#
# 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]
#
#
import logging
from http import HTTPStatus
from typing import (
    TYPE_CHECKING,
    Any,
    Collection,
    Iterable,
    Mapping,
    Sequence,
    cast,
)

from twisted.internet import defer

from synapse.api.errors import Codes, StoreError, SynapseError
from synapse.config.homeserver import ExperimentalConfig
from synapse.logging.context import make_deferred_yieldable, run_in_background
from synapse.replication.tcp.streams import PushRulesStream
from synapse.storage._base import SQLBaseStore
from synapse.storage.database import (
    DatabasePool,
    LoggingDatabaseConnection,
    LoggingTransaction,
)
from synapse.storage.databases.main.appservice import ApplicationServiceWorkerStore
from synapse.storage.databases.main.events_worker import EventsWorkerStore
from synapse.storage.databases.main.pusher import PusherWorkerStore
from synapse.storage.databases.main.receipts import ReceiptsWorkerStore
from synapse.storage.databases.main.roommember import RoomMemberWorkerStore
from synapse.storage.engines import PostgresEngine, Sqlite3Engine
from synapse.storage.push_rule import InconsistentRuleException, RuleNotFoundException
from synapse.storage.util.id_generators import IdGenerator, MultiWriterIdGenerator
from synapse.synapse_rust.push import FilteredPushRules, PushRule, PushRules
from synapse.types import JsonDict
from synapse.util import unwrapFirstError
from synapse.util.async_helpers import gather_results
from synapse.util.caches.descriptors import cached, cachedList
from synapse.util.caches.stream_change_cache import StreamChangeCache
from synapse.util.json import json_encoder

if TYPE_CHECKING:
    from synapse.server import HomeServer

logger = logging.getLogger(__name__)


def _load_rules(
    rawrules: list[tuple[str, int, str, str]],
    enabled_map: dict[str, bool],
    experimental_config: ExperimentalConfig,
) -> FilteredPushRules:
    """Take the DB rows returned from the DB and convert them into a full
    `FilteredPushRules` object.

    Args:
        rawrules: List of tuples of:
            * rule ID
            * Priority lass
            * Conditions (as serialized JSON)
            * Actions (as serialized JSON)
        enabled_map: A dictionary of rule ID to a boolean of whether the rule is
            enabled. This might not include all rule IDs from rawrules.
        experimental_config: The `experimental_features` section of the Synapse
            config. (Used to check if various features are enabled.)

    Returns:
        A new FilteredPushRules object.
    """

    ruleslist = [
        PushRule.from_db(
            rule_id=rawrule[0],
            priority_class=rawrule[1],
            conditions=rawrule[2],
            actions=rawrule[3],
        )
        for rawrule in rawrules
    ]

    push_rules = PushRules(ruleslist)

    filtered_rules = FilteredPushRules(
        push_rules,
        enabled_map,
        msc1767_enabled=experimental_config.msc1767_enabled,
        msc3664_enabled=experimental_config.msc3664_enabled,
        msc3381_polls_enabled=experimental_config.msc3381_polls_enabled,
        msc4028_push_encrypted_events=experimental_config.msc4028_push_encrypted_events,
        msc4210_enabled=experimental_config.msc4210_enabled,
        msc4306_enabled=experimental_config.msc4306_enabled,
    )

    return filtered_rules


def _push_rule_size_for_limits(*, conditions_json: str, actions_json: str) -> int:
    """
    Returns the size of a push rule, as used for applying the size limit.

    We aren't tied to any particular definition, but currently this is
    simply the size in bytes of the conditions and actions JSON added together,
    so not rocket science, but this function provides a 'label' for it.
    """
    # This is not a very predictable way of calculating the size from the
    # point of view of the client, but since it's an out-of-spec limit
    # entirely at our discretion, we don't really have to worry about
    # the exact calculation.
    # FIXME: Spec a predictable push rule size limit
    return len(conditions_json.encode("utf-8")) + len(actions_json.encode("utf-8"))


class PushRulesWorkerStore(
    ApplicationServiceWorkerStore,
    PusherWorkerStore,
    RoomMemberWorkerStore,
    ReceiptsWorkerStore,
    EventsWorkerStore,
    SQLBaseStore,
):
    """This is an abstract base class where subclasses must implement
    `get_max_push_rules_stream_id` which can be called in the initializer.
    """

    _push_rules_stream_id_gen: MultiWriterIdGenerator

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

        self._is_push_writer = (
            hs.get_instance_name() in hs.config.worker.writers.push_rules
        )

        self._push_rules_stream_id_gen = MultiWriterIdGenerator(
            db_conn=db_conn,
            db=database,
            notifier=hs.get_replication_notifier(),
            stream_name="push_rules_stream",
            server_name=self.server_name,
            instance_name=self._instance_name,
            tables=[
                ("push_rules_stream", "instance_name", "stream_id"),
            ],
            sequence_name="push_rules_stream_sequence",
            writers=hs.config.worker.writers.push_rules,
        )

        push_rules_prefill, push_rules_id = self.db_pool.get_cache_dict(
            db_conn,
            "push_rules_stream",
            entity_column="user_id",
            stream_column="stream_id",
            max_value=self.get_max_push_rules_stream_id(),
        )

        self.push_rules_stream_cache = StreamChangeCache(
            name="PushRulesStreamChangeCache",
            server_name=self.server_name,
            current_stream_pos=push_rules_id,
            prefilled_cache=push_rules_prefill,
        )

        self._push_rule_id_gen = IdGenerator(db_conn, "push_rules", "id")
        self._push_rules_enable_id_gen = IdGenerator(db_conn, "push_rules_enable", "id")

        self._config = hs.config.push_rules

    def get_max_push_rules_stream_id(self) -> int:
        """Get the position of the push rules stream.

        Returns:
            int
        """
        return self._push_rules_stream_id_gen.get_current_token()

    def get_push_rules_stream_id_gen(self) -> MultiWriterIdGenerator:
        return self._push_rules_stream_id_gen

    def process_replication_rows(
        self, stream_name: str, instance_name: str, token: int, rows: Iterable[Any]
    ) -> None:
        if stream_name == PushRulesStream.NAME:
            self._push_rules_stream_id_gen.advance(instance_name, token)
            for row in rows:
                self.get_push_rules_for_user.invalidate((row.user_id,))
                self.push_rules_stream_cache.entity_has_changed(row.user_id, token)
        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 == PushRulesStream.NAME:
            self._push_rules_stream_id_gen.advance(instance_name, token)
        super().process_replication_position(stream_name, instance_name, token)

    @cached(max_entries=5000)
    async def get_push_rules_for_user(self, user_id: str) -> FilteredPushRules:
        rows = cast(
            list[tuple[str, int, int, str, str]],
            await self.db_pool.simple_select_list(
                table="push_rules",
                keyvalues={"user_name": user_id},
                retcols=(
                    "rule_id",
                    "priority_class",
                    "priority",
                    "conditions",
                    "actions",
                ),
                desc="get_push_rules_for_user",
            ),
        )

        # Sort by highest priority_class, then highest priority.
        rows.sort(key=lambda row: (-int(row[1]), -int(row[2])))

        enabled_map = await self.get_push_rules_enabled_for_user(user_id)

        return _load_rules(
            [(row[0], row[1], row[3], row[4]) for row in rows],
            enabled_map,
            self.hs.config.experimental,
        )

    async def get_push_rules_enabled_for_user(self, user_id: str) -> dict[str, bool]:
        results = cast(
            list[tuple[str, int | bool | None]],
            await self.db_pool.simple_select_list(
                table="push_rules_enable",
                keyvalues={"user_name": user_id},
                retcols=("rule_id", "enabled"),
                desc="get_push_rules_enabled_for_user",
            ),
        )
        return {r[0]: bool(r[1]) for r in results}

    async def have_push_rules_changed_for_user(
        self, user_id: str, last_id: int
    ) -> bool:
        if not self.push_rules_stream_cache.has_entity_changed(user_id, last_id):
            return False
        else:

            def have_push_rules_changed_txn(txn: LoggingTransaction) -> bool:
                sql = (
                    "SELECT COUNT(stream_id) FROM push_rules_stream"
                    " WHERE user_id = ? AND ? < stream_id"
                )
                txn.execute(sql, (user_id, last_id))
                (count,) = cast(tuple[int], txn.fetchone())
                return bool(count)

            return await self.db_pool.runInteraction(
                "have_push_rules_changed", have_push_rules_changed_txn
            )

    @cachedList(cached_method_name="get_push_rules_for_user", list_name="user_ids")
    async def bulk_get_push_rules(
        self, user_ids: Collection[str]
    ) -> Mapping[str, FilteredPushRules]:
        if not user_ids:
            return {}

        raw_rules: dict[str, list[tuple[str, int, str, str]]] = {
            user_id: [] for user_id in user_ids
        }

        # gatherResults loses all type information.
        rows, enabled_map_by_user = await make_deferred_yieldable(
            gather_results(
                (
                    cast(
                        "defer.Deferred[list[tuple[str, str, int, int, str, str]]]",
                        run_in_background(
                            self.db_pool.simple_select_many_batch,
                            table="push_rules",
                            column="user_name",
                            iterable=user_ids,
                            retcols=(
                                "user_name",
                                "rule_id",
                                "priority_class",
                                "priority",
                                "conditions",
                                "actions",
                            ),
                            desc="bulk_get_push_rules",
                            batch_size=1000,
                        ),
                    ),
                    run_in_background(self.bulk_get_push_rules_enabled, user_ids),
                ),
                consumeErrors=True,
            ).addErrback(unwrapFirstError)
        )

        # Sort by highest priority_class, then highest priority.
        rows.sort(key=lambda row: (-int(row[2]), -int(row[3])))

        for user_name, rule_id, priority_class, _, conditions, actions in rows:
            raw_rules.setdefault(user_name, []).append(
                (rule_id, priority_class, conditions, actions)
            )

        results: dict[str, FilteredPushRules] = {}

        for user_id, rules in raw_rules.items():
            results[user_id] = _load_rules(
                rules, enabled_map_by_user.get(user_id, {}), self.hs.config.experimental
            )

        return results

    async def bulk_get_push_rules_enabled(
        self, user_ids: Collection[str]
    ) -> dict[str, dict[str, bool]]:
        if not user_ids:
            return {}

        results: dict[str, dict[str, bool]] = {user_id: {} for user_id in user_ids}

        rows = cast(
            list[tuple[str, str, int | None]],
            await self.db_pool.simple_select_many_batch(
                table="push_rules_enable",
                column="user_name",
                iterable=user_ids,
                retcols=("user_name", "rule_id", "enabled"),
                desc="bulk_get_push_rules_enabled",
                batch_size=1000,
            ),
        )
        for user_name, rule_id, enabled in rows:
            results.setdefault(user_name, {})[rule_id] = bool(enabled)
        return results

    async def get_all_push_rule_updates(
        self, instance_name: str, last_id: int, current_id: int, limit: int
    ) -> tuple[list[tuple[int, tuple[str]]], int, bool]:
        """Get updates for push_rules 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_push_rule_updates_txn(
            txn: LoggingTransaction,
        ) -> tuple[list[tuple[int, tuple[str]]], int, bool]:
            sql = """
                SELECT stream_id, user_id
                FROM push_rules_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, tuple[str]]],
                [(stream_id, (user_id,)) for stream_id, user_id in txn],
            )

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

            return updates, upper_bound, limited

        return await self.db_pool.runInteraction(
            "get_all_push_rule_updates", get_all_push_rule_updates_txn
        )

    async def add_push_rule(
        self,
        user_id: str,
        rule_id: str,
        priority_class: int,
        conditions: Sequence[Mapping[str, str]],
        actions: Sequence[Mapping[str, Any] | str],
        before: str | None = None,
        after: str | None = None,
    ) -> None:
        if not self._is_push_writer:
            raise Exception("Not a push writer")

        conditions_json = json_encoder.encode(conditions)
        actions_json = json_encoder.encode(actions)

        rule_id_len = len(rule_id.encode("utf-8"))
        if rule_id_len > self._config.limits.rule_id_length:
            raise SynapseError(
                HTTPStatus.REQUEST_ENTITY_TOO_LARGE,
                f"Push rule ID length exceeds server limit ({rule_id_len} bytes > {self._config.limits.rule_id_length} bytes).",
                # FIXME: Provide a better error code.
                # None of the existing options seem entirely correct, though.
                Codes.UNKNOWN,
            )

        rule_body_size = _push_rule_size_for_limits(
            conditions_json=conditions_json, actions_json=actions_json
        )
        if rule_body_size > self._config.limits.rule_size:
            raise SynapseError(
                HTTPStatus.REQUEST_ENTITY_TOO_LARGE,
                f"Push rule size exceeds server limit ({rule_body_size} bytes > {self._config.limits.rule_size} bytes).",
                # FIXME: Provide a better error code.
                # None of the existing options seem entirely correct, though.
                Codes.UNKNOWN,
            )

        async with self._push_rules_stream_id_gen.get_next() as stream_id:
            event_stream_ordering = self._stream_id_gen.get_current_token()

            if before or after:
                await self.db_pool.runInteraction(
                    "_add_push_rule_relative_txn",
                    self._add_push_rule_relative_txn,
                    stream_id,
                    event_stream_ordering,
                    user_id,
                    rule_id,
                    priority_class,
                    conditions_json,
                    actions_json,
                    before,
                    after,
                )
            else:
                await self.db_pool.runInteraction(
                    "_add_push_rule_highest_priority_txn",
                    self._add_push_rule_highest_priority_txn,
                    stream_id,
                    event_stream_ordering,
                    user_id,
                    rule_id,
                    priority_class,
                    conditions_json,
                    actions_json,
                )

    def _add_push_rule_relative_txn(
        self,
        txn: LoggingTransaction,
        stream_id: int,
        event_stream_ordering: int,
        user_id: str,
        rule_id: str,
        priority_class: int,
        conditions_json: str,
        actions_json: str,
        before: str,
        after: str,
    ) -> None:
        if not self._is_push_writer:
            raise Exception("Not a push writer")

        relative_to_rule = before or after

        sql = """
            SELECT priority, priority_class FROM push_rules
            WHERE user_name = ? AND rule_id = ?
        """

        if isinstance(self.database_engine, PostgresEngine):
            sql += " FOR UPDATE"
        else:
            # Annoyingly SQLite doesn't support row level locking, so lock the whole table
            self.database_engine.lock_table(txn, "push_rules")

        txn.execute(sql, (user_id, relative_to_rule))
        row = txn.fetchone()

        if row is None:
            raise RuleNotFoundException(
                "before/after rule not found: %s" % (relative_to_rule,)
            )

        base_rule_priority, base_priority_class = row

        if base_priority_class != priority_class:
            raise InconsistentRuleException(
                "Given priority class does not match class of relative rule"
            )

        if before:
            # Higher priority rules are executed first, So adding a rule before
            # a rule means giving it a higher priority than that rule.
            new_rule_priority = base_rule_priority + 1
        else:
            # We increment the priority of the existing rules to make space for
            # the new rule. Therefore if we want this rule to appear after
            # an existing rule we give it the priority of the existing rule,
            # and then increment the priority of the existing rule.
            new_rule_priority = base_rule_priority

        sql = (
            "UPDATE push_rules SET priority = priority + 1"
            " WHERE user_name = ? AND priority_class = ? AND priority >= ?"
        )

        txn.execute(sql, (user_id, priority_class, new_rule_priority))

        self._upsert_push_rule_txn(
            txn,
            stream_id,
            event_stream_ordering,
            user_id,
            rule_id,
            priority_class,
            new_rule_priority,
            conditions_json,
            actions_json,
        )

    def _add_push_rule_highest_priority_txn(
        self,
        txn: LoggingTransaction,
        stream_id: int,
        event_stream_ordering: int,
        user_id: str,
        rule_id: str,
        priority_class: int,
        conditions_json: str,
        actions_json: str,
    ) -> None:
        if not self._is_push_writer:
            raise Exception("Not a push writer")

        if isinstance(self.database_engine, PostgresEngine):
            # Postgres doesn't do FOR UPDATE on aggregate functions, so select the rows first
            # then re-select the count/max below.
            sql = """
                SELECT * FROM push_rules
                WHERE user_name = ? and priority_class = ?
                FOR UPDATE
            """
            txn.execute(sql, (user_id, priority_class))
        else:
            # Annoyingly SQLite doesn't support row level locking, so lock the whole table
            self.database_engine.lock_table(txn, "push_rules")

        # find the highest priority rule in that class
        sql = (
            "SELECT COUNT(*), MAX(priority) FROM push_rules"
            " WHERE user_name = ? and priority_class = ?"
        )
        txn.execute(sql, (user_id, priority_class))
        res = txn.fetchall()
        (how_many, highest_prio) = res[0]

        new_prio = 0
        if how_many > 0:
            new_prio = highest_prio + 1

        self._upsert_push_rule_txn(
            txn,
            stream_id,
            event_stream_ordering,
            user_id,
            rule_id,
            priority_class,
            new_prio,
            conditions_json,
            actions_json,
        )

    def _upsert_push_rule_txn(
        self,
        txn: LoggingTransaction,
        stream_id: int,
        event_stream_ordering: int,
        user_id: str,
        rule_id: str,
        priority_class: int,
        priority: int,
        conditions_json: str,
        actions_json: str,
        update_stream: bool = True,
    ) -> None:
        """Specialised version of simple_upsert_txn that picks a push_rule_id
        using the _push_rule_id_gen if it needs to insert the rule.

        Preconditions:
            - this worker is a push writer
            - the "push_rules" table is locked
            - the push rule has already been validated,
              including for rule ID length and rule body size.
        """

        if not self._is_push_writer:
            raise Exception("Not a push writer")

        sql = (
            "UPDATE push_rules"
            " SET priority_class = ?, priority = ?, conditions = ?, actions = ?"
            " WHERE user_name = ? AND rule_id = ?"
        )

        txn.execute(
            sql,
            (priority_class, priority, conditions_json, actions_json, user_id, rule_id),
        )

        if txn.rowcount == 0:
            # About to add a new rule, so check our limits first.
            txn.execute(
                """
                SELECT COUNT(*) FROM push_rules
                WHERE user_name = ?
                """,
                (user_id,),
            )
            (num_push_rules,) = cast(tuple[int], txn.fetchone())
            if num_push_rules >= self._config.limits.rule_count:
                raise SynapseError(
                    HTTPStatus.BAD_REQUEST,
                    f"Creating a push rule would exceed the limit on the number of push rules associated with your account ({num_push_rules + 1} rules > {self._config.limits.rule_count} rules)",
                    # FIXME: Provide a better error code, especially for this case.
                    # None of the existing options seem entirely correct, though.
                    # `M_USER_LIMIT_EXCEEDED` comes closest but needs an `info_uri`.
                    # Should follow up and add a built-in error page template, similarly to
                    # https://github.com/element-hq/synapse/pull/18876 ?
                    Codes.UNKNOWN,
                )

            # We didn't update a row with the given rule_id so insert one
            push_rule_id = self._push_rule_id_gen.get_next()

            self.db_pool.simple_insert_txn(
                txn,
                table="push_rules",
                values={
                    "id": push_rule_id,
                    "user_name": user_id,
                    "rule_id": rule_id,
                    "priority_class": priority_class,
                    "priority": priority,
                    "conditions": conditions_json,
                    "actions": actions_json,
                },
            )

        if update_stream:
            self._insert_push_rules_update_txn(
                txn,
                stream_id,
                event_stream_ordering,
                user_id,
                rule_id,
                op="ADD",
                data={
                    "priority_class": priority_class,
                    "priority": priority,
                    "conditions": conditions_json,
                    "actions": actions_json,
                },
            )

        # ensure we have a push_rules_enable row
        # enabledness defaults to true
        if isinstance(self.database_engine, PostgresEngine):
            sql = """
                INSERT INTO push_rules_enable (id, user_name, rule_id, enabled)
                VALUES (?, ?, ?, 1)
                ON CONFLICT DO NOTHING
            """
        elif isinstance(self.database_engine, Sqlite3Engine):
            sql = """
                INSERT OR IGNORE INTO push_rules_enable (id, user_name, rule_id, enabled)
                VALUES (?, ?, ?, 1)
            """
        else:
            raise RuntimeError("Unknown database engine")

        new_enable_id = self._push_rules_enable_id_gen.get_next()
        txn.execute(sql, (new_enable_id, user_id, rule_id))

    async def delete_push_rule(self, user_id: str, rule_id: str) -> None:
        """
        Delete a push rule. Args specify the row to be deleted and can be
        any of the columns in the push_rule table, but below are the
        standard ones

        Args:
            user_id: The matrix ID of the push rule owner
            rule_id: The rule_id of the rule to be deleted
        """
        if not self._is_push_writer:
            raise Exception("Not a push writer")

        def delete_push_rule_txn(
            txn: LoggingTransaction,
            stream_id: int,
            event_stream_ordering: int,
        ) -> None:
            # we don't use simple_delete_one_txn because that would fail if the
            # user did not have a push_rule_enable row.
            self.db_pool.simple_delete_txn(
                txn, "push_rules_enable", {"user_name": user_id, "rule_id": rule_id}
            )

            self.db_pool.simple_delete_one_txn(
                txn, "push_rules", {"user_name": user_id, "rule_id": rule_id}
            )

            self._insert_push_rules_update_txn(
                txn, stream_id, event_stream_ordering, user_id, rule_id, op="DELETE"
            )

        async with self._push_rules_stream_id_gen.get_next() as stream_id:
            event_stream_ordering = self._stream_id_gen.get_current_token()

            await self.db_pool.runInteraction(
                "delete_push_rule",
                delete_push_rule_txn,
                stream_id,
                event_stream_ordering,
            )

    async def set_push_rule_enabled(
        self, user_id: str, rule_id: str, enabled: bool, is_default_rule: bool
    ) -> None:
        """
        Sets the `enabled` state of a push rule.

        Args:
            user_id: the user ID of the user who wishes to enable/disable the rule
                e.g. '@tina:example.org'
            rule_id: the full rule ID of the rule to be enabled/disabled
                e.g. 'global/override/.m.rule.roomnotif'
                  or 'global/override/myCustomRule'
            enabled: True if the rule is to be enabled, False if it is to be
                disabled
            is_default_rule: True if and only if this is a server-default rule.
                This skips the check for existence (as only user-created rules
                are always stored in the database `push_rules` table).

        Raises:
            RuleNotFoundException if the rule does not exist.
        """
        if not self._is_push_writer:
            raise Exception("Not a push writer")

        async with self._push_rules_stream_id_gen.get_next() as stream_id:
            event_stream_ordering = self._stream_id_gen.get_current_token()
            await self.db_pool.runInteraction(
                "_set_push_rule_enabled_txn",
                self._set_push_rule_enabled_txn,
                stream_id,
                event_stream_ordering,
                user_id,
                rule_id,
                enabled,
                is_default_rule,
            )

    def _set_push_rule_enabled_txn(
        self,
        txn: LoggingTransaction,
        stream_id: int,
        event_stream_ordering: int,
        user_id: str,
        rule_id: str,
        enabled: bool,
        is_default_rule: bool,
    ) -> None:
        if not self._is_push_writer:
            raise Exception("Not a push writer")

        new_id = self._push_rules_enable_id_gen.get_next()

        if not is_default_rule:
            # first check it exists; we need to lock for key share so that a
            # transaction that deletes the push rule will conflict with this one.
            # We also need a push_rule_enable row to exist for every push_rules
            # row, otherwise it is possible to simultaneously delete a push rule
            # (that has no _enable row) and enable it, resulting in a dangling
            # _enable row. To solve this: we either need to use SERIALISABLE or
            # ensure we always have a push_rule_enable row for every push_rule
            # row. We chose the latter.
            for_key_share = "FOR KEY SHARE"
            if not isinstance(self.database_engine, PostgresEngine):
                # For key share is not applicable/available on SQLite
                for_key_share = ""
            sql = (
                """
                SELECT 1 FROM push_rules
                WHERE user_name = ? AND rule_id = ?
                %s
            """
                % for_key_share
            )
            txn.execute(sql, (user_id, rule_id))
            if txn.fetchone() is None:
                raise RuleNotFoundException("Push rule does not exist.")

        self.db_pool.simple_upsert_txn(
            txn,
            "push_rules_enable",
            {"user_name": user_id, "rule_id": rule_id},
            {"enabled": 1 if enabled else 0},
            {"id": new_id},
        )

        self._insert_push_rules_update_txn(
            txn,
            stream_id,
            event_stream_ordering,
            user_id,
            rule_id,
            op="ENABLE" if enabled else "DISABLE",
        )

    async def set_push_rule_actions(
        self,
        user_id: str,
        rule_id: str,
        actions: list[dict | str],
        is_default_rule: bool,
    ) -> None:
        """
        Sets the `actions` state of a push rule.

        Args:
            user_id: the user ID of the user who wishes to enable/disable the rule
                e.g. '@tina:example.org'
            rule_id: the full rule ID of the rule to be enabled/disabled
                e.g. 'global/override/.m.rule.roomnotif'
                  or 'global/override/myCustomRule'
            actions: A list of actions (each action being a dict or string),
                e.g. ["notify", {"set_tweak": "highlight", "value": false}]
            is_default_rule: True if and only if this is a server-default rule.
                This skips the check for existence (as only user-created rules
                are always stored in the database `push_rules` table).

        Raises:
            RuleNotFoundException if the rule does not exist.
        """
        if not self._is_push_writer:
            raise Exception("Not a push writer")

        actions_json = json_encoder.encode(actions)

        def set_push_rule_actions_txn(
            txn: LoggingTransaction,
            stream_id: int,
            event_stream_ordering: int,
        ) -> None:
            if is_default_rule:
                # Add a dummy rule to the rules table with the user specified
                # actions.
                priority_class = -1
                priority = 1
                self._upsert_push_rule_txn(
                    txn,
                    stream_id,
                    event_stream_ordering,
                    user_id,
                    rule_id,
                    priority_class,
                    priority,
                    "[]",
                    actions_json,
                    update_stream=False,
                )
            else:
                try:
                    # Before updating the push rule, we need to check that we won't exceed
                    # the size limit on push rules.
                    # For that, we need to fetch the `conditions` JSON.
                    conditions_json = self.db_pool.simple_select_one_onecol_txn(
                        txn,
                        "push_rules",
                        {"user_name": user_id, "rule_id": rule_id},
                        "conditions",
                    )

                    rule_body_size = _push_rule_size_for_limits(
                        conditions_json=conditions_json, actions_json=actions_json
                    )
                    if rule_body_size > self._config.limits.rule_size:
                        raise SynapseError(
                            HTTPStatus.REQUEST_ENTITY_TOO_LARGE,
                            f"Push rule size exceeds server limit ({rule_body_size} bytes > {self._config.limits.rule_size} bytes).",
                            # FIXME: Provide a better error code.
                            # None of the existing options seem entirely correct, though.
                            Codes.UNKNOWN,
                        )

                    self.db_pool.simple_update_one_txn(
                        txn,
                        "push_rules",
                        {"user_name": user_id, "rule_id": rule_id},
                        {"actions": actions_json},
                    )
                except StoreError as serr:
                    if serr.code == 404:
                        # this sets the NOT_FOUND error Code
                        raise RuleNotFoundException("Push rule does not exist")
                    else:
                        raise

            self._insert_push_rules_update_txn(
                txn,
                stream_id,
                event_stream_ordering,
                user_id,
                rule_id,
                op="ACTIONS",
                data={"actions": actions_json},
            )

        async with self._push_rules_stream_id_gen.get_next() as stream_id:
            event_stream_ordering = self._stream_id_gen.get_current_token()

            await self.db_pool.runInteraction(
                "set_push_rule_actions",
                set_push_rule_actions_txn,
                stream_id,
                event_stream_ordering,
            )

    def _insert_push_rules_update_txn(
        self,
        txn: LoggingTransaction,
        stream_id: int,
        event_stream_ordering: int,
        user_id: str,
        rule_id: str,
        op: str,
        data: JsonDict | None = None,
    ) -> None:
        if not self._is_push_writer:
            raise Exception("Not a push writer")

        values = {
            "instance_name": self._instance_name,
            "stream_id": stream_id,
            "event_stream_ordering": event_stream_ordering,
            "user_id": user_id,
            "rule_id": rule_id,
            "op": op,
        }
        if data is not None:
            values.update(data)

        self.db_pool.simple_insert_txn(txn, "push_rules_stream", values=values)

        txn.call_after(self.get_push_rules_for_user.invalidate, (user_id,))
        txn.call_after(
            self.push_rules_stream_cache.entity_has_changed, user_id, stream_id
        )

    async def copy_push_rule_from_room_to_room(
        self, new_room_id: str, user_id: str, rule: PushRule
    ) -> None:
        """Copy a single push rule from one room to another for a specific user.

        Args:
            new_room_id: ID of the new room.
            user_id : ID of user the push rule belongs to.
            rule: A push rule.
        """
        if not self._is_push_writer:
            raise Exception("Not a push writer")

        # Create new rule id
        rule_id_scope = "/".join(rule.rule_id.split("/")[:-1])
        new_rule_id = rule_id_scope + "/" + new_room_id

        new_conditions = []

        # Change room id in each condition
        for condition in rule.conditions:
            new_condition = condition
            if condition.get("key") == "room_id":
                new_condition = dict(condition)
                new_condition["pattern"] = new_room_id

            new_conditions.append(new_condition)

        # Add the rule for the new room
        await self.add_push_rule(
            user_id=user_id,
            rule_id=new_rule_id,
            priority_class=rule.priority_class,
            conditions=new_conditions,
            actions=rule.actions,
        )

    async def copy_push_rules_from_room_to_room_for_user(
        self, old_room_id: str, new_room_id: str, user_id: str
    ) -> None:
        """Copy all of the push rules from one room to another for a specific
        user.

        Args:
            old_room_id: ID of the old room.
            new_room_id: ID of the new room.
            user_id: ID of user to copy push rules for.
        """
        if not self._is_push_writer:
            raise Exception("Not a push writer")

        # Retrieve push rules for this user
        user_push_rules = await self.get_push_rules_for_user(user_id)

        # Get rules relating to the old room and copy them to the new room
        for rule, enabled in user_push_rules.rules():
            if not enabled:
                continue

            conditions = rule.conditions
            if any(
                (c.get("key") == "room_id" and c.get("pattern") == old_room_id)
                for c in conditions
            ):
                await self.copy_push_rule_from_room_to_room(new_room_id, user_id, rule)
