simple_select_many_batch(
            table="event_to_state_groups",
            column="event_id",
            iterable=event_ids,
            keyvalues={},
            retcols=("event_id", "state_group"),
            desc="_get_state_group_for_events",
        )

        res = {row["event_id"]: row["state_group"] for row in rows}
        for e in event_ids:
            if e not in res:
                raise RuntimeError("No state group for unknown or outlier event %s" % e)
        return res

    async def get_referenced_state_groups(
        self, state_groups: Iterable[int]
    ) -> Set[int]:
        """Check if the state groups are referenced by events.

        Args:
            state_groups

        Returns:
            The subset of state groups that are referenced.
        """

        rows = await self.db_pool.simple_select_many_batch(
            table="event_to_state_groups",
            column="state_group",
            iterable=state_groups,
            keyvalues={},
            retcols=("DISTINCT state_group",),
            desc="get_referenced_state_groups",
        )

        return {row["state_group"] for row in rows}

    async def update_state_for_partial_state_event(
        self,
        event: EventBase,
        context: EventContext,
    ) -> None:
        """Update the state group for a partial state event"""
        await self.db_pool.runInteraction(
            "update_state_for_partial_state_event",
            self._update_state_for_partial_state_event_txn,
            event,
            context,
        )

    def _update_state_for_partial_state_event_txn(
        self,
        txn: LoggingTransaction,
        event: EventBase,
        context: EventContext,
    ) -> None:
        # we shouldn't have any outliers here
        assert not event.internal_metadata.is_outlier()

        # anything that was rejected should have the same state as its
        # predecessor.
        if context.rejected:
            assert context.state_group == context.state_group_before_event

        self.db_pool.simple_update_txn(
            txn,
            table="event_to_state_groups",
            keyvalues={"event_id": event.event_id},
            updatevalues={"state_group": context.state_group},
        )

        self.db_pool.simple_delete_one_txn(
            txn,
            table="partial_state_events",
            keyvalues={"event_id": event.event_id},
        )

        # TODO(faster_joins): need to do something about workers here
        txn.call_after(self.is_partial_state_event.invalidate, (event.event_id,))
        txn.call_after(
            self._get_state_group_for_event.prefill,
            (event.event_id,),
            context.state_group,
        )


class MainStateBackgroundUpdateStore(RoomMemberWorkerStore):

    CURRENT_STATE_INDEX_UPDATE_NAME = "current_state_members_idx"
    EVENT_STATE_GROUP_INDEX_UPDATE_NAME = "event_to_state_groups_sg_index"
    DELETE_CURRENT_STATE_UPDATE_NAME = "delete_old_current_state_events"

    def __init__(
        self,
        database: DatabasePool,
        db_conn: LoggingDatabaseConnection,
        hs: "HomeServer",
    ):
        super().__init__(database, db_conn, hs)

        self.server_name: str = hs.hostname

        self.db_pool.updates.register_background_index_update(
            self.CURRENT_STATE_INDEX_UPDATE_NAME,
            index_name="current_state_events_member_index",
            table="current_state_events",
            columns=["state_key"],
            where_clause="type='m.room.member'",
        )
        self.db_pool.updates.register_background_index_update(
            self.EVENT_STATE_GROUP_INDEX_UPDATE_NAME,
            index_name="event_to_state_groups_sg_index",
            table="event_to_state_groups",
            columns=["state_group"],
        )
        self.db_pool.updates.register_background_update_handler(
            self.DELETE_CURRENT_STATE_UPDATE_NAME,
            self._background_remove_left_rooms,
        )

    async def _background_remove_left_rooms(
        self, progress: JsonDict, batch_size: int
    ) -> int:
        """Background update to delete rows from `current_state_events` and
        `event_forward_extremities` tables of rooms that the server is no
        longer joined to.
        """

        last_room_id = progress.get("last_room_id", "")

        def _background_remove_left_rooms_txn(
            txn: LoggingTransaction,
        ) -> Tuple[bool, Set[str]]:
            # get a batch of room ids to consider
            sql = """
                SELECT DISTINCT room_id FROM current_state_events
                WHERE room_id > ? ORDER BY room_id LIMIT ?
            """

            txn.execute(sql, (last_room_id, batch_size))
            room_ids = [row[0] for row in txn]
            if not room_ids:
                return True, set()

            ###########################################################################
            #
            # exclude rooms where we have active members

            sql = """
                SELECT room_id
                FROM local_current_membership
                WHERE
                    room_id > ? AND room_id <= ?
                    AND membership = 'join'
                GROUP BY room_id
            """

            txn.execute(sql, (last_room_id, room_ids[-1]))
            joined_room_ids = {row[0] for row in txn}
            to_delete = set(room_ids) - joined_room_ids

            ###########################################################################
            #
            # exclude rooms which we are in the process of constructing; these otherwise
            # qualify as "rooms with no local users", and would have their
            # forward extremities cleaned up.

            # the following query will return a list of rooms which have forward
            # extremities that are *not* also the create event in the room - ie
            # those that are not being created currently.

            sql = """
                SELECT DISTINCT efe.room_id
                FROM event_forward_extremities efe
                LEFT JOIN current_state_events cse ON
                    cse.event_id = efe.event_id
                    AND cse.type = 'm.room.create'
                    AND cse.state_key = ''
                WHERE
                    cse.event_id IS NULL
                    AND efe.room_id > ? AND efe.room_id <= ?
            """

            txn.execute(sql, (last_room_id, room_ids[-1]))

            # build a set of those rooms within `to_delete` that do not appear in
            # the above, leaving us with the rooms in `to_delete` that *are* being
            # created.
            creating_rooms = to_delete.difference(row[0] for row in txn)
            logger.info("skipping rooms which are being created: %s", creating_rooms)

            # now remove the rooms being created from the list of those to delete.
            #
            # (we could have just taken the intersection of `to_delete` with the result
            # of the sql query, but it's useful to be able to log `creating_rooms`; and
            # having done so, it's quicker to remove the (few) creating rooms from
            # `to_delete` than it is to form the intersection with the (larger) list of
            # not-creating-rooms)

            to_delete -= creating_rooms

            ###########################################################################
            #
            # now clear the state for the rooms

            logger.info("Deleting current state left rooms: %r", to_delete)

            # First we get all users that we still think were joined to the
            # room. This is so that we can mark those device lists as
            # potentially stale, since there may have been a period where the
            # server didn't share a room with the remote user and therefore may
            # have missed any device updates.
            rows = self.db_pool.simple_select_many_txn(
                txn,
                table="current_state_events",
                column="room_id",
                iterable=to_delete,
                keyvalues={"type": EventTypes.Member, "membership": Membership.JOIN},
                retcols=("state_key",),
            )

            potentially_left_users = {row["state_key"] for row in rows}

            # Now lets actually delete the rooms from the DB.
            self.db_pool.simple_delete_many_txn(
                txn,
                table="current_state_events",
                column="room_id",
                values=to_delete,
                keyvalues={},
            )

            self.db_pool.simple_delete_many_txn(
                txn,
                table="event_forward_extremities",
                column="room_id",
                values=to_delete,
                keyvalues={},
            )

            self.db_pool.updates._background_update_progress_txn(
                txn,
                self.DELETE_CURRENT_STATE_UPDATE_NAME,
                {"last_room_id": room_ids[-1]},
            )

            return False, potentially_left_users

        finished, potentially_left_users = await self.db_pool.runInteraction(
            "_background_remove_left_rooms", _background_remove_left_rooms_txn
        )

        if finished:
            await self.db_pool.updates._end_background_update(
                self.DELETE_CURRENT_STATE_UPDATE_NAME
            )

        # Now go and check if we still share a room with the remote users in
        # the deleted rooms. If not mark their device lists as stale.
        joined_users = await self.get_users_server_still_shares_room_with(
            potentially_left_users
        )

        for user_id in potentially_left_users - joined_users:
            await self.mark_remote_user_device_list_as_unsubscribed(user_id)  # type: ignore[attr-defined]

        return batch_size


class StateStore(StateGroupWorkerStore, MainStateBackgroundUpdateStore):
    """Keeps track of the state at a given event.

    This is done by the concept of `state groups`. Every event is a assigned
    a state group (identified by an arbitrary string), which references a
    collection of state events. The current state of an event is then the
    collection of state events referenced by the event's state group.

    Hence, every change in the current state causes a new state group to be
    generated. However, if no change happens (e.g., if we get a message event
    with only one parent it inherits the state group from its parent.)

    There are three tables:
      * `state_groups`: Stores group name, first event with in the group and
        room id.
      * `event_to_state_groups`: Maps events to state groups.
      * `state_groups_state`: Maps state group to state events.
    """

    def __init__(
        self,
        database: DatabasePool,
        db_conn: LoggingDatabaseConnection,
        hs: "HomeServer",
    ):
        super().__init__(database, db_conn, hs)
