# -*- coding: utf-8 -*-
# Copyright 2015 OpenMarket 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.

from synapse.http.servlet import parse_integer, parse_string
from synapse.http.server import request_handler, finish_request
from synapse.replication.pusher_resource import PusherResource
from synapse.replication.presence_resource import PresenceResource
from synapse.api.errors import SynapseError

from twisted.web.resource import Resource
from twisted.web.server import NOT_DONE_YET
from twisted.internet import defer

import ujson as json

import collections
import logging

logger = logging.getLogger(__name__)

REPLICATION_PREFIX = "/_synapse/replication"

STREAM_NAMES = (
    ("events",),
    ("presence",),
    ("typing",),
    ("receipts",),
    ("user_account_data", "room_account_data", "tag_account_data",),
    ("backfill",),
    ("push_rules",),
    ("pushers",),
    ("caches",),
    ("to_device",),
    ("public_rooms",),
)


class ReplicationResource(Resource):
    """
    HTTP endpoint for extracting data from synapse.

    The streams of data returned by the endpoint are controlled by the
    parameters given to the API. To return a given stream pass a query
    parameter with a position in the stream to return data from or the
    special value "-1" to return data from the start of the stream.

    If there is no data for any of the supplied streams after the given
    position then the request will block until there is data for one
    of the streams. This allows clients to long-poll this API.

    The possible streams are:

    * "streams": A special stream returing the positions of other streams.
    * "events": The new events seen on the server.
    * "presence": Presence updates.
    * "typing": Typing updates.
    * "receipts": Receipt updates.
    * "user_account_data": Top-level per user account data.
    * "room_account_data: Per room per user account data.
    * "tag_account_data": Per room per user tags.
    * "backfill": Old events that have been backfilled from other servers.
    * "push_rules": Per user changes to push rules.
    * "pushers": Per user changes to their pushers.
    * "caches": Cache invalidations.

    The API takes two additional query parameters:

    * "timeout": How long to wait before returning an empty response.
    * "limit": The maximum number of rows to return for the selected streams.

    The response is a JSON object with keys for each stream with updates. Under
    each key is a JSON object with:

    * "position": The current position of the stream.
    * "field_names": The names of the fields in each row.
    * "rows": The updates as an array of arrays.

    There are a number of ways this API could be used:

    1) To replicate the contents of the backing database to another database.
    2) To be notified when the contents of a shared backing database changes.
    3) To "tail" the activity happening on a server for debugging.

    In the first case the client would track all of the streams and store it's
    own copy of the data.

    In the second case the client might theoretically just be able to follow
    the "streams" stream to track where the other streams are. However in
    practise it will probably need to get the contents of the streams in
    order to expire the any in-memory caches. Whether it gets the contents
    of the streams from this replication API or directly from the backing
    store is a matter of taste.

    In the third case the client would use the "streams" stream to find what
    streams are available and their current positions. Then it can start
    long-polling this replication API for new data on those streams.
    """

    def __init__(self, hs):
        Resource.__init__(self)  # Resource is old-style, so no super()

        self.version_string = hs.version_string
        self.store = hs.get_datastore()
        self.sources = hs.get_event_sources()
        self.presence_handler = hs.get_presence_handler()
        self.typing_handler = hs.get_typing_handler()
        self.notifier = hs.notifier
        self.clock = hs.get_clock()

        self.putChild("remove_pushers", PusherResource(hs))
        self.putChild("syncing_users", PresenceResource(hs))

    def render_GET(self, request):
        self._async_render_GET(request)
        return NOT_DONE_YET

    @defer.inlineCallbacks
    def current_replication_token(self):
        stream_token = yield self.sources.get_current_token()
        backfill_token = yield self.store.get_current_backfill_token()
        push_rules_token, room_stream_token = self.store.get_push_rules_stream_token()
        pushers_token = self.store.get_pushers_stream_token()
        caches_token = self.store.get_cache_stream_token()
        public_rooms_token = self.store.get_current_public_room_stream_id()

        defer.returnValue(_ReplicationToken(
            room_stream_token,
            int(stream_token.presence_key),
            int(stream_token.typing_key),
            int(stream_token.receipt_key),
            int(stream_token.account_data_key),
            backfill_token,
            push_rules_token,
            pushers_token,
            0,  # State stream is no longer a thing
            caches_token,
            int(stream_token.to_device_key),
            int(public_rooms_token),
        ))

    @request_handler()
    @defer.inlineCallbacks
    def _async_render_GET(self, request):
        limit = parse_integer(request, "limit", 100)
        timeout = parse_integer(request, "timeout", 10 * 1000)

        request.setHeader(b"Content-Type", b"application/json")

        request_streams = {
            name: parse_integer(request, name)
            for names in STREAM_NAMES for name in names
        }
        request_streams["streams"] = parse_string(request, "streams")

        def replicate():
            return self.replicate(request_streams, limit)

        writer = yield self.notifier.wait_for_replication(replicate, timeout)
        result = writer.finish()

        for stream_name, stream_content in result.items():
            logger.info(
                "Replicating %d rows of %s from %s -> %s",
                len(stream_content["rows"]),
                stream_name,
                request_streams.get(stream_name),
                stream_content["position"],
            )

        request.write(json.dumps(result, ensure_ascii=False))
        finish_request(request)

    @defer.inlineCallbacks
    def replicate(self, request_streams, limit):
        writer = _Writer()
        current_token = yield self.current_replication_token()
        logger.debug("Replicating up to %r", current_token)

        if limit == 0:
            raise SynapseError(400, "Limit cannot be 0")

        yield self.account_data(writer, current_token, limit, request_streams)
        yield self.events(writer, current_token, limit, request_streams)
        # TODO: implement limit
        yield self.presence(writer, current_token, request_streams)
        yield self.typing(writer, current_token, request_streams)
        yield self.receipts(writer, current_token, limit, request_streams)
        yield self.push_rules(writer, current_token, limit, request_streams)
        yield self.pushers(writer, current_token, limit, request_streams)
        yield self.caches(writer, current_token, limit, request_streams)
        yield self.to_device(writer, current_token, limit, request_streams)
        yield self.public_rooms(writer, current_token, limit, request_streams)
        self.streams(writer, current_token, request_streams)

        logger.debug("Replicated %d rows", writer.total)
        defer.returnValue(writer)

    def streams(self, writer, current_token, request_streams):
        request_token = request_streams.get("streams")

        streams = []

        if request_token is not None:
            if request_token == "-1":
                for names, position in zip(STREAM_NAMES, current_token):
                    streams.extend((name, position) for name in names)
            else:
                items = zip(
                    STREAM_NAMES,
                    current_token,
                    _ReplicationToken(request_token)
                )
                for names, current_id, last_id in items:
                    if last_id < current_id:
                        streams.extend((name, current_id) for name in names)

            if streams:
                writer.write_header_and_rows(
                    "streams", streams, ("name", "position"),
                    position=str(current_token)
                )

    @defer.inlineCallbacks
    def events(self, writer, current_token, limit, request_streams):
        request_events = request_streams.get("events")
        request_backfill = request_streams.get("backfill")

        if request_events is not None or request_backfill is not None:
            if request_events is None:
                request_events = current_token.events
            if request_backfill is None:
                request_backfill = current_token.backfill

            no_new_tokens = (
                request_events == current_token.events
                and request_backfill == current_token.backfill
            )
            if no_new_tokens:
                return

            res = yield self.store.get_all_new_events(
                request_backfill, request_events,
                current_token.backfill, current_token.events,
                limit
            )

            upto_events_token = _position_from_rows(
                res.new_forward_events, current_token.events
            )

            upto_backfill_token = _position_from_rows(
                res.new_backfill_events, current_token.backfill
            )

            if request_events != upto_events_token:
                writer.write_header_and_rows("events", res.new_forward_events, (
                    "position", "internal", "json", "state_group"
                ), position=upto_events_token)

            if request_backfill != upto_backfill_token:
                writer.write_header_and_rows("backfill", res.new_backfill_events, (
                    "position", "internal", "json", "state_group",
                ), position=upto_backfill_token)

            writer.write_header_and_rows(
                "forward_ex_outliers", res.forward_ex_outliers,
                ("position", "event_id", "state_group"),
            )
            writer.write_header_and_rows(
                "backward_ex_outliers", res.backward_ex_outliers,
                ("position", "event_id", "state_group"),
            )
            writer.write_header_and_rows(
                "state_resets", res.state_resets, ("position",),
            )

    @defer.inlineCallbacks
    def presence(self, writer, current_token, request_streams):
        current_position = current_token.presence

        request_presence = request_streams.get("presence")

        if request_presence is not None and request_presence != current_position:
            presence_rows = yield self.presence_handler.get_all_presence_updates(
                request_presence, current_position
            )
            upto_token = _position_from_rows(presence_rows, current_position)
            writer.write_header_and_rows("presence", presence_rows, (
                "position", "user_id", "state", "last_active_ts",
                "last_federation_update_ts", "last_user_sync_ts",
                "status_msg", "currently_active",
            ), position=upto_token)

    @defer.inlineCallbacks
    def typing(self, writer, current_token, request_streams):
        current_position = current_token.typing

        request_typing = request_streams.get("typing")

        if request_typing is not None and request_typing != current_position:
            # If they have a higher token than current max, we can assume that
            # they had been talking to a previous instance of the master. Since
            # we reset the token on restart, the best (but hacky) thing we can
            # do is to simply resend down all the typing notifications.
            if request_typing > current_position:
                request_typing = 0

            typing_rows = yield self.typing_handler.get_all_typing_updates(
                request_typing, current_position
            )
            upto_token = _position_from_rows(typing_rows, current_position)
            writer.write_header_and_rows("typing", typing_rows, (
                "position", "room_id", "typing"
            ), position=upto_token)

    @defer.inlineCallbacks
    def receipts(self, writer, current_token, limit, request_streams):
        current_position = current_token.receipts

        request_receipts = request_streams.get("receipts")

        if request_receipts is not None and request_receipts != current_position:
            receipts_rows = yield self.store.get_all_updated_receipts(
                request_receipts, current_position, limit
            )
            upto_token = _position_from_rows(receipts_rows, current_position)
            writer.write_header_and_rows("receipts", receipts_rows, (
                "position", "room_id", "receipt_type", "user_id", "event_id", "data"
            ), position=upto_token)

    @defer.inlineCallbacks
    def account_data(self, writer, current_token, limit, request_streams):
        current_position = current_token.account_data

        user_account_data = request_streams.get("user_account_data")
        room_account_data = request_streams.get("room_account_data")
        tag_account_data = request_streams.get("tag_account_data")

        if user_account_data is not None or room_account_data is not None:
            if user_account_data is None:
                user_account_data = current_position
            if room_account_data is None:
                room_account_data = current_position

            no_new_tokens = (
                user_account_data == current_position
                and room_account_data == current_position
            )
            if no_new_tokens:
                return

            user_rows, room_rows = yield self.store.get_all_updated_account_data(
                user_account_data, room_account_data, current_position, limit
            )

            upto_users_token = _position_from_rows(user_rows, current_position)
            upto_rooms_token = _position_from_rows(room_rows, current_position)

            writer.write_header_and_rows("user_account_data", user_rows, (
                "position", "user_id", "type", "content"
            ), position=upto_users_token)
            writer.write_header_and_rows("room_account_data", room_rows, (
                "position", "user_id", "room_id", "type", "content"
            ), position=upto_rooms_token)

        if tag_account_data is not None:
            tag_rows = yield self.store.get_all_updated_tags(
                tag_account_data, current_position, limit
            )
            upto_tag_token = _position_from_rows(tag_rows, current_position)
            writer.write_header_and_rows("tag_account_data", tag_rows, (
                "position", "user_id", "room_id", "tags"
            ), position=upto_tag_token)

    @defer.inlineCallbacks
    def push_rules(self, writer, current_token, limit, request_streams):
        current_position = current_token.push_rules

        push_rules = request_streams.get("push_rules")

        if push_rules is not None and push_rules != current_position:
            rows = yield self.store.get_all_push_rule_updates(
                push_rules, current_position, limit
            )
            upto_token = _position_from_rows(rows, current_position)
            writer.write_header_and_rows("push_rules", rows, (
                "position", "event_stream_ordering", "user_id", "rule_id", "op",
                "priority_class", "priority", "conditions", "actions"
            ), position=upto_token)

    @defer.inlineCallbacks
    def pushers(self, writer, current_token, limit, request_streams):
        current_position = current_token.pushers

        pushers = request_streams.get("pushers")

        if pushers is not None and pushers != current_position:
            updated, deleted = yield self.store.get_all_updated_pushers(
                pushers, current_position, limit
            )
            upto_token = _position_from_rows(updated, current_position)
            writer.write_header_and_rows("pushers", updated, (
                "position", "user_id", "access_token", "profile_tag", "kind",
                "app_id", "app_display_name", "device_display_name", "pushkey",
                "ts", "lang", "data"
            ), position=upto_token)
            writer.write_header_and_rows("deleted_pushers", deleted, (
                "position", "user_id", "app_id", "pushkey"
            ), position=upto_token)

    @defer.inlineCallbacks
    def caches(self, writer, current_token, limit, request_streams):
        current_position = current_token.caches

        caches = request_streams.get("caches")

        if caches is not None and caches != current_position:
            updated_caches = yield self.store.get_all_updated_caches(
                caches, current_position, limit
            )
            upto_token = _position_from_rows(updated_caches, current_position)
            writer.write_header_and_rows("caches", updated_caches, (
                "position", "cache_func", "keys", "invalidation_ts"
            ), position=upto_token)

    @defer.inlineCallbacks
    def to_device(self, writer, current_token, limit, request_streams):
        current_position = current_token.to_device

        to_device = request_streams.get("to_device")

        if to_device is not None and to_device != current_position:
            to_device_rows = yield self.store.get_all_new_device_messages(
                to_device, current_position, limit
            )
            upto_token = _position_from_rows(to_device_rows, current_position)
            writer.write_header_and_rows("to_device", to_device_rows, (
                "position", "user_id", "device_id", "message_json"
            ), position=upto_token)

    @defer.inlineCallbacks
    def public_rooms(self, writer, current_token, limit, request_streams):
        current_position = current_token.public_rooms

        public_rooms = request_streams.get("public_rooms")

        if public_rooms is not None and public_rooms != current_position:
            public_rooms_rows = yield self.store.get_all_new_public_rooms(
                public_rooms, current_position, limit
            )
            upto_token = _position_from_rows(public_rooms_rows, current_position)
            writer.write_header_and_rows("public_rooms", public_rooms_rows, (
                "position", "room_id", "visibility"
            ), position=upto_token)


class _Writer(object):
    """Writes the streams as a JSON object as the response to the request"""
    def __init__(self):
        self.streams = {}
        self.total = 0

    def write_header_and_rows(self, name, rows, fields, position=None):
        if position is None:
            if rows:
                position = rows[-1][0]
            else:
                return

        self.streams[name] = {
            "position": position if type(position) is int else str(position),
            "field_names": fields,
            "rows": rows,
        }

        self.total += len(rows)

    def __nonzero__(self):
        return bool(self.total)

    def finish(self):
        return self.streams


class _ReplicationToken(collections.namedtuple("_ReplicationToken", (
    "events", "presence", "typing", "receipts", "account_data", "backfill",
    "push_rules", "pushers", "state", "caches", "to_device", "public_rooms",
))):
    __slots__ = []

    def __new__(cls, *args):
        if len(args) == 1:
            streams = [int(value) for value in args[0].split("_")]
            if len(streams) < len(cls._fields):
                streams.extend([0] * (len(cls._fields) - len(streams)))
            return cls(*streams)
        else:
            return super(_ReplicationToken, cls).__new__(cls, *args)

    def __str__(self):
        return "_".join(str(value) for value in self)


def _position_from_rows(rows, current_position):
    """Calculates a position to return for a stream. Ideally we want to return the
    position of the last row, as that will be the most correct. However, if there
    are no rows we fall back to using the current position to stop us from
    repeatedly hitting the storage layer unncessarily thinking there are updates.
    (Not all advances of the token correspond to an actual update)

    We can't just always return the current position, as we often limit the
    number of rows we replicate, and so the stream may lag. The assumption is
    that if the storage layer returns no new rows then we are not lagging and
    we are at the `current_position`.
    """
    if rows:
        return rows[-1][0]
    return current_position
