# -*- coding: utf-8 -*-
# Copyright 2017 Vector Creations Ltd
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""The server side of the replication stream.
"""

import logging
import random

from six import itervalues

from prometheus_client import Counter

from twisted.internet import defer
from twisted.internet.protocol import Factory

from synapse.metrics import LaterGauge
from synapse.metrics.background_process_metrics import run_as_background_process
from synapse.util.metrics import Measure, measure_func

from .protocol import ServerReplicationStreamProtocol
from .streams import STREAMS_MAP
from .streams.federation import FederationStream

stream_updates_counter = Counter(
    "synapse_replication_tcp_resource_stream_updates", "", ["stream_name"]
)
user_sync_counter = Counter("synapse_replication_tcp_resource_user_sync", "")
federation_ack_counter = Counter("synapse_replication_tcp_resource_federation_ack", "")
remove_pusher_counter = Counter("synapse_replication_tcp_resource_remove_pusher", "")
invalidate_cache_counter = Counter(
    "synapse_replication_tcp_resource_invalidate_cache", ""
)
user_ip_cache_counter = Counter("synapse_replication_tcp_resource_user_ip_cache", "")

logger = logging.getLogger(__name__)


class ReplicationStreamProtocolFactory(Factory):
    """Factory for new replication connections.
    """

    def __init__(self, hs):
        self.streamer = ReplicationStreamer(hs)
        self.clock = hs.get_clock()
        self.server_name = hs.config.server_name

    def buildProtocol(self, addr):
        return ServerReplicationStreamProtocol(
            self.server_name, self.clock, self.streamer
        )


class ReplicationStreamer(object):
    """Handles replication connections.

    This needs to be poked when new replication data may be available. When new
    data is available it will propagate to all connected clients.
    """

    def __init__(self, hs):
        self.store = hs.get_datastore()
        self.presence_handler = hs.get_presence_handler()
        self.clock = hs.get_clock()
        self.notifier = hs.get_notifier()
        self._server_notices_sender = hs.get_server_notices_sender()

        self._replication_torture_level = hs.config.replication_torture_level

        # Current connections.
        self.connections = []

        LaterGauge(
            "synapse_replication_tcp_resource_total_connections",
            "",
            [],
            lambda: len(self.connections),
        )

        # List of streams that clients can subscribe to.
        # We only support federation stream if federation sending hase been
        # disabled on the master.
        self.streams = [
            stream(hs)
            for stream in itervalues(STREAMS_MAP)
            if stream != FederationStream or not hs.config.send_federation
        ]

        self.streams_by_name = {stream.NAME: stream for stream in self.streams}

        LaterGauge(
            "synapse_replication_tcp_resource_connections_per_stream",
            "",
            ["stream_name"],
            lambda: {
                (stream_name,): len(
                    [
                        conn
                        for conn in self.connections
                        if stream_name in conn.replication_streams
                    ]
                )
                for stream_name in self.streams_by_name
            },
        )

        self.federation_sender = None
        if not hs.config.send_federation:
            self.federation_sender = hs.get_federation_sender()

        self.notifier.add_replication_callback(self.on_notifier_poke)

        # Keeps track of whether we are currently checking for updates
        self.is_looping = False
        self.pending_updates = False

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

    def on_shutdown(self):
        # close all connections on shutdown
        for conn in self.connections:
            conn.send_error("server shutting down")

    def on_notifier_poke(self):
        """Checks if there is actually any new data and sends it to the
        connections if there are.

        This should get called each time new data is available, even if it
        is currently being executed, so that nothing gets missed
        """
        if not self.connections:
            # Don't bother if nothing is listening. We still need to advance
            # the stream tokens otherwise they'll fall beihind forever
            for stream in self.streams:
                stream.discard_updates_and_advance()
            return

        self.pending_updates = True

        if self.is_looping:
            logger.debug("Notifier poke loop already running")
            return

        run_as_background_process("replication_notifier", self._run_notifier_loop)

    @defer.inlineCallbacks
    def _run_notifier_loop(self):
        self.is_looping = True

        try:
            # Keep looping while there have been pokes about potential updates.
            # This protects against the race where a stream we already checked
            # gets an update while we're handling other streams.
            while self.pending_updates:
                self.pending_updates = False

                with Measure(self.clock, "repl.stream.get_updates"):
                    # First we tell the streams that they should update their
                    # current tokens.
                    for stream in self.streams:
                        stream.advance_current_token()

                    all_streams = self.streams

                    if self._replication_torture_level is not None:
                        # there is no guarantee about ordering between the streams,
                        # so let's shuffle them around a bit when we are in torture mode.
                        all_streams = list(all_streams)
                        random.shuffle(all_streams)

                    for stream in all_streams:
                        if stream.last_token == stream.upto_token:
                            continue

                        if self._replication_torture_level:
                            yield self.clock.sleep(
                                self._replication_torture_level / 1000.0
                            )

                        logger.debug(
                            "Getting stream: %s: %s -> %s",
                            stream.NAME,
                            stream.last_token,
                            stream.upto_token,
                        )
                        try:
                            updates, current_token = yield stream.get_updates()
                        except Exception:
                            logger.info("Failed to handle stream %s", stream.NAME)
                            raise

                        logger.debug(
                            "Sending %d updates to %d connections",
                            len(updates),
                            len(self.connections),
                        )

                        if updates:
                            logger.info(
                                "Streaming: %s -> %s", stream.NAME, updates[-1][0]
                            )
                            stream_updates_counter.labels(stream.NAME).inc(len(updates))

                        # Some streams return multiple rows with the same stream IDs,
                        # we need to make sure they get sent out in batches. We do
                        # this by setting the current token to all but the last of
                        # a series of updates with the same token to have a None
                        # token. See RdataCommand for more details.
                        batched_updates = _batch_updates(updates)

                        for conn in self.connections:
                            for token, row in batched_updates:
                                try:
                                    conn.stream_update(stream.NAME, token, row)
                                except Exception:
                                    logger.exception("Failed to replicate")

            logger.debug("No more pending updates, breaking poke loop")
        finally:
            self.pending_updates = False
            self.is_looping = False

    @measure_func("repl.get_stream_updates")
    def get_stream_updates(self, stream_name, token):
        """For a given stream get all updates since token. This is called when
        a client first subscribes to a stream.
        """
        stream = self.streams_by_name.get(stream_name, None)
        if not stream:
            raise Exception("unknown stream %s", stream_name)

        return stream.get_updates_since(token)

    @measure_func("repl.federation_ack")
    def federation_ack(self, token):
        """We've received an ack for federation stream from a client.
        """
        federation_ack_counter.inc()
        if self.federation_sender:
            self.federation_sender.federation_ack(token)

    @measure_func("repl.on_user_sync")
    @defer.inlineCallbacks
    def on_user_sync(self, conn_id, user_id, is_syncing, last_sync_ms):
        """A client has started/stopped syncing on a worker.
        """
        user_sync_counter.inc()
        yield self.presence_handler.update_external_syncs_row(
            conn_id, user_id, is_syncing, last_sync_ms
        )

    @measure_func("repl.on_remove_pusher")
    @defer.inlineCallbacks
    def on_remove_pusher(self, app_id, push_key, user_id):
        """A client has asked us to remove a pusher
        """
        remove_pusher_counter.inc()
        yield self.store.delete_pusher_by_app_id_pushkey_user_id(
            app_id=app_id, pushkey=push_key, user_id=user_id
        )

        self.notifier.on_new_replication_data()

    @measure_func("repl.on_invalidate_cache")
    def on_invalidate_cache(self, cache_func, keys):
        """The client has asked us to invalidate a cache
        """
        invalidate_cache_counter.inc()
        getattr(self.store, cache_func).invalidate(tuple(keys))

    @measure_func("repl.on_user_ip")
    @defer.inlineCallbacks
    def on_user_ip(self, user_id, access_token, ip, user_agent, device_id, last_seen):
        """The client saw a user request
        """
        user_ip_cache_counter.inc()
        yield self.store.insert_client_ip(
            user_id, access_token, ip, user_agent, device_id, last_seen
        )
        yield self._server_notices_sender.on_user_ip(user_id)

    def send_sync_to_all_connections(self, data):
        """Sends a SYNC command to all clients.

        Used in tests.
        """
        for conn in self.connections:
            conn.send_sync(data)

    def new_connection(self, connection):
        """A new client connection has been established
        """
        self.connections.append(connection)

    def lost_connection(self, connection):
        """A client connection has been lost
        """
        try:
            self.connections.remove(connection)
        except ValueError:
            pass

        # We need to tell the presence handler that the connection has been
        # lost so that it can handle any ongoing syncs on that connection.
        self.presence_handler.update_external_syncs_clear(connection.conn_id)


def _batch_updates(updates):
    """Takes a list of updates of form [(token, row)] and sets the token to
    None for all rows where the next row has the same token. This is used to
    implement batching.

    For example:

        [(1, _), (1, _), (2, _), (3, _), (3, _)]

    becomes:

        [(None, _), (1, _), (2, _), (None, _), (3, _)]
    """
    if not updates:
        return []

    new_updates = []
    for i, update in enumerate(updates[:-1]):
        if update[0] == updates[i + 1][0]:
            new_updates.append((None, update[1]))
        else:
            new_updates.append(update)

    new_updates.append(updates[-1])
    return new_updates
