# -*- coding: utf-8 -*-
# Copyright 2018 New Vector 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.

import logging
import re

from twisted.internet import defer

from synapse.api.errors import (
    CodeMessageException,
    MatrixCodeMessageException,
    SynapseError,
)
from synapse.events import FrozenEvent
from synapse.events.snapshot import EventContext
from synapse.http.servlet import RestServlet, parse_json_object_from_request
from synapse.types import Requester, UserID
from synapse.util.caches.response_cache import ResponseCache
from synapse.util.metrics import Measure

logger = logging.getLogger(__name__)


@defer.inlineCallbacks
def send_event_to_master(clock, client, host, port, requester, event, context,
                         ratelimit, extra_users):
    """Send event to be handled on the master

    Args:
        clock (synapse.util.Clock)
        client (SimpleHttpClient)
        host (str): host of master
        port (int): port on master listening for HTTP replication
        requester (Requester)
        event (FrozenEvent)
        context (EventContext)
        ratelimit (bool)
        extra_users (list(UserID)): Any extra users to notify about event
    """
    uri = "http://%s:%s/_synapse/replication/send_event/%s" % (
        host, port, event.event_id,
    )

    payload = {
        "event": event.get_pdu_json(),
        "internal_metadata": event.internal_metadata.get_dict(),
        "rejected_reason": event.rejected_reason,
        "context": context.serialize(event),
        "requester": requester.serialize(),
        "ratelimit": ratelimit,
        "extra_users": [u.to_string() for u in extra_users],
    }

    try:
        # We keep retrying the same request for timeouts. This is so that we
        # have a good idea that the request has either succeeded or failed on
        # the master, and so whether we should clean up or not.
        while True:
            try:
                result = yield client.put_json(uri, payload)
                break
            except CodeMessageException as e:
                if e.code != 504:
                    raise

            logger.warn("send_event request timed out")

            # If we timed out we probably don't need to worry about backing
            # off too much, but lets just wait a little anyway.
            yield clock.sleep(1)
    except MatrixCodeMessageException as e:
        # We convert to SynapseError as we know that it was a SynapseError
        # on the master process that we should send to the client. (And
        # importantly, not stack traces everywhere)
        raise SynapseError(e.code, e.msg, e.errcode)
    defer.returnValue(result)


class ReplicationSendEventRestServlet(RestServlet):
    """Handles events newly created on workers, including persisting and
    notifying.

    The API looks like:

        POST /_synapse/replication/send_event/:event_id

        {
            "event": { .. serialized event .. },
            "internal_metadata": { .. serialized internal_metadata .. },
            "rejected_reason": ..,   // The event.rejected_reason field
            "context": { .. serialized event context .. },
            "requester": { .. serialized requester .. },
            "ratelimit": true,
            "extra_users": [],
        }
    """
    PATTERNS = [re.compile("^/_synapse/replication/send_event/(?P<event_id>[^/]+)$")]

    def __init__(self, hs):
        super(ReplicationSendEventRestServlet, self).__init__()

        self.event_creation_handler = hs.get_event_creation_handler()
        self.store = hs.get_datastore()
        self.clock = hs.get_clock()

        # The responses are tiny, so we may as well cache them for a while
        self.response_cache = ResponseCache(hs, "send_event", timeout_ms=30 * 60 * 1000)

    def on_PUT(self, request, event_id):
        return self.response_cache.wrap(
            event_id,
            self._handle_request,
            request
        )

    @defer.inlineCallbacks
    def _handle_request(self, request):
        with Measure(self.clock, "repl_send_event_parse"):
            content = parse_json_object_from_request(request)

            event_dict = content["event"]
            internal_metadata = content["internal_metadata"]
            rejected_reason = content["rejected_reason"]
            event = FrozenEvent(event_dict, internal_metadata, rejected_reason)

            requester = Requester.deserialize(self.store, content["requester"])
            context = yield EventContext.deserialize(self.store, content["context"])

            ratelimit = content["ratelimit"]
            extra_users = [UserID.from_string(u) for u in content["extra_users"]]

        if requester.user:
            request.authenticated_entity = requester.user.to_string()

        logger.info(
            "Got event to send with ID: %s into room: %s",
            event.event_id, event.room_id,
        )

        yield self.event_creation_handler.persist_and_notify_client_event(
            requester, event, context,
            ratelimit=ratelimit,
            extra_users=extra_users,
        )

        defer.returnValue((200, {}))


def register_servlets(hs, http_server):
    ReplicationSendEventRestServlet(hs).register(http_server)
