# 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.
"""A replication client for use by synapse workers.
"""
import logging
from typing import TYPE_CHECKING, Dict, Iterable, List, Optional, Set, Tuple

from twisted.internet.defer import Deferred
from twisted.internet.interfaces import IAddress, IConnector
from twisted.internet.protocol import ReconnectingClientFactory
from twisted.python.failure import Failure

from synapse.api.constants import EventTypes, ReceiptTypes
from synapse.federation import send_queue
from synapse.federation.sender import FederationSender
from synapse.logging.context import PreserveLoggingContext, make_deferred_yieldable
from synapse.metrics.background_process_metrics import run_as_background_process
from synapse.replication.tcp.protocol import ClientReplicationStreamProtocol
from synapse.replication.tcp.streams import (
    AccountDataStream,
    DeviceListsStream,
    PushersStream,
    PushRulesStream,
    ReceiptsStream,
    TagAccountDataStream,
    ToDeviceStream,
    TypingStream,
)
from synapse.replication.tcp.streams.events import (
    EventsStream,
    EventsStreamEventRow,
    EventsStreamRow,
)
from synapse.types import PersistedEventPosition, ReadReceipt, StreamKeyType, UserID
from synapse.util.async_helpers import Linearizer, timeout_deferred
from synapse.util.metrics import Measure

if TYPE_CHECKING:
    from synapse.replication.tcp.handler import ReplicationCommandHandler
    from synapse.server import HomeServer

logger = logging.getLogger(__name__)

# How long we allow callers to wait for replication updates before timing out.
_WAIT_FOR_REPLICATION_TIMEOUT_SECONDS = 30


class DirectTcpReplicationClientFactory(ReconnectingClientFactory):
    """Factory for building connections to the master. Will reconnect if the
    connection is lost.

    Accepts a handler that is passed to `ClientReplicationStreamProtocol`.
    """

    initialDelay = 0.1
    maxDelay = 1  # Try at least once every N seconds

    def __init__(
        self,
        hs: "HomeServer",
        client_name: str,
        command_handler: "ReplicationCommandHandler",
    ):
        self.client_name = client_name
        self.command_handler = command_handler
        self.server_name = hs.config.server.server_name
        self.hs = hs
        self._clock = hs.get_clock()  # As self.clock is defined in super class

        hs.get_reactor().addSystemEventTrigger("before", "shutdown", self.stopTrying)

    def startedConnecting(self, connector: IConnector) -> None:
        logger.info("Connecting to replication: %r", connector.getDestination())

    def buildProtocol(self, addr: IAddress) -> ClientReplicationStreamProtocol:
        logger.info("Connected to replication: %r", addr)
        return ClientReplicationStreamProtocol(
            self.hs,
            self.client_name,
            self.server_name,
            self._clock,
            self.command_handler,
        )

    def clientConnectionLost(self, connector: IConnector, reason: Failure) -> None:
        logger.error("Lost replication conn: %r", reason)
        ReconnectingClientFactory.clientConnectionLost(self, connector, reason)

    def clientConnectionFailed(self, connector: IConnector, reason: Failure) -> None:
        logger.error("Failed to connect to replication: %r", reason)
        ReconnectingClientFactory.clientConnectionFailed(self, connector, reason)


class ReplicationDataHandler:
    """Handles incoming stream updates from replication.

    This instance notifies the slave data store about updates. Can be subclassed
    to handle updates in additional ways.
    """

    def __init__(self, hs: "HomeServer"):
        self.store = hs.get_datastores().main
        self.notifier = hs.get_notifier()
        self._reactor = hs.get_reactor()
        self._clock = hs.get_clock()
        self._streams = hs.get_replication_streams()
        self._instance_name = hs.get_instance_name()
        self._typing_handler = hs.get_typing_handler()

        self._notify_pushers = hs.config.worker.start_pushers
        self._pusher_pool = hs.get_pusherpool()
        self._presence_handler = hs.get_presence_handler()

        self.send_handler: Optional[FederationSenderHandler] = None
        if hs.should_send_federation():
            self.send_handler = FederationSenderHandler(hs)

        # Map from stream to list of deferreds waiting for the stream to
        # arrive at a particular position. The lists are sorted by stream position.
        self._streams_to_waiters: Dict[str, List[Tuple[int, Deferred]]] = {}

    async def on_rdata(
        self, stream_name: str, instance_name: str, token: int, rows: list
    ) -> None:
        """Called to handle a batch of replication data with a given stream token.

        By default this just pokes the slave store. Can be overridden in subclasses to
        handle more.

        Args:
            stream_name: name of the replication stream for this batch of rows
            instance_name: the instance that wrote the rows.
            token: stream token for this batch of rows
            rows: a list of Stream.ROW_TYPE objects as returned by Stream.parse_row.
        """
        self.store.process_replication_rows(stream_name, instance_name, token, rows)

        if self.send_handler:
            await self.send_handler.process_replication_rows(stream_name, token, rows)

        if stream_name == TypingStream.NAME:
            self._typing_handler.process_replication_rows(token, rows)
            self.notifier.on_new_event(
                StreamKeyType.TYPING, token, rooms=[row.room_id for row in rows]
            )
        elif stream_name == PushRulesStream.NAME:
            self.notifier.on_new_event(
                StreamKeyType.PUSH_RULES, token, users=[row.user_id for row in rows]
            )
        elif stream_name in (AccountDataStream.NAME, TagAccountDataStream.NAME):
            self.notifier.on_new_event(
                StreamKeyType.ACCOUNT_DATA, token, users=[row.user_id for row in rows]
            )
        elif stream_name == ReceiptsStream.NAME:
            self.notifier.on_new_event(
                StreamKeyType.RECEIPT, token, rooms=[row.room_id for row in rows]
            )
            await self._pusher_pool.on_new_receipts(
                token, token, {row.room_id for row in rows}
            )
        elif stream_name == ToDeviceStream.NAME:
            entities = [row.entity for row in rows if row.entity.startswith("@")]
            if entities:
                self.notifier.on_new_event(
                    StreamKeyType.TO_DEVICE, token, users=entities
                )
        elif stream_name == DeviceListsStream.NAME:
            all_room_ids: Set[str] = set()
            for row in rows:
                if row.entity.startswith("@"):
                    room_ids = await self.store.get_rooms_for_user(row.entity)
                    all_room_ids.update(room_ids)
            self.notifier.on_new_event(
                StreamKeyType.DEVICE_LIST, token, rooms=all_room_ids
            )
        elif stream_name == PushersStream.NAME:
            for row in rows:
                if row.deleted:
                    self.stop_pusher(row.user_id, row.app_id, row.pushkey)
                else:
                    await self.start_pusher(row.user_id, row.app_id, row.pushkey)
        elif stream_name == EventsStream.NAME:
            # We shouldn't get multiple rows per token for events stream, so
            # we don't need to optimise this for multiple rows.
            for row in rows:
                if row.type != EventsStreamEventRow.TypeId:
                    continue
                assert isinstance(row, EventsStreamRow)
                assert isinstance(row.data, EventsStreamEventRow)

                if row.data.rejected:
                    continue

                extra_users: Tuple[UserID, ...] = ()
                if row.data.type == EventTypes.Member and row.data.state_key:
                    extra_users = (UserID.from_string(row.data.state_key),)

                max_token = self.store.get_room_max_token()
                event_pos = PersistedEventPosition(instance_name, token)
                await self.notifier.on_new_room_event_args(
                    event_pos=event_pos,
                    max_room_stream_token=max_token,
                    extra_users=extra_users,
                    room_id=row.data.room_id,
                    event_id=row.data.event_id,
                    event_type=row.data.type,
                    state_key=row.data.state_key,
                    membership=row.data.membership,
                )

        await self._presence_handler.process_replication_rows(
            stream_name, instance_name, token, rows
        )

        # Notify any waiting deferreds. The list is ordered by position so we
        # just iterate through the list until we reach a position that is
        # greater than the received row position.
        waiting_list = self._streams_to_waiters.get(stream_name, [])

        # Index of first item with a position after the current token, i.e we
        # have called all deferreds before this index. If not overwritten by
        # loop below means either a) no items in list so no-op or b) all items
        # in list were called and so the list should be cleared. Setting it to
        # `len(list)` works for both cases.
        index_of_first_deferred_not_called = len(waiting_list)

        for idx, (position, deferred) in enumerate(waiting_list):
            if position <= token:
                try:
                    with PreserveLoggingContext():
                        deferred.callback(None)
                except Exception:
                    # The deferred has been cancelled or timed out.
                    pass
            else:
                # The list is sorted by position so we don't need to continue
                # checking any further entries in the list.
                index_of_first_deferred_not_called = idx
                break

        # Drop all entries in the waiting list that were called in the above
        # loop. (This maintains the order so no need to resort)
        waiting_list[:] = waiting_list[index_of_first_deferred_not_called:]

    async def on_position(
        self, stream_name: str, instance_name: str, token: int
    ) -> None:
        await self.on_rdata(stream_name, instance_name, token, [])

        # We poke the generic "replication" notifier to wake anything up that
        # may be streaming.
        self.notifier.notify_replication()

    def on_remote_server_up(self, server: str) -> None:
        """Called when get a new REMOTE_SERVER_UP command."""

        # Let's wake up the transaction queue for the server in case we have
        # pending stuff to send to it.
        if self.send_handler:
            self.send_handler.wake_destination(server)

    async def wait_for_stream_position(
        self, instance_name: str, stream_name: str, position: int
    ) -> None:
        """Wait until this instance has received updates up to and including
        the given stream position.
        """

        if instance_name == self._instance_name:
            # We don't get told about updates written by this process, and
            # anyway in that case we don't need to wait.
            return

        current_position = self._streams[stream_name].current_token(self._instance_name)
        if position <= current_position:
            # We're already past the position
            return

        # Create a new deferred that times out after N seconds, as we don't want
        # to wedge here forever.
        deferred: "Deferred[None]" = Deferred()
        deferred = timeout_deferred(
            deferred, _WAIT_FOR_REPLICATION_TIMEOUT_SECONDS, self._reactor
        )

        waiting_list = self._streams_to_waiters.setdefault(stream_name, [])

        waiting_list.append((position, deferred))
        waiting_list.sort(key=lambda t: t[0])

        # We measure here to get in flight counts and average waiting time.
        with Measure(self._clock, "repl.wait_for_stream_position"):
            logger.info("Waiting for repl stream %r to reach %s", stream_name, position)
            await make_deferred_yieldable(deferred)
            logger.info(
                "Finished waiting for repl stream %r to reach %s", stream_name, position
            )

    def stop_pusher(self, user_id: str, app_id: str, pushkey: str) -> None:
        if not self._notify_pushers:
            return

        key = "%s:%s" % (app_id, pushkey)
        pushers_for_user = self._pusher_pool.pushers.get(user_id, {})
        pusher = pushers_for_user.pop(key, None)
        if pusher is None:
            return
        logger.info("Stopping pusher %r / %r", user_id, key)
        pusher.on_stop()

    async def start_pusher(self, user_id: str, app_id: str, pushkey: str) -> None:
        if not self._notify_pushers:
            return

        key = "%s:%s" % (app_id, pushkey)
        logger.info("Starting pusher %r / %r", user_id, key)
        await self._pusher_pool.start_pusher_by_id(app_id, pushkey, user_id)


class FederationSenderHandler:
    """Processes the fedration replication stream

    This class is only instantiate on the worker responsible for sending outbound
    federation transactions. It receives rows from the replication stream and forwards
    the appropriate entries to the FederationSender class.
    """

    def __init__(self, hs: "HomeServer"):
        assert hs.should_send_federation()

        self.store = hs.get_datastores().main
        self._is_mine_id = hs.is_mine_id
        self._hs = hs

        # We need to make a temporary value to ensure that mypy picks up the
        # right type. We know we should have a federation sender instance since
        # `should_send_federation` is True.
        sender = hs.get_federation_sender()
        assert isinstance(sender, FederationSender)
        self.federation_sender = sender

        # Stores the latest position in the federation stream we've gotten up
        # to. This is always set before we use it.
        self.federation_position: Optional[int] = None

        self._fed_position_linearizer = Linearizer(name="_fed_position_linearizer")

    def wake_destination(self, server: str) -> None:
        self.federation_sender.wake_destination(server)

    async def process_replication_rows(
        self, stream_name: str, token: int, rows: list
    ) -> None:
        # The federation stream contains things that we want to send out, e.g.
        # presence, typing, etc.
        if stream_name == "federation":
            send_queue.process_rows_for_federation(self.federation_sender, rows)
            await self.update_token(token)

        # ... and when new receipts happen
        elif stream_name == ReceiptsStream.NAME:
            await self._on_new_receipts(rows)

        # ... as well as device updates and messages
        elif stream_name == DeviceListsStream.NAME:
            # The entities are either user IDs (starting with '@') whose devices
            # have changed, or remote servers that we need to tell about
            # changes.
            hosts = {row.entity for row in rows if not row.entity.startswith("@")}
            for host in hosts:
                self.federation_sender.send_device_messages(host, immediate=False)

        elif stream_name == ToDeviceStream.NAME:
            # The to_device stream includes stuff to be pushed to both local
            # clients and remote servers, so we ignore entities that start with
            # '@' (since they'll be local users rather than destinations).
            hosts = {row.entity for row in rows if not row.entity.startswith("@")}
            for host in hosts:
                self.federation_sender.send_device_messages(host)

    async def _on_new_receipts(
        self, rows: Iterable[ReceiptsStream.ReceiptsStreamRow]
    ) -> None:
        """
        Args:
            rows: new receipts to be processed
        """
        for receipt in rows:
            # we only want to send on receipts for our own users
            if not self._is_mine_id(receipt.user_id):
                continue
            # Private read receipts never get sent over federation.
            if receipt.receipt_type == ReceiptTypes.READ_PRIVATE:
                continue
            receipt_info = ReadReceipt(
                receipt.room_id,
                receipt.receipt_type,
                receipt.user_id,
                [receipt.event_id],
                receipt.data,
            )
            await self.federation_sender.send_read_receipt(receipt_info)

    async def update_token(self, token: int) -> None:
        """Update the record of where we have processed to in the federation stream.

        Called after we have processed a an update received over replication. Sends
        a FEDERATION_ACK back to the master, and stores the token that we have processed
         in `federation_stream_position` so that we can restart where we left off.
        """
        self.federation_position = token

        # We save and send the ACK to master asynchronously, so we don't block
        # processing on persistence. We don't need to do this operation for
        # every single RDATA we receive, we just need to do it periodically.

        if self._fed_position_linearizer.is_queued(None):
            # There is already a task queued up to save and send the token, so
            # no need to queue up another task.
            return

        run_as_background_process("_save_and_send_ack", self._save_and_send_ack)

    async def _save_and_send_ack(self) -> None:
        """Save the current federation position in the database and send an ACK
        to master with where we're up to.
        """
        # We should only be calling this once we've got a token.
        assert self.federation_position is not None

        try:
            # We linearize here to ensure we don't have races updating the token
            #
            # XXX this appears to be redundant, since the ReplicationCommandHandler
            # has a linearizer which ensures that we only process one line of
            # replication data at a time. Should we remove it, or is it doing useful
            # service for robustness? Or could we replace it with an assertion that
            # we're not being re-entered?

            async with self._fed_position_linearizer.queue(None):
                # We persist and ack the same position, so we take a copy of it
                # here as otherwise it can get modified from underneath us.
                current_position = self.federation_position

                await self.store.update_federation_out_pos(
                    "federation", current_position
                )

                # We ACK this token over replication so that the master can drop
                # its in memory queues
                self._hs.get_replication_command_handler().send_federation_ack(
                    current_position
                )
        except Exception:
            logger.exception("Error updating federation stream position")
