# -*- coding: utf-8 -*-
# Copyright 2017 Vector Creations Ltd
# Copyright 2019 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
from collections import namedtuple
from typing import Any, Awaitable, Callable, Iterable, List, Optional, Tuple

import attr

from synapse.replication.http.streams import ReplicationGetStreamUpdates

logger = logging.getLogger(__name__)

# the number of rows to request from an update_function.
_STREAM_UPDATE_TARGET_ROW_COUNT = 100


# Some type aliases to make things a bit easier.

# A stream position token
Token = int

# The type of a stream update row, after JSON deserialisation, but before
# parsing with Stream.parse_row (which turns it into a `ROW_TYPE`). Normally it's
# just a row from a database query, though this is dependent on the stream in question.
#
StreamRow = Tuple

# The type returned by the update_function of a stream, as well as get_updates(),
# get_updates_since, etc.
#
# It consists of a triplet `(updates, new_last_token, limited)`, where:
#   * `updates` is a list of `(token, row)` entries.
#   * `new_last_token` is the new position in stream.
#   * `limited` is whether there are more updates to fetch.
#
StreamUpdateResult = Tuple[List[Tuple[Token, StreamRow]], Token, bool]

# The type of an update_function for a stream
#
# The arguments are:
#
#  * from_token: the previous stream token: the starting point for fetching the
#    updates
#  * to_token: the new stream token: the point to get updates up to
#  * target_row_count: a target for the number of rows to be returned.
#
# The update_function is expected to return up to _approximately_ target_row_count rows.
# If there are more updates available, it should set `limited` in the result, and
# it will be called again to get the next batch.
#
UpdateFunction = Callable[[Token, Token, int], Awaitable[StreamUpdateResult]]


class Stream(object):
    """Base class for the streams.

    Provides a `get_updates()` function that returns new updates since the last
    time it was called.
    """

    NAME = None  # type: str  # The name of the stream
    # The type of the row. Used by the default impl of parse_row.
    ROW_TYPE = None  # type: Any

    @classmethod
    def parse_row(cls, row: StreamRow):
        """Parse a row received over replication

        By default, assumes that the row data is an array object and passes its contents
        to the constructor of the ROW_TYPE for this stream.

        Args:
            row: row data from the incoming RDATA command, after json decoding

        Returns:
            ROW_TYPE object for this stream
        """
        return cls.ROW_TYPE(*row)

    def __init__(
        self,
        current_token_function: Callable[[], Token],
        update_function: UpdateFunction,
    ):
        """Instantiate a Stream

        current_token_function and update_function are callbacks which should be
        implemented by subclasses.

        current_token_function is called to get the current token of the underlying
        stream.

        update_function is called to get updates for this stream between a pair of
        stream tokens. See the UpdateFunction type definition for more info.

        Args:
            current_token_function: callback to get the current token, as above
            update_function: callback go get stream updates, as above
        """
        self.current_token = current_token_function
        self.update_function = update_function

        # The token from which we last asked for updates
        self.last_token = self.current_token()

    def discard_updates_and_advance(self):
        """Called when the stream should advance but the updates would be discarded,
        e.g. when there are no currently connected workers.
        """
        self.last_token = self.current_token()

    async def get_updates(self) -> StreamUpdateResult:
        """Gets all updates since the last time this function was called (or
        since the stream was constructed if it hadn't been called before).

        Returns:
            A triplet `(updates, new_last_token, limited)`, where `updates` is
            a list of `(token, row)` entries, `new_last_token` is the new
            position in stream, and `limited` is whether there are more updates
            to fetch.
        """
        current_token = self.current_token()
        updates, current_token, limited = await self.get_updates_since(
            self.last_token, current_token
        )
        self.last_token = current_token

        return updates, current_token, limited

    async def get_updates_since(
        self, from_token: Token, upto_token: Token
    ) -> StreamUpdateResult:
        """Like get_updates except allows specifying from when we should
        stream updates

        Returns:
            A triplet `(updates, new_last_token, limited)`, where `updates` is
            a list of `(token, row)` entries, `new_last_token` is the new
            position in stream, and `limited` is whether there are more updates
            to fetch.
        """

        from_token = int(from_token)

        if from_token == upto_token:
            return [], upto_token, False

        updates, upto_token, limited = await self.update_function(
            from_token, upto_token, _STREAM_UPDATE_TARGET_ROW_COUNT,
        )
        return updates, upto_token, limited


def db_query_to_update_function(
    query_function: Callable[[Token, Token, int], Awaitable[Iterable[tuple]]]
) -> UpdateFunction:
    """Wraps a db query function which returns a list of rows to make it
    suitable for use as an `update_function` for the Stream class
    """

    async def update_function(from_token, upto_token, limit):
        rows = await query_function(from_token, upto_token, limit)
        updates = [(row[0], row[1:]) for row in rows]
        limited = False
        if len(updates) >= limit:
            upto_token = updates[-1][0]
            limited = True

        return updates, upto_token, limited

    return update_function


def make_http_update_function(hs, stream_name: str) -> UpdateFunction:
    """Makes a suitable function for use as an `update_function` that queries
    the master process for updates.
    """

    client = ReplicationGetStreamUpdates.make_client(hs)

    async def update_function(
        from_token: int, upto_token: int, limit: int
    ) -> StreamUpdateResult:
        result = await client(
            stream_name=stream_name, from_token=from_token, upto_token=upto_token,
        )
        return result["updates"], result["upto_token"], result["limited"]

    return update_function


class BackfillStream(Stream):
    """We fetched some old events and either we had never seen that event before
    or it went from being an outlier to not.
    """

    BackfillStreamRow = namedtuple(
        "BackfillStreamRow",
        (
            "event_id",  # str
            "room_id",  # str
            "type",  # str
            "state_key",  # str, optional
            "redacts",  # str, optional
            "relates_to",  # str, optional
        ),
    )

    NAME = "backfill"
    ROW_TYPE = BackfillStreamRow

    def __init__(self, hs):
        store = hs.get_datastore()
        super().__init__(
            store.get_current_backfill_token,
            db_query_to_update_function(store.get_all_new_backfill_event_rows),
        )


class PresenceStream(Stream):
    PresenceStreamRow = namedtuple(
        "PresenceStreamRow",
        (
            "user_id",  # str
            "state",  # str
            "last_active_ts",  # int
            "last_federation_update_ts",  # int
            "last_user_sync_ts",  # int
            "status_msg",  # str
            "currently_active",  # bool
        ),
    )

    NAME = "presence"
    ROW_TYPE = PresenceStreamRow

    def __init__(self, hs):
        store = hs.get_datastore()

        if hs.config.worker_app is None:
            # on the master, query the presence handler
            presence_handler = hs.get_presence_handler()
            update_function = db_query_to_update_function(
                presence_handler.get_all_presence_updates
            )
        else:
            # Query master process
            update_function = make_http_update_function(hs, self.NAME)

        super().__init__(store.get_current_presence_token, update_function)


class TypingStream(Stream):
    TypingStreamRow = namedtuple(
        "TypingStreamRow", ("room_id", "user_ids")  # str  # list(str)
    )

    NAME = "typing"
    ROW_TYPE = TypingStreamRow

    def __init__(self, hs):
        typing_handler = hs.get_typing_handler()

        if hs.config.worker_app is None:
            # on the master, query the typing handler
            update_function = db_query_to_update_function(
                typing_handler.get_all_typing_updates
            )
        else:
            # Query master process
            update_function = make_http_update_function(hs, self.NAME)

        super().__init__(typing_handler.get_current_token, update_function)


class ReceiptsStream(Stream):
    ReceiptsStreamRow = namedtuple(
        "ReceiptsStreamRow",
        (
            "room_id",  # str
            "receipt_type",  # str
            "user_id",  # str
            "event_id",  # str
            "data",  # dict
        ),
    )

    NAME = "receipts"
    ROW_TYPE = ReceiptsStreamRow

    def __init__(self, hs):
        store = hs.get_datastore()
        super().__init__(
            store.get_max_receipt_stream_id,
            db_query_to_update_function(store.get_all_updated_receipts),
        )


class PushRulesStream(Stream):
    """A user has changed their push rules
    """

    PushRulesStreamRow = namedtuple("PushRulesStreamRow", ("user_id",))  # str

    NAME = "push_rules"
    ROW_TYPE = PushRulesStreamRow

    def __init__(self, hs):
        self.store = hs.get_datastore()
        super(PushRulesStream, self).__init__(
            self._current_token, self._update_function
        )

    def _current_token(self) -> int:
        push_rules_token, _ = self.store.get_push_rules_stream_token()
        return push_rules_token

    async def _update_function(self, from_token: Token, to_token: Token, limit: int):
        rows = await self.store.get_all_push_rule_updates(from_token, to_token, limit)

        limited = False
        if len(rows) == limit:
            to_token = rows[-1][0]
            limited = True

        return [(row[0], (row[2],)) for row in rows], to_token, limited


class PushersStream(Stream):
    """A user has added/changed/removed a pusher
    """

    PushersStreamRow = namedtuple(
        "PushersStreamRow",
        ("user_id", "app_id", "pushkey", "deleted"),  # str  # str  # str  # bool
    )

    NAME = "pushers"
    ROW_TYPE = PushersStreamRow

    def __init__(self, hs):
        store = hs.get_datastore()

        super().__init__(
            store.get_pushers_stream_token,
            db_query_to_update_function(store.get_all_updated_pushers_rows),
        )


class CachesStream(Stream):
    """A cache was invalidated on the master and no other stream would invalidate
    the cache on the workers
    """

    @attr.s
    class CachesStreamRow:
        """Stream to inform workers they should invalidate their cache.

        Attributes:
            cache_func: Name of the cached function.
            keys: The entry in the cache to invalidate. If None then will
                invalidate all.
            invalidation_ts: Timestamp of when the invalidation took place.
        """

        cache_func = attr.ib(type=str)
        keys = attr.ib(type=Optional[List[Any]])
        invalidation_ts = attr.ib(type=int)

    NAME = "caches"
    ROW_TYPE = CachesStreamRow

    def __init__(self, hs):
        store = hs.get_datastore()
        super().__init__(
            store.get_cache_stream_token,
            db_query_to_update_function(store.get_all_updated_caches),
        )


class PublicRoomsStream(Stream):
    """The public rooms list changed
    """

    PublicRoomsStreamRow = namedtuple(
        "PublicRoomsStreamRow",
        (
            "room_id",  # str
            "visibility",  # str
            "appservice_id",  # str, optional
            "network_id",  # str, optional
        ),
    )

    NAME = "public_rooms"
    ROW_TYPE = PublicRoomsStreamRow

    def __init__(self, hs):
        store = hs.get_datastore()
        super().__init__(
            store.get_current_public_room_stream_id,
            db_query_to_update_function(store.get_all_new_public_rooms),
        )


class DeviceListsStream(Stream):
    """Either a user has updated their devices or a remote server needs to be
    told about a device update.
    """

    @attr.s
    class DeviceListsStreamRow:
        entity = attr.ib(type=str)

    NAME = "device_lists"
    ROW_TYPE = DeviceListsStreamRow

    def __init__(self, hs):
        store = hs.get_datastore()
        super().__init__(
            store.get_device_stream_token,
            db_query_to_update_function(store.get_all_device_list_changes_for_remotes),
        )


class ToDeviceStream(Stream):
    """New to_device messages for a client
    """

    ToDeviceStreamRow = namedtuple("ToDeviceStreamRow", ("entity",))  # str

    NAME = "to_device"
    ROW_TYPE = ToDeviceStreamRow

    def __init__(self, hs):
        store = hs.get_datastore()
        super().__init__(
            store.get_to_device_stream_token,
            db_query_to_update_function(store.get_all_new_device_messages),
        )


class TagAccountDataStream(Stream):
    """Someone added/removed a tag for a room
    """

    TagAccountDataStreamRow = namedtuple(
        "TagAccountDataStreamRow", ("user_id", "room_id", "data")  # str  # str  # dict
    )

    NAME = "tag_account_data"
    ROW_TYPE = TagAccountDataStreamRow

    def __init__(self, hs):
        store = hs.get_datastore()
        super().__init__(
            store.get_max_account_data_stream_id,
            db_query_to_update_function(store.get_all_updated_tags),
        )


class AccountDataStream(Stream):
    """Global or per room account data was changed
    """

    AccountDataStreamRow = namedtuple(
        "AccountDataStream", ("user_id", "room_id", "data_type")  # str  # str  # str
    )

    NAME = "account_data"
    ROW_TYPE = AccountDataStreamRow

    def __init__(self, hs):
        self.store = hs.get_datastore()
        super().__init__(
            self.store.get_max_account_data_stream_id,
            db_query_to_update_function(self._update_function),
        )

    async def _update_function(self, from_token, to_token, limit):
        global_results, room_results = await self.store.get_all_updated_account_data(
            from_token, from_token, to_token, limit
        )

        results = list(room_results)
        results.extend(
            (stream_id, user_id, None, account_data_type)
            for stream_id, user_id, account_data_type in global_results
        )

        return results


class GroupServerStream(Stream):
    GroupsStreamRow = namedtuple(
        "GroupsStreamRow",
        ("group_id", "user_id", "type", "content"),  # str  # str  # str  # dict
    )

    NAME = "groups"
    ROW_TYPE = GroupsStreamRow

    def __init__(self, hs):
        store = hs.get_datastore()
        super().__init__(
            store.get_group_stream_token,
            db_query_to_update_function(store.get_all_groups_changes),
        )


class UserSignatureStream(Stream):
    """A user has signed their own device with their user-signing key
    """

    UserSignatureStreamRow = namedtuple("UserSignatureStreamRow", ("user_id"))  # str

    NAME = "user_signature"
    ROW_TYPE = UserSignatureStreamRow

    def __init__(self, hs):
        store = hs.get_datastore()
        super().__init__(
            store.get_device_stream_token,
            db_query_to_update_function(
                store.get_all_user_signature_changes_for_remotes
            ),
        )