#
# This file is licensed under the Affero General Public License (AGPL) version 3.
#
# Copyright 2014-2016 OpenMarket Ltd
# Copyright (C) 2023 New Vector, Ltd
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as
# published by the Free Software Foundation, either version 3 of the
# License, or (at your option) any later version.
#
# See the GNU Affero General Public License for more details:
# <https://www.gnu.org/licenses/agpl-3.0.html>.
#
# Originally licensed under the Apache License, Version 2.0:
# <http://www.apache.org/licenses/LICENSE-2.0>.
#
# [This file includes modifications made by New Vector Limited]
#
#
from typing import (
    TYPE_CHECKING,
    Any,
    Iterable,
    Mapping,
    cast,
)

from synapse.api.presence import PresenceState, UserPresenceState
from synapse.replication.tcp.streams import PresenceStream
from synapse.storage._base import SQLBaseStore, make_in_list_sql_clause
from synapse.storage.database import (
    DatabasePool,
    LoggingDatabaseConnection,
    LoggingTransaction,
)
from synapse.storage.databases.main.cache import CacheInvalidationWorkerStore
from synapse.storage.engines._base import IsolationLevel
from synapse.storage.types import Connection
from synapse.storage.util.id_generators import MultiWriterIdGenerator
from synapse.util.caches.descriptors import cached, cachedList
from synapse.util.caches.stream_change_cache import StreamChangeCache
from synapse.util.iterutils import batch_iter

if TYPE_CHECKING:
    from synapse.server import HomeServer


class PresenceBackgroundUpdateStore(SQLBaseStore):
    def __init__(
        self,
        database: DatabasePool,
        db_conn: LoggingDatabaseConnection,
        hs: "HomeServer",
    ) -> None:
        super().__init__(database, db_conn, hs)

        # Used by `PresenceStore._get_active_presence()`
        self.db_pool.updates.register_background_index_update(
            "presence_stream_not_offline_index",
            index_name="presence_stream_state_not_offline_idx",
            table="presence_stream",
            columns=["state"],
            where_clause="state != 'offline'",
        )


class PresenceStore(PresenceBackgroundUpdateStore, CacheInvalidationWorkerStore):
    def __init__(
        self,
        database: DatabasePool,
        db_conn: LoggingDatabaseConnection,
        hs: "HomeServer",
    ) -> None:
        super().__init__(database, db_conn, hs)

        self._instance_name = hs.get_instance_name()
        self._presence_id_gen: MultiWriterIdGenerator

        self._can_persist_presence = (
            self._instance_name in hs.config.worker.writers.presence
        )

        self._presence_id_gen = MultiWriterIdGenerator(
            db_conn=db_conn,
            db=database,
            notifier=hs.get_replication_notifier(),
            stream_name="presence_stream",
            server_name=self.server_name,
            instance_name=self._instance_name,
            tables=[("presence_stream", "instance_name", "stream_id")],
            sequence_name="presence_stream_sequence",
            writers=hs.config.worker.writers.presence,
        )

        self.hs = hs
        self._presence_on_startup = self._get_active_presence(db_conn)

        presence_cache_prefill, min_presence_val = self.db_pool.get_cache_dict(
            db_conn,
            "presence_stream",
            entity_column="user_id",
            stream_column="stream_id",
            max_value=self._presence_id_gen.get_current_token(),
        )
        self.presence_stream_cache = StreamChangeCache(
            name="PresenceStreamChangeCache",
            server_name=self.server_name,
            current_stream_pos=min_presence_val,
            prefilled_cache=presence_cache_prefill,
        )

    async def update_presence(
        self, presence_states: list[UserPresenceState]
    ) -> tuple[int, int]:
        assert self._can_persist_presence

        stream_ordering_manager = self._presence_id_gen.get_next_mult(
            len(presence_states)
        )

        async with stream_ordering_manager as stream_orderings:
            # Run the interaction with an isolation level of READ_COMMITTED to avoid
            # serialization errors(and rollbacks) in the database. This way it will
            # ignore new rows during the DELETE, but will pick them up the next time
            # this is run. Currently, that is between 5-60 seconds.
            await self.db_pool.runInteraction(
                "update_presence",
                self._update_presence_txn,
                stream_orderings,
                presence_states,
                isolation_level=IsolationLevel.READ_COMMITTED,
            )

        return stream_orderings[-1], self._presence_id_gen.get_current_token()

    def _update_presence_txn(
        self,
        txn: LoggingTransaction,
        stream_orderings: list[int],
        presence_states: list[UserPresenceState],
    ) -> None:
        for stream_id, state in zip(stream_orderings, presence_states):
            txn.call_after(
                self.presence_stream_cache.entity_has_changed, state.user_id, stream_id
            )
            txn.call_after(self._get_presence_for_user.invalidate, (state.user_id,))

        # Delete old rows to stop database from getting really big
        sql = "DELETE FROM presence_stream WHERE stream_id < ? AND "

        for states in batch_iter(presence_states, 50):
            clause, args = make_in_list_sql_clause(
                self.database_engine, "user_id", [s.user_id for s in states]
            )
            txn.execute(sql + clause, [stream_id] + list(args))

        # Actually insert new rows
        self.db_pool.simple_insert_many_txn(
            txn,
            table="presence_stream",
            keys=(
                "stream_id",
                "user_id",
                "state",
                "last_active_ts",
                "last_federation_update_ts",
                "last_user_sync_ts",
                "status_msg",
                "currently_active",
                "instance_name",
            ),
            values=[
                (
                    stream_id,
                    state.user_id,
                    state.state,
                    state.last_active_ts,
                    state.last_federation_update_ts,
                    state.last_user_sync_ts,
                    state.status_msg,
                    state.currently_active,
                    self._instance_name,
                )
                for stream_id, state in zip(stream_orderings, presence_states)
            ],
        )

    async def get_all_presence_updates(
        self, instance_name: str, last_id: int, current_id: int, limit: int
    ) -> tuple[list[tuple[int, list]], int, bool]:
        """Get updates for presence replication stream.

        Args:
            instance_name: The writer we want to fetch updates from. Unused
                here since there is only ever one writer.
            last_id: The token to fetch updates from. Exclusive.
            current_id: The token to fetch updates up to. Inclusive.
            limit: The requested limit for the number of rows to return. The
                function may return more or fewer rows.

        Returns:
            A tuple consisting of: the updates, a token to use to fetch
            subsequent updates, and whether we returned fewer rows than exists
            between the requested tokens due to the limit.

            The token returned can be used in a subsequent call to this
            function to get further updatees.

            The updates are a list of 2-tuples of stream ID and the row data
        """

        if last_id == current_id:
            return [], current_id, False

        def get_all_presence_updates_txn(
            txn: LoggingTransaction,
        ) -> tuple[list[tuple[int, list]], int, bool]:
            sql = """
                SELECT stream_id, user_id, state, last_active_ts,
                    last_federation_update_ts, last_user_sync_ts,
                    status_msg, currently_active
                FROM presence_stream
                WHERE ? < stream_id AND stream_id <= ?
                ORDER BY stream_id ASC
                LIMIT ?
            """
            txn.execute(sql, (last_id, current_id, limit))
            updates = cast(
                list[tuple[int, list]],
                [(row[0], row[1:]) for row in txn],
            )

            upper_bound = current_id
            limited = False
            if len(updates) >= limit:
                upper_bound = updates[-1][0]
                limited = True

            return updates, upper_bound, limited

        return await self.db_pool.runInteraction(
            "get_all_presence_updates", get_all_presence_updates_txn
        )

    @cached()
    def _get_presence_for_user(self, user_id: str) -> None:
        raise NotImplementedError()

    @cachedList(
        cached_method_name="_get_presence_for_user",
        list_name="user_ids",
        num_args=1,
    )
    async def get_presence_for_users(
        self, user_ids: Iterable[str]
    ) -> Mapping[str, UserPresenceState]:
        # TODO All these columns are nullable, but we don't expect that:
        #      https://github.com/matrix-org/synapse/issues/16467
        rows = cast(
            list[tuple[str, str, int, int, int, str | None, int | bool]],
            await self.db_pool.simple_select_many_batch(
                table="presence_stream",
                column="user_id",
                iterable=user_ids,
                keyvalues={},
                retcols=(
                    "user_id",
                    "state",
                    "last_active_ts",
                    "last_federation_update_ts",
                    "last_user_sync_ts",
                    "status_msg",
                    "currently_active",
                ),
                desc="get_presence_for_users",
            ),
        )

        return {
            user_id: UserPresenceState(
                user_id=user_id,
                state=state,
                last_active_ts=last_active_ts,
                last_federation_update_ts=last_federation_update_ts,
                last_user_sync_ts=last_user_sync_ts,
                status_msg=status_msg,
                currently_active=bool(currently_active),
            )
            for user_id, state, last_active_ts, last_federation_update_ts, last_user_sync_ts, status_msg, currently_active in rows
        }

    async def should_user_receive_full_presence_with_token(
        self,
        user_id: str,
        from_token: int,
    ) -> bool:
        """Check whether the given user should receive full presence using the stream token
        they're updating from.

        Args:
            user_id: The ID of the user to check.
            from_token: The stream token included in their /sync token.

        Returns:
            True if the user should have full presence sent to them, False otherwise.
        """

        token = await self._get_full_presence_stream_token_for_user(user_id)
        if token is None:
            return False

        return from_token <= token

    @cached()
    async def _get_full_presence_stream_token_for_user(
        self, user_id: str
    ) -> int | None:
        """Get the presence token corresponding to the last full presence update
        for this user.

        If the user presents a sync token with a presence stream token at least
        as old as the result, then we need to send them a full presence update.

        If this user has never needed a full presence update, returns `None`.
        """
        return await self.db_pool.simple_select_one_onecol(
            table="users_to_send_full_presence_to",
            keyvalues={"user_id": user_id},
            retcol="presence_stream_id",
            allow_none=True,
            desc="_get_full_presence_stream_token_for_user",
        )

    async def add_users_to_send_full_presence_to(self, user_ids: Iterable[str]) -> None:
        """Adds to the list of users who should receive a full snapshot of presence
        upon their next sync.

        Args:
            user_ids: An iterable of user IDs.
        """
        # Add user entries to the table, updating the presence_stream_id column if the user already
        # exists in the table.
        presence_stream_id = self._presence_id_gen.get_current_token()

        def _add_users_to_send_full_presence_to(txn: LoggingTransaction) -> None:
            self.db_pool.simple_upsert_many_txn(
                txn,
                table="users_to_send_full_presence_to",
                key_names=("user_id",),
                key_values=[(user_id,) for user_id in user_ids],
                value_names=("presence_stream_id",),
                # We save the current presence stream ID token along with the user ID entry so
                # that when a user /sync's, even if they syncing multiple times across separate
                # devices at different times, each device will receive full presence once - when
                # the presence stream ID in their sync token is less than the one in the table
                # for their user ID.
                value_values=[(presence_stream_id,) for _ in user_ids],
            )
            self._invalidate_cache_and_stream_bulk(
                txn,
                self._get_full_presence_stream_token_for_user,
                [(user_id,) for user_id in user_ids],
            )

        return await self.db_pool.runInteraction(
            "add_users_to_send_full_presence_to", _add_users_to_send_full_presence_to
        )

    async def get_presence_for_all_users(
        self,
        include_offline: bool = True,
    ) -> dict[str, UserPresenceState]:
        """Retrieve the current presence state for all users.

        Note that the presence_stream table is culled frequently, so it should only
        contain the latest presence state for each user.

        Args:
            include_offline: Whether to include offline presence states

        Returns:
            A dict of user IDs to their current UserPresenceState.
        """
        users_to_state = {}

        exclude_keyvalues = None
        if not include_offline:
            # Exclude offline presence state
            exclude_keyvalues = {"state": "offline"}

        # This may be a very heavy database query.
        # We paginate in order to not block a database connection.
        limit = 100
        offset = 0
        while True:
            # TODO All these columns are nullable, but we don't expect that:
            #      https://github.com/matrix-org/synapse/issues/16467
            rows = cast(
                list[tuple[str, str, int, int, int, str | None, int | bool]],
                await self.db_pool.runInteraction(
                    "get_presence_for_all_users",
                    self.db_pool.simple_select_list_paginate_txn,
                    "presence_stream",
                    orderby="stream_id",
                    start=offset,
                    limit=limit,
                    exclude_keyvalues=exclude_keyvalues,
                    retcols=(
                        "user_id",
                        "state",
                        "last_active_ts",
                        "last_federation_update_ts",
                        "last_user_sync_ts",
                        "status_msg",
                        "currently_active",
                    ),
                    order_direction="ASC",
                ),
            )

            for (
                user_id,
                state,
                last_active_ts,
                last_federation_update_ts,
                last_user_sync_ts,
                status_msg,
                currently_active,
            ) in rows:
                users_to_state[user_id] = UserPresenceState(
                    user_id=user_id,
                    state=state,
                    last_active_ts=last_active_ts,
                    last_federation_update_ts=last_federation_update_ts,
                    last_user_sync_ts=last_user_sync_ts,
                    status_msg=status_msg,
                    currently_active=bool(currently_active),
                )

            # We've run out of updates to query
            if len(rows) < limit:
                break

            offset += limit

        return users_to_state

    def get_current_presence_token(self) -> int:
        return self._presence_id_gen.get_current_token()

    def get_presence_stream_id_gen(self) -> MultiWriterIdGenerator:
        return self._presence_id_gen

    def _get_active_presence(self, db_conn: Connection) -> list[UserPresenceState]:
        """Fetch non-offline presence from the database so that we can register
        the appropriate time outs.
        """

        # The `presence_stream_state_not_offline_idx` index should be used for this
        # query.
        sql = (
            "SELECT user_id, state, last_active_ts, last_federation_update_ts,"
            " last_user_sync_ts, status_msg, currently_active FROM presence_stream"
            " WHERE state != ?"
        )

        txn = db_conn.cursor()
        txn.execute(sql, (PresenceState.OFFLINE,))
        rows = txn.fetchall()
        txn.close()

        return [
            UserPresenceState(
                user_id=user_id,
                state=state,
                last_active_ts=last_active_ts,
                last_federation_update_ts=last_federation_update_ts,
                last_user_sync_ts=last_user_sync_ts,
                status_msg=status_msg,
                currently_active=bool(currently_active),
            )
            for user_id, state, last_active_ts, last_federation_update_ts, last_user_sync_ts, status_msg, currently_active in rows
        ]

    def take_presence_startup_info(self) -> list[UserPresenceState]:
        active_on_startup = self._presence_on_startup
        self._presence_on_startup = []
        return active_on_startup

    def process_replication_rows(
        self,
        stream_name: str,
        instance_name: str,
        token: int,
        rows: Iterable[Any],
    ) -> None:
        if stream_name == PresenceStream.NAME:
            for row in rows:
                self.presence_stream_cache.entity_has_changed(row.user_id, token)
                self._get_presence_for_user.invalidate((row.user_id,))
        return super().process_replication_rows(stream_name, instance_name, token, rows)

    def process_replication_position(
        self, stream_name: str, instance_name: str, token: int
    ) -> None:
        if stream_name == PresenceStream.NAME:
            self._presence_id_gen.advance(instance_name, token)
        super().process_replication_position(stream_name, instance_name, token)
